(Advances in agronomy 116) donald l sparks (eds ) advances in agronomy 116 academic press, elsevier (2012)

manage-success in intensive agricultural areas Cassman et al., 2002; Drinkwater andSnapp, 2007.In INM, crop yields can be increased while minimizing nutrient losses tothe environment by

Texas A&M University

Emeritus Advisory Board Members

Prepared in cooperation with the

American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America Book and Multimedia Publishing Committee

DAVID D BALTENSPERGER, CHAIR

SALLY D LOGSDON

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ISBN: 978-0-12-394277-7

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12 13 14 15 10 9 8 7 6 5 4 3 2 1

Numbers in Parentheses indicate the pages on which the authors’ contributions begin.

Univer-Department of Plant Nutrition, China Agricultural University, Beijing, PR China Mingsheng Fan (1)

Department of Plant Nutrition, China Agricultural University, Beijing, PR China Steven J Fonte (123)

International Center for Tropical Agriculture (CIAT), Cali, Colombia

Olivier Gru ¨nberger (71)

IRD (Institut de Recherche pour le De´veloppement), UMR-LISAH, Montpellier cedex, France

Uttam Kumar (41)

International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh, India

Patrick Lavelle (125)

International Center for Tropical Agriculture (CIAT), Cali, Colombia, and Institut

de Recherche sur le De´veloppement (IRD)/Universite´ Pierre et Marie Curie (UPMC), Paris, France

Department of Agronomy, Kansas State University, Manhattan, Kansas, USA Fusuo Zhang (1)

Department of Plant Nutrition, China Agricultural University, Beijing, PR China Weifeng Zhang (1)

Department of Plant Nutrition, China Agricultural University, Beijing, PR China Chengsong Zhu (217)

Department of Agronomy, Kansas State University, Manhattan, Kansas, USA

Volume 116 contains six excellent reviews dealing with environmentalsustainability and food security Chapter 1 is an enlightening review on anintegrated nutrient management (INM) approach, developed on more than

20 years of research, to address serious environmental quality challenges,related to excess use of nutrients, in China The INM approach has led toincreased nutrient use efficiency and decreased inputs of fertilizers Chapter

2 deals with the effect of climate change factors on crop growth, ment, and yield of groundnut Chapter 3 is a comprehensive review onpractices used in oil palm plantations and impacts on hydrological changes,nutrient fluxes, and water quality in Indonesia Chapter 4 is an enlighteningoverview of soil fertility decline in the high Andes of Bolivia, Ecuador, andPeru Approaches are presented to enhance nutrient cycling, crop nutrientuptake, and overall increased productivity Chapter 5 addresses an impor-tant global factor affecting future food security, phosphorus utilizationefficiency (PUE) by plants The review focuses on grain crops and coverspast attempts to improve PUE via plant breeding, and new approaches forimproving PUE Chapter 6 is a stimulating review on the importance ofcomputer simulation in plant breeding

develop-I am grateful to the authors for their outstanding reviews

DONALDL SPARKSNewark, Delaware, USA

xiii

Integrated Nutrient Management for Food Security and Environmental

Quality in China

Fusuo Zhang, Zhenling Cui, Xinping Chen, Xiaotang Ju,

Jianbo Shen, Qing Chen, Xuejun Liu, Weifeng Zhang,

Guohua Mi, Mingsheng Fan, and Rongfeng Jiang

Contents

2.1 Optimizing nutrient inputs and taking all possible sources of

2.2 Dynamically matching soil nutrient supply with crop

2.3 Effectively reducing N losses in intensive managed Chinese

2.4 Taking all possible yield increase measures into consideration 15

3 Technology and Demonstration of INM in Different Cropping

Advances in Agronomy, Volume 116 # 2012 Elsevier Inc ISSN 0065-2113, DOI: 10.1016/B978-0-12-394277-7.00001-4 All rights reserved Department of Plant Nutrition, China Agricultural University, Beijing, PR China

1

be partly attributed to a 37-fold increase in N fertilization and a 91-fold increase

in P fertilization, but the environment costs have been very high New advances for sustainability of agriculture and ecosystem services will be needed during the coming 50years to improve nutrient use efficiency (NUE) while increasing crop productivity and reducing environmental risk Here, we advocate and develop integrated nutrient management (INM) based on more than 20years

of studies In this INM approach, the key components comprise (1) optimizing nutrient inputs by taking all possible nutrient sources into consideration, (2) matching nutrient supply in root zone with crop requirements spatially and temporally, (3) reducing N losses in intensively managed cropping systems, and (4) taking all possible yield-increasing measures into consideration Recent large-scale application of INM for cereal, vegetable, and fruit cropping systems has shed light on how INM can lead to significantly improved NUE, while increasing crop yields and reducing environmental risk The INM has already influenced Chinese agricultural policy and national actions, and resulted in increasing food production with decreased climb of chemical fertilizer consump- tion at a national scale over recent years The INM can thus be considered an effective agricultural paradigm to ensure food security and improve environmen- tal quality worldwide, especially in countries with rapidly developing economies.

Abbreviations

1 Introduction

The Green Revolution helped to create the world’s “Miracle in China,”with 9% of the world’s arable land feeding 22% of the world population In thepast 49years (1961–2009), cereal grain yields have increased 3.5-fold from 1.2

to 5.4tha
1, while total grain production has increased 3.4-fold from 110 to

483 million ton (MT) (FAO, 2011) In 1998, grain, meat, and egg productionper capita in China exceeded the world average The increased demand inChinese grain production has affected the global food supply and the natural

resource bases required for nutrient production (fossil fuels, mineral sources of

P and K) and has attained world recognition

However, this 3.4-fold increase in Chinese agricultural food productionduring the past 49years can be partly attributed to a 48-fold increase inchemical fertilizers from 1 to 49MT, including a 37-fold increase in Nfertilizer application and a 91-fold increase in P fertilizer use, and a 442-foldincrease in the area of irrigated croplands (Fig 1) Total consumption ofchemical fertilizers worldwide increased by 3.9-fold from 32 to 164MT,indicating that 36% of the global increase (132MT) came from Chinaduring the past 49years In the past 10years (2000–2009), 54% of the globalincrease in chemical fertilizer consumption (27MT) was contributed

by China, including 11MT fertilizer N (54% of the global increase), 2.5

MT fertilizer P (52% of the global increase), and 1.1MT fertilizer K (58% ofthe global increase) (Figs 1 and 2A,B)

Cereal yields in the past 10years have continued to increase with noproportional increases in fertilizer use in many developed countries orregions such as Western Europe (rainfed cereal systems), North America(rainfed and irrigated corn), and Japan and South Korea (irrigated rice)(Dobermann and Cassman, 2005) For example, in the past 10years, chem-ical fertilizer consumption in the United States increased by only 0.04MTwith 0.23% of total fertilizer consumption in 2009 and decreased by 0.32

MT in Western Europe (Fig 2A) By contrast, the application rate of

80 Grain production

chemical fertilizers in China was continually increasing and reached 448kg

ha
1in 2009, which is 2.8, 2.9, and 1.4 times the world average and rates inthe United States and Western Europe, respectively (Fig 2B)

On the other hand, Chinese cereal crop production has stagnated atapproximately 450MT since 1998 From 1998 to 2009, grain yields increased

0 40 80

160

120 200

0 100 200

China Western Europe

A

B

Figure 2 Trend of total chemical fertilizer consumption (A) and fertilizer rate per hectare (B) for global scale, China, United States, and Western European Source: IFA (2011)

by only 10%, while the consumption of chemical fertilizers increased bynearly 49%, 19%, and 33% for N, P, and K, respectively (Fig 1) Thatmeans that the large increase in fertilizer nutrient inputs did not result in acorresponding yield increase in the past decade in China For example, the

REN(the percentage of N fertilizer recovered in the aboveground plant parts

at maturity) in Chinese cereal grain production decreased from about 35% inthe 1980s (Zhu, 1998) to 28% in the 2000s (Zhang et al., 2008a), lower thanthe world average of 33% (Raun and Johnson, 1999) Often twice as muchfertilizer N or P is applied compared with the removed nutrients by crops,and this nutrient imbalance in turn drives severe environmental problems,such as eutrophication of surface waters (Le et al., 2010), soil acidification(Guo et al., 2010), greenhouse gas emissions (Zheng et al., 2004), and otherforms of air pollution (Liu et al., 2011) For example, about 60% of inlandlakes in China show eutrophication, and 57% of N inputs and 67% of P inputsare derived from agriculture (Chinese Ministry of Environmental Protection,

2010) Soil pH declined significantly (P<0.001) from the 1980s to the 2000s

in the major Chinese crop lands due to overuse of N fertilizer (Guo et al.,

2010) On the North China Plain (NCP), total wet and dry deposition of Naveraged 80–90kgNha
1yr
1in the 2000s (Liu et al., 2006b; Shen et al., 2009;Zhang et al., 2008b), a value nearly 10 times that at Rothamsted, Harpenden,

UK (Goulding et al., 1998) or in central New York in the USA (Fahey et al.,

1999) These problems are meaningful on a global scale

To meet the demand for grain and to feed a growing population on theremaining arable land by 2030, crop production must reach 5.8MT (anincrease of>40%) and yields have to increase by 2% annually (Zhang et al.,

2011) Due to environmental and economic (e.g., rising cost of fossil fuels)constraints, further increases in food supplies projected for the coming 50years must be attained through improved resource use efficiency rather thanmore agricultural inputs, especially N and P fertilizer applications (Cassman,1999; Matson et al., 1997; Tilman et al., 2002) Toward this end, soundagronomic and environmentally acceptable integrated nutrient management(INM) is an essential approach for the achievement of a reduction in fertilizer-derived environmental risk while also increasing crop productivity and NUE

In most intensive agricultural areas, however, current nutrient ment strategies are focused on delivering soluble inorganic N and P fromfertilizers directly to crops and have uncoupled soil and environmental Nand P cycles spatially and temporally As a result, agricultural ecosystems aremaintained in a state of N saturation and are inherently leaky because chronicsurplus additions of N and P are required to meet the goal of maximum yields(Drinkwater and Snapp, 2007) For example, the N and P surpluses inintensive wheat–maize systems on the NCP were recently estimated to be ashigh as 227 and 53kgha
1yr
1(Vitousek et al., 2009) Therefore, all theseapproaches have been successful in terms of maintaining grain yields; however,attempts to reduce nutrient losses and improve NUE have met with limited

manage-success in intensive agricultural areas (Cassman et al., 2002; Drinkwater andSnapp, 2007).

In INM, crop yields can be increased while minimizing nutrient losses tothe environment by managing nutrient supply in the root zone within areasonable range, which realizes the biological potential of crops, matcheshigh-yielding crop N requirement, and controls minimal nutrient losses.Nutrient supply and nutrient requirements in high-yielding cropping sys-tems must be matched in quantity and synchronized in time and space(Chen et al., 2010; Cui et al., 2010a) To realize this goal, some improve-ments must be made: using a variety of N sources from fertilizers, theenvironment, and the soil to meet crop demand; calculating the nutrientbalance between the inputs and outputs to manage a variety of intrinsicecosystem processes at multiple scales to recouple elemental cycles; andconsidering the biological potential of the root system and matching croprequirements by supplying sufficient N only when plant demand exists (Cui

et al., 2010a;Fig 3) In this chapter, we discuss the principles of INM andthe development of INM technology on a large scale with dissemination ofINM in different cropping systems up to national scale

2 Principles of INM

The overall principle of INM is to maximize biological potential forimproving crop productivity and resources use efficiency through rootzone/rhizosphere management Plant roots take up nutrients from soils

Nutrient supplies in root-zone Nutrient demand for high-yield crop

Nutrient management strategy

Integrated Nutrient Management

Root response

Correction when deficient for trace elements

Building-up and maintenance for

P and K

In-season management for N

Quantify

root-zone nutrient

supplies

High-yielding crop management

Optimal water management

Figure 3 Conceptual model illustrating the principles of Integrated Nutrient ment (INM).

Manage-via the rhizosphere, a narrow zone of the soil that is directly influenced byroot growth, root secretions, and associated soil microorganisms In crop-ping systems, a rhizosphere continuum in the root zone can be formed due

to root/rhizosphere interactions among individual plants The rhizosphere

is the important interface where interactions among plants, soils, and organisms occur and is a “bottleneck” controlling nutrient transformations,availability, and flow from soils to plants Therefore, the chemical andbiological processes occurring in the rhizosphere determine the mobiliza-tion and acquisition of soil nutrients together with microbial dynamics, andalso control NUE by crops, and thus profoundly influence cropping systemproductivity and sustainability (Zhang et al., 2004, 2010)

micro-As plant growth proceeds, the roots can respond to and/or sense changes

in soil nutrient availability including nutrient supply intensity and tion These responses involve a series of adaptive alterations in root mor-phology and root physiology P-deficient plants can commonly increasetheir root/shoot ratio, root branching, root elongation, root topsoil forag-ing, and formation of cluster roots and root hairs (Lynch and Brown, 2008;Shen et al., 2011b; Vance, 2008) Mycorrhizal associations can also enhancethe spatial availability of P, extending the nutrient absorptive surface byformation of mycorrhizal hyphae (Marschner, 1995) On the other hand,root-induced chemical and biological changes in the rhizosphere affect thebioavailability of soil P, mainly involving rhizosphere acidification, carboxy-late exudation, secretion of phosphatases or phytases, and Pi transporterexpression (Neumann and Ro¨mheld, 2002; Zhang et al., 2010) It has beenreported that P deficiency increases the formation of cluster roots by whitelupin (Lupinus albus L.;Shen et al., 2005; Wang et al., 2007), axial root lengthand total root length, and larger amounts of lateral roots and more root hairformation in maize (Zea mays L.) or Arabidopsis (Bates and Lynch, 1996;Linkohr et al., 2002; Liu et al., 2004b; Schachtman et al., 1998; Schenk andBarber, 1979) In crop species,Liu et al (2004b)found that efficient use of

composi-P in calcareous soil by maize is related to its large root system, with a greaterability to acidify the rhizosphere, and a positive response of acid phosphataseproduction and excretion in low P conditions High P acquisition efficiency

by modifying root morphology and root physiology in terms of rhizospherebiological and chemical processes is important for achieving high cropyields with savings in nutrient inputs The nutrient supply intensity orconcentrations in the rhizosphere/root zone in cropping systems can beoptimized to a critical level through nutrient management to maximize thebiological potential for efficient use of soil P by plants

Nitrogen fertilization is the most common practice for the regulation ofroot growth in field conditions Maize roots respond to N supply in twoways First, in uniform N supply systems, N deficiency increases maize rootlength, resulting in longer axial roots (primary, seminal, and nodal roots;Tian et al., 2006; Wang et al., 2003) This helps the roots to explore a larger

soil volume and thus increases spatial N availability However, root tion can be inhibited if the N supply is too high In maize, for example, theoptimum nitrate level for root length seems to be around 5mmolL
1(Tian

elonga-et al., 2008) Second, root growth can be stimulated when plant rootsexperience nutrient-rich patches, particularly when the patches are rich in

N and P (Drew, 1975; Hodge, 2004) When a maize plant is suffering from

N deficiency and part of the root mass is supplied with nitrate locally, thegrowth of lateral roots in the supplied area is enhanced (Granato and Raper,1989; Guo et al., 2005; Sattelmacher and Thoms, 1995) This helps plants tocompete with other plant species and/or microbes for limited N resources(Hodge, 2004) It is suggested that NO3
plays a key role as a nutrient signal

in regulating root proliferation (Zhang and Forde, 1998) Localized Papplication effectively enhances crop growth and P use efficiency More-over, manipulating and managing nutrient supply intensity and composition

in the local fertilization zone can greatly strengthen root growth andnutrient uptake through modifying rhizosphere processes and enlargingthe root absorbing surface A field experiment showed that localized appli-cation of P with addition of ammonium significantly enhanced P uptakeand crop growth through stimulating root proliferation and rhizosphereacidification (Jing et al., 2010) The leaf expansion rate was 20–50% higher,the total root length 23–30% greater, and the plant growth rate 18–77%greater with a localized supply of P plus ammonium compared with broad-casting of these nutrients Localized application of P combined with addi-tion of ammonium significantly decreased rhizosphere pH in the fertilizedzone compared with the bulk soil (Jing et al., 2010) The results suggest thatmodifying rhizosphere processes in the field may be an effective manage-ment strategy for increasing NUE and plant growth

Rhizosphere management emphasizes maximizing the efficiency ofroot/rhizosphere processes in nutrient acquisition and use by crops ratherthan simply depending on excessive fertilizer inputs, which involves reg-ulating the root system, rhizosphere acidification, carboxylate exudation,microbial associations with plants, rhizosphere interactions in terms ofintercropping and rotation (Li et al., 2007), localized application of nutri-ents, use of efficient crop genotypes and synchronizing rhizosphere nutri-ent supply with crop demand Rhizosphere management has been shown

to be an effective approach for increasing NUE and crop productivitythrough “small causes with big effects” for sustainable agricultural produc-tion (Zhang et al., 2010) Based on a better understanding of rhizosphereprocesses, the key steps of INM are (1) optimizing nutrient inputs andtaking all possible sources of nutrients into consideration, (2) dynamicallymatching soil nutrient supply with crop requirement spatially and tempo-rally, (3) effectively reducing N losses in intensively managed Chinesecropping systems, and (4) taking all possible yield increase measures intoconsideration (Fig 4)

2.1 Optimizing nutrient inputs and taking all possible

sources of nutrients into consideration

Since the 1990s, excessive chemical N fertilization has often been considered

as the main practical strategy to pursue high yields in China The average Nfertilizer application rate has far exceeded crop requirements for maximumgrain yield, up to double the crop N demand in some areas (Cui et al., 2010a).Clearly, applying large amounts of N fertilizer does affect grain yield and Nuptake but also increases the potential for N losses to the environment Forexample, N fertilizer could be cut from 588 to 286kgNha
1yr
1without

a loss in yield or grain quality and, in the process, reduce N losses by<50%(Ju et al., 2009) Therefore, we believe that “Controlling the total fertilizer Napplication rate” should be a top priority policy and practice to reduceoveruse of N in China under current conditions

Increasing N fertilizer application rates and associated increases in ronmental pollution have led to N derived from the soil and the environmentbecoming an important N source for crop plants in China Across numerouson-farm experiments (n¼269), indigenous N supply (average N uptake incontrol) typically provides around 274kgNha
1yr
1and accounts for 76% ofcrop N uptake in intensive wheat–maize systems (Cui et al., 2010a) As aFigure 4 Rhizosphere/root-zone nutrient management is a key component of INM for achieving high grain yield and high NUE at the same time.

envi-result, high crop yields can be readily obtained in arable soils withoutapplication of N fertilizers (Tong et al., 2004) This large indigenous N supplyaggravates N surpluses and increases the potential for N losses from agro-ecosystems unless it is considered to be a component part of the plant-available N when constructing an integrated N management plan.

The large indigenous N supply is attributed to high soil nitrate-N mulation and environmental N supply Soil nitrate-N (NO3
-N) accumula-tion in the top 90 or 100cm of the soil was above 200kgNha
1 underconventional N practice in intensive wheat–maize systems (Cui et al.,2008a,d; Liu et al., 2003); this residual NO3
-N supply can reach 1173 and613kgNha
1, respectively, in greenhouse vegetable and orchard systems inNorth China (Ju et al., 2004, 2006).Ju et al (2006)observed that residual soilnitrate-N after winter wheat harvest was 275kgNha–1in the top 90cm of thesoil profile and 213kgNha–1in the 90–180cm soil depth increment.Liu et al.(2004a)reported an average residual soil nitrate-N content of 314kgNha–1inthe top 2m of the soil profile and 145kgNha–1at 2–4m soil depth based onon-farm soil tests in annual winter wheat production systems in Beijingsuburbs on the surroundings of NCP (n¼93) Wheat grain yields on theNCP showed no response to applied N when initial nitrate-N beforesowing in the top 90cm soil layer exceeded 200kgNha–1, but residualnitrate-N content after harvest and N losses significantly increased (Cui

accu-et al., 2008a) High nitrate-N accumulation in the soil profile is like a “timebomb” that could explode at any moment and will finally be lost to theenvironment through either denitrification or leaching under high N appli-cation rates (Ju et al., 2009; Zhao et al., 2006) Ju et al (2002) observedresidual nitrate-N from the first growing season (wheat) to leach from the

0 to 1m soil profile during the second growing season (maize) on the NCPdue to high rainfall in summer

The total amount of N available from the environment in China in the2000s has more than doubled compared with the 1980s because of the rapidcontinuing increases in both oxidized and reduced N emissions (Liu andZhang, 2009; Liu et al., 2010, 2011) According to Fig 5, N inputs fromatmospheric N deposition and irrigation water in China were up to 33 and12kgNha
1yr
1in the 2000s but only 14 and 4kgNha
1yr
1in the 1980s.Similar rapid increases in environmental sources of N from atmosphericdeposition and irrigation water were reported on the NCP and in the TaihuLake region (Ju et al., 2009) Nitrogen input from deposition plus irrigationwas only 30kgNha
1yr
1 on the NCP and in Taihu Lake region in the1980s, and this value has increased to 99 and 89kgNha
1yr
1, respectively,

in these two intensive agricultural regions in the 2000s (Ju et al., 2009).Evidence from the NCP indicates that dry N deposition (50–60kgNha
1

yr
1) (Shen et al., 2009, 2011a) is likely to be a major contributor to theenvironmental N in this semihumid/semiarid region compared with wet

N deposition (30kgNha
1yr
1) (Liu et al., 2006b; Zhang et al., 2008b)

Further studies confirm that about 50% of this air-borne N input (52kgNha
1yr
1) can be utilized by current crops, according to the ITNI-systemwhich is based on a15N dilution approach (He et al., 2007a, 2010).

2.2 Dynamically matching soil nutrient supply with crop

requirement spatially and temporally

Nutrient applications that meet, but do not exceed, crop nutrient ments are essential for achieving maximum yields and minimizing environ-mental risk Recent research on improving NUE in crop production systemshas emphasized the need for greater synchrony between crop nutrientdemand and nutrient supply from all sources throughout the growing season(Cassman et al., 2002; Cui et al., 2010a; Fan et al., 2008) Nitrogen fertilizersapplied during periods of the greatest crop demand, at or near the plant roots,and in small quantities and frequent applications, can potentially reduce losseswhile maintaining or increasing crop yield and quality (Matson et al., 1998;Tilman et al., 2002)

require-In INM, we attempt to manage soil nutrient supply in the root zonewithin a reasonable range that matches the quantity required by the crop, issynchronized in terms of time and crop growth, and is coupled in space tonutrient supply and crop nutrient requirements, especially in N manage-ment (Chen et al., 2010, 2011; Cui et al., 2010b) Dry matter productionand thus N requirement is relatively low before the rapid growth stages ofcrops, that is, stem elongation of wheat and the expanded leaf stage of maize

In most cases, a small amount of N fertilizer and indigenous N supply can

meet the crop N requirement, establish growth, and promote the ment of healthy roots during the early periods of crop growth (Cui et al.,2008a,d) Nitrogen application in excess of crop N demand during thisperiod increases the potential for nitrate-N leaching and results in excessivecrop growth that is more susceptible to disease and lodging Therefore,more N fertilizer (around 60–70% of the total N fertilizer input) should beapplied during the most rapid growth stages of the crop to achieve synchro-nization between the N supply and crop demand (Cui et al., 2008b,c).Restricted by old knowledge and habits, farmers often apply largeamounts of N fertilizers before planting or at the early growth stages as aconventional management practice in crop production For example, the Nsupply before planting is usually about 50% of the total amount given (Chen,2003; Cui et al., 2008c,d) Many rice farmers in China apply 50–90% of the N

develop-as a bdevelop-asal dressing and an early top-dressing within the first 10 days aftertransplanting to reduced transplanting shock and stimulate early tillering(Zhang et al., 2011) Clearly, this large amount of N fertilizer at the earlygrowth stages has resulted in poor synchronization between soil N supply andcrop demand, leading to high soil inorganic N concentrations before theoccurrence of rapid crop N uptake (Chen et al., 2006; Tilman et al., 2002).Although the average N application rate in China is excessive for themaximum crop N requirement, some low-income farmers or those inremote areas apply N inadequately If we simply use 150–200kgNha–1as

a reasonable amount of N fertilizer for the main wheat and maize growingregions of China (n¼10,000), only one-third of farmers would be in thisrange, one-third would be applying too much (N rate>200kgNha
1), andone-third would be applying too little (N rate<150kgNha
1) (Wang,

2007) On a regional scale, higher crop yields are likely to be achievedthrough a combination of increased N application in regions with a low Ninput and improved NUE in regions where N fertilizer use is already high

2.3 Effectively reducing N losses in intensive managed

Chinese cropping systems

The fate of fertilizer N in cropping systems is an integrated result of crop Nuptake, immobilization, and residues in the soil, and losses to the environ-ment, including ammonia volatilization, denitrification, N leaching andrunoff There are close relationships among these three major fates of appliedfertilizer N, which are influenced by many factors such as crop characteristics,soil properties, climatic conditions, and management practices According

to an integrated study,Ju et al (2009)found that the mechanisms of N losswere very different in two major intensively managed crop rotation systems,that is, wheat–maize and rice–wheat systems Understanding N processes willhelp us control the N losses and their harmful environmental effects whilemaintaining high crop productivity

Under current farming practice (about 550kgNha
1yr
1in both ping systems and usually without deep placement of urea or ammoniumbicarbonate), ammonia volatilization in the wheat–maize is about 20–25%

crop-of applied N and this is the main N loss pathway due to high pH (around8.0) in calcareous soils together with surface broadcasting of urea beforeirrigation or rainfall under most farmers’ practices (Fig 6) In paddy soils,ammonia volatilization is about 12% of applied fertilizer N in the ricegrowing phase and is very low and about 2% in the wheat phase (Fig 6).Another important N loss pathway in paddy soils is denitrification, whichwas found to be 36–44% of applied N (Fig 6) Because of low levels ofgroundwater in these soils and copious rainfall in the wheat season, dryingand wetting cycles frequently occur and these are favorable for denitrifica-tion (Zhao and Xing, 2009), with N2 and N2O representing the mainproducts of denitrification Within wheat/maize systems under conven-tional agricultural N management practices, nitrate-N leaching below theroot zone was found to be the important N loss pathway (Liu et al., 2003)due to concentrated rainfall in summer and flooding irrigation, whichcontradicts the conventional wisdom that leaching losses are not an impor-tant N loss pathway in semihumid upland agricultural systems on the NCP(Ju et al., 2004)

North China Plain

NH3 volatilization Leaching Denitrification

Total fertilizer N losses in wheat–maize rotation averaged 31%, lowerthan the 48% in rice–wheat rotation (Fig 6); correspondingly, the residual

N in the soil is higher than that in the latter system, so that the capacity toretain synthetic N is higher than that in rice–wheat However, releasedreactive N in wheat–maize rotation systems is higher than in rice–wheatrotations Upland–upland crop rotations on calcareous soils lead to substan-tial ammonia volatilization and nitrate-N accumulation or leaching, whichare the main loss pathways of fertilizer N in North China, and the frequentflooding and drying cycles lead to N losses via denitrification and ammoniavolatilization in paddy-upland crop rotation systems (Ju et al., 2009)

In practice, the amount of NH3 volatilization is largely influenced byfertilization method and N fertilizer type Deep placement of urea or ammo-nium bicarbonate increases N use efficiency For example, N loss through

NH3 volatilization during the maize growing season can be reduced by11–48% of applied urea-N fertilizer with deep placement compared withsurface broadcasting (Li et al., 2002; Zhang et al., 1992) In China, N isgenerally recommended to be applied to wheat before irrigation because of avery low recovery of broadcast urea when precipitation is low and the fertilizercannot reach the rooting zone In contrast, when urea is applied beforeirrigation or plowing, NH3 volatilization is significantly reduced, indicatingthe necessity for irrigation or rainfall to leach N fertilizer into the rooting zone.The strategy to reduce nitrate leaching can be achieved simply bydecreasing the nitrate-N content in the soil profile For environmentallysound crop production, the residual nitrate-N content in soil should beminimized, especially at the end of the growing season, because nitrate-Nleaching is directly related to the mineral N content in the root zone(Dinnes, et al., 2002; Roth and Fox, 1990; Sogbedji, et al., 2000) However,achieving high maize yields is impossible if nitrate-N in the root zone is toolow It then becomes important to consider “the suitable soil nitrate-N level

at which the lower limit does not restrict grain yield and the upper limitdoes not lead to unacceptable N losses to the environment.” According toEuropean experience and our own results (Cui et al., 2008b,c; Hofman,1999; Schleef and Kleihanss, 1994), residual nitrate-N content after harvest

in the top 90cm soil layer should be maintained around 90kgNha
1 Wheninorganic N exceeds 190kg nitrate-N ha
1in the top 90cm of soil profilesbefore planting, an increase in grain yield in response to added N is unlikely

in Chinese intensive wheat–maize systems (Cui et al., 2008b,d)

Application of nitrification inhibitors such as DCD, DMPP, and pyrin together with NH4þ-based fertilizer can reduce N2O emission by 77%

nitra-on the North China because N2O emissions occur mostly during thenitrification processes after fertilizer N application and irrigation (Ju et al.,

2011) Recently, we estimated that N2O emission was 33.1GgNyr
1frompaddy fields and 255.3GgNyr
1 from upland soils in 2007 (Gao et al.,

2011) If 50% of the total area is taken into account and 77% reduction by

using nitrification inhibitors in upland crops, the total emission in uplandsoil will be 169.7GgNyr
1 The total N2O emission from Chinese crop-lands would be reduced by 30% from the current amount with careful use ofnitrification inhibitors.

2.4 Taking all possible yield increase measures into

consideration

Many recently developed approaches and tools for fine-tuning N managementhave increased the NUE by decreasing the N fertilizer rate, but substantialand consistent yield increases have been demonstrated in only a few studies(Dobermann and Cassman, 2005) The major challenge of current nutrientmanagement in China is how to increase crop yields to meet food demandwhile also increasing NUE to protect the environment Large numbers ofexperiments indicate that the grain yield potential of currently grown cerealvarieties in China far exceeds actual yields obtained For example, the averagemaize yields in farmers’ fields are 5.3Mgha
1 in northeast China, 5.1tha
1

on the NCP, and 4.0tha
1 in hilly areas in south China (ECCAY, 2006).However, maize yields in new variety trials in these regions typically average8.5, 7.3, and 6.7tha
1, 60%, 45%, and 68% above the average farming yields(Fan et al., 2010b) The highest attainable maize yields recorded, achieved withhigh inputs of nutrients, water, and labor, were 16.8tha
1in northeast China,18.0tha
1in the NCP, and 14.7tha
1in south China (Fan et al., 2010a,b).Similar results have been obtained for wheat and rice over the whole country.This implies that, when an integrated management approach to crop produc-tion is used, there is great potential to increase cereal grain yields above currentfarming yields with significant enhancement of the ability of Chinese agricul-ture to meet food demands in the coming decades

Increased yields can be attributed to greater NUE from both indigenousand applied nutrient sources, especially N sources, because rapidly growingplants have larger root systems that more effectively exploit available soilresources (Cassman et al., 2002) Crop health, insect and weed management,moisture and temperature regimes, supplies of nutrients, and use of the bestadapted cultivars or hybrids all contribute to efficient uptake of availablenutrients and conversion of plant nutrients to grain yields Key contributoryfactors include (a) increased yields and more vigorous crop growth asso-ciated with greater stress tolerance of modern hybrids, (b) improved man-agement of production factors other than N (conservation tillage, seedquality, and higher plant densities), and (c) improved N fertilizer manage-ment For example, the nitrogen partial factor productivity (PFPN) in NorthChina increased to 50 and 47kgkg
1using integrated N management forwheat and maize production compared with 15 and 25kgka
1over thosewith farmers’ N management practice The PFPNcould further to 60 and59kgkg
1when N-efficient varieties were used (Cui et al., 2009, 2011)

Additional improvements in soil quality can occur when the benefits of Csequestration are coupled with increases in crop yields from adoption ofcultivation practices that reduce yield losses from abiotic and biotic stresses,such as returning straw back to the soil, increasing applications of organicmanures, and using reduced tillage Over the past two decades, the soil organicmatter content of soils in north China has significantly increased because ofincreasing incorporation of crop residues and organic manure and the devel-opment of no-tillage and reduced-tillage practices (Huang and Sun, 2006).Crop yields increased in this region at the same time (ECCAY, 2006).

3 Technology and Demonstration of INM in

Different Cropping Systems

Nitrogen is unique among the major nutrients since it is synthesizedfrom the atmosphere using the Haber–Bosch process and its transformationand transport in the pedosphere and hydrosphere are mediated almostentirely by biological processes (Galloway and Cowling, 2002) As a result,

N is mobile, hard to contain, and even N that is efficiently conserved andtaken away in crop harvest eventually makes its way back into the environ-ment (Robertson and Vitousek, 2009) Hence, efficient use of N in cropproduction is essential for increasing crop yields, environmental safety, andthe consequent economic considerations (Campbell et al., 1995)

Recent literature on improving N use efficiency in crop production hasemphasized the need for greater synchronization between crop N demandand N supply from all sources throughout the growing season (Cassman et al.,2002; Chen et al., 2010; Cui et al., 2009) Considering site-specific soil Nsupply and crop demand, current research has demonstrated that in-seasonapplied N results in a high grain yield and high N use efficiency (Table 1;Cui

et al., 2009; Chen et al., 2010) As a net result of soil N transformation,transport, and previous fertilizer applications, soil N supply can significantlyinfluence crop N uptake It is very important to quantify the total N balanceincluding initial soil Nmin(NO3
þNH4 þ), N mineralization, environmental

N supply, crop N uptake, N losses, and N immobilization during the growingseason However, it is very difficult to measure accurately N balance with allcomponents, especially under field conditions (Blankenau et al., 2000; Engelsand Kuhlmann, 1993) The amount of soil Nminat rooting depth may be agood index to estimate the N balance situation Substantial attempts should bemade to manage the N supply in the root zone in order to match the totalquantity of N required by the crop in both space and time

Unlike N, management of fertilizer P and K focuses on maintenance ofadequate soil available P or K levels to ensure that neither P nor K supplylimits crop growth or becomes excessive due to overfertilization (Table 1)

In China, maintenance of fertilizer P or K rates is recommended on the basis

of constant monitoring of soil nutrient supplies and nutrient holding cities (Li et al., 2011; Wang et al., 1995) In soils with low P status and/orhigh fixation capacity, capital investment is required to build up soil nutri-ents until the system becomes profitable and sustainable On soils withmoderate P and K levels and little fixation, management must focus onbalancing inputs and outputs at field and farm scales to maximize profit,avoid excessive accumulation, and minimize risk of P losses (Dobermann,

capa-2007) Therefore, managing nutrients to achieve synchrony between ent supply and crop demand is crucial to increase NUE while maintainingagricultural productivity and improving technical operability

nutri-The management strategy of trace elements such as boron (B), chlorine(Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel(Ni), and zinc (Zn) is based on their plant availability in both soil and plant.Their available contents in soil and (or) critical concentrations in plants aredetermined and then the corresponding micronutrient fertilizers are applied

so that trace elements do not become a yield limiting factor (Table 1) Thisstrategy follows the law of the minimum and uses dose–response curves.This type of curves for all the essential micronutrients show that the yieldscan be affected by deficiencies and can also be reduced by toxicity due toexcessive concentrations Not all micronutrients should therefore be applied

in the field It is therefore important to monitor soils and/or crops to ensurethat the available micronutrient concentrations in soils are within theoptimum range and neither too low nor too high (Alloway, 2008)

Table 1 Resource characteristics of nutrient and the technologies of INM for different nutrients

Multidirectional losses Serious environmental harm Crop sensitivity

In-season root-zone management

P and K Limited resources

Large soil pools but low effectiveness

Long-term effects Crop sensitivity

Building-up and maintenance approach

a Trace elements include boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), num (Mo), nickel (Ni), and zinc (Zn), respectively.

molybde-3.1 INM for intensive wheat and maize system

From 1961 to 2009, wheat production in China increased sevenfold from

14 to 115MT and maize production also increased sevenfold from 18 to 164

MT In 2009, wheat production represented 24% of the Chinese cerealoutput and 17% of global wheat output (FAO, 2011) Similarly, maizeproduction represented 34% of Chinese cereal output and 20% of globalcorn output (FAO, 2011) The rapid development of wheat and maizeproduction has been attributed to increasing grain yield During the sameperiod (1961–2009), wheat grain yield increased seven times from 0.56 to4.74tha
1and maize grain yield increased three times from 1.18 to 5.26tha
1(FAO, 2011)

With simultaneous increases in fertilizer application rates and grain yieldsbefore the mid 1990s, especially N and P fertilizers, most extension staff andfarmers still believed that the more fertilizer they use and the higher thegrain yields that would be obtained Based on extensive on-farm investiga-tions from 1997 to 2007 (Cui et al., 2010a; Ma et al., 1999), the typicalannual N rate for farmers was>500kgNha–1for the intensive wheat–maizerotation system in the NCP and approached 600kgNha–1in some regions.Average grain yields were around 11.5tha–1yr–1(around 5.5 and 6.0tha–1for wheat and maize, respectively), and the estimated N uptake was only300kgNha–1yr–1 (around 160 and 140kgNha–1 for wheat and maize,respectively) Results from region-wide experiments have demonstratedthat the economically optimal N rate is 130–160kgNha–1crop–1 for theintensive wheat–maize system (Cui et al., 2008b,c) Similar results showingexcess fertilizer application also observed for P As a result, nutrient sur-pluses in the main cropping systems, and hence environmental losses, arevery high (Vitousek et al., 2009) In addition, wheat and maize production

in China has stagnated since 1996 From 1996 to 2009, wheat and maizegrain yields increased by only 1% and 27%, with annual growth rates of

<0.1% and <2% (FAO, 2011)

Soil N tests (NO3-NþNH4-N) for upland soils are an important tool forassessing soil N supply capacity (Wehrmann and Scharpf, 1979) However,the original soil Nmin method that is based on a single soil N test beforeplanting and that disregards variations in the soil N cycle (N mineralization,

N immobilization, and losses) may result in underuse or overuse of Nfertilizer Several versions of the presidedress soil nitrate-N test only estab-lish the critical threshold above which there is a low probability of a yieldresponse to sidedress N application, but do not provide an accurate estimate

of the optimal N rate below a critical value (Magdoff et al., 1984; Meisinger

et al., 1992; Schmitt and Randall, 1994) Uncertainties in the prediction ofthe seasonal crop N demand and soil N movement require the use of Nstatus indicators for fine-tuning of N rate and timing of N applications Thisrequires monitoring soil N concentrations in the root zone at different

growth stages of crops to achieve the synchronization of crop N nutrientuptake and N supply from wastes, indigenous soil resources, and environ-mental sources For optimum management of soil N supply in the rootzone, we have developed an in-season root-zone N management strategyfor intensive wheat–maize systems on the NCP (Chen et al., 2006; Cui et al.,2008b,c; Zhao et al., 2006) According to this strategy, the total amount of

N fertilizer is divided into two or three applications over the course of thegrowing season, with the optimum N fertilizer rate (ONR) for each applica-tion being determined from soil nitrate-N tests in the root zone and a target

N value for the corresponding growth period of the crop (Fig 7)

To confirm whether ONR using in-season root-zone N managementwas the economically optimum N rate, we conducted on-farm experiments(wheat, n¼121; maize, n¼148) with three N levels during 2003–2007 toevaluate this N management in terms of agronomic performance andenvironmental impact Compared with farming practice (FNP), the in-season root-zone N management strategy reduced N fertilizer by 60% and40% for wheat and maize, and simultaneously increased grain yield by 4%

Soil nitrate-N testing in root-zone

Planting

Planting

Nutrient spatial availability

Nutrient temporal and spatial variability

Target yield (t ha -1) 8.0–8.5

160 220

20 85 175

20 60 140

25 75 160 95

190

9.5–10.0 7.0–7.5 5.5–6.0 6.5–7.0 Before sowing (kg N ha -1)

Three leaf stage (kg N ha -1)

Ten leaf stage (kg N ha -1)

Nitrogen target value for different grain yield for Chinese maize production

differ-and 5%, respectively As expected, the ONR treatment had higher N useefficiency and reduced apparent N loss compared with FNP (P<0.05).Compared to FNP, apparent N losses were reduced by 73% from 159 to43kgNha
1 and 43% from 151 to 86kgNha
1 in the wheat and maizegrowing seasons, respectively (Fig 8).

Clearly, in this study ONR using in-season root-zone N managementstrategy was close to optimal, sustained high yields, and increased profits,while minimizing the potential environmental impacts of N fertilization.This superiority of in-season root-zone N management strategy can beattributed to three major factors: (1) efficient utilization of all N sourcesfrom the soil, environment, and fertilizer; (2) achievement of synchroniza-tion between N supply and crop demand; and (3) addressing site-specific Nmanagement In China, small-scale farming has intensified variations in soil

N supply In the research region, indigenous N supplies (average N uptake

in 0 N control) varied from 69 (site 14) to 191kgNha
1 (site 5), with acoefficient of variation of 24% The large disparity among experimental sitesreflects the net variation in soil N transformations (mineralization, immobi-lization, denitrification, and volatilization), possible N transport (leachingand runoff), and crop uptake Clearly, one rate does not fit all circumstances

Figure 8 Performance of INM for wheat and maize in the North China Plain (A) INM can reduce N fertilizer by 30% while increasing grain yield of 16% compared with farmers’ practice in Binzhou, Shandong province (B) Maize lodging for FNP in Xiaoxian, Anhui Province (C) Mean N fertilizer application rate, apparent N losses,

AE N and PFP N of INM compared with FNP Modified from Cui et al (2008b,c)

The in-season root-zone N management strategy can address variations due

to site-specific conditions using 3-tiered soil nitrate testing, as supported by

a close correlation between ONR and initial soil nitrate-N content Ourresults are consistent with earlier studies in demonstrating that yieldresponse to applied N is strongly affected by soil N supply or initial soilnitrate-N content before planting (Binford et al., 1992) In addition, thein-season root-zone N management strategy considers variation in yieldresponse to N application rate between fields, and increased fertilizer N rate

in 4% (wheat) or 18% (maize) of sites compared to farming practice As aresult, higher crop yields are likely to be achieved through a combination ofincreased N application in fields with low N fertilizer use and improvedNUE in fields where N fertilizer use is already high

3.2 INM for paddy rice

Rice is a staple crop in China, accounting for 34% and 47% of the nationaltotal cultivated area and cereal production in 2009, respectively (FAO,

2011) China was responsible for around 29% of global rice productionwith 19% of the production area in 2009 (FAO, 2011) Intensification ofrice production over the past 50years has been achieved by using modernhigh-yielding varieties and larger inputs of chemical fertilizers and weed andpest control, and has led to higher yields From 1961 to 2009, there was a3.2-fold increase in the productivity of rice (from 2.0 to 6.6tha
1).Unfortunately, since about 1990 the increase in rice grain productionwas associated with a major decline in NUE, especially N, and withwidespread environmental damage The RENfor Chinese rice productiondeclined from 30–35% (Zhu, 1998) to 28.3% (Zhang et al., 2008a), which islower than the world values (40–60%).The RENcan be lower in some riceproduction areas, for example, the provincial average RENof rice was only19.9% in Jiangsu (Li, 2000).Yoshida (1981)estimated AEN(the agronomy

N efficiency) to be 15–25kg rough rice per kg applied N in the tropics.Cassman et al (1996) reported that AEN was 15–18kgkg
1N in the dryseason in agricultural fields in the Philippines In China, AENwas 15–20kg

kg
1N from 1958 to 1963 and declined to only 10.4kgkg
1N in 2000s(Zhang et al., 2008a)

The low NUE may be attributed to fertilizer overuse and high nutrientloss resulting from inappropriate timing and methods of fertilizer applica-tion For example, the average fertilizer N application rate for rice of 150

kg N ha
1is higher than in most countries and up to 67% above the globalaverage, but current application rates of 150–250 kg N ha
1are commonand can reach 300kg N ha
1in some regions (Peng et al., 2010; Roelcke

et al., 2004) Based on a national farm survey,Li et al (2010) found thatfertilizer N rates for rice showed an increasing trend from 217 kg N ha
1in

2000 to 231kg N ha
1in 2007

Fertilizer application is often not based on real-time nutrient ments of the crop and/or site-specific knowledge of soil nutrient status Forexample, in rice production systems, most farmers apply N in two splitdressings (basal and top-dressing) within the first 10 days of the rice growingseason (Fan et al., 2007) This large amount of basal fertilizer N is prone toloss over an extended period because the plants require time to developtheir root systems and a substantial demand for N Overuse fertilizer withhigh nutrient losses has directly or indirectly led to a series of environmentalproblems such as groundwater pollution and eutrophication of surfacewaters It is therefore becoming a major challenge for rice production toincrease fertilizer N use efficiency by crops through improved rice nutrientmanagement (Cassman et al., 1996) This is a very important step towardsustainable development of agricultural production and environmentalprotection.

require-The INM for paddy rice has been developed and implemented out China since 2002 The overall nutrient management strategy has focused

through-on optimizing fertilizer N applicatithrough-on rates and timing in combinatithrough-on withmaintenance of P and K supply The total fertilizer N application rate for arice field can be estimated by calculating the difference in N budget between

N requirement and N supply from the soil (Dobermann and Fairhurst,2000a,b) On average, irrigated rice needs to absorb 17.5, 3.0, and 17.0kg

N, P, and K, respectively, to produce each ton of grain yield The croprequirement can be calculated from a yield target selected as 75–80% of theclimate yield potential Soil N supply capacity is estimated using the yield ofnutrient omission plots including nutrient inputs from atmospheric deposi-tion (rainfall and dust), irrigation, floodwater, and sediments (dissolved andsuspended nutrients) and biological N2-fixation Based on soil nitrogensupply capacity, the basal fertilizer N is recommended Top-dressings areapplied through SPAD fine-tuning Therefore, the split pattern is in accor-dance with soil N supply capacity, crop growth stage, cropping season, thevariety used, and the crop establishment method Critical levels of SPAD andthe corresponding fertilizer application rates have been developed for fertil-izer N distribution at different growth stages in China If the SPAD tests arenot available to farmers, a simplified distribution method for fertilizer N can

be used according to the nutrient uptake pattern by the rice crop at a specificsite with fixed distribution rates based on previous investigations on nutrientmanagement (e.g., 35–40% for basal fertilization, 20–25% for early tillering,25–30% for panicle initiation, and 0–10% for heading)

Nearly 560 demonstration sites have been established in major producing areas since 2001 (Fig 9) On average, rice yields using INMhave increased by 11% compared with FNP with fertilizer N use reduced by24% Across all sites, Heilongjiang province increased yields by 15% andZhejiang province saved fertilizer N by 35% The AENof INM increased

rice-by 96% from 9 to 19kgkg
1compared with FNP

3.3 INM for vegetable systems

China has become the world’s largest center for vegetable production Thevegetable industry has developed rapidly since the mid-1980s and is animportant land use type with a total area of 1.84million ha, accounting for11.3% of the total cropping area Production reached 62MT in 2009, 7.7times that in 1980, respectively (China Statistical Yearbook, 2011) Thecropping area of greenhouse vegetables has increased 500 times from 7.00

103ha in the 1980s to 3.35106

ha in 2008 to provide sufficient vegetables

in winter and accounts for 18.7% and 25%, respectively, of total vegetablecropping area and production (Wang, 2011)

High nutrient demand and high variation in rooting depth (especially ingreenhouse vegetables with shallow root systems) are important character-istics of vegetable crops For example, rooting depth can range from 25cm(onion) to>100cm (long season cabbage) Substantial quantities of fertilizerare applied because of limited information or technology and strong incen-tive to produce maximum yields and profits Frequent furrow irrigation

Figure 9 Performance of INM for rice in China (A) Experimental bases (red dots) for INM demonstration of rice in China; (B) INM reduced N fertilizer by 38% while increasing grain yield of 11% compared with FNP; (C) rice yield, N rate and AE N for INM and FNP for paddy rice in Chinese main rice production since 2001.

with flushing of water-soluble fertilizer is typical in vegetable productionusing heavy basal applications of fertilizer and manure Based on a literaturesurvey, mean N, P, and K application rates for open field vegetables (n¼320) were 443kgN, 232kgP2O5, and 302kgK2Oha
1, respectively, com-pared with 1817kgN, 1144kgP2O5, and 1465kgK2Oha
1for greenhousevegetables (n¼2478) Conventional fertilizer inputs are more than two toeight times crop nutrient uptake (Cong et al., 2011; Fan et al., 2010a; Ge,2009; Jiao et al., 2010; Ma, 2010; Ye et al., 2008).

Excessive use of fertilizers is a typical practice to maintain relatively highnutrient intensity in the root zone It was observed that crop productivitydecreased distinctly over time (Du et al., 2006) and secondary salinization islikely to be a major obstacle, particularly in greenhouses because of theexcessive use of N fertilizers (Cao et al., 2004; Chen et al., 2004; Shi et al.,

2008) Moreover, overirrigation at each event far exceeds the water-holdingcapacity of the soil and leads to ready nutrient loss from the root zone In thecase of N, NO3-N will accumulate in soils and crops, and NO3-N mayreduce crop quality if taken up in very large amounts Ecological problemscomprise gaseous N losses to the atmosphere, leaching of NO3-N, eutrophi-cation of water bodies and soil salinization, particularly when vegetable cropsare grown in greenhouses

A failed example with chili pepper has indicated that the ONR (Fig 10A)cannot reach the same high yield as in FNP with a total volume irrigation

of 600mm applied over five occasions High fertilizer rates for cucumbercan be greatly reduced when irrigation is optimized (Fig 10B) High fertilizer

N inputs associated with high irrigation have resulted in the agronomicproblems, that is, low yields and low N use efficiency The RENin Chinesevegetable production was only 8–12% (Liang, 2011) On the other hand, in32–71% of shallow groundwater samples in Beijing and Shandong from

Figure 10 Two examples of INM for vegetables in Shouguan, Shandong Province (A) Chili pepper yield reduced when reduced N rate from 1600 of FNP to 300kgha
1per season of ONR without optimized irrigation water; (B) cucumber can maintain yield when reducing N rate from 2800 of FNP to 470kg ha
1of ONR and optimizing irrigation water.

intensive greenhouse production areas, the nitrate concentrations exceededthe drinking water standards (10.8mgL
1NO3-N) (Song et al., 2009; Zhu

et al., 2005)

The INM method was developed for sustainable vegetable croppingsystems on the basis of understanding the pattern of crop nutrient demandand the characteristics of the soil nutrient supply Real-time N managementtools can be used to balance the N input and output in the root zone.Nitrogen target values, which vary among different crops and different yieldlevels, include the components N uptake, critical Nminsupply in the rootzone, and avoidable N loss On the basis of N balance strategies, various Nsources such as fertilizer N, Nminin the root zone before N recommenda-tions, and nitrate from irrigation water can be taken into consideration Nrecommendations are therefore calculated taking account of the N targetvalue in the root zone and different N sources (Fig 11)

N fertilization¼target N value
soil Nmin in the root-zone
(NO3
-Nfrom irrigation)

The N target values for different cropping systems were determinedwith crop N uptake curves based on the analysis of metadata or long-termexperiments (Ren et al., 2010) Soil Nmin in the root zone and the nitratecontent in irrigation water can be measured before N recommendationsare made Compared with FNP, INM can reduce chemical N fertilizer

inputs by 72% on average, N losses by 54%, and N2O emissions by 38% of

in year-round greenhouse tomato cropping systems (He et al., 2006, 2007b,2009; Ren et al., 2010; Tang et al., 2005) In greenhouse cucumber crop-ping systems, 55% of chemical N fertilizer inputs and 40% of N losses onaverage were reduced using the INM methods compared with FNP (Guo,2007; Guo et al., 2008; Peng, 2006)

A P management strategy with a buildup and maintenance approach hasbeen established for major vegetable species in China In this strategy, thesoil available P content in the root zone can be tested at intervals of 3–5years P fertilization was controlled as “buildup,” “maintenance,” or “draw-down” strategies in response to “low,” “moderate,” and “high” soil avail-able P levels, respectively, to maintain soil available P at an optimum level inthe long term Considering the agronomic threshold to obtain high yieldsand environmental thresholds, the optimum soil Olsen-P level has beendeveloped for several vegetable crops based on plant response to P fertiliza-tion For example, in open fields the optimum Olsen-P level in the rootzone for tomato production in North China was found to be 50mgPkg
1(Zhang et al., 2007) and was 43.7mgPkg
1 for leafy vegetables in SouthChina (Zhang et al., 2007)

Fertigation techniques with INM, combining irrigation with tion to achieve integrated effects, was also developed in our INM to controlnutrients, especially N and K concentrations in the root zone in order tofurther improve NUE and water use efficiency Since 2005, fertigationtechniques have been developed in different vegetable systems and demon-strated in different Chinese regions On average (n¼46), fertigation canincrease vegetable yields by 5–20% while reducing inputs of chemicalfertilizers and water by 20–60% and 20–50%, respectively Fertigation canalso reduce the environmental risk For example, N losses declined by over40% in greenhouse experiments on tomato compared with farming practice(Gao et al., 2009; Zhang, 2010) Catch crops such as sweet corn duringsummer fallow periods were considered to reduce N and P losses and retainsoil N deep soil profile in our INM In greenhouse cucumber and tomatosystems, the accumulated Nmin in the soil (0–180cm) was reduced by303–343 and 154–403kgNha
1 after introducing sweet corn as a catchcrop during the summer fallow period (Guo, 2007)

fertiliza-3.4 INM for orchards

Fruit production in China has developed rapidly since 1992 and includesthe most important cash crops with the highest production and acreage offruit trees in the world, with an area of 11.1million ha, accounting for7.02% of the total area of crops, and output reached 203.95MT in China in

2009 (FAO, 2011) Among deciduous fruit crops, apples are far ahead inacreage and production and pears, peach, and grapes are also leading crops

Apricot, plum, walnut, chestnut, and kiwifruit are next in importance.Citrus is the commonest of the tropical and subtropical fruit species, andbanana, pineapple, and lychee are also major tropical fruits in China.Although arable land may be scarce, labor is available for labor-intensivefruit production Subsequently, China has substantially raised its profile inthe global fruit market and increased farmer’s income.

Much higher incomes can be obtained from orchard than cereal crops

in mountain and hilly areas In many regions, the fertile lowlands haveswitched from cereals to fruit and form the major fruit production areas.Some soils may be too shallow for good root development However, deeptillage has been used to improve soil conditions in hilly areas for establish-ment of orchards Fruit and vegetable production relies on high inputs ofmanures and fertilizers and this can adversely affect the safety and quality ofthe produce Nutrient inputs for orchards are often higher than the nutrientrecommendations in the effort to obtain higher yields and net returns (Ju

et al., 2006; Liu et al., 2006a)

Compared to other organic fertilizers, animal manures are most sively used in orchards in conventional practice Based on a survey of 916orchards in North China, excessive N and P applications were common,with average input rates of 588.4kgN and 156.7kgPha
1, respectively,which were 2.5–3.0-fold higher than the fruit N and P requirements (Lu

exten-et al., 2008) However, nutrient deficiency was observed in some orchards,especially in hilly areas For example, in Shaanxi province about 20–80% oforchards received no fertilizers and about 80% of orchards received nomanures (Liu et al., 2002) Most farmers are accustomed to applying basalfertilizers once a year after autumn leaf fall or before the spring bud burst andadditional fertilizer dressings are applied at the beginning of the phenologi-cal period (Chai et al., 2009; Zhou, 2009)

Misuse of fertilizers is associated with widespread problems of fruitproduction and environments Unstable yields and poor fruit quality includ-ing serious physiological diseases of fruit trees (i.e., bitter pit, shrinking fruit,yellow leaves, internal bark necrosis) occur widely due to calcium and borondeficiencies (Shorrocks and Nicholson, 1980), iron deficiency, and manga-nese toxicity (Berg, 1973; Gao et al., 2006; Xu et al., 2008) with serious effects

on fruit exports and marketable values (Ferguson and Watkins, 1989; Wang

et al., 2001, 2010b; Zhao et al., 2007)

High proportions of surplus N and P and low NUE have been found

in vineyards and in apple, pear, and peach orchards in the plains regionswith high economic returns N surplus reduces soil C/N ratio on the plains,plateaus, and mountain regions Controlling N and P fertilization is the key

to maintaining sustainable fruit production in North China (Lu et al., 2008,Ren, 2007) Soil acidification is a growing problem in most orchards Forexample, in the Bohai Gulf area, high soil pH (>6.5) accounts for only 7.5%

of 1338 orchards in Jiaodong peninsula (Li et al., 2009) and the pH value has

declined from 6.8–7.6 in 1982 to 4.0–5.3 in 2008 in Jiaodong peninsula(Wang et al., 2010a).

Nutrient management is an important component in orchard agement for high efficiency and high fruit quality Fruit trees areperennial woody plants which can store nutrients and then releasethem for growth Therefore, the nutrient uptake of fruit trees includesthe total nutrients of the fruits, leaves, new branches, and time incre-ments of storage Nutrient uptake is different under different yieldlevels For example, the N uptake of apple trees was 100–120, 110–130,120–140, and 130–150 kg ha
1under yield levels of 30, 45, 60, and

man-75 t ha
1, respectively Nitrogen fertilizer strategies have been studied indetail by Zhang et al (2009)

Basal fertilization is considered to be important for high-quality fruitproduction by providing nutrients for tree growth and also improvingsoil structure which promotes better root development It is usuallyrecommended and immediately applied during the dormant season up toautumn, after fruit harvest This application coincides with the third peak

of annual root growth The fertilizers not only help trees to recover fromthe nutrient depletion caused by a heavy fruit load but also enhancedevelopment of quality fruit buds In our studies, 60% of N fertilizer wasapplied in autumn after fruit picking to add N storage and restore treevigor Top dressing applications are usually chemical fertilizers which areapplied two to four times before bud break or prior to or after bloomingand at the fruit enlargement stage, depending on the requirements ofeach type of fruit tree For apple trees, 20% or so of N fertilizer is appliedfrom the period of blooming to speed growth of new branches, a further20% of N applied to speed growth of new branches until before fruitpicking, and about 60% of N fertilizer is applied from fruit picking to leaffall (Jiang et al., 2007) However, over 50% of N fertilizer is commonlyapplied after flower bud breaking or fruit forming in farming practice.This might cause the phenomenon of alternate bearing due to inadequatestorage of nutrients

Using this INM method, the total nutrient demand is calculated ing to target fruit yield level and NPK fertilizers are recommended based onsoil fertility index (High, Moderate, and Low soil fertility) and nutrientdemand with different stages For moderate apply trees, most of N fertilizer

accord-is applied in autumn after picking to add N storage and renew tree vigor,and most of the P fertilizer is applied in spring with flowing stage to improveflower bud quality, and most of the K fertilizer is applied in summer fruitingperiod to improve fruit quality Management of high-yielding fruits usingsuitable pruning, and irrigation, are combined in this INM

Since 2005, INM has been developed in different orchard and vineyardsystems, such as apple, peach, jujube, grape, cherry, mandarin orange,banana, lychee, and citrus, and demonstrated for different regions of the

country (total demonstration area of 7460ha) On average, compared tofarming practice, INM increased fruit yields by 11.1–18.3% while reducingchemical fertilizers (N, P2O5, and K2O) by 23.1–36.2%, 10.4–17.4%, and10.4–16.6%, respectively.

4 Large-Scale Dissemination of INM

From 2003 to 2010, a large number of on-farm demonstration trials(n¼5147) were conducted with 158 experimental bases by >30 researchunits including universities and academies of agricultural sciences Acrossall 5147 sites, on average, reduce N fertilizer inputs by 24%, increase yield

by 12%, and increased net farming income by $132 per ha (Fig 12) Fourfactors contributed to this improvement: (1) elite varieties capable ofproducing well at high planting densities and also with high yield poten-tial; (2) integrated nutrient and water management, especially N manage-ment; (3) better crop management including plowing, sowing, density,and pest management; and (4) improved soil quality, largely due to morewidespread adoption of the practice of returning straw to soils as opposed

to burning and the growth of conservation tillage Improved N ment includes significant reduction in fertilizer N application rate byefficient utilization of all N sources in the soil, N entering soils from theenvironment, and fertilizers; greater use of split fertilizer N applications tomatch crop demands; and addressing field-to-field variation by predicting

manage-Figure 12 Performance of INM in China (A) 158 experimental bases (red dots) for INM dissemination in China; (B) increased yield, reduced N fertilizer rate, and increased net income of INM for different crops including wheat, maize, rice, vegeta- ble, fruit, rape, and cotton, compared farmers’ practice D yield, N fertilizer, and net income mean the different yields, N fertilizer rate, and net income between INM and farmer’s practice.

plant-available soil N through soil mineral N or soil nitrate-N testingduring the crop growing season (Cui et al., 2008b,c) Poor crop manage-ment by farmers may lead to lower exploitation of yield potential in theirfields than in the regional variety test experiments For example, our study

in southwest China showed that combining a triangular transplantingpattern with split N fertilizer applications increased rice yields by 20%,saved fertilizer N inputs by 18%, and reduced N losses by 44% comparedwith traditional farming practice (Fan et al., 2009)

The Chinese government regards agriculture as the primary field ofdevelopment of the national economy in the twenty-first century OurINM, as a major agricultural development technology, has been advocated

in Chinese policy and national actions For example, since 2005 INM hasbeen practiced as most important nutrient management strategy for soiltesting and fertilizer recommendation project, covering all agriculturalcounties with total funding of nearly 6 billion Yuan until 2010 ($923million) As a result, fertilizer application rates in the project area havedecreased and NUE has also improved As shown in Fig 13, fertilizerconsumption has decreased steadily since 2004, coupled with a trend ofincreasing partial factor productivity for chemical fertilizers from 17kgkg
1

produc-on how to achieve high yields without excessive nutrient losses to theenvironment worldwide (Cassman, 1999; Matson et al., 1997; Tilman,

1999) This challenge is particularly daunting in rapidly developingcountries such as China, India, Brazil, Mexico, Indonesia, Vietnam, Paki-stan, and Sri Lanka First, rapidly growing populations need further increases

in grain production while rates of gain in cereal yields have slowed markedly

in the past 10–20years (FAO, 2011), even though agricultural inputs such as

N and P have continued to increase Second, rapidly developing countriesaccount for 89% of the total global increase in N fertilizer use (25MT)since 2000, especially in China (12MT) and India (4MT) By 2050, 59% ofall fertilizer N will be applied in developing regions (Beman et al., 2005).Environmental pollution is becoming an issue of serious concern due toexcessive use of fertilizer N in crop production (Guo et al., 2010; Le et al.,2010; Zheng et al., 2004) Third, some developed nutrient managementstrategies using sophisticated decision-support tools for large-scale enter-prises are not available for hundreds of millions of holder farmers on smallparcels of land such as site-specific management based on GPS, GIS, andremote sensing (Chen et al., 2011; Raun et al., 2002) The challenge inrapidly developing economies is to increase global food production whilealso protecting environmental quality and conserving natural resources

as in Chinese agricultural production The success of INM in China asindicated by our INM in this study shows that advanced methodologiescan be employed, to ensure food security and protect environmentalquality in rapidly developing countries

5 Summary and Conclusions

Demonstration in different cropping systems and large-scale ination of INM has indicated the potential of significant increase in cropyields and NUE However, there is still a long way to go to realize the aims

dissem-of the “Four WINs,” namely, increasing crop yield and NUE whilesimultaneously improving soil productivity and environmental quality.Achieving these goals will require continued and expanded efforts nation-wide to develop new technologies by integration of different disciplinessuch as plant breeding, agronomy, soil science, plant nutrition, plantprotection, and agricultural engineering, and to extend these technologies

to millions of small-holder farmers Fortunately, the Chinese Government

is aware of the importance of INM in the sustainable development ofChinese agriculture and supports the adoption of these technologies on anational scale INM can also be used as part of the global strategy to ensurefood security and protect the environment now that there are over 7billion human beings on the planet

UK, and Prof C Tang in La Trobe University, Bundoora, Australia, for their comments and linguistic revisions.

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