IMPROVING FARMER’S PROFITABILITY BY MINIMIZING GRAIN LOSS AND MAINTAINING QUALITY THROUGH CORRECT PROCEDURES DURING HARVESTING AND POST-HARVEST OPERATIONS " potx

Extension Manual MS7 Eng.doc IMPROVING FARMER’S PROFITABILITY BY MINIMIZING GRAIN LOSS AND MAINTAINING QUALITY THROUGH CORRECT PROCEDURES DURING HARVESTING AND POST- HARVEST OPERATIONS

Extension Manual MS7 Eng.doc

IMPROVING FARMER’S PROFITABILITY BY MINIMIZING GRAIN LOSS AND MAINTAINING QUALITY THROUGH CORRECT PROCEDURES DURING HARVESTING AND POST-

HARVEST OPERATIONS

EXTENSION WORKERS MANUAL

INTRODUCTION

Reduced whole rice grain yield and value due to cracking is one of the major issues that directly reduce income and availability of staple food to the farmers in the Mekong River Delta The cracking or partial fissuring of rice kernels may occur right in the paddy field due to incorrect harvesting time/practice, improper post-harvest drying conditions and inappropriate milling operations

There is a chain of activities during harvesting and post-harvest processing of rice Figure 1 is a diagram showing a post-production system of rice in the MRD of Vietnam currently All chains in this system can contribute to losses Some of the important factors can be dependent to each other Here we consider two aspects:

1 Grain loss (G): Harvesting and post-harvesting losses in which grain is not fully recovered during a particular operation on farm

2 Value loss (V): Grain cracking and reduced head rice yield which result in downgrade in grain quality value, such as broken rice during milling The value of rice might be reduced by 50% or less

The main factors which contribute to the rice cracking and value losses are:

• Harvesting time- before and after grain maturity

• Harvesting methods- manual, reaper, combined harvester

• Drying methods- sun drying and mechanical drying

• Milling losses- small, medium, large rice milling plants and milling procedure

Accordingly, the manual is divided into 4 sections in relation to:

Types of Losses

Harvesting

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Method Manual cutting + Hand collecting + Mechanical Threshing

Reaper + Combined-Collector (collecting + threshing)

Figure 1: Post-production system of rice in the Mekong River Delta of Vietnam and loss

components G is grain loss, V is value loss, *, ** and *** signs indicate relative degree of losses

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SUMMARY OF POST-HARVEST LOSSES

Table 1 is the summary of total post-harvest losses based on the data collected in the past two years from Mekong Delta region In this table, the values are the overall estimation from different varieties The values presented are in the relative term between the cases For instance, late harvesting has 3.5%

of losses in comparison to harvesting at correct time The value loss at correct harvesting time is considered to be 0%

• From the milling survey data, an average milling quality system caused a value loss of about 4% in comparison to a good quality system which was considered to be 0% value losses

• Experimental data of flat-bed drying gave that incorrect drying procedure resulted in 5% value losses in comparison to correct case which was considered to be 0% value losses

• Sun drying of panicle means that paddy after cutting was left in the field for sun drying (field drying) The value losses of 8.7% and 4% of field drying and sun drying on yard, respectively, were the relative values compared to correct drying procedure

Table 1: Overall evaluation of total post – harvest losses (late harvesting, moderate milling quality)

Harvesting

time

Harvesting method Threshing Sun drying Drying Milling

Total (%)

Yes (V=1.5%)

V = 1.5%)

No (0%)

Incorrect (V=5%)

Good quality (0%)

Yes (V=1.5%)

V = 1.5%)

No (0%)

Incorrect (V=5%)

Average quality (4%)

15.2 Note: V= Value losses, G = Grain losses

There are two cases of losses that can be highlighted in Table 1

1 The highest total losses is 20.6% including late harvesting (3.5%), manual cutting (2.9%), threshing (1.5%), field drying (8.7%), incorrect drying procedure (5%) and using average milling quality (4%)

2 The common cases of total losses are in the range of 12.4 to 15.9% including correct (or late) harvesting time, manual cutting, threshing, sun drying on yard, average milling quality applied

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1 INFLUENCE OF HARVESTING TIME ON THE RICE

CRACKING AND QUALITY LOSSES

Physical grain losses during harvesting can be divided into various types, depending on the operation and the machinery used

Losses during cutting crops

• Shattering loss: shedding of mature grains from the panicle caused by birds, wind, rats, and handling

• Lodging loss: plants with mature grains fall on the ground making the grains difficult to recover

• Standing crop loss: standing plants with mature grains are left standing in the field after harvesting

Losses during threshing and cleaning

• Separation loss or “blower loss”: grains that are mixed with straw or chaff during the cleaning operation

• Scatter loss: grains that are scattered on the ground during the threshing and cleaning operation

• Threshing loss or unseparated loss: mature grains that remain attached to the panicle in the straw after

completion of the threshing operation

Losses during crop and grain handling:

• Handling loss: mature grain lost during lifting, hauling, stacking, pouring, and bagging of crop and grains

Incorrect time of harvesting increases harvest losses The main problem is caused by delayed harvesting, as this increases susceptibility to shattering, lodging and standing crop losses

Incorrect harvesting time is also one of the major factors that cause the losses due to cracking Cracking can develop in the field as a result of changes in grain moisture or moisture cycles after the rice matures due to hot sunny days followed by humid nights The cracking behaviour of the rice in the field is expected to depend on the season due to the different patterns of temperature fluctuation during day and night, degree and strength of sunshine and frequency of rain During the rainy season, the rice grain can develop cracks during the late maturity stage due to rewetting At the same time, during dry season it is likely that the grains over-dry if not harvested at correct time Thus we need to identify the correct time for harvesting

Estimating the correct time of harvesting

Recommended time of harvesting for each variety is estimated from the time of sowing in each season Table 2 presents the estimated days from sowing to harvest for various varieties in MRD

Table 2 Growing time recommended by extension center

AG24 85-90

While this is useful way to estimate correct harvesting time, each crop differs in the correct harvesting time, as some mature faster and others mature more slowly, e.g crops affected by salinity

Thus more accurate date of correct harvesting time can be made with observation during growth of each crop Probably the most common way is to estimate harvest time from the observation of heading date, and add number of days to allow duration for grain filling In dry season, an optimum time of harvest is 28 to 35 days after heading In wet season, optimum time is 32 to 38 days after heading

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When the crop approaches the estimated optimum time of harvesting, then further observation is made

to determine the exact time of harvesting For harvesting the grain moisture content ideally is between

20-25% (wet basis) Grains should be firm but not brittle when squeezed between the teeth However,

in the Summer-Autumn season in Mekong Delta River, the moisture content is normally 28-30% due to frequent rains This means that prompt drying of grain is very critical to avoid rice cracking, germination and fungal damage

At around this time, the crop should be cut when 80-85% of the grains are straw (i.e yellow) coloured (see photograph) Harvesting also needs to be timed so that threshing can be done as soon as possible after cutting to avoid re-wetting and reduce grain breakage Thus, combine-harvester is the best harvesting method If the crop has a lot of surface moisture, e.g from previous rainfall or early in the morning, it is advisable to wait to cut the crop until the surface moisture dries off

From the experiments on 7 rice varieties in three seasons in the past 2 years (2006-2008), the optimal harvesting time to maximise head rice yield for each variety in each season (dry/rainy) is presented in Table 4 Most of the cases fell within the recommended day mentioned in Table 3 However, some cases were outside of this range such as OM2517 (94 days in rainy season), AG24 (94 days in rainy season) and OM2718 (88 days in rainy season)

Table 3: Optimal harvesting time for highest HRY (coloured numbers are the optimal growing time

Yield loss

Correct timing of harvest is crucial in order to prevent crop loss Grain losses may occur from rats,

birds, crop lodging, insects, and shattering Timely harvesting ensures good grain quality and high

market value

Harvesting too early will result in a larger percentage of unfilled or immature grains, which will result

in a lower yield and in higher grain breakage during milling

Harvesting too late will lead to excessive losses and increased breakage in rice

Grain cracking and head rice yield (HRY)

The following figures (Figure 2 and 3) show the mean of grain cracking and also that of heat rice yield

among several varieties obtained in Mekong Delta during 4 seasons of experiments in 2006-2008

0.80

3.20

9.60 4.80 10.80 15.20 23.60

0 2 4 6 8 10 12

Variety: 1490 (Rainy season 2006) Variety: 2718 (Rainy season 2006)

Figure 2: Effect of harvesting time on grain cracking The X axis indicates days of early or late harvesting compared to maturity date (day 0)

51.06 52.3 50.73

47.99 42.23 36.51 34.53

0 5 10 15 20 25 30 35 40 45 50 55

Variety:OM2718 (Rainy season 2006) Variety: OM 1490 (Rainy season 2006)

Figure 3: Effects of harvesting time on head rice yield The X axis indicates days of early or late

harvesting compared to maturity date (day 0)

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Do Not harvest late after the maturity date in order to avoid cracking and to increase HRY

Field experiments indicated

that: 4-6 days late harvesting

Table 4: Losses of Head Rice Yield (HRY %) due to late or early harvesting

Variety Season Losses of HRY (%) in comparison to optimal harvesting time

Rainy 0 1.57 4.31 10.07 15.79 17.77 OM1490 Dry 1.69 0.97 0 3.33 7.65 11.55

Rainy - - 0 5.15 7.08 3.20 OM2718 Dry 0.47 1.08 0 1.26 3.67 5.07

Rainy 5.08 11.36 7.05 4.77 0 4.9 OM2517

Rainy 4.65 6.59 3.07 4.55 0 7.07 OM4498

Jasmine Rainy 0.71 3.54 0 0.77 7.21 6.2

AG 24 Rainy 6.23 4.48 3.49 0.66 0 4.27

IR50404 Rainy -0.25 0.89 0 5.97 1.29 2.16

Note:: 0 is the optimal day After (before) this day is late (early) harvesting From one cell to the adjacent cell the

harvesting time changed by two days

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The survey data shows that most of the farmers were late harvesting by 1 to 3 days For varieties, OM1490, OM2718, Jasmine and AG24 were harvested late by 80%, 90%, 55% and 50% of farmers, respectively

1 The harvesting time is one of the important factors to control the rice cracking and eventual head rice recovery There is a clear trend that a few days early harvesting (before maturity) is better than the late harvesting

2 The same effect persists in rainy or dry season

3 Varieties differ in their grain cracking and those with small cracking such as AG24 is recommended When head rice recovery is also considered, OM4498 had smaller loss even it was harvested later than the optimum harvest time In one of the varieties tested in this investigation, a proportion of cracked rice was as high as 24%

The results have highlighted the importance of rapid harvesting of the crop Farmers are encouraged to make their crop management in such a way that they can harvest earlier (e.g., organize labour for harvesting) This is expected to impact the farmers’ decision to determine the harvesting time

In addition, the farmers are encouraged to plant varieties with different maturities so that each crop can be harvested at the correct time of harvesting There may also be some opportunities to plant at different times of the same variety, so that the harvesting is spread for a longer time period However, the best option is to introduce mechanical harvesting (see Section 2)

2 INFLUENCE OF HARVESTING METHOD ON THE RICE

CRACKING AND QUALITY LOSSES

Harvesting systems vary from region to region and include different methods for harvesting, hauling, threshing and cleaning The goal of good harvesting is to ensure maximum grain yield through minimizing grain loss and the prevention of quality deterioration, including cracking

A wide variety of harvesting tools is used, such as knives, sickles, animals, stationary threshing machines, tractor-mounted harvesters, and self-propelled combine harvesters In Vietnam including Mekong Delta, the most common systems for paddy harvesting are:

1 Manual harvesting, collecting by hand, followed by machine threshing (no more manual threshing

in Vietnam)

Manual cutting Manual collecting Machine threshing

2 Harvesting by reaper, manual collecting followed by machine threshing

Cutting by reaper Manual collecting Machine threshing

A lot of labours are required for manual collecting after harvesting by reaper

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3 Machine harvesting with a reaper, followed by combined collection-threshing

Cutting by reaper Combined collection and threshing

Cutting and laying the crop on a windrow is done using a reaper, followed by collection and threshing using a machine

Table 5: Advantages, disadvantages of the applied harvesting methods used in the Mekong Delta

Method Advantages Disadvantages

Multi-step harvesting:

+ Manual harvesting, field drying,

piling and threshing

- Cut rice stem is short reducing threshing energy

- Field drying reduces energy for drying and threshing

- Independent to soil condition and the degree of lodged rice

- High cleanness of rice

- Low capacity, require a large number

Dependency on availability of contractor

Piling: a hard work

The grain germinated

20 hours after harvesting due to wetting in the rain (Spring-Summer)

+ Harvesting by reaper, field

drying, piling, threshing

- The machine is not heavy, high capacity (1-6 ha/day); it can work

in the soft soil field

- The strength of reaper is moderate and rarely damaged seriously The spare parts are available locally

- High cleanness of rice

- High mobility

- Moderate investment

- High amount of rice stem (2-3 times compared to manual harvesting) increased time and energy for piling and threshing; it’s hard to harvest lodged rice This is the major disadvantage of the reaper

- High losses during harvesting and piling over-matured rice

- Grain quality is not as good as in the case of manual harvesting if field drying is applied

Harvesting by reaper, combine-

collection and threshing

- The reaper machine is not heavy, high capacity (1-6 ha/day); it can work in the soft soil field

- The combine- collecting and threshing machine can work in soft soil field where heavy combine harvester could not work

- High capacity, less labours requirement

- Higher capital cost

- More straw left behind in the field

- The mobility of the machine in the field depends on the weight of machine and the size of field

One step harvesting:

- Grain quality good

- The mobility of the machine in the field depends on the weight of machine and the size of field

- Hard to harvest lodged rice

- The machine consists of many parts and elements which lead to complex Extension Manual MS7 Eng.doc