Advances in agronomy volume 02

In net effect, the entire new market created by rising standards of living has been fact we have an indication of what competition has done to the cotton There are at least 35 materials

IS SOU 168104

OOlNo 2>t>/ fltFlf /4 Acomioalo,

Author

ADVANCES IN AGRONOMY

ADVANCES IN

AGRONOMY

Prepared under the Auspices of the

AMERICAN SOCIETY OF AGRONOMY

125 EAST 23RD STREET

NEW YORK 10, N Y.

form, by photostat, microfilm, or any other meanst

without written permission from the publishers.

J. E ADAMS, Head, Department of Agronomy, Texas Agricultural and

Brunswick,NewJersey.

Experi-mentStation, Ames,Iowa

HENRY D BARKER, Principal Pathologist, U S. Department of

CHARLES A BENNETT, Principal Agricultural Engineer, U S. Department

of Agriculture, Cotton Ginning Laboratory, Stoneville, Mississippi

Experi-mentStation,Auburn, Alabama.

Illinois.

J. C GAINES, Professor ofEntomology, Texas Agriculturaland

N. COLLIS-GEORGE, Demonstrator, School of Agriculture, University of

Cambridge, England

WESLEY KELLER, Geneticist, U S. Department of Agriculture, Logan,Utah

W K KENNEDY, Professor of Agronomy, Cornell University, Ithaca,

California

Uni-versity Agricultural Experiment Station, Lafayette, Indiana

VI CONTRIBUTORS TO VOLUME II

0 A LORENZ, Assistant Professor of Truck Crops, University of

Cali-fornia, Davis, California

Agriculture, Stoneville, Mississippi

R W. PEARSON, Senior Soil Scientist, U S. Department of Agriculture,Auburn,Alabama.

MAURICE L PETERSON, Assistant Agrononvist, California Agricultural

Ex-periment Station, Davis, California

JOHNT PRESLEY,Head, Department of Plant Pathology andPhysiology,

Missis-sippi.

F F RIECKEN, Research Professor of Soil*, Iowa Agricultural mentStation,Ames,Iowa

Experi-GUY D. SMITH, Senior Soil Correlator, U S. Department of Agriculture,

HARRIS P SMITH, Professor of Agricultural Engineering, Texas tural Experiment Station, College Station, Texas

Agricul-In the preface to Volume I it was pointed out that the pressure of

developments somewhat removed from their immediate interests, yet ofprofessional importance to them It was further explained that the edi-tors were not inclined to quibble about the precise definition of the word

what constitutes agronomy The authors arc urged to present, as far

as possible, unified, complete and authoritative accounts of the recent

developments in their particular fields. Topics will reappear from time

This isthemid-century year Itwould be presumptious on the part of

prepare a mid-century number delineating and weighing the

had no difficulty in resisting the urge to follow the lead set in this matter

thought did set in train some speculations as to what topics might have

been selected for a similar volume had one been prepared fifty years ago

have been included because their development has taken place almostentirely since 1900. Crop improvement through genetics, soil physics,and soil genesis are examples A cursory glance at the contents of this

that about half of them would not have appeared in

any form in a 1900 edition Thus fast has agronomy grown

of the changes in U S. agriculture and agricultural practice. These are

dramatic enough Here is a nation which in fifty years has doubled in

consumption has increased eight-fold, but there are fewer sheep, and

Perhaps in the last lies a clue to much that has been accomplished by the

mechanization of many operations through the availability of power

equipment

Vlii PREFACE

dissipated by population increase? Shouldproduction be curtailed in the

interests of conservation? Will there be changes in food habits on the

The resolution of many vital questions such as these will not

pri-marily lie in the hands of those practicing the profession of agronomy,

prob-lems that taken together will determine the answers to such major

questions Subsequent volumes of the Advances will record and

sum-marize their methods, recount their achievements and measure theiraccomplishments

A.G NORMAN

Cotton

COORDINATED BY J E ADAMS, Texas Agricultural and Mechanical College System,

II. Competitive Position of Cotton Among Fibers, BY M. K HORNE, JR 5

III. Physiology of the Cotton Plant, BY F. M. EATON 11

IX Breeding and Improvement, BY T R RICHMOND 63

IV. Nitrogen Transformations 89

V Effect of Cropping Practices on Nitrogen Level 94

VI. Nitrogen Economy of Eroded Soils 98

X CONTENTS

Page

Agri-culture, Ames, Iowa, and the Iowa Agricultural Experiment Station, Ames, Iowa

IV. Classification of Prairie Soils 192

BY GILBERT H AHLURENAND R F. FUELLEMAN, Rutgers University, New Brunswick,

NewJersey,and UniversityofIllinois, Urbana,Illinois

III. Establishment and Management 213

The Control of SoilWater

Cambridge, England

I. The Scope of the Review ^ 234

IV. Drainage and Irrigation 258

PreservationandStorageofForageCrops

III.

VI Artificial Drying 304 VII. Experiments Comparing Silage, Barn-Cured and Field-Cured Hay . 306

BY HELMUTKOHNKE,Purdue University Agricultural Experiment Station,

II. The Condition of Spoil Banks 319

BY WESLEY KELLER AND MAURICE L. PETERSON, U ft. Department of Agriculture,

Logan, Utah, andCalifornia AgriculturalExperimentStation, Davis, California

III. Choosing Productive Mixtures 356

II. Competitive Position of Cotton Among Fibers by M. K HORNE, JR 5

3. A Static vs. a Dynamic Position for Cotton 8

4. Need for Expanded Research 9

III. Physiology of the Cotton Plant by F. M EATON 11

4. Carbohydrates, Nitrogen and Fruitfulness 22

7. Oxygen Requirements for Root Growth 25

IV. Diseases of Cotton by J. T PRESLEY 26

10. General Recommendations for Chemical Control 40

2. In Low-Rainfall and Subhumid Areas by H P. SMITH 46

1. Fiber Structure and Development 56

5 Significance of Fiber Properties 62

IX Breeding and Improvement by T. R RICHMOND 63

millionpeople are wholly or partially dependent on cotton as a source of

unusual crop. In addition^to lint, the embryos or "meats" of the seed

furnish both a protein concentrate and a high-grade oil. The "hulls"

Although cottonlint is the most versatile fiber known when all end-usesare considered, economic conditions since the early thirties, with inter-

re-flected in Table released as of December 1949, by the Bureau of

Agricultural Economics, Austin, Texas Every cotton-producing state

shows anincrease in acreage in 1949 over 1948 In spite of lower

the increase of 4,728,000 bales in 1949 over the average of 11,306,000

bales in the 1938-1947 period. The increase in production in the

is phenomenal

Although the sections on production treat mechanization of the cotton

was an intensification in research and more ready acceptance by the

farmer due to the dearth of labor Development of flame cultivation,

Estimates furnished by the National Cotton Council indicate that

approximately 2900 spindle-type pickers were used in 1949 Mississippi

of better than 7000 stripperswere used,with the Texas High-Plains area

be radically lowered, leads to the conclusion that production per acre

must be increased Better fertility practices, control of insects and

dis-eases, better varieties of cotton for mechanical harvesting, along with

All of the cottons of the world, whether cultivated or wild, belong

cultivated (n = 26), and (3) wild, (n = 13, with one anomalous tion) Though the reported number of species of Gossypium varies

inclina-tion of the taxonomist, a recent work by Hutchinson et al. (1947) (see

J E. ADAMS

bar-badense L The firsttwo are designated as Asiatic and the last two as

distinguishes them from the wild cottons which do not have spinnable

lint. American cultivated cottons (n = 26), according to the theory

independently by Beasley (1940) and Harland (1940) (see References

in IX), aretetraploids which have arisen by amphidiploidy from hybrids

This paper will present important aspects of the production of cotton

II. COMPETITIVE POSITION OF COTTON AMONG FIBERS

M. K HORNE, JR

1. Cotton Loses Markets

Except for the abnormal experience of the war and early postwar

years, it can be said that over the past 4 decades the per capita

con-sumption of cotton in this country has shown no tendency to rise. Over

this long period, it has gravitated around a central figure of 25 or 26

Ibs. a year, displaying no trend either up or down In net effect, the

entire new market created by rising standards of living has been

fact we have an indication of what competition has done to the cotton

There are at least 35 materials which give cotton substantial

seems helpful, and in some degree defensible, to think primarily in terms

problems of the Cotton Belt," presented in 1947 before the Cotton committee of the Committee on Agriculture, U S. House of Represen-tatives, it was found that some form of rayon was cotton's closest

rayon has advanced from a trivial position among all fibers to second

1,124,000,-000 Ibs. of rayon were produced in this country Factory capacity has

now reached an estimated 1,235,000,000 Ibs., or the equivalent in usable

of the average annual consumption of cotton in this

6 HORNE,

decadeof the 1930's, and to 35 per cent of the cotton consumption in the

feeling a terrific impact from a competitor which has grown so rapidly

for every competing material Most materials are quite different from

number of end-uses where their special characteristics give them an

quality Within a limited range of uses, these factors can sometimesovercome the important advantages of cotton in other properties. Paper

of the towel, cordage, napkin, and handkerchief markets Its quality

texture, strength, and absorbency quite obviously restrict itto a fraction

considered They are all far above the price range of cotton One may

be tempted to reason that since rayon came down to the price of cotton,

time, these various synthetics are quite superior to cotton in some

quali-ties, and quite inferior to it in others There are certain uses for cotton

Rayon,is distinguished by the fact that to an ever-increasing degree

it competes for markets, not because of its differences from cotton, butbecause of its similarities to cotton Its price and quality pattern has

shaped itself toward the and of cotton

Very generally, it can be said that today rayon is in the same price

range with cotton Inreference to quality, there still are sharpdifferencesbetween the two fibers, but rayon has made marvelous progress in over-

seen in the development of staple fiber, in delustering, in crimping, in

di-mensional stability. Several ofrayon's biggest quality handicaps remain,but we cannot overlook the fact that the extensive research program

of the rayon industry is going vigorously forward As a competitor ofcotton, rayon looks less and less like aspecialty fiber and more and more

markets

The two chief weapons with which rayon might be expected to prove its present competitive position are: (1) the lowering of price;

years, it now seems fairly clear that the rayon industry is likely to rely

ended in 1938 The average production cost of viscose staple at a recent

time was 29 cents a pound. This of course was before any allowance

for income tax The selling price of viscose staple was 35 cents in

a serious turn for the worse On the side of cost reductions, it must be

a serious business recession occurs For types of rayon other thanviscose staple, the possibilities of cost reductions, through technical ad-

on research, a major part of it apparently aimed at the improvement ofquality It isperhaps a reasonable guess that the present rayon research

and technical-service programs of the 5 leading companies are costing

ten million dollars a year We can never predict what research

rayon research program down to the present time A continued, and

perhaps an accelerated, improvementin the quality ofthe various rayons

tobe the greatest threatto the market for cotton A continuing

8 HOENE,

3. A Static vs. a Dynamic Position for Cotton

In the face of this trend, how shall we appraise the competitive

position of cotton?

Although the situation is essentially dynamic, let us examine it first

under assumed conditions which would make it static. The assumptions

relative qualities of cotton and rayon products; (2) no change in the

relative merchandising efficiency of the two fibers; (3) no war-created

January, 1946

price actually prevailing in January 1946, or about25 cents, and second,

a price about half as high, or 12 cents.

With these assumptions a group of textile economists made a

in 127 end-uses, representing about 83 per cent of the domestic market

that changes would follow the pattern of the 83 per cent. The sources

which numbers of the best informed business executives were questioned

were as follows: first,that at25 cents per Ib. cottonwould find a domestic

logically be increased to this -extent. With this revision, and under the

price level, the domestic market for cotton would tend to be 7,700,000

bales at 35 cents, compared with 9,600,000 bales at 17 cents.

Two lessons from these figures are outstanding:

con-sidered in this sense, is inelastic, evenwhen allowance is made (as it was

a real influence on an end-use market For certain end-uses (notablytire cord, bags, insulation, and plastic laminates) the demand is elastic,

consump-tion atthe two price levelswould be quite small, so small as to make the

overall domestic demand rather inelastic. The inelasticity results chiefly

change inquality, the substitutability of other materials is quite limited

advantages for cotton in many important uses Despite rayon's gains,

good absorbency and dyeing properties, vapor permeability, chemical

In view of this finding and of what we have already said about rayon,

it seems that two facts should be made equally emphatic on the vital

markets from rayon. Since that time there has been no drastic change

mere tokenof what is needed

4. Need for Expanded Research

op-portunities in the fiber. The Project IV report outlined 41 broad fields

of in which cotton's markets might be through

10 HORNE,

research Cotton is a promising subject for quality improvement at

and weaving, finishing and fabricating. Cotton has the opportunity to

rayon will overtake it in quality The opportunities exist, but in spite

of recent expansion, an adequate program does not

Let us now attempt to summarize the significance of two

competi-tive factors, price and quality, and their interrelationship with one

an-other, in the domestic market for cotton There seem to be 3 points

which deserve attention: (1) as long as cotton holds its present quality

rayon continues to improve in quality more rapidly than cotton, in the

decline; (3) if rayon continues to improve in quality more rapidly thancotton, in the course of time the significance of price as a competitivefactor will increase As rayon becomes more substitutable for cotton,

the demand for cotton will become more elastic in its response to price

cotton, and cotton makes no offsetting gains in quality, it will then be

which would not give it a marked price advantage over rayon

Thus, from the standpoint of the cotton economy, the largely

neg-lected opportunity to build an adequate research and development

dollars annually If, through the lack of such a program, it becomes

In this statement many factors which bear upon the competitive

can the special natureof the export market In the limited space

significance of quality improvement

III. PHYSIOLOGY OF THE COTTON PLANT

a. Branching Habits of the Cotton Plant Some of the most

basis in the type of branches which are produced According to

condi-tions of growth, the branches arising from the main stalk may be clusively vegetative branches or exclusively fruiting branches In the

ex-tixil of each leaf on the main stalk, and also on vegetative branches,there are two buds One of these buds, if it develops, will produce a

de-velop Morphologically, the vegetative branches, or limbs, are like the

bud, even though it may absciss while still a millimeter or two in

Althoughthere arevarious complexities,American Upland cottons, unless

starting between the seventh to tenth nodes, only fruiting branches are

developed from the main-stalk nodes In addition to developing fromthe main stalk and from vegetative branches, vegetative branches may

Gaines (1947) has found that, in the absence of insect control, a loss

is without effect on final yields. This is in conformity with earlier

agronomic and physiological observations showing that the loss of some

andthatnew buds were developedto replace those thatwerelost. Under some conditions, the removal of early buds and flowers has resulted in

flowers at fruiting-branch nodes near the main stalk are more apt to

environmental conditions permitting

by temperature and by length-of-day (Fig 1). Also the number of

12 FRANK M EATON

darkening the tips of plants (Eaton and Rigler, 1948) and by treatments

with growth substances which cause buds to shed Whether or not there

(left) and cool nights (right) at San Diego, California, where the days are cool.

produce only vegetative branches under long days (Eaton, 1924).

the fruiting activities of some, but not all, of the perennial arborescent

cottons, particularly those from equatorial regions, and to a slight extent,

reactions were basic change consisted in a lowering of the

position of the first fruiting branches All cottons exhibiting

c. Temperature The striking influence that temperature may exert

on the kind of branches produced, and, therefore, on the fruiting of ton plants, is illustrated in Fig 1. Dastur (1948) makes mention of

was observed in 1947 (unpublished data) to develop 10 times as many

spaced at Sacaton, Arizona, where the average minimum nightly

under a dust mulch along the two sides of a row of cotton plants at

above ground and in turn lessened the development of vegetativebranches

d. 2,4-D and Hormone Responses. Attention was first directed by

traces of 2,4-dichlorophenoxyacetic acid and its derivatives The

by Dunlap (1948) to be the growth repression of the mesophyll of leaves

which the veins were especially prominent. Brown et cd. (1948)

ground level. Each of the foregoing investigators has shown that

branches of normal appearance and develop late bolls. He also showed

vege-tative branches of cotton plants. Changes were found in the

concentra-tions of several organic constituents of the leaves that were associated,possibly, with the altered proportions of vein andmesophyll tissue. The

tensile strength of fiber.

Singh and Greulach (1949) concluded from a planned

green-14 FRANK M EATON

house experiment that spraysof a-naphthaleneacetic acid and

In California, in either of two years, during periods when 60 to 70

only the 20 p.p.m concentration of 4-chlorophenoxyacetate alteredgrowth or fruiting. This latter material reducedsignificantly the number

branches were regarded as probably the result of reduced fruiting caused

by extra bud shedding. As a part of this work, attempts were made

particu-larly any that influence floral initiaton or repression

2. Mineral Nutrition

impetus during the past ten years from rapidly developing evidence and

views on the exchange of cations between the plant and soil. A recent

review by Wadleigh (1949) deals extensively with the relations sented The order of ease of release of cations from soil colloids by

repre-exchange reaction is headed by sodium which is released most easily

relative to calcium is always greater than the ratio of adsorbed sodium

to adsorbed calcium, but the calcium on kaolinitic clay may be 10 or

potassium or sodium may prevent calcium uptake. Hydrogen ions

metabolismis the antecedent agent in the transfer of hydrogen from root

to clay. Of like recognized importance, but less well understood, are

surfaces and their relative rates of transference inwardly

energyarising fromrespiration is directlyinvolved inthe intake of anions

whereasthe CO2product of respiratory activity functionsin the hydrogentransfer that is instrumental in cation accumulation by exchange

Lundegardh's review (1947) deals extensively with this phase of mineral

nutrition In the instanceof cotton, Eaton and Joham (1944) found that

defruiting to increase sugar concentrations resulted in significant

in-creases in both bromine and potassium in the fibrous roots; there was

a. Constant Sum of Cations Recent papers by van Itallie (1948)and Wallace et al. (1948b), who worked with oats and alfalfa, respec-

development tends to be uniform even though the species is grown on

con-clusioncan be extended to cotton is not yet clear. Cooper et al. (1948)

thought that it might not be applicable to cotton where there is a widevariability in hydrogen-ion concentration As grown on 7 plots at

the South to the roll of sodium as a plant nutrient for cotton has appliedalso in an important manner to other plants in other regions. Although

no one has assumed, or concluded, that sodium is an essential element,

Furthermore, in some plants, such as the beet (Sayre and Vittum, 1947),

ac-cumulate more sodium than potassium, such as beets, cabbages, carrots,

and perhaps are more often benefited by sodium

Collander (1941) has reported sodium to be higher in the roots than

16 FRANK M EATON

Cotton contains much less Na than K above ground, and, as found in

much Na as K (Table II). Cooper et al. (1947) have considered the

TABLE II

Cotton Yields and 3-Year Average Ca, K and Na Accumulations in Plants Equally

Supplied withNitrate onNorfolk SandyLoama

*

agreements and discrepancies between the order of accumulation of

arranged on the basis of their electrode potentials measured in equivalent

selec-tive accumulation ofpotassium from K and Na mixtures by sand columns

Thepossible fit ofpreferredions inthe lattice structure of the solid phasehas been pointed to as one explanation.

Potassium is customarily credited with promoting not only the

and oils. Itis evident that sodium cannot perform all functions of

potas-sium in cotton, or in cotton does not accumulate in the right places in

that Na alleviated but did not eliminate cotton Leaf

important symptomofpotassiumdeficiency in cotton Biddulph's (1949)

radioautographs show K concentrations in cotton leaves to be much more

the Georgia Coastal Plain, Turner (1944) found that potash deficiency

the weight of seed per boll by only 10 per cent

Gains from sodium applications have been common in field

conclud-ing that the same yield increase might not have been gained from

mentioned investigators obtained no benefit from Na additions in

green-house tests, using both sand and potted soil cultures In the field,

how-ever, they obtained gains of 98 to 213 Ibs. of seed cotton per acre in

plots supplied with sodium in addition to 24 to 48 Ibs. K20 Mathews

availability of K (but not of Na) having been determined in both soils,

Data by Cooper and Garman (1942) are notable in showing nearly

uniform gains of approximately 200 Ibs. of seed cotton per acre from

caused nearly uniform increases in accumulation of Na from about 1.5

to 11 meq per 100 g. of plant tissue. Adding but 60 Ibs. of K2 was

above-ground portions of the plants.

Skinner et al. (1944) observed that extra K fertilization increased

also of N and P in cotton plants. Like Cooper (1945), they concluded

non-acid forming fertilizers.

c. Phosphorus In each of 5 years Brown and Pope (1939) reported

18 FRANK M EATON

first two weeks of the flowering period With heavy P2 5 applications,

gath-ered at the first picking Potassium on the other hand appeared to

de-crease the determinatenessof the plant and to increase ultimate yields.

Radio-phosphorus injected into a leaf vein by Biddulph and Markle

rate of 21 cm per hour was thought too high to be accounted for by

move-ment From 30 days before to 25 days after anthesis, Biddulph and Brown (1945) found that the accumulation of both tagged and untagged

phosphorus in floral buds and bolls was at rates nearly proportional to

with phosphorus in amounts from that causing acute starvation to anexcess, and found that both the soluble and insoluble fractions in the

main-stalk leaves increased throughout the full range; the former

in-crease was linear whereas the latter tended to flatten.

in-vestigators have found high levels of nitrate to depress the uptake of

The use of radio-phosphorus has permitted some significant

con-clusions on the availability to cotton of various types of phosphate

fertilizer. Measurements by Hall et al. (1949), showing the proportion

of accumulating phosphorus derived from the soil and from the tagged

fertilizer, have been made with a number of crops under various

calcium metaphosphate and least from dicalcium phosphate, but the

defi-ciences that had resulted from previous fertilizer practices

d. Sulfwr By classical interpretation, sulfur is essential to the

syn-thesis of proteins and when sulfur is deficient various plants become aschlorotic as they do when nitrogen is deficient. With insufficient sulfur,

In the leaf sap from cotton (Eaton, 1942), much more sulfur and much

lessphosphorus were found than inthat from the other plants examined

During the last war, the substitution of rock phosphates for phate resultedinpoor cotton yields in some localities. Willis (1936) has

appli-cations Younge (1941) noted that sulfur deficiency reduced the number

and delayed the development of cotton bolls on a Coastal Plain soil.

amount of sulfur in superphosphate and in the gases released to the

atmosphere by some industries, more information on the sulfur

metabo-lism of cotton might now be available

e. Boron This element, which is now thought to be involved in

the flower buds fail to develop Boron has continued to be regarded as

an important constituent of cotton fertilizers under some conditions

Coleman (1945) reports beneficial results from applying boron at the

rate of 20 Ibs. per acre to Grenada silt loam in Mississippi Boll sizeand number of bolls were increased, but no effects were found on per-

/. Copper Like iron, copper functions as a coenzyme in oxidation

producesubstantial increases inyields of cotton when added to fertilizers

found copper applications to cotton in Texas to produce greater yieldincreases when applied to the leaves as a dust with insecticides than

nutri-ent has been reviewed by Somner (1945), but no indication is afforded

investiga-tions of the accumulation of minerals in the cotton plant by the various

were about half as rich in P2 5 (0.44% on dry weight), CaO (2.08%)

20 IANK M EATON

and MgO (0.99%), and four-tenths as high in percentage of N (1.60%)

and K2 (1.39%) As calculated from data from plants on Cecil sandy

de-veloped on thebasis of analyses of barley plants The efficiency of the

the total dry weight of the plant andto contain 57.3 per cent of nitrogen,

According to data by Phillis and Mason (1942) the percentage

com-position of K, Ca, Mg, P, Cl and N in cotton leaves rises during the day

made about midnight contained an abundance of potassium and only

traces of calcium The authors regard the results as being in harmony

8. Nitrogen

In the Sudan, Crowther (1934) found 60 per cent or more of the total

the first bolls had started to open until the plants were mature

the leaves This progressive exhaustion of leaf nitrogen continued from

Bledsoe (1942) found nearly the same proportion of the total nitrogen

Wadleigh's (1944) extensive inquiry into the forms of nitrogen and

con-stituted from two-thirds to three-quarters of the total nitrogen in all

selected for sampling bothtotal nitrogen and protein nitrogenwere much

propor-tion of protein is in accord with earlier results by Rigler et al (1937)

experiment nitrate nitrogen varied from 3.1 per cent of the totalnitrogen

(high nitrogen plants) Mason and Phillis (1945) obtained a high linearcorrelation between soluble and protein nitrogen in leaves until a rela-tively high level of supply was reached, beyond which there was nofurther increase in protein. Potassium and phosphorus starvation both

caused reductions in the proportion of protein The total nitrogen of

in the former than the latter.

were no wide or very consistent differences in the yield benefits, or in

that ammonium fertilization initiated more flowers, but more of these

flowerswereshed Although these conclusions are valid, the data through

per plant, and also in relative fruitfulness (computed by the writer)

in Table III, ammonium salts produced a nonsignificant increase in

bolls per plant and in relative fruitfulness; the latter amounted to 12per cent. All of these effects are in the direction to be expected on the

cNumberof bolls contributing to seed cotton.

and

22 FRANK M EATON

basis of the extra energy required for the reduction of nitrate ions. The

literature on nitrate and ammonium nutrition, as well as many other

features of nitrogen nutrition of green plants, has been extensively

re-viewed by Nightingale (1948)

4. Carbohydrates, Nitrogen and Fruitfulness

soil. As the reserves within the plant are exhaustedthere is a yellowing

meta-bolic activity. The onset of nitrogen exhaustion is delayed as the ternal supply becomes more abundant, and also when the variety is

tempera-tures and low light intensity. The level of starch and dextrin decreased

growth (i.e., boll retention) depends on carbohydrate supply.

Experiments by Eaton and Rigler (1945) were conducted with the

objective of learning whether in cotton there are particular relationsbetween nitrogen and carbohydrate levels that are conducive or non-conducive to fruitfulness. Plants were grown in sand cultures supplied

with 1, 4, 16, and 64 meq nitrate per liter: (1) in a greenhouse in the

about 1000 foot-candles, and^(2) freely exposed outdoors in the summerwhere the light averaged about10,000 foot-candles at midday Between

starch at allnitrate levels. In the plants supplied with 16 meq N03 per

1. this increase was 4-fold in the leaves and 2-fold in the root bark Theweight of leaves and stems in the high and the low light experiments(Table III) were alike, but the plants under high light produced

with very low light thus caused decreased fruitfulness, i.e., influenced

the partition of growth materials between vegetative and fruiting