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II. Rice Culture in the United States

II. Rice Culture in the United States

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RICE IMPROVEMENT AND CULTURE IN UNITED STATES



69



organic soils (Green, 1956), and sandy loams are often used. Satisfactory

rice soils must have an impervious stratum within 2 to 5 feet of the

surface or the texture must be fine enough to reduce water percolation

so that seepage is reduced. Because of excessive percolation losses, rice

grown on open permeable soil may require two to three times as much

water as rice of comparable yield grown on "rice" soil. The surface of

the soil must be level so that a uniform depth of about 6 inches of water

can be maintained with a minimum number of levees, yet with enough

slope so that surface water can be drained for seedbed preparation and

harvest.

Rice requires a relatively long, frost-free growing period. The optimum

growing period for United States varieties is 105 to 170 days. The range

of air temperature for rice production is about 70°F. minimum to

about 95" maximum. Ormrod (1961) showed that CALORO rice seedlings

maintain an appreciable net photosynthetic rate at low air temperature

(40" or 60" ) and a wide range of light intensities. Low light intensities

at a higher temperature (80' ) resulted in net losses of carbon dioxide

from the plants. Rice often is considered to be a tropical crop, although

it is grown throughout the tropical, subtropical, and temperate zones

from the equator to nearly 50" latitude. The range in the United States

is from the Gulf Coast (30"N) to about mid-United States (40"N).

The yields generally are higher in the temperate than in the more tropical

areas. This difference may be due partly to varieties grown, but climate

and soil contribute to this difference.



B. CROPPING

SYSTEMS

The riceland cropping systems now used in the United States have

evolved over the years. These systems are based on experience of

growers and information gained from controlled experiments. The cropping system used depends on the soil type and climatic conditions. In

most rice-producing areas of the United States, crop rotation is followed

because, if cropped continuously, the soil usually becomes depleted

in fertility, the organic content becomes so low that the deteriorating

physical conditions make seedbed preparation difficult. The soil also

becomes progressively infested with weeds that lower the yield and

quality of the rice.

In the early years in the Carolinas, rice was grown continuously in

the same field, with occasional rest, according to Gray and Thompson

( 1941). Rice fields in that area were sometimes planted to oats in the

fall, followed by potatoes the next year. Some farmers made a practice

of growing rice and cotton on alternate years. This helped to control

the weeds in both crops. In the South Central States, the fields were



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C . ROY ADAIR, M. D. MILLER, AND H. M. BEACHELL



cropped to rice year after year until the yield became low and the quality

was poor because of mixture of weed seeds and red rice in the threshed

grain. Fields were then allowed to lay idle for a year or two and then

put back into rice. This practice improved the yield but did not control

the weeds satisfactorily, so the rice fields were grazed during years they

were “laid-out.” This helped control the grass and weeds but did not

control the red rice. Some farmers practiced summer fallowing for a

year or two between rice crops and thus controlled the weeds and red

rice more effectively than when the fields were not cultivated.

In Arkansas, starting about 1930, rice was rotated with soybeans and

lespedeza. Fall-sown oats had been rotated with rice to some extent

before the use of the legume crops. A common rotation system for

Arkansas was rice, soybeans, followed by fall-sown oats with lespedeza

sown in the oats in the early spring. This is a difficult rotation to manage

because of the likelihood of rain at a critical time which may prevent the

seeding of the oats. However, when this rotation can be used, four crops

are produced in three years, the soil is benefited, and weeds are controlled to some extent. Farming systems for rice farms in Arkansas

are described and discussed by Mullins and Slusher ( 1950, 1951) . More

recently, fish culture has been beneficially inserted into the rice rotation

system in Arkansas and Mississippi (Green and Mullins, 1959).

Because of weather conditions and diseases, oats and soybeans have

not been grown in rotation with rice in the Gulf Coast area. The usual

cropping system in this area is to rotate rice with improved pastures

and to raise beef cattle as a supplemental enterprise. This system of rice

farming and this method of establishing pastures are discussed by

Moncrief and Weihing ( 1950). Walker and Sturgis (1946) conducted

experiments on the establishment of pastures following rice on three soil

types in Louisiana and described the results with respect to improving

the pasture and the results of this treatment on the following rice crop.

They found that fertilizer at the rate of 400 pounds of 3-12-6 and 1 ton

of ground limestone an acre before seeding the pasture with white clover,

Persian clover, common lespedeza, carpet grass, and bermudagrass, and

200 pounds an acre of the same fertilizer the next year almost doubled

the production of the pasture compared with growth that occurred

naturally following rice. Rice yields following the improved pasture were

over 10oO pounds an acre higher than rice following unimproved pasture.

This system or some modification of it is commonly used in Louisiana

and Texas, according to Jones et al. (1952).

In California, no definite system of crop rotation has yet emerged

(Jones et al., 1950). To date no serious rice disease in that State has

made crop rotation on riceland necessary. When rapidly advancing



RICE IMPROVEMENT AND CULTURE IN UNITED STATES



71



knowledge of weed control, fertilization, and other improved cultural

practices are used, fields can be cropped continuously to rice with everincreasing per acre yields. Some California farmers follow rice with

spring- or summer-plowed fallow, on which wheat or oats and vetch is

fall-sown. After the ensuing grain crop, the field is returned to rice for

an indefinite numbers of years. Currently, spring-sown grain sorghum,

field beans, and saf3ower are being used on the medium-textured soil

types for 1 or 2 years, the land then being returned to rice. To a limited

extent, imgated ladino or strawberry clover-trefoil-grasspastures may be

inserted in the rotation for a continuing period of 4 to 7 years.

C. LANDPREPARATION

The seedbed for rice is prepared in much the same manner as that

for other small grains. The procedures generally followed are given by

Davis (1950), Jones et al. (1950, 1952>,Reynolds (1954), and Finfrock

and Miller (1958). The primary aim is to destroy weeds and to provide

a suitable seedbed. Whether it should be rough or mellow on the surface

will be governed by the seeding method used. If the rice is to be sown

in the water, the soil surface should be rough; and if it is to be drilled,

the soil surface should be mellow.

Rice fields are usually plowed in the late summer, fall, or winter

in Louisiana and Texas. Land that has been in pasture for several years,

when plowed at that time, will be mellowed by the frost and rain during

winter and early spring. A good seedbed can be prepared by disking,

harrowing, and floating (dragging) in the spring. When the land is

plowed in the spring, it is disked and harrowed immediately to prevent

clod formation by baking. When cropped successively to rice, the land

is disked as soon after harvest of the rice crop as soil condition permits.

In Arkansas, rice fields usually are disked immediately after harvest.

The tractors used to pull the grain carts while the combines are operating

often are used early in the morning to disk the land harvested the previous day. Disking chops the stubble and straw and puts it in contact

with the soil and thus hastens its decay. The fields may be disked

another time or two during the winter as weather permits so that it can

be seeded to lespedeza in early spring without further seedbed preparation. When rice follows soybeans that have been intertilled, a seedbed may be prepared by working the soil with a heavy disk, followed

by a lighter disk and smoothing harrow. When rice follows lespedeza,

the land is plowed, usually with a moldboard plow, disked, and harrowed.

In California, the land is plowed in the spring to a depth of 4 to 6

inches, disked, and then harrowed or smoothed with a drag. Sometimes

where rice follows beans, sorghum, or safflower, the seedbed may be



72



C . ROY AD=,



M. D. MILLER, A h 9 H. M.



BEACHELL



prepared by spring disking. When the rice is to be sown in the water,

the soil should not be worked too soon after a rain and it should be

left loose and rough on the surface. Since water seeding is the predominant method, a clod size ranging from 5 inch to 4 inches in diameter is the goal. As the clods slake down after flooding and seeding,

the silt covers the seed. If the soil is compacted and puddled by working

when it is too wet, algal growth is induced and oxygen essential for good

root development is excluded from the soil. Usually, in Arkansas, the

last field operation before flooding is to till the soil with a spring-tooth

harrow or field cultivator. A heavy spike-tooth harrow is generally used

for this last operation in California. In addition to the other advantage, a

rough seedbed helps prevent drifting of the seed in the water.

An essential part of rice culture is to have the soil surface as level

as possible within each subfield. That is, knolls should be cut down and

shallow sloughs and dead furrows filled so that the field is uniformly

graded to the natural slope of the terrain. This will make it possible to

keep the fields drained of winter water thus expediting seedbed preparation and speeding harvest by providing for rapid field drainage at

maturity. The levees can be straightened when the fields are graded to

a uniform slope from the upper to the lower side. This will reduce

tillage and harvesting costs by cutting turning time and increase the rice

yields by eliminating “drowned-out” and weedy spots.

In most cases a rice field can be improved for water management

by land planing before or during seedbed preparation. Regular earthmoving equipment is required to grade very rough fields. Grading rice

fields while flooded has been successfully demonstrated in Louisiana

(Faulkner and Miears, 1961). After a field has been adequately graded,

it then can be maintained by regular land planing or floating prior to

seeding the rice.

Levee construction is an integral and important part of preparation

for growing rice. Levees are the key device used to control the depth

of application of water to the crops. The levees must be located accurately

in order to maintain a uniform depth of water; they are constructed

on the contour, that is, on lines of equal elevation. They should be

located by an experienced surveyor or operator using an accurate

instrument. The soil should be smooth, so the surveying can best be

done immediately after the land has been floated. The contour interval

between levees is usually 0.2 to 0.3 foot, depending upon the slope- of

the land. On flat land they are built OR 0.1 to 0.2 foot contour, and on

steep, sloping land on 0.3 foot.

The levee should be as compact as possible and high enough to

hold the water at the desired level. In the southern States, the levees



RICE IMPROVEMENT AND CULTURE IN UNITED STATES



73



have gently sloping sides so that the rice can be drilled and harvested

over the levee. In this case the levees are complete after drilling the rice.

In California, the levees are higher and have steep sides so that the area

between pairs of levees is harvested as a field or unit. In the southern

States, the base of the levee is made by plowing one round with a 3bottom plow and then finishing with a single-or a double-blade pusher

on clayey soils or with a levee disk on sandy loam and loam. The levee

base is built as early as possible so that it can settle. In California, a

V-type diker or soil crowder that is 14 to 16 feet wide in front and 4

feet wide in the back is used. Two or more crawler-type tractors are

used to pull the diker. The levees usually are 30 to 36 inches high when

freshly made and settle to 16 to 20 inches. Levees usually are made in

the fall and allowed to settle during the winter. A bulldozer or a tractor

with front-end scoop is used to close the gap at the water-control boxes

and at the end of each levee. Scott st al. (1961) reported on the possibilities of using plastic film rice levees in lieu of soil levees. Their studies

show that plastic levees are physically feasible but of undetermined

economic benefit. A machine to install plastic levees mechanically is

required before this type of levee will be commercially feasible.



D. IRRIGATION

AND DRAINAGE

The water requirement of rice is high. Flood irrigation is used for

all rice grown in the United States. That is, the soil is submerged in

4 to 8 inches of water most or all of the time from seeding until the

grain is nearly ripe. Upland, or rain-fed, rice is grown in some areas

of the world, but only where rain is almost a daily occurrence. Rice will

not produce a profitable crop on stored soil moisture or infrequent rains

as will some other cereals. Senewiratne and Mikkelsen (1Wl) suggest

that differences in growth responses of flooded and unflooded rice may

be due to differences in auxin metabolism. They found that plants grown

under unfiooded conditions had a low catalase activity and a high

peroxidase activity which favored accelerated auxin degradation. They

suggested that high manganese levels in plants grown under unflooded

conditions affect the indoleacetic oxidase mechanism resulting in retarded

growth and depressed grain yields. Rice grown with ammonium nitrogen

(flooded) collected small amounts of manganese, whereas plants grown

with nitrate nitrogen (typical of upland rice) contained much more

manganese. Clark et al. (1957) “concluded that the better growth of

rice in submerged as compared to upland culture in at least some soils is

due to greater Mn availability under submerged soil conditions.”

A reliable source of comparatively salt-free irrigation water is required, The total amount required will depend upon seepage, average



74



C . ROY ADAIR, M. D. MILLER, AND H. M. BEACHELL



temperature, relative humidity of the air, and the amount and distribution

of rainfall, as well as the length of growing season of the variety being

produced. The amount varies from 1.5 to 3 acre-feet per acre in Arkansas

and Louisiana to 3 to 8 acre-feet in California (Adair and Engler, 1955).

A rate of %owequal to 1 cubic foot per second (450 gallons per minute)

for each 50 acres being irrigated is usually required to maintain water

levels in California rice fields ( Finfrock et aZ., 1960).

In the United States, irrigation water is diverted from streams or

is pumped from rivers, bayous, wells, lakes, or reservoirs. Water is

conveyed to the fields in canals. If a large canal serves many farms, as

in some areas in California, Louisiana, and Texas, the water is diverted

to lateral canals for each farm or small group of farms. The water

generally is turned into the top check of a field and flows through boxgates in the levee to reach each succeeding check. Some fields will have

a lateral canal down the side so that each check can be watered

separately.

The water must be relatively free of salts toxic to rice. The characteristics of irrigation water which determine quality include: total concentration of soluble salts, relative ratio of sodium to other cations, concentration of boron or other toxic elements, and under some conditions, the

bicarbonate concentration as related to the concentration of calcium plus

magnesium. According to Finfrock et al. (1960), the qualities to look for

in excellent to good water for rice irrigation are the following: specific

electrical conductivity, ( K x lo6) less than 750; boron, parts per

million (ppm) less than 1; S.A.R. Index (tendency to form alkali soil)

less than 10. Other points to consider are the initial salinity of the soil,

the effect of internal drainage while the soil is flooded, and the total

salt content of the soil.

The point of greatest importance is the nature of the soil solution or

saturation extract found in the zone of rice roots. If soil saturation

extracts have a conductivity index of 4 to 8 millimhos (mmhos) or more,

the yield of CALORO rice may be reduced 50 per cent (Pearson, 1958).

Rice seedlings are very sensitive to salinity during early development

but are progressively less so at 3 and 6 weeks of age (Pearson, 1958).

When soils are strongly saline, having an excessively high concentration

of sodium, calcium, or potassium, the concentration of salts in the soil

solution (including the standing water) may be so great that it will

injure or kill the seedling rice (Pearson and Ayers, 1960). Excessive salt

concentration results in restriction in downward percolation. Therefore

the flood water is subject to a longer period of evaporation with an

ensuing increase in salt concentration. Thus water having a higher salt



RICE IMPROVEMENT AND CULTURE IN UNITED STATES



75



concentration enters the soil, and the concentration of the soil solution

is increased.

Flooding, draining, and reflooding before seeding will help prevent

such injury on fields known to give difficulty. Prompt draining and

reflooding seedling stands in difficulty has usually corrected the condition.

In Arkansas, the continued use of water from shallow wells, which may

contain 75 ppm. of calcium and 22 ppm. of magnesium, for several years

may change the soil reaction from acid (pH 5) to alkaline ( pH 8 ) . Hall

(1959) reported that the condition can be corrected to some extent by

alternate flooding and draining at about weekly intervals and by applying

nitrogen fertilizer.

When the rainfall is below normal, the amount of water pumped

for rice from a bayou near the Gulf Coast may be more than the flow

of the stream. In this case, brackish water may encroach from the Gulf.

Quereau (1920) and Fraps (1909, 1927) reported the effect of brackish

water on the growth of rice. The damage depends on the concentration

of salts in the water, the time the salt water is applied, the length

of time the injurious water is used, the amount of rainfall, and the

variety of rice. In addition to causing a loss in yield of rice, the excessive

use of salt water or the continued use of salt water for several years

may deflocculate the soil so that stickiness, compactness, and impermeability increase and the soil is hard to cultivate.

California experience has shown that rice culture is useful in the

reclamation of saline soils, provided the fields to be reclaimed are first

well drained. Mackie (1943) reported that one rice crop grown on

Imperial clay near ImperiaI reduced the saline content 72 per cent to a

depth of 6 feet. In his experiments he found the usual reduction in saline

content from the first rice crop to be one-third to two-thirds.

The temperature of the irrigation water should be not less than

70°F. or more than 85" for best results. Raney (1959) showed that the

critical seasonal threshold of water temperature for normal growth of

CALORO rice was near 69". If the mean temperature is 5" lower, maturity

is delayed 30 days beyond the normal 160 days. Rice yield was highest

when the mean water temperature was 80". At water temperature above

85", yield was reduced, and root development was poor, probably

because of the low oxygen content of the water.

Ehrler and Bernstein (1958) reported that at a constant root

temperature of 64.4"F. CALORO shoot growth was twice that at 86" and

root growth one and a half times as great; however, grain yield was only

three-fourths as much at the lower root temperature. No significant

interaction was found between root temperature and cationic concentration or cationic rates.



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C. ROY ADAIR, X I . D. MILLER, A h 3 H. M. BEACIIELL



Seeds germinate slowly when the temperature is less than 70°F. The

temperature of water from rivers in northern California and shallow wells

in some southern States may be 65" or lower. This temperature will retard

and lower the germination of rice sown in the water and retard the

development of plants so that the stand may be thin and late near the

inlet to the field. According to Raney et al. (1957), field studies over a

3-year period showed that plant-free warming basins, 6 to 12 inches

in depth, equal in size to 2 per cent of the area to be served, successfully

raised the mean water temperature of 60" water to 70".

Water management systems vary widely, depending upon method

of seeding, soil type, climate, crop rotation, diseases, and insects.

Methods of irrigating rice in Texas vary widely, according to Reynolds

(1954). Where rice is drilled, the fields may be flushed for germination.

Thereafter the drilled rice is irrigated for the first time when the plants

reach a height of 4 to 6 inches. At this time water is applied to a depth

of 1to 2 inches and is gradually increased to 4 to 6 inches as the plants

increase in height. The water then is held at 5 inches until drained for

harvest. Water may be drained once or twice during the growing season

for fertilization and pest control. M'here rice is sown in water, some

growers drain as soon as possible after seeding; others may delay draining

as much as 36 hours. After the seedlings are well established, the

practices are essentially as outlined for drilled rice.

\Vater management is very similar in Louisiana and Arkansas. In

Louisiana, water seeding is not common, but where it is practiced, the

water is drained when the rice seedlings are 9 inch long ( Wasson and

Walker, 1955). It then is allowed to grow until flooding is needed.

Drilled rice may be flushed if necessary for uniform germination. Normally the rice is not flooded until it is 6 to 8 inches tall, and then only to

a depth of 4% inches. Fields are drained as necessary for top-dressing

with fertilizer and for pest control.

In California, where japonica-derived varieties predominate, rice

fields normally are flooded to a depth of 6 to 8 inches just before seeding

and seeded by air with soaked seed. The water is maintained at that

depth until drainage for harvest. Water may be lowered to about a

3-inch depth for weed control and at stand establishment time during

cool weather.

Good drainage, including winter rain water, of rice fields is necessary

for several important reasons. Spring plowing and fall harvest are

expedited by good drainage. Crops grown in rotation with rice may be

damaged by impounded water from rains or irrigation if provision is

not made for proper drainage. Drainways around and through the field

that connect with main drainage ditches leading to natural drainage



RICE IMPROVEMENT AND CULTURE IN UNITED STATES



77



channels are essential. These ditches should be of sufficient size and

depth to allow the removal of large quantities of water quickly.

The time to drain the water before harvest varies with the soil type,

rice variety, weather conditions, and drainage system. The water should

be drained when the panicles are turned down and the grains at the

tips of the panicles are ripe and those at the base of the panicle are in

the hard-dough stage. This stage ordinarily is about 2 weeks before the

crop is mature. When drained at this stage, there usually will be

sufficient soil moisture so the rice matures normally, and within 2 weeks

the soil will be firm enough to support the harvesting machinery.



E. SEEDINGRICE

1. Quality and Treatment of the Seed

The choice of seed is an important part of rice culture. To achieve

top yield, the variety to be grown must be adapted for the area. This

is discussed in Section V, C. After deciding upon the variety, it is

necessary to select a lot of rice that is free from varietal mixtures, does

not contain red rice and weed seed, is high in percentage of viable seeds,

and has high bushel weight. The seed requirements have been discussed

by Jones et aE. (1950,1952) and Finfrock and Miller (1958).All rice-producing States have a rice seed certification program designed to provide

high quality seed for the rice industry.

The seed should be treated with a fungicide to control seedborne

diseases, and with an insecticide in areas where there is likely to be a

heavy infestation of rice water weevils. In California, soaking seed in a

sodium hypochlorite solution (5.25 per cent by weight) at the rate

of 1 gallon per 100 gallons of water is recommended as a seed protectant

and to deactivate germination inhibitors located in rice hulls.

Mikkelsen and Sinah (1961) reported the presence of six compounds

in the hulls that inhibit germination of CALQRO rice. When present

in large amounts, these compounds diffuse into the embryo and inhibit

germination. Compounds identified include vanillic acid, ferulic acid,

p-hydroxybenzoic acid, p-coumaric acid, p-hydroxybenzaldehyde, and

possibly indoleacetic acid. In low concentrations, these chemical substances prove stimulatory to germination and ensuing growth. Leaching

the seed by soaking with water reduces the concentration to stimulatory

levels. The probable action of sodium hypochlorite solution is to modify

these inhibitors, so that seedling growth is stimulated.



2. Methods of Seeding

Several methods are used to seed rice in the United States. It may

be sown with a grain drill much the same as other small grains, sown



78



C . ROY ADAIR, M. D. MILLER, AND H. M. BEACHELL



broadcast on dry soil and disked or harrowed to cover, or sown in water

by airplane. On nonsubmerged soil, the rice is sown 1% to 2 inches deep.

The field may be flushed and drained immediately to provide moisture

for germination or there may be sufficient moisture in the soil or from

rain for germination and seedling growth. When drilled rice is imgated

before emergence, the water is drained immediately because the rice

seedling cannot emerge through 1 to 3 inches of soil and thence through

4 to 8 inches of water. Several modifications of the water-seeding method

are used.

In California, the usual practice is to soak the seed for 18 to 24 hours,

drain for 94 to 48 hours, and seed in the water. Seed rice will absorb

the maximum amount of water in 18 to 24 hours. In Arkansas, rice sometimes is sown in water. When this is done, the fields are flooded to a

depth of about 6 inches just before seeding. Dry seed is then sown by

airplane, the water being maintained at a constant level for about 5

weeks; then it may be drained off to apply fertilizer or to control root

maggots. In Texas (Reynolds, 1954) and sometimes in Louisiana, a

water-seeding method that is different from the method used in California

or Arkansas is used. In this method, which generally is used on clayey

soils, a rough seedbed is prepared and levees are constructed. The field

is flooded with enough water to cover the soil. The soil is then tilled with

a spike-tooth or disk harrow, and sprouted seed is sown immediately.

The soil suspended in the water lightly covers the seed when it settles

out of the water. The water is drained from the field within 12 to 24

hours. In 7 to 10 days after draining, the field is reflooded to a shallow

depth; and as the seedlings develop, the depth of water is increased

gradually to 5 to 6 inches.

When rice is sown with a drill in clayey soils in Texas, it is seldom

sown over 1 inch deep and is flushed as soon after seeding as possible. In

sandy loams, the rice is sown 3 or more inches deep and cultipacked

immediately to conserve soil moisture. Frequently a harrow or a rotary

hoe is used to break the crust to allow the rice to emerge. Water is not

applied until the rice is 30 or more days old.



3. Time and Rate of Seeding

Most rice in the southern States is sown from April 1 to May 30,

but occasionally some fields are sown in late March and others as late

as June 30. When rice is sown early while the soil or the water is relatively

cool, it is subject to very slow germination and to rotting, so the seed

should be treated with a fungicide. Seed germinates more quickly if

sown later when the soil or water temperature is more nearly optimum.

Date-of-seeding tests reported by Jenkins ( 1936), Adair ( 1940), Jodon



RICE IMPROVEMENT AND CULTURE IN UNITED STATES



79



(1953), and Reynolds (1954) show that there is a comparatively long

seeding period for rice in the South. Most farmers take advantage of

this fact to spread the work load both at seeding time and at harvest. By

doing this, they can also make better use of the available irrigation

water, especially if a well is the source of irrigation water.

In California, the period for seeding rice is more restricted than in

the South. Some rice is sown in California soon after April 1 and some

as late as June 15, but most of it is sown from April 15 to May 15 (Finfrock and Miller, 1958). When rice is sown as late as May 30 in California, it should be fertilized at a moderate rate and a short-season variety

such as COLUSA preferably should be grown.

In the South, the seeding rate is about 90 to 100 pounds per acre

when drilled and 110 to 140 pounds per acre when sown broadcast on

dry soil or in the water. In California, seeding rates when sown in the

water average about 150 pounds and range from 125 to 200 pounds

(dry-weight basis) per acre. Rice seeds average 15,000 per pound; with

a seeding rate of 150 pounds per acre, seeds are sown at the rate of 50

seeds per square foot. Excellent yields have been reported, from plant

populations ranging from 8 to 30 per square foot. Seeding rates between

these extremes apparently do not influence yields. Extremely dense

stands lodge more readily than optimum stands. Rice in denser stands

heads and matures more uniformly than thinner stands with abundant

tillering. The higher seeding rates usually are used on old land.



F. CROPFERTILIZATION

1. Commercial Fertilizers

Fertilizers were not commonly used for rice in the United States

until comparatively recent years. Allston ( 1854) reviewed rice-fertilization practices up to about 1850. He reported that it was a fairly

common practice to return the rice straw and chaff to the rice fields and

to apply farmyard manure. At about that time some rice growers started

to use lime ( 100 bushels an acre) and to apply rice-flour (bran) between

the rows prior to the “long-flow.” Knapp (1899) reported that an

application of 300 pounds of cottonseed meal, 150 pounds of acid

phosphate, and 50 pounds of kainite plowed under before seeding

increased the yield of grain and straw 25 per cent in Louisiana.

Chambliss and Adams (1915) and Chambliss (1920b) do not mention

the use of fertilizer for rice in California. Jones ( 1923), Dunshee (1928),

and Davis and Jones (1940) report results of rice fertilizer experiments

with good response to nitrogen. Jones et al. (1950) and Davis (1950)

recommend ammonium sulfate at rates up to 250 pounds, 50 pounds of

nitrogen an acre applied before flooding to 65 days after seeding.



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