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III. Recent Developments in Fertilizer Use

III. Recent Developments in Fertilizer Use

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It is apparent that no substantial progress was made in increasing

corn yields in this area from 1909 to 1945. Cotton and tobacco yields,

however, began an upward trend during the thirties and for the 1941-1945

period were 171 and 134 per cent, respectively, of the 1909-1913 yields.

Increased per acre applications of fertilizer to cotton and tobacco has

been an important factor in increasing the yields of these crops. It would

be expected that in this region of favorable climatic conditions for corn

production higher rates of fertilization should also result in increased

corn yields. The importance of increased corn yields in the Southeast is

emphasized.by the fact that approximately one-third of the crop acreage

is devoted to corn, which is not greatly different from the proportion

of land planted to this crop in the Corn Belt.

Volk (1942) estimated that 65 per cent of the land in Alabama

planted to corn would produce about 11 bushels per acre without applying

nitrogen, and that only 12 per cent of the acreage would produce 30

bushels or more without adding this plant nutrient. Jones (1942), summarizing 12 years’ results from seven experiment fields in Alabama,

showed that the increase in yield due to increments of nitrogen was nearly

a linear response up to 36 lbs. of nitrogen per acre. At that time, very

few experiments in which high rates of nitrogen were used had been conducted, and most of the tests employed open-pollinated varieties of corn

with relatively wide spacing of plants. Generally, the genetic 1imitat.ion

of open-pollinated varieties combined with a low number of plants per

acre had concealed the possibilities of fertilization in the few cases where

high rates had been used.

Volk (1944), however, reported results from 15 tests in Alabama conducted cooperatively with farmers, which showed substantial increases in

corn yields for each 15-lb. increment of nitrogen from 0 to 75 lbs. per

acre. The potential for high yields was pointed up when Krantz (1945)

reported an increase from 19 bushels per acre without nitrogen to 107

bushels of corn with 120 lbs. of nitrogen added to Norfolk sandy loam.

Cummings (1947), summarizing 3 years’ results of 38 fertilizer tests in

North Carolina with corn, reported average yields of 28, 50, 68, and 78

bushels per acre from plots receiving 0 , 40, 80, and 120 lbs. of nitrogen,

respectively. All plots received adequate phosphate and potash and were

planted to adapted hybrids with 9,000 to 10,000 plants per acre.

Investigators in Georgia, Mississippi, and North Carolina (Brooks,

1948; Jordan, 1947; Krantz, 1947) demonstrated the need for an adequate

number of plants per acre with high levels of fertilization for maximum

yields. Krantz (1947), using spacings of 4,000, 9,000, and 12,000 plants

per acre in one experiment, obtained per acre yields of 53, 82, and 93

bushels, respectively. Brooks (1948) found that there was no yield



increase for spacings above about 10,000 plants per acre, even when

fertilized with adequate phosphate and potash and rates of nitrogen up

to 150 lbs. per acre.

In the Georgia tests, maximum yields ranged from 78 to 117 bushels

per acre at different locations, and increases were obtained for rates of

nitrogen up to 90 lbs. per acre. I n the North Carolina tests, nearly linear

response was obtained to rates of nitrogen up to 120 lbs. per acre when

fair to good moisture condiTions prevailed. Similarly, Jordan (1947)

showed increases in yields of corn from rates of nitrogen up to 120

pounds per acre a t several locations in Mississippi. In most of the experiment,al work on high rates of fertilization for corn, nitrogen has been

the nutrient producing most of the spectacular increases. The results

from Georgia, however, show that either phosphate or potash may be as

limiting as nitrogen on some soils. At one location, a 40-bushel increase

was obtained for the application of 60 Ibs. of PzOs per acre. Likewise,

a t one location, a 32-bushel increase was attributed to the application of

60 lbs. of K 2 0 per acre. While only one experiment out of seven, in

1947, gave less than 30 bushels per acre increase for 90 Ibs. of nitrogen,

in most cases the increase duc to either phosphate or potash was less

than 10 bushels per acre.

Krantz (1947) pointed out the need for nutrient balance, although in

most tests nitrogen was the key to high yields. For example, Dunbar

sandy loam produced a 24-bushel increase for potash when high rates

of nitrogen wc3re applied, but no response to potash without nitrogen.

Conversely, a striking response to nitrogen was obtained when potash

was supplied, but no nitrogen response occurred without potash.

Striking crop response to high rates of fertilization is not restricted

to the southeastern states. Scarseth et al. (1943) showed that during

1939 yields of corn on Clermont silt loam in Indiana were increased from

11 bushels per acre without nitrogen to 71 bushels where 120 lbs. of

nitrogen per acre were applied. Likewise, yields on Vigo silt loam were

increased from 26 bushels without nitrogen to 91 bushels wit.h 120 Ibs. of

nitrogen. This is indicative of the response that may be expected under

some conditions in the Midwest. Results obtained by various investigators (Jones, 1942; Krantz, 1945; Ohlrogge et al., 1944) show that,

within the range in which nitrogen is a limiting factor, about one bushel

of corn is produced for every 2 Ibs. of commercial nitrogen applied.

Widespread interest in these experimental results and in corn fertilizer

demonstrations has been evident, but, the supply of nitrogen fertilizer

has been inadequate to meet the demand in recent years. Statistics are

not available to show to what extent the recent increased consumption

of fertilizers in the southeastern states is due to heavier fertilization of



the corn crop. From 1946 to 1948, however, the average corn yield for

the 7 southeastern stat,es previously mentioned was 129 per cent of the

yield during the 1909-1913 base period. This was the first significant

increase in corn yields in this area for over 30 years.

6. Use of Anhydrous Ammonia as a Fertilizer

Some of the advantages that have been suggested for using anhydrous

ammonia as a fertilizer, as compared with solid nitrogen materials, include (a) a cost approximately 50 per cent less than solid forms of

nitrogen, (b) immediate absorption by the soil, even at low moisture

content, (c) more uniform distribution, and (d) less expense in application under certain conditions.

Anhydrous ammonia is a gas at ordinary temperatures and pressure

and contains 82 per cent nitrogen. Thirty per cent aqueous ammonia has

also been used to some extent. At 100°F. the pressure over anhydrous

ammonia in a closed vessel is about 200 lbs. per square inch. It is in

liquid form under high pressures and changes to a gas as it is released

from the container.

Waynick (1934) claim the first attempt to apply anhydrous ammonia as a fertilizer material in surface irrigation water. The use of

anhydrous ammonia in irrigation water for citrus began in California

about 1934 and appears to have steadily increased until it is now a

widespread practice and is being used on a variety of crops in that state.

Chapman (1944) stated that anhydrous ammonia was being used in

California on practically every type of irrigated crop which requires

nitrogen fertilizat,ion. The field crops thus treated include cotton, corn,

barley, oats, wheat, flax, sugarcane, sugar beets, hops, and rice, as reported by various investigators. Among the fruit crops are citrus, nearly

all varieties of deciduous tree crops, and cane berries. Anhydrous ammonia has also been used on melons, carrots, onions, artichokes, tomatoes,

beets, and other vegetables.

Merrill (1948) estimated that 18,000 to 20,000 tons of anhydrous

ammonia were used in California during the 1947-1948 crop year. Anhydrous ammonia constituted about one-third of the total sales of

nitrogen for fertilizer in Arizona during t.he past crop season.

Since about 1944, the practice of direct application of anhydrous

ammonia to the soil has developed rapidly in California and in the

Mississippi Delta area. I n Mississippi, Louisiana, and Arkansas approximately 15,500 tons of anhydrous ammonia were used during the

1947-1948 crop year. Moat of this nitrogen was applied to cotton on

more than 600,000 acres of land a t an average rate of about 40 lbs. per

acre (Andrews et al., 1948; Garman, 1948,* Louisiana Dept. Agr. and



Immigration, 1948"). The indications are that a limited supply of

ammonia was hhe major factor in restrirting the wider use of this material

in 1948.

Waynick (1934) studied the behavior of anhydrous ammonia in

alkaline soils and found that the rate of nitrification was more rapid

than t.hat of ammonium sulfate.

The Arizona Agricultural Experiment Station (1945) reported that

the applicatior, of anhydrous ammonia to some soils raised the pH t o as

high as 9.5 immediately after treatment. I n these desert soils the pH

soon dropped to about 7.7, where it remained for a period, and nitrification proceeded a t a satisfactory rate. Anhydrous ammonia was nitrified

as readily as urea or ammonium sulfate in highly buffered soils. Ammonia applied in irrigation water was retained in the surface inch of

soil where it was readily nitrified.

Jackson and Chang (1947) studied the factors affecting absorption

of NH3 by soil by releasing ammonia gas into a beaker of soil which

was placed in a vacuum desiccator with suitable connections for aspiration, These investigators concluded that (a) soil of intermediate texture,

moisture content, and p H value will absorb 60 lbs. of nitrogen per acre

from NH, released a t a depth of only 1 to 2 inches, (b) a soil containing

only 6 per cent clay provided adequate sorption capacity for NH3,

(c) soils of high pH value with free calcium carbonate will retain 600 lbs.

of nitrogen per acre from NH3 released 2 to 4 inches below the surface,

and (d) air-dry soil absorbed instantly almost three times its own bulk

volume of NH3.

Chapman (1944) concluded that the major factors affecting the

evaporational loss of ammonia from irrigation water were soil permeability, temperature, and degree of agitation of the water. His results indicated that under most conditions losses would be under 10 per cent by

furrow irrigation. With high water temperahre and low soil permeability, however, losses may be of the order of 25 per cent. Dyke (1948)

pointed out that rather high losses of ammonia may occur by floodirrigation methods such as those used on rice fields. Kennedy (1944)"

studied the effects of concentrat,ion and drop size on losses of ammonia

applied in sprinkler irrigation water. He reported losses of the order

of 20 per cent.

Although few data are available on the efficiency of anhydrous ammonia in comparison with other sources of nitrogen in California and

adjoining states, there have been rather sat,isfactory yield increases from

this material. Rhoades (1948) " reported increases from the application

of anhydrous ammonia to wheat equivalent to those obtained from the

use of ammonium nitrate. When 30 lbs. of nitrogen were applied, the



average yield increases a t two locations were 9.9 bushels per acre for

ammonium nitrate and 13.4 bushels for anhydrous ammonia. According

to Garman (1948)*, a rice experiment in Arkansas showed a yield of

76.9 bushels from use of anhydrous ammonia and 72.7 bushels from

ammonium nitrate when each was applied a t t,he rate of 50 lbs. of nitrogen per acre.

Rather extensive field studies have been made by Andrews et al.

(1948) in Mississippi. These investigators reported that when 32 lbs. of

nitrogen were applied 4 inches deep as a side dressing anhydrous ammonia gave an average yield of 44.3 bushels per acre and ammonium

nitrate produced 42.8 bushels in 13 tests on corn. In similar tests with

cotton a t 18 different locations, anhydrous ammonia gave an average

increase in yiela of 296 lbs. of seed cotton per acre, as compared with

313 Ibs. for ammonium nitrate. Anhydrous ammonia was used successfully for preplanting application on oats, but some difficulty was experienced in making top dressings in the spring due to excessive soil moisture.

Leavitt (1948) * described the development of equipment for the introduction of anhydrous ammonia into irrigation water and for direct application to the soil in California. Approximately 15,000 steel cylinders of

150-lb. capacity are being used in that area to transport ammonia from

filling depots to the farm where the ammonia is metered into the irrigation water. A machine built especially for injection of anhydrous ammonia directly into the soil was adapted from a Killifer cultivator.

This machine has self-sealing injection shanks. I n the latest model, a

trailer with a 4,500-lb. capacity tank is attached behind the applicator.

In California the rate of application ranges from about 60 to 120 lbs.

of nitrogen per acre on the various crops.

Andrews et al. (1948) listed the specifications of equipment for storage

of ammonia, transportation to farms, and application to the soil in the

Mississippi Delta area. Anhydrous ammonia is transported from the

railhead or from storage tanks in 1,000-gallon field transport trucks from

which it is transferred to smaller tractor tanks of 80- to 110-gallon

capacity. These invest.igators point out that anhydrous ammonia has

been satisfactorily applied in the Delta area under the following conditions: (a) to prepared level land before planting, (b) to bedded land

before planting, (c) during the process of bedding before planting, (d)

during the planting operation, and (e) as a side dressing. Machines

have been designed to apply the ammonia in the soil 4 to 6 inches deep.

Applicators are specially designed knife-type openers with flat suctiontype points equipped with disc hillers or other apparatus for sealing in

the ammonia vapor.

The use of ammonia as a fertilizer will probably continue to expand



since it is a low cost source of nitrogen, and there appear to be no serious

mechanical difficulties in the application of either the anhydrous or

aqueous form to the soil.

3. Methods of Application

a. Furrow-Bottowh or “Plow-Sole” Placement of Fertilizers. Generally accepted principles which might be considered the basis for determining best methods of fertilizer placement have been described by the

National Joint Committee on Fertilizer Application (1948). Some of

the important factors affecting placement are (1) nutrient balance within

the root zone, (2) early stimulation of seedlings, (3) fixat,ion of added

nutrients by the soil, (4) suitable crop rotations to utilize available plant

nutrients to a maximum, (5) adaptation of methods to fit soil and plant

requirements, and (6) avoidance of high salt concentration in contact

with seed or roots.

Various advantages have been suggested for deep placement of fertilizer. It was t,heorized that (a) the fertilizer would be kept in a moist

zone of soil throughout the growing season, (b) band placement on the

furrow-bottom should reduce fixation of phosphate by the soil, (c) reduced nitrification of ammonia nitrogen by deep placement would decrease leaching losses during wet years and prevent upward movement

of the nitrogen during dry seasons, (d) possible injury by high salt concentration from larger amounts of fertilizer would be avoided, and (e)

the application of fertilizer before the rush season would give better

labor distribution.

Scarseth et al. (1943) proposed plow-sole application of fertilizer in

Indiana as a possible means of insuring ample plant nutrient supply,

particularly nitrogen, during dry seasons. They reported that up until

about 1939 response to small amounts of nitrogen applied in the row

or as side dressing to corn was uncertain. These investigators used

higher rates of fertilizer than were generally used in the fertilization of

corn in the Corn Belt a t that time and showed significant increases in

corn yields by supplementing row applications with furrow-bottom placement of additional nitrogen. These tests were not designed to compare

equal amounts of plant nutrients supplied by different methods. Essentially, these experiments showed that high rates of fertilizer would greatly

increase the yields of corn, particularly on the less fertile soils of the

Corn Belt. Furthermore, they showed t.hat good response to corn fertilization was possible during years of low rainfall. These investigation3

stimulated interest in deep placement of fertilizers throughout the Corn


Yoder (1945), reporting results on Wooster-Canfield silt loam in





Ohio, compared plow-sole application with row application and concluded

that plow-down fertilization was no more effective for corn than other

methods, even under extreme drouth conditions. I n these tests equal

amounts of plant nutrients were used by several methods of placement,

including combinations of row and plow-sole fertilization. Millar (1944)

reported ll-year averages of corn yields on Hillsdale sandy loam, showing that equivalent amounts of R complete fertilizer were more effective

when applied in the row at planting than when placed on the furrow

bottom or broadcast and plowed under. Caldwell et al. (1946) concluded from 3 years of tests on deep placement that this method was not

effective in Minnesota even during dry periods.

Rich and Odland (1947) concluded after one dry season and two

normal years that the usual band application was fully as effective for

silage corn in Rhode Island as plow-sole or other deep placement of all

or part of the fertilizer. These investigators pointed out that the rapid

early growth obtained by row placement lessened weed competition. In

placement tests in Nebraska with nitrogen on corn, Fitts et al. (1946)

showed that nitrogen applied a t planting time or last cultivation was

equally as good as furrow-bottom placement.

Volk (1946) pointed out that deep placement of fertilizer has been

long practiced in the southeastern United States, since farmers in the

Cotton Belt placed fertilizer in the “middle burster” bottom by hand

and bedded on it, many years before mechanical distributors were developed. Tests in the southern states, however, have failed to show that

deep placement of fertilizers for corn has any marked advantage over

row placement. Bartholomew (1948) reported that there was no consistent benefit from plow-sole application in 37 tests a t various locations

in Arkansas. Krantz (1948) found no difference between side-dressed

and plow-sole applications of nitrogen on corn in experiments in North


A limited number of tests has been conducted with small grain and

other crops. Smith (1947) failed to obtain response to nitrogen and

phosphate on winter wheat in Kansas from furrow-bottom placement,

although significant increases in yields were obtained when these fertilizers

were placed with the seed or when the nitrate was top-dressed in the

spring. Yoder (1945) concluded that all of the fertilizers for small grain

should be applied with the drill a t time of seeding, and Weidemann

(1943) reported that placing the fertilizer deep in the soil by plow-under

methods or deep drilling was not as effective on wheat yields as broadcasting and discing the fertilizer materials into the surface soil.

Experiments with soybeans on Miami loam in Michigan failed t o give

favorable increases for plowed-under applications of fertilizer, according



to Millar (1944). Karraker and Freeman (1944) failed to obtain any

benefit to yield or quality of burley tobacco from placing part of the

fertilizer on the furrow hottom as compared with row-side band placement.

Merrill (1948) pointed out that the best method of application of

fertilizers has been such a controversial matter that it has been very

difficult for the equipment manufacturer to develop new machines for

distributing fertilizers. Widespread interest in plow-sole placement encouraged farm equipment manufacturers to develop special fertilizer

distributors. It is estimated that a total of approximately 30,000 attachments for plow-sole application has been sold, principally in the Corn

Belt. The practice was most widely used in Wisconsin, Illinois, and

Indiana, but recent reports from the Corn Belt states reveal that many

of the fertilizer distributors developed for plow-sole applications. have

been discarded by the farmers. Interest in this method of placement is

apparently decreasing, as evidenced by the following record of sales of

one manufacturer of plow-sole fertilizer distributors:






Number of

distributors sold





Some of the disadvantages of furrow-bottom placement which have

been mentioned in various reports include (a) fertilizer is placed too

far below roots of small plants, (b) in cool, wet seasons conversion of

ammonia nitrogen to nitrate is too slow, (c) plowing operations are

interfered with, (d) distributors on the market have insufficient hopper

capacity and are adapted only to two-bottom plows, and (e) restricted

aeration in the fertilizer zone in some soils results in poor response to

plow-sole application.

Experimental findings to date show little or no advantage of deep

placement over conventional methods for most crops on which it has

been tested, when equivalent amounts of fertilizer are used.

b. Subsurface Placement of Fertilizers for Sod Crops. Agronomists

have been interested for a t least 20 years in the idea of subsurface placement of fertilizers and liming materials for sod crops. Rogers (1942)

found that appreciable losses of surface-applied fertilizer may occur

through runoff from pasture lands under certain conditions. It has been

commonly observed that poor growth is obtained from permanent pasture

sods during dry seasons. Furthermore, experimental data show that



phosphate fertilizer moves down in the soil very slowly. These observations suggest that there might be some benefit from subsurface placement

of this material as contrasted with the conventional method of surface


Before the development of suitable machines for subsurface placement

of fertilizers in grasslands, Midgley (1931) placed superphosphate in

knife grooves 4 inches apart and 6 inches deep in small plots of bluegrass

sod. He reported a 57 per cent increase in growth of the bluegrass over

surface application. An experimental fertilizer placement machine which

will place the fertilizer in sod crops in bands a t any desired depth from

about 2 to 9 inches and a t any spacing from about 6 to 32 inches was

described by Schroeder (1947).

Placement tests were conducted a t two locations by the Kentucky

Agricultural Experiment Station (1947)" in which phosphate from four

different sources was placed in bands 12 inches apart and 4 inches below

the surface. There were no beneficial effects the first year from placing

all of the phosphate below the surface. These tests did not include a

combination of surface and subsurface placement. More recently tests

have been initiated in Virginia, Kentucky, and Georgia which have included a split spplication with part of the phosphate on the surface

and part below the surface a t various depths and spacings, but results

are not yet available. Studies are under way in New York state using

the tracer technique with radioactive phosphorus to compare subsurface

placement of phosphate fertilizer with surface applications on permanent

pasture sods.

Drake (1948)" failed to find any benefit on alfalfa from subsoil

placement of part of the phosphate in bands 12 inches apart and 8 inches

deep over 'standard placement in Cecil clay loam during a dry season.

Caldwell et al. (1946) reported that broadcast surface applications of

fertilizer for alfelfa were as effective as plow-sole placement on Clarion

soil in tests in Minnesota. Reports from the North Carolina Agricultural

Experiment Station (1947)" did not show any benefit to alfalfa or to

a lespedeza-Dallis grass mixture from subsurface localized applications

of phosphate or potash fertilizers over mixing in the upper 4 inches of

soil or broadcasting on the surface. I n this test the subsurface treatment

was the application of 90 per cent of the fertilizer a t a depth of 4 inches,

with the remaining 10 per cent applied to the surface. Parberry (1946),

however, reported that a 400-lb. per acre application of superphosphate

placed 1 inch below the surface of a brown iateritic soil in Australia was

definitely superior to surface applications in stimulating ryegrass yields.

Placement a t the l-inch depth was as good as 2- or 3-inch placements.

Brown and Munsell (1938) found that limestone applied on the sur-



face a t the rate of 2 tons per acre to a fine sandy loam had penetrated

to a depth of 6 inches in a pasture sod after 10 years. They concluded,

however, that the rate of penetration was sufficient to make surface

application to grassland an effective and efficient method of liming.

Pohlman (1946), using glazed tile cylinders, showed that liming the

16-24 inch layer of Gilpin silt loam tripled the yield of alfalfa when

the surface 0-8 inches had a pH of 5.6. Maximum yields were obtained

when the entire 0-16 inch layer was limed to neutrality. A 50-per cent

increase in root growth in the 16-24 inch zone was obtained by liming

this layer.

I n tests conducted by the North Carolina Agricultural Experiment

Station (1947) ,+'either eubsurface placement of limestone or mixing the

liming material with the surface 4 inches of soil was superior to surface

placement on alfalfa.

Experimental findings thus far on subsurface placement of fertilizers

for sod crops do not consistently show an advantage for this method.

Possibly, Volk's (1946) observation that plants appear t o be able to

take plant nutrients from a soil zone the moisture content of which is

below wilting point, if some of the plant roots are in a moist medium,

may be related to this problem. The need for more fundamental studies

on root distribution and plant nutrient feeding a t various moisture levels

is apparent.

c. Application of Fertilizers in Irrigation Water. Various liquid fertilizer materials have been applied through irrigation waters, including

both anhydrous and aqueous ammonia, phosphoric acid, sulfuric acid,

sulfur dioxide, ond water solutions of various carriers of nitrogen and

phosphate, as well as mixed fertilizers.

The application of fertilizer in surface irrigation wat,er, according to

Proebsting (1948),* started in California about 30 years ago; and McGeorge (1948)* reported that it began in Arizona about 1933. The practice, however, has become reasonably widespread only within the last 5

years, as indicated by statistics on liquid fertilizers compiled by the

California State Department of Agriculture (1947). The combined

amount of liquid mixed fertilizer and phosphoric acid used in California

increased from about 2,000 tons in 1943 to over 13,000 tons in 1947. I n

addition, a large tonnage of anhydrous ammonia was used in that state

during the 1947-1948 crop year, most of which was applied in irrigation

water. During the first quarter of 1948, approximately $750,000 was

spent in California for liquid mixed fertilizer, although plant nutrients

in this form cost approximately 4 times as much per unit as in solid

materials. This represented about one-sixth of the total expenditure for





mixed fertilizer during these 3 months, according to the California State

Department of Agriculture (1948).

McCollam and Fullmer (1948) reviewed the history of the use of

fertilizer solutions in California from 1923, when the first liquid fertilizer

plant was built, to 1948 when 30 companies were distributing fertilizers

in “liquid” form. They pointed out the following developments in the

compounding of liquid mixed fertilizers: (a) nitrogen is generally added

in the forms of ammonium nitrate, nitrogen liquors, urea, and potassium

nitrate; (b) phosphorus is added almost exclusively as phosphoric acid,

with some ammonium phosphate being used; and (c) muriate of potash

and potassium nitrate are used as sources of potash.

One manufacturer sold for agricultural use 5,500 tons of 53-per cent

phosphoric acid during 1947 and approximately 6,000 tons in 1948. The

largest tonnage was applied in California and most, of the remainder in

Arizona, Utah, and Colorado.

Records of the Arizona Fertilizer Control Office (1948) show that 11

registrants listed 36 products for sale as liquid fertilizer in that state

during 1947. -4side-dressing service by which any desired fertilizer mixture can be applied t,hrough irrigation waters is the latest development

in Arizona (McGeorge, 1948)*. These mixtures are usually made from

“simples” which are mixed a t the time of application in the water a t the

irrigation ditch.

The Washington State Department of Agriculture (1948)* reported

statistics showing that 23 per cent of the nitrogen sold as straight nitrogen

materials in that state during the 1946-1947 crop year was in the form

of liquid ammonia which is assumed to have been used in irrigation water.

Although Jones and Green (1946) did not report supporting data,

they stated that, phosphorus added as phosphoric acid in irrigation water

penetrated the root zone of such crops as citrus, sugar beets, and alfalfa

and tended to convert native soil phosphates to more available forms.

Chapman et al. (1945) concluded that experimental findings did not

show a sound basis for the use of sulfur, sulfur dioxide, sulfuric acid, and

other acidifying agents in California citrus groves. Surveys by Smith

(1946) and Turnell (1948), however, indicated widespread interest in

this practice and rather extensive use of sulfur for acidifying soils in some

of the western states.

Fertilizers are applied through sprinkler irrigation in the Willamette

Valley, according to Powers (1947). He has stated also that the fertilization of mint in Oregon through irrigation water is a general practice.

The addition of fertilizer to pastures through irrigation in the coastal

area of Oregon and Washington is becoming increasingly important.

King et al. (1943) in Oregon, Nissley (1946) in New Jersey, and Davis

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III. Recent Developments in Fertilizer Use

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