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IV. Methods of Chemical Analysis

IV. Methods of Chemical Analysis

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324



DALE E. BAKER AND LEON CHESNIN



50% error. From results for six sewage treatment plants of Pennsylvania

being sampled every 2 weeks, prepared and analyzed in duplicate, a 50%

coefficient of variation over time appears to be a realistic goal for a composite sample from a treatment plant.

In a discussion of the criteria for judging acceptability of analytical

methods, McFarren et al. (1970) point out that a method must be sufficiently precise (measured by coefficient of variation within one laboratory)

and sufficiently accurate (mean error from collaborative studies) if the

results are to be sensible and unbiased. Generally the results for trace elements are biased on the positive side especially when their concentrations

approach the detection limit of the procedure. The total error is defined

as the sum of two standard deviations plus the mean error expressed as

a percentage of the “true” value. Excellent methods have total errors of

25% or less; acceptable methods have total errors of 50% or less; and

unacceptable methods have total errors greater than 50%. McFarren et

al. (1970) concluded that atmic absorption spectrometry was acceptable

for the determination of Zn, Cr, Cu, Mg, Mn, Fe, and Ag but unacceptable

for the determination of Pb and Cd.

Adequate definitions of precision and accuracy are difficult (Murphy,

1961), especially when applied to an overall process or a “system of

causes” including the material, operator, instrument, laboratory and day.

Verification of the precision or accuracy is another measurement process

distinct from the one existing for the purpose of testing materials on a

routine basis. Chow et al. (1974) report a study in which prepared unlabeled samples of sea water were standardized for Pb at one university

by isotope dilution and circulated among participating oceanographic laboratories at seven United States universities and one in the United Kingdom. None of the laboratories obtained reliable values by either atomic

absorption or anodic stripping voltammetry.

B.



INSTRUMENTAL

METHODS



Whitney and Risby (1975) suggested that methods of analysis should

be judged on the basis of seven factors: (1) required sensitivity, ( 2 ) accuracy of the method, (3) presence of interferences, (4) time per sample,

( 5 ) number and technical skill of laboratory personnel required, ( 6 ) required use of standard or reference methods, (7) cost per sample. Their review included 224 references providing an excellent summary of the current

status of optical, electrochemical, neutron activation, and chromatographic

methods. For optical methods, theoretical considerations are presented

for colorimetry, spectrophotometry, atomic fluorescence specrtrometry,

X-ray fluorescence spectrometry, and atomic absorption spectrometry.

Electrochemistry techniques are discussed for polarography, anodic strip-



325



CHEMICAL MONITORING OF SOILS



ping voltammetry, and ion selective electrodes. No one technique will enable the analysis of all desired elements and simultaneously solve problems

associated with all factors above. The choice of a method involves a series

of compromises. Whitney and Risby developed a system of factor weightings to compare methods for first row transition metals. With respect to

Zn, for example, on a scale of 0 for poor to 100 for excellent methods,

colorimetry was given a value of 90 for cost per sample, 62 for sensitivity,

and only 55 for technical skill and number of personnel; while Zn by

atomic absorption spectrometry rated 92, 98, and 75 for the respective

factors. When sensitivity and accuracy weightings were readjusted to three

for sensitivity and accuracy and five for interferences, the results presented

in Table VII were obtained. Morrison and Pierce (1974) and Lisk ( 1974)

have reviewed methods of analyses of trace elements. The review of Lisk

was especially valuable in that specific references are included for several

instrumental methods and their applications for different elements. Because

of the valuable contributions by Walsh (1971), Whitney and Risby

( 1975), and Lisk (1974), a discussion here of the theoretical aspects of

the various methods seems unnecessary.

The results presented in Table VII and developments in flameless atomic

TABLE VII

Results of an Unequal Weighting of Factors Considered Important in the Analysis

of First Row Transition Metals”

Method

Colorimetry

Spectrophotometry

Atomic fluorescence

spectrometry

X-ray fluorescence

spectrometry

Atomicabsorption

spectrometry

Polarography

Anodicstripping

voltammetry

Ion selective

electrodes

Neutronactivation

analysis

Chromatography



Sc



Ti



V



Cr



Mn



Fe



Co



Ni



Cu



Zn



- 65.0 70.0 - 72.4 72.4 - 69.6 75.0 72.4

67.5 71.5 75.1 76.5 78.9 76.5 71.5 73.9 80.5 75.3

- 81.7 81.7 89.7 89.3 88.7 89.1 84.1 89.7 90.7

-



- 76.3 78.7 74.9 78.3



-



80.3 80.3 80.3



81.8 87.0 87.2 91.8 91.8 89.2 89.0 86.6 91.0 91.4

83.7 83.7 83.7 86.1 86.1 86.7 87.7 87.5 83.7 88.7

89.3 89.3 89.3 89.3 89.3 89.3 89.3 89.3 89.3 89.3



-



-



-



-



-



-



-



-



78.0



-



74.8 72.2 79.8 79.8 79.8 76.4 79.8 62.2 79.8 19.8

81.3 81.3 85.9 81.3 81.3 81.3 81.3 86.3 86.3 81.3



a R. G. Whitney and T. H. Risby, “Selected Methods in the Determination of First Row

Transition Metals in Natural Fresh Water,” Pennsylvania State Univ. Press, University

Park, Pennsylvania, 1975.

bZero rating = poor; 100 = excellent. Methods of equal or maximum ratings are

italicized.



3 26



DALE E. BAKER AND LEON CHESNIN



absorption spectrometry explain the popularity of this method for trace

element analysis. Flameless atomic absorption has been useful for about

60 elements and is especially useful where sample size is limiting. For example, Cd may be determined on the kidney of a single chick or mouse.

Spectrographic methods have been used extensively for plant analysis

work involving several essential elements, Mitchell ( 1956) described arc

emission spectrographic methods, and Jones and Warner (1968) and

Baker et al. ( 1964) described procedures for direct-reading spark emission

spectrographs. The direct-reading spark emission spectrograph has the advantage that it is possible to determine concentrations of several elements

simultaneously. The precision of the method using rotating disk electrodes

is acceptable when the matrix of the samples remains relatively uniform

as with plant samples. Several of the principles of soil testing and plant

analysis with respect to essential macro and trace elements (Walsh and

Beaton, 1973) are applicable to other metals and compounds. Kopp and

Kroner (1965) determined 19 trace elements in natural water with a

direct-reading spectrochemical procedure. The elements determined were

Ag, Al, As, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Mo, Mn, Ni, Pt, Pb, Sr, V,

and Zn. Concentrations in processed samples were in the order of 0.01-100

ppm. While the sensitivity for most of the elements was satisfactory for

detecting potentially toxic elements in agricultural chemicals added to cropland it would not be adequate for most of the trace elements in soil testing

solutions. The echelle grating spectrometer (Matz, 1973) with the argon

plasma jet for atomization and excitation of elements or the use of the

argon plasma jet with conventional emission spectrographs may prove satisfactory for multielement analyses where sensitivity is important and freedom from interferences and wide concentration ranges are encountered.

Neutron activation analysis received relatively low ratings in Table VII

because of technical skill and laboratory personnel requirements. However,

when these services are available, the method is extremely sensitive for

several elements (Haskin and Ziege, 1971 ; Koloczkowski and Jester,

1973). Morrison and Potter (1972) obtained quantitative and qualitative

results for 3 1 elements using chemical group separations and high-resolution gamma spectrometry. The method was used at The Pennsylvania State

University to determine the relative amounts of elements in several samples

to help with the decision regarding which elements present in sewage sludge

should be monitored routinely.

Although gas chromatography is used extensively for the determination

of organochlorine and other pesticides, techniques are being developed for

its use in metal analysis (Chesters et al., 1971; Serravallo and Risby,

1974). With respect to soil monitoring, however, the technique has been

most useful in pesticide residue analysis. Taylor (1970) described the theory and design of columns for the separation of pesticides by order of



CHEMICAL MONITORING OF SOILS



327



their vapor pressures. Identification techniques and principles of gas

chromatography have been published by Leathard and Shurlock ( 1970).

The fundamental principles of retention and column selectivity are

emphasized.

References to other analysis methods will be discussed with the specific

elements. The tendency among analytical laboratories is to seek greater

and greater sensitivity for each analysis. Although greater sensitivity is desirable when the existing sensitivity is inadequate €or detecting significant

levels of biological activity, the preparation of a larger sample could often

be a realistic alternative to the use of more sensitive methods. However,

it must be realized that interference problems are greater for more concentrated samples. For methods, such as flameless atomic absorption, anodic stripping voltammetry, neutron activation analysis, X-ray fluorescence,

and gas chromatography, which allow the use of relatively small samples,

the accuracy is determined largely by the use of “clean-room” techniques

and finally the competence of the analyst with respect to preparation of

solutions, use of instruments, and evaluation of the data. Once methods

have been made operational, quality control must be an essential part of

the routine laboratory operations; and periodic reevaluation of methods

and techniques should be provided for. Standard reference materials including orchard leaves and bovine liver, available from the National Bureau

of Standards (Table VIII), are most useful in determining the overall accuracy of a method. For trace element analysis such as that for Mo by

some spectrographic methods (Baker et al., 1964) and for Cd in plants

and sewage sludge by flame atomic absorption without background correction, the precision can be very good and yet the accuracy may be in error

by 100 to 1000% of the true value. These are the errors of concern to

Chow et al. (1974). Standards or limits set on the basis of erroneous results are not very useful. For example, if biological material from control

treatments are reported to contain 10 times their actual concentrations of

a toxic metal and the treatment causes an increase of 10 times the control,

then the biological change being induced into the food chain would be

up to 100 times the true value for the control.



V.



Monitoring of Macroelements



A.



SOLUBLE

SALTS



Elements present in macro amounts in soils and considered essential

for plants are N, K, Ca, Mg, P, S, and Fe, whereas sodium chloride is

required in macro amounts only by animals. Because of this requirement,

the relative abundance of Na in animal wastes is greater than in most soils.



328



DALE E. BAKER AND LEON CHESNIN



TABLE VllI

Biological Standards of the U.S.National

Bureau of Standards"



Element

I

F

L



Orchard leaves,

SRM-1571

(PPm)



Cr

Cd



(4Y

(14)

(2.3)

0.11 f 0.02



Zn



25 k 3



Pb



45 k 3



Se



0.08 k 0.01



Te

cu

Mo



12f2



Bovine liver,

SRM-1577

(PPm)



0.28 f 0.04 IDSSMS

0.27 f 0.04 ATA

0.25 f 0.06 POL

126 k 1 I IDSSMS

127 k 6 NAA

133 f 2 ATA

0.36 f 0.08 IDSSMS

0.31 k 0.08 POL

1 . I 2 k 0.04 NAA

1 . I 1 k 0.04 IDSSMS

L



k 12 IDSSMS

193 k 8 ATA

193 k 3 IDMS

184



3.23 f 0.26 IDSSMS



SRM, standard reference material; IDSSMS, isotope dilution-spark-source spectrometry; ATA, atomic absorption ;

POL, polarography; NAA, neutron-activation analysis; IDMS,

isotope dilution-mass spectrometry.

* Values in parentheses are tentative.



The monitoring of sodium chloride and other soluble salts in soils has been

adequately developed. An excellent bibliography for the period 1965 to

1970 is available as Serial Number 1425 from the Commonwealth Bureau

of Soils, Harpenden, England.

Chesnin et al. (1 975) stated that salt is the most serious pollutant of

animal manure in western states where irrigation and dry-land farming is

practiced extensively and where salt balances in the soil are critical to plant

growth and economic agricultural food and fiber production. High levels

of salt are fed to cattle to stimulate appetite, increase water intake to prevent the formation of urinary calculi, and to save labor through self-feeding. Rations for self-feeding involving salt additions to control the amount

of feed consumed by dairy and beef cattle contain as much as 5-9% salt.

In Colorado some cattle are being fed 10-100 times more salt than is



CHEMICAL MONITORING OF SOILS



329



needed to achieve optimum gains. Most of the salt is eliminated in the

urine of the animals, and a smaller amount is in the feces. Under feedlot

or confined feeding conditions, the solid or slurry wastes can be relatively

high in salts. Samples of feedlot manures (Table IX) from the desert

Southwest confirm the high salt and Na content of these wastes. The soluble

salts in feedlot wastes range from 4.2 to 14.3% (Chesnin et al., 1975).

The Na content of feedlot manure usually ranges from 0.3 to 2.8%. Usually the soluble salt fraction of feedlot manure is dominated by K, which

exceeds Na content by about 10-fold. Manure content of K ranging from

1.2 to 10.7% on a dry matter basis is also dependent on the amount of

urine present in the waste. According to Miner (1971), K in dairy cattle

manure ranged from 0.34 to 3.0% on a dry basis, which is lower than

the range indicated above for beef cattle feedlot manure. Since less salt

is fed to dairy cattle and self-feeding of high salt rations is not a common

practice, Na in dairy cattle manure is generally lower than in beef cattle

manure.

In a study of the composition of chicken manure collected in southern

California, Bell ( 197 1 ) found that the average salt content of 40 samples

was 6.15% . The salt content of poultry manure is generally less than that

of beef cattle manures in a feedlot environment. Poultry rations tend to

be low in salt content, and this is evident in the manure (Table X). K

content of poultry manure is higher than that of Na (Chesnin et al., 1975).

TABLE IX

Some Chemical Characteristics of Feedlot Manure

from the Phoenix, Arizona Area0.b



Moisture



Ash



Total

soluble

salts



Sample



PH



(%)



( %)



( %)



( %)



Feedlot 1

Feedlot 2

Feedlot A

Feedlot B

Feedlot C

Feedlot D

Feedlot E

4 Feedlots X

Range

Average



6.7

7.4

7.3

7.1

8.0

6.8

7.8



21

24

42

31

25

20

24



44

29

38

47

60

56

62



6.6

10.8

10.6

8.0

9.5

4.2

7.2



0.6

0.87

0.6

0.8

1.2

0.5

0. 8



6.5-8.1

7.3



28-58



9-38

20



4.4-8.7

6.1



0.34.7

0.5'



40



Sodium



Data for feedlots 1 , 2, and X are from Stubblefield and Smith (1964).

Data for feedlots A through E are from Abbott (1968).

All figures reported on an oven-dry basis.



330



DALE E. BAKER AND LEON CHESNIN



TABLE X

Composition of Fresh-Dried Poultry Excreta

~



~~



~



~



~



~~~~~~



12 Samples of dried

poultry excreta'



Major components

( 73



Experimental

sample"



Moisture

Ether extract

Crude protein

Uric acid and salts

Crude fiber

Nitrogen-free extract

Ash

Mujor minerals ( %)

Sand

Sodium chloride

Calcium

Phosphorus

Magnesium



Truce elements (ppm)

Iron

Manganese

Copper

Cobalt

Zinc

(I



Average, 4

samp1es

dehydrated

manurl



Range



Mean



7 -8

1.4

26.6

11.4

8.2

39.3

16.7



6.5-10.2

1.3-1.9

24.3 -29.3



7.74

1.61

26.52



7.36



8.2-12.5

33.9-41 .O

14.3-18.7



10.72

38.21

15.81



13.72

39.55

26.90



I .o

1.3

2.5

0.8

0.2



0.6-1.3

1.1-2.9

2.5-5.8

0.8-2.1



0.98

1.48

4.82

1.45



905

260

52



450-950

21 7-330

20-52

1

232-530



1



530



-



-



-



-



245

29



7.78

2.56

0.48



2570

310

51



1



43 1



423



Lowman and Knight (1970).

Sheppard (1970). Data for Mg, Fe, Mn, Cu, Co, and Zn from 2 samples only.



On an oven-dry basis, K in poultry manure ranges from 1.0 to 4.5%. The

average of a large number of samples from Georgia was 1.70 and 1.88 %

K for broiler and hen manures, respectively.

The monovalent cation K is generally not viewed with alarm, although

present in much higher amounts in manures than is Na. The presence of

large amounts of K in manures may be an additional negative factor deserving of further consideration.

In a field study (Cross et al., 1973) of the influence of heavy applications

of manure from beef cattle feedlots to an irrigated soil in eastern Nebraska,

3.9 pounds of Na and 13.4 pounds of K were removed per inch of runoff

water. The plots had received 260 tons (dry weight basis) of manure per

acre. The hydraulic conductivity of disturbed samples, measured 4 months

after the application of manure, decreased. This decrease was related to

the high levels of Na and K in the percolate.

Murphy et al. (1972) found large increases in exchangeable Na and



CHEMICAL MONITORING OF SOILS



331



K contents of a Kansas soil after the application of 324 tons of manure

per acre. The electrical conductivity of the soil saturation extract increased

linearly with rate of application of manure. Crop yield reduction occurred

when more than 140 tons of manure per acre was applied probably because

of the soluble salts in the manure.

Weeks et al. (1972) found that application of 193 tons of manure (wet

weight) during the winter increased the NaCl content of a sandy loam

soil to 1920 ppm. While leaching tended to reduce the salt content, additional applications of manure increased it.

Mathers and Stewart ( 1971) applied 242 tons of manure per acre per

year in western Texas. After one year, the electrical conductivity of the

saturated paste increased to 11.7 mmho. At the end of the second year,

samples from plots that received a second manure application had a conductivity of 10.6 mmho, while samples from plots that did not receive the

second application of manure had a conductivity of 3.0 mmho.

Mathers et al. (1 973) indicated that high rates of application of manure

may increase salinity sufficiently to reduce crop growth. During the early

season, salt injury to plants, especially during germination, is a problem

with application rates above 10 tons of manure per acre, except where

sufficient rainfall or irrigation water is applied.

The problem of salt in animal wastes can be alleviated by reducing the

amount of salt added to the rations. Klett (1973) found that decreasing

the levels of salt added to a cattle ration resulted in a linear decline in

the Na content of the waste produced with no effect on animal

performance.

When high rates of manure are applied, the salt content of the soil should

be monitored periodically to determine the level of pollution hazard and

the amelioration procedures needed. Where pastures are grown on acid

sandy soils, a high K status in the soil suggests the possibility of grass

tetany (Baker, 1972).

The effect of land applications of municipal sewage sludge and especially

effluents on the ionic balance and soluble salt content of soils (Kardos

and Sopper, 1973) is critical, especially when it involves possible salt accumulation in arid regions and significant changes in the cationic ratios

within the plant rooting zone of soils which can impair plant growth in

both arid and humid areas. For manure effluent, the concentrations of K

were found excessive compared with other macroelements (Baker et al.,

1975). For municipal effluent, Kardos and Sopper ( 1973) concluded that

only small changes in soil chemical quality occurred after 6 years of sewage

effluent treatment and that these changes posed no problems for the future.

Soluble salt buildup in soils from applications of animal wastes and municipal effluent is more easily estimated and controlled than is that resulting



332



DALE E. BAKER AND LEON CHESNIN



from the use of NaCl and CaCl, on highways. Westing (1969) estimated

that six million tons of salt were used on the highways of the northern

states in 1969, and the rate was expected to increase to 10 or 12 million

tons. Thus, the amount of salt used to keep ice off the highways in the

northern United States is about equal to the amounts of commercial fertilizers used for crop production by all 48 states. A typical highway in

New England receives up to 20 tons of salt per mile or 4 pounds per linear

foot along each side of the road. Although winter salting is essential for

safe, uninterrupted use of highways, these amounts of salt can be harmful

to vegetation for some distance away from the roadside. In addition, the

excess salt can be poisonous to wildlife and adds to the pollution of

streams, lakes, and groundwater. The use of snow fencing or windbreaks,

more plowing and less salting, highway engineering modifications to prevent drifting and provide drainage systems to keep the salt off cropland,

and more use of CaCl, and less use of NaCl could prevent the salt damage

to vegetation and reduce pollution of streams and lakes. Soluble salts are

determined routinely in soil testing where soluble salt problems are expected. Methods of analysis and their interpretation are adequate and will

not be discussed. The presentation by Bower and Wilcox ( 1965) includes

adequate detail regarding procedures and instrumentation.

AND NITROSAMINES

B. NITROGEN-NITRATE,

NITRITE,AMMONIA,



Even though some algae fix atmospheric N, environmental problems associated with soil nitrogen, N, include its contribution to eutrophication.

In addition, toxic levels of nitrate (NO,) and nitrite (NO,) in water and

more recently carcinogenic nitrosamines have been under investigation. Nitrogen is usually the most deficient of the essential plant nutrients in soils

for nonlegume crops. Almost all the manufactured N and about an equal

amount in the form of animal manure reach United States soils each year

(Lathwell et al., 1970). The agricultural N requirements for the United

States are estimated to be 16.8 million metric tons per year (Alexander

et al., 1972). The role that agriculture plays in the N pollution of groundwater, streams, and lakes is being studied. Results of studies by Bower

and Wilcox (1965) indicate that soils vary greatly with respect to the

downward movement of NO,- and N losses through denitrification.

The biochemistry of nitrogen oxidation and the production of nitrosamines and related compounds which are reported to be carcinogenic, teratogenic, and/or mutagenic when present in food products, are under investigation (Ayanaba and Alexander, 1973, 1974). An excellent review on

N in the environment has been prepared by a committee of the National

Research Council (Alexander et al., 1972).



CHEMICAL MONITORING OF SOILS



333



The current situation with respect to N fertilization of crops is somewhat

analogous to the “soil acidity Merry-Go-Round” (Jenny, 1961 ) . Systems

of management to make the most efficient use of available N either from

crop residues, manure, or commercial fertilizers were developed during

most of the first half of the twentieth century when the supply of available

N was the dominant limiting factor for crop production. With declining

costs for N after World War 11, the question of efficient recovery became

a declining issue. The objective was to fertilize until the value of the expected yield increase no longer compensated for the cost of the last increment of fertilizer.

Public concern regarding possible N and P pollution of streams, lakes,

and groundwater required a reassessment of the present practices of N

fertilization of crops. The recovery of fertilizer N by cultivated crops often

represents only 3 0 4 0 % . Allison (1955) and Cooke (1964) reported recoveries in the range of 70-100% for pastures. Field studies of Owens

( 1960) using 15N showed 15-25 % recovery in corn stover and grain from

150 pounds of N per acre from NH,NO,. Leaching losses accounted for

5-20%, 38% remained in the soil, and 33% was presumably lost by denitrification. Broadbent and Clark (1965) showed nitrogen losses of 1 4 0 %

for greenhouse studies and cited results for field studies of N losses in excess of 50%.

Denitrification may be one solution to N pollution problems. Tofflemire

and Van Alstyne (1974) reviewed several projects where systems were

being developed to achieve biological nitrification and subsequent denitrification where wastewater and sewage sludge were applied. With the current

energy crisis and rapidly increasing cost of commercial fertilizer, the problem has changed from one of obtaining highest possible economic yields

without pollution of water to one of obtaining greater efficiency from the

fertilizer applied.

Stevenson and Wagner (1970) presented an excellent review on the

chemistry of N in soils. From the principles developed, crop rotations and

management system decisions are possible without additional experimentation (Lathwell et al., 1970; Bouldin et al., 1971). On the other hand,

monitoring techniques to relate soil properties to biological and chemical

parameters will become increasingly important. For example, the practice

of fall application of N for the production of corn the following year might

have been economically feasible at some locations and might have been

equal to spring plow-down when the N rates were maximum. However,

maximum yields of corn have been obtained in Pennsylvania for three years

with only 75 pounds of N per acre per year when applied as a side-dress

application with an application of 20 pounds per acre banded at planting

time (Shuford and Baker, 1974).



334



DALE E. BAKER AND LEON CHESNIN



The feasibility of using controlled-release fertilizers is being studied extensively (Lunt, 1971). The problem of concern is the development of

systems to supply N at desirable levels of availability at the time it is needed

by the crop fertilized and recover the remaining amounts in subsequent

crops. Such a system using dairy cattle manure effluent has been proposed

by Baker et al. (1975). Where leaching occurs during late fall, winter,

and early spring, cover crops are required to remove residual NOs--N and

the N released by nitrification. On many soils, small amounts of N banded

in the row will enable corn to grow normally and utilize the N released

by nitrification until silking time. During grain development, relatively large

amounts of N are utilized, so side-dress applications are important. Other

management systems involving the use of N-SERVE to retard nitrification

has been studied by Boswell et al. (1974). The merit of a system to increase the efficiency of N uptake to decrease water pollution and maximize

production has been demonstrated by Bouldin et al. ( 197 1) .

Chesnin et al. (1975) point out that the recent history of high cost and

shortages of commercial fertilizers has stimulated a new interest in animal

manures. In a short time, animal manures changed from a waste delivered

free by the producer to a resource picked up and paid for by the consumer.

A continuation of this trend could partially restore the position manures

enjoyed as suppliers of crop nutrients prior to the large-scale production

of chemical fertilizers. Manure is without question an important crop production resource. Recommendations for the application of animal wastes

are usually adjusted to the nitrogen content of the material and the N needs

of the crop.

Nitrogen in feedlot manure is mostly in an organic form. Chesnin et

al. (1975) found the N content of feedlot manure (dry weight basis) in

11 feedlots in the Phoenix, Arizona, area to range from 1.29 to 2.66%,

with an average of 1.67%. Petersen et al. ( 1971 ) reported on the distribution of N in slurry manure ( a mixture of feces and urine) of confined

beef cattle feeding in Nebraska. The total N, NH,+-N, and NO,--N contents

of the waste were 1.9%, 0.33%, and 0%, respectively (Table X I ) . Additional manure composition data are presented in Tables XI1 and XIII.

The N content of dairy cattle manure varies from less than 1 % to about

4% (dry weight basis); almost all this N is in the organic form (Chesnin

et al., 1975). Hart (1960) reported the N content of poultry and sheep

manures was 5.4%, whereas the N content of dairy, beef cattle and swine

manures as 3.5%, 3.1 %, and 3.3%, respectively. Management practices,

such as the use of bedding, method of handling manure, and the diet of

animals, will have a marked influence on the N content of the waste.

Research by one of the authors in Nebraska has shown that so-called

“untidy” feedlots, with accumulated manure and the soil surface being



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