Loss of nitrogen during sprinkler irrigation of swine lagoon liquid

Bioresource Technology 40 ( 1992 ) 7-15

Loss of Nitrogen during Sprinkler Irrigation of Swine Lagoon Liquid L. M. Safley, Jr, J. C. Barker & R W. Westerman Biological and Agricultural Engineering Department, North Carolina State University, Raleigh, North Carolina 27695-7625, USA (Received 28 September 1990; revised version received 11 February 1991; accepted 12 February 1991 )

Abstract Irrigation experiments were conducted using center pivot and big gun equipment to determine losses of nitrogen that occur during sprinkler irrigation. Anaerobic lagoon liquid was irrigated onto bare ground and nitrogen losses were evaluated for different application rates. The p H of the applied lagoon liquid was found to increase during irrigation. TKN losses occurring during sprinkler irrigation using the center pivot were found to range from 14"9% to 43"4%. Of this amount 53.5-100% was accounted for in volumetric loss (evaporation and drift). Ammonia-N losses occurring during sprinkler irrigation (center pivoO were found to range from 13"9% to 37.3%. Volumetric loss of the liquid during sprinkler irrigation accounted for 62"2-100% of the ammonia-N loss. Due to the sampling technique used it was not possible to estimate volumetric losses for the big gun equipment. However, pH and concentration changes in the irrigated liquid were similar to those observed in the center pivot tests. Key words: Ammonia volatilization, irrigation, swine waste, anaerobic lagoon. INTRODUCTION Organic waste materials are often applied to land as a source of nutrients. One of the primary Paper No. BAE 90-13 of the Journal Series of the Department of Biological and Agricultural Engineering, North Carolina AgriculturalResearch Service,Raleigh,NC 276957601. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similarones not mentioned.

nutrients of interest is nitrogen. Nitrogen can be in both organic and inorganic (typically ammonia) forms. The relative percentages of organic and inorganic nitrogen in wastes are specific to the given waste. Ammonia nitrogen often represents a major portion (70-90%) of the nitrogen in anaerobic lagoon liquid. Typical laboratory methods determine the total ammonia concentration. In the total ammonia concentration of anaerobic lagoon liquid both un-ionized ammonia (NH3) and ionized ammonium (NH~) exist in equilibrium. For typical soil, lagoon liquid temperature and pH conditions the majority of the total ammonia concentration is ionized ammonium (NH~). The unionized ammonia is subject to loss via volatilization. This volatilization process can occur prior to, during and after the application process. Numerous researchers have reported on the volatilization of ammonia nitrogen from liquid and slurry wastes. There is a wide range of reported ammonia losses occurring during and immediately following application of liquid wastes. Table 1 presents the results from several studies. Ammonia loss has been estimated using several approaches: micrometeorological mass balance models (Beauchamp et al., 1982; Gordon et al., 1988; Pain et al., 1989), wind tunnels (Thompson et al., 1987; Lockyer et al., 1989) and concentration difference (Westerman et al., 1982). Most of the reported research on ammonia loss has been done using slurries as opposed to relatively dilute anaerobic lagoon liquid. A number of factors influence loss of ammonia nitrogen. Emst and Massey (1960) reported that ammonia loss was directly related to soil pH, ambient temperature and the rate of soil drying. Brunke et al. (1988) have determined that a micrometeorological variable such as a hay drying

Bioresource Technology 0960-8524/92/S03.50 © 1992 Elsevier Science Publishers Ltd, England. Printed in Great Britain

8

L . M . Safley, Jr, J. C. Barker, P. W. Westerman

Table 1. Reported ammonia losses from applied liquid wastes Waste type

Application technique

Conditions

Ammonia loss (% of applied)

Source

Liquid swine manure

Surfaceapplied to soil

Spring; 90 t/ha of manure; 3"5 day measurement

14.0

Hoff et aL (1981)

Liquid swine manure

Surface applied to plastic

Spring; 90 t/ha of manure; 3.5 day measurement

65.8

Hoff et al. (1981)

Liquid swine manure

Surface applied to soil

Greenhouse conditions; 8 day measurement

82.5

Hoff etal. (1981)

Cattle slurry

Surface applied

Spring; 262 kg N/ha Winter; 248 kg N/ha

31.0 20.2

Thompson et al. (1987)

Sewagesludge

Surface applied

Spring; 5 day test; 150 kg ammonia/ha Fall; 7 day test; 89 kg ammonia/ha 22.9 kg ammonia/ha; 4 day test 73.4 kg ammonia/ha; 4 day test 139"6 kg ammonia/ha; 4 day test 48.4 kg ammonia/ha; 5 day test 44.1 kg ammonia/ha; 3 day test

60

Beauchamp et al. (1978)

Swine slurry

Swine slurry

Dairy cattle slurry

Swine lagoon liquid

Surface applied to grassland

Surface applied to grassland

Surface applied

Sprinkler irrigation

56 53.0 56-9 36.1 77.6 60.4

106 kg ammonia/ha; 3 day test 57 kg ammonia/ha; 3 day test

24-1

197 kg ammonia/ha; 6 days; spring 176 kg ammonia/ha 7 days; spring 145 kg ammonia/ha; 6 days; spring

30

Overnight; spring and summer

index may be more appropriate than individual meteorological parameters such as windspeed or temperature for forecasting ammonia loss. Crane et al. (1981) have reported that applications of slurry poultry manure can significantly increase soil p H soon after application. Such p H rises can also increase ammonia volatilization. Previous research has considered collective losses of ammonia that occur both during and after application (Table 1). To date little, if any, research has been done to define ammonia loss that occurs during the process of sprinkler irrigating liquid waste.

Lockyer et al. (1989)

Pain etaL (1989)

61.9 Beauchamp et al. (1982)

33 24 9-23

Westerman et at (i 9 8 2)

T h e objective of this research was to determine the amount of nitrogen in swine lagoon liquid that is lost during sprinkler irrigation.

METHODS Center pivot irrigation Trials were conducted using a center pivot irrigation system (Valmont M o d e l 4871 ). T h e pivot was 278 m long and had five supporting towers spaced as indicated on Fig. 1. T h e sprinkler irrigation nozzles on the pivot were spaced and sized

Loss of nitrogen during sprinkler irrigation of swine lagoon liquid (0-28-0-44 cm orifice inside diameter) by the manufacturer to give a near-uniform application. The pivot system was used to apply liquid from an anaerobic lagoon which received flushed waste from a swine farrow-to-feeder pig facility. Four tests were conducted on eacti of three different days using the center pivot system. The different trials consisted of varying the percentage of

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9

pivot operation time which in turn varied the amount of lagoon liquid applied. The area of coverage was held constant for all trials. Weather conditions, line pressure at the pivot and pipe flow rate information are given in Table 2. Wind velocity was determined using an Alnor Model 6000P velometer with a Model 6060P probe (0-23 km/h range). Wet and dry bulb temperatures were determined using a Model 566 Bendix thermometer. Six sampling stations were positioned as indicated in Fig. 1. The sampling stations consisted of a Taylor Instruments Model 2701 rain gauge attached to a wooden stake. The top of the rain gauge was approximately 45 cm above the ground surface. The collection funnel of this gauge has an inside diameter of approximately 9"5 cm. For each trial the pivot was rotated either clockwise or counterclockwise through a 10"6° arc. Prior to a test the pivot was positioned 5.3 ° to one side of the line of sampling stations. When the trial was initiated no sprinkler irrigation liquid could reach sampling station number 1. The test was terminated when the pivot had gone 5.3 ° past the line of sampling stations. At this point sampling station number 1 would have just stopped receiving sprinkler irrigation liquid. Liquid flow through the center pivot system was determined using a Polysonics Model DHT-P Hydra (R) ultrasonic flowmeter. The meter was attached to the metal vertical pipe at the pivot point and flow rates were determined for different operating pressures (top of pivot). Table 3 indicates the results of this calibration. Lagoon liquid samples were collected from near the irrigation pump intake approximately

Table 2. Conditions during center pivot tests

Date

6/23/87

7/7/87

7/15/87

Test No.

Pivot pressure (kPa)

System flowrate (liters/min)

Dry bulb temp.

Relative humidity (%)

Wind speed (km/h)

Winds from

1 2 3 4 1 2 3 4

365 365 365 365 379 379 379 379

1186 1186 1186 1186 1360 1360 1360 1360

28-0 28.5 31.0 33.0 30-0 30.0 34-0 30-0

80 72 67 58

0-16 0-18 0-16 0-18

SW W-SW SW S-SW

Sunny Sunny Sunny Sunny

70 73 63 65

0-4 0-2 0-10 0-21

NE NE S, NW SW

1 2 3 4

376 376 376 376

1325 1325 1325 1325

24.5 24.0 23.0 27-0

82 82 85 78

0-14 0-9 0-5 0-16

NE E NE NE

Partly cloudy Partly cloudy Partly cloudy Thunderstorm approaching Sunny Sunny Sunny Sunny

(°c)

General conditions

10

L. M. Safley, Jr, J. C. Barker, P. W. Westerman

every 2 h during the day for a given set of tests. Once a test was completed the amount of captured liquid was determined by reading the rain gauges at the different sampling stations. Liquid from each sampling station was collected for analysis. All liquid samples were refrigerated and transported within 24 h to the laboratory for analysis. Samples were analyzed for total solids (TS), total Kjeldahl nitrogen (TKN), ammonia nitrogen, and pH. TS was determined by evaporation at 103°C (US EPA, 1979). TKN was analyzed using persulfate digestion modified for automated procedures (Technicon, 1973; US EPA, 1979) ammonia was determined using a salicylate reaction modified for automated procedures (Technicon, 1973; US EPA, 1979).

Big gun irrigation system Three sets of sprinkler irrigation trials were conducted using a big gun irrigation system. Table 4 gives the operating conditions for the three trials. A Model 125-340 (Type 11D) Bauer hose reel with 12.9 cm outside diameter (10.5 cm inside diameter) hard hose was used to apply swine anaerobic lagoon liquid through a Nelson Model 200R Big Gun (R) nozzle (4.06 cm inside diameter). A calibration test using the instrumentation identified previously was conducted to determine flow at different nozzle pressures. The transducers were attached to the hose approximately 50 m from the hose reel for this determination. The results of the calibration are given

in Table 5. Figures 2-4 present the orientation of the irrigation equipment for the three test dates. Four sampling stations (Taylor Instruments Model 2701) were used to measure the amount of lagoon liquid applied at the points indicated in Figs 2-4. At the conclusion of each test, samples of the irrigated liquid were collected for analysis. Lagoon liquid samples were also collected approximately every 2 h throughout the day of each trial. All samples were refrigerated at the test site and transported to the laboratory for analysis within 24 h. RESULTS AND DISCUSSION Table 6 indicates the results of the three trials using the center pivot equipment. Considerable variation was noted in application rates between different sampling stations for a given test. The theoretical application rate was determined using the flow information determined from the calibration test, the amount of time the system was operated and the amount of land covered. Comparing the mean application rate to the theoretical application rate for a given test indicates reasonable consistency between tests in a given trial but definite differences between trials (Table 6). The percentage of the theoretical application rate actually collected and measured varied from 67% to 87% for the center pivot. Therefore, the Table 5. Calibration data for big gun tests

Table 3. Calibration data for center pivot test

Pivot (kPa)

Water velocity (m/s)

Flow (litres/min)

379 365 345

0.72 0-62 0.56

1360 1186 1071

Pressure at gun (kPa)

Water velocity (m/s)

Pipe flow (liters/min)

483 524 552 621

3.4 3"5 3-7 3-9

1779 1843 1908 2018

Table 4. Conditions during big gun tests

Date

Test No.

Big gun pressure (kea)

7/23/87

1 2

621 586

9/29/87

1 2

3/18/88

1 2

System flowrate (liters~m)

Application diameter (m)

Dry bulb temp. (*C)

Relative humidity (%)

Wind speed (km/h)

2018 1963

133 133

35-5 36.5

52 41

4-22 0-7

E-NE E-NE

Sunny Sunny

524 504

1843 1811

113 113

26.0 29"5

62 46

4-16 0-9

SE W-SW

Sunny Sunny

510 510

1822 1822

119 119

10-5 12.5

61 52

7-10 0-10

S-SW S-SW

Cloudy Cloudy

Winds from

General conditions

Loss of nitrogen during sprinkler irrigation of swine lagoon liquid /

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amount of applied liquid that was lost from evaporation and drift accounted for 13-33% of the applied liquid. The mean loss (mass) for the 11 values given in Table 6 is 23%. This loss is comparable to typical assumptions for the amount of

Big gun irrigation test layout (3/18/88).

water lost during irrigation ( - 2 0 % ) using this type of equipment. The losses were higher for 7/7/87 as compared to the other two trial dates. Part of this may be explained by the reduced relative humidity noted for this date (see Table 2). There was little, if any, difference in the TS concentration of the lagoon liquid and the irrigated liquid. Table 7 presents data on the big gun irrigation trials. There was appreciable variation in application rate between sampling stations for all tests. By coincidence the wind direction on each of the trial dates favored increased sample point accumulation for stations number 1 and 2 as compared to stations 3 and 4 (see Figs 2-4). These data illustrate the difficulty in achieving a uniform application with big gun equipment. Comparing the mean application rates for a given test with the test's theoretical application rate indicated that the mean actually exceeded the theoretical application rate for all of the trials. This indicates that the positioning of the sampling stations was inappropriate for determination of true application rates in the trials. For these trials, sampling stations were no further than 30.5 m from the travel path of the big gun. By comparison the measured application radius of the big gun varied from 56 m to 66 m. To get a more accurate value for the true application rate over the entire area

12

L. M. Safley, Jr, J. C Barker, P. W. Westerman

Table 6. Center pivot application rates Date

Test

Sampling station

Theoretical application

% Liquid recovered

Measured liquid application (cm) 1

2

3

4

5

6

Mean

1 2 3 4

0.51 1-02 2.01 --"

0"66 1.40 2"39 3.10

0.48 1.04 1-93 2.39

0"51 1.12 2"03 2-67

0.61 1.19 2.21 2.74

0.61 1.30 2-49 3"25

0.56 1.17 2.18 2-84

1.47 2.51 3.53

79"6 86"9 80"4

7/7/87

1 2 3 4

0-41 0-89 1"30 1.93

0"51 0"97 1-50 2.06

0-41 0.91 1.40 1-78

0"46 0-99 1-52 2.13

0.56 1.12 1.83 2.33

0-51 1"12 1"78 2.24

0.46 0.99 1"55 2-08

0-66 1.37 2-31 3"12

69"7 72"2 67-1 66"7

7/15/87

1 2 3 4

0.48 1.02 1.88 2-29

0-41 0-91 1.96 2"03

0.43 0-99 1"62 2-06

0"36 0-89 1"73 1.93

0.41 1.07 2.01 2.36

0"51 1-19 2-18 2-69

0-43 1.02 1-88 2.24

0-56 1.30 2.16 2-69

76"8 78-5 87"0 83-3

6/23/87

"Sample container broken.

Table 7. Big gun application rates Date

Test

Sampling station

Theoretical application

Measured liquid application

(cm) 1

7/23/87

1 2

9/29/87

1 2

3/18/88

1 2

6-22 3-51

2

3

4

Mean

4.19 1.68 1.42 2.97 1.12 0-71

3-38 2.08

2.41 1.93

11.18 10.34 5.92 5.72 3.25 3-40 2.54 1.14

8.28 2.59

8-15 2-39

1.68 1.47

1-47 --"

3.33 3"56

1.93 0.79 0-61 1-52 0.43 0.41

"Application timer malfunctioned.

tion tests the pH of the liquid collected in the rain gauges was higher than the parent lagoon liquid. The elevated pH may have been the result of CO 2 loss during the irrigation process. The higher pH may contribute to ammonia volatilization after the lagoon liquid has contacted the soil. Losses of TKN and ammonia that occurred were determined using eqn (1).

TNL= 1 A---~LJ 100

(1)

where

TNL= total nitrogen loss (%), actual application, Co--- concentration in captured liquid, A-r = theoretical application, C,--- concentration in lagoon liquid. mc=

sampling stations should have been located over the entire wetted diameter. Tables 8 and 9 give characterization data for the center pivot and big gun experiments, respectively. For most of the tests the concentrations of both TKN and ammonia in the captured liquid is less than that for the lagoon liquid. However, the amount of decrease in the concentrations of TKN and ammonia in the captured liquid is highly dependent on the given test. For two of the center pivot tests (Table 8; 7/7/87) the TKN and ammonia-N concentrations in the sprinkler irrigation liquid are slightly higher than that of the lagoon liquid. This is indicative of the variability of nitrogen in the lagoon liquid. This also indicates that no nitrogen concentration loss occurred during sprinkler irrigation. For all irriga-

Equation (2) was used to determine the amount of the loss that could be attributed to a loss of liquid volume:

VLN=

x 100

(2)

where VLN = volume nitrogen loss, Lv - volume loss. Lv was taken from Table 6 for the center pivot tests (100 minus percentage recovered). Nitrogen losses could not be accurately calculated from the

Loss of nitrogen during sprinkler irrigation of swine lagoon liquid

13

Table 8. Center pivot tests -- liquid characterization

Date 6/23/87

Material Test 1 Test 2 Test 3 Test 4 Lagoon liquid

7/7/87

Test 1 Test 2 Test 3 Test 4 Lagoon liquid

7/15/87

Test 1 Test 2 Test 3 Test 4 Lagoon liquid

TKN (ppm)

Ammonia-N (ppm)

pH

TS (%)

No. of samples

338 a (14) b 359 (10) 383 (12) 388 (9) 391 (15) 344 (8) 351 (20) 371 (18) 406 (16) 379 (55) 274 (25) 329 (9) 324 (12) 335 (26) 372 (117)

269 (7) 274 (10) 283 (5) 279 (2) 299 (1) 313 (1) 307 (27) 328 (5) 334 (4) 327 (4) 244 (19) 291 (4) 296 (4) 303 (2) 299 (1)

8.21 (0"05) 8.12 (0.02) 8.04 (0.03) 7.88 (0-02) 7.41 (0.02) 8.20 (0-02) 8-11 (0.01) 8.11 (0.02) 8.02 (0.02) 7.41 (0.02) 8.31 (0.07) 8.19 (0.04) 8.17 (0-01) 8.22 (0.02) 7.45 (0.04)

0"15 (0"01) 0-17 (0-01) 0.16 (0.01) 0.17 (0.01) 0-17 (0.03) 0-14 (0-01) 0-17 (0-02) 0.17 (0-02) 0-17 (0.01) O"16 (0.03) 0.12 (0.12) 0.14 (0-01) 0-14 (0-01) 0-14 (0-01) 0.14 (0-01)

6 6 6 6 5 6 6 6 6 5 6 6 6 6 5

aMean. hStandard deviation.

big gun data since the mean application rates exceeded the theoretical application rates. Table 10 presents a summary of the nitrogen loss for the center pivot tests. These data indicate that the majority of the nitrogen loss occurred as a result of loss of liquid volume either from evaporation or drift. Depending on the given irrigation system, drift losses of nitrogen relative to the particular test site might not be true system losses since drift could contribute to nitrogen loading on areas adjacent to the irrigated sites. Although the total loss values computed for both the T K N and ammonium-N compared favorably the amounts that each contributed to volume and concentration did not. This inconsistency may have been due to normal sampling and analytical error.

CONCLUSIONS On the basis of the experiments described the following observations were made: 1. T h e p H of anaerobic lagoon liquid increased during sprinkler irrigation (approximately 7.4-8.2 for center pivot tests; approximately 7-4-8-0 for big gun tests). 2. T K N losses during sprinkler irrigation ranged from 14.9% to 43-4% using the center pivot equipment. Of this amount 53-5-100% could be accounted for in liquid volume loss. 3. A m m o n i a losses during sprinkler irrigation ranged from 13-9 to 37"3% using the center

14

L. M. Safley, Jr, J. C Barker, P. W. Westerman

Table 9. Big gun tests -- liquid characterization Date

Material

7/23/87

TKN (ppm)

Ammonia-N (ppm)

pH

TS (%)

No. of samples

434 ~ (5) b 414 (25) 431 (9) 516 (14)

330 (6) 308 (13) 340 (6) 499 (14)

8.27 (0.12) 8.32 (0-03) 7.73 (0.13) 7-89 (0.04)

0"22 (0-01) 0"36 (0.06) 0.26 (0.03) 0-20 (0.01)

4

Test 2

538 (13)

504 (4)

7.94 (0.11)

0.25 (0-09)

4

Lagoon liquid

617 (98)

510 (12)

7.49 (0.04)

0.37 (0.21)

6

Test 1

246 (10) 243 (1) 251 (4)

211 (2) 213 (6) 214 (3)

7-67 (0.09) 7-73 (0.13) 7"13 (0.02)

0.11 (0.02) 0.10 (0-01) 0"11 (0-01)

3

Test 1 Test 2 Lagoon liquid

9/29/87

Test 1

3/18/88

Test 2 Lagoon liquid

4 3 4

3 4

aMean. hStandard deviation. Table 10. Summary of nitrogen loss from center pivot irrigation tests Date

Test

Volume loss (%)

TKN Total loss

Amount of total loss attributed to Volume

7/7/87

7/15/87

1 2 3 4 1 2 3 4 1 2 3 4

. 20-4 13.1 19.6 30-3 27.8 32-9 33.3 23.2 21-5 13-0 16.7

.

. 26.9 14.9 20.2 36-7 33.1 34-3 28.5 43.4 30-6 24-2 25.0

pivot equipment. Of this amount 62.2%-100% of the loss c o u l d be a c c o u n t e d for in the liquid v o l u m e loss.

Amount of total loss attributed to

(%)

. 75.8 87.9 97.0 82"6 84.0 95.9 100.0 53.5 70-3 53.5 66-8

Total loss

Concentration

(%)

6/23/87

Ammonia-N

. 24-2 12-1 3-0 17.4 16.0 4.1 0 46.5 29-7 46-3 33.2

Volume

Concentration

75.3 73.6 78.4 91-0 86.3 100 100 62.2 91.1 93.5 100

24-7 26-4 21.6 9.0 13.7 0 0 37.8 8.9 6-5 0

(%)

.

(%)

. 27.1 17.8 25.0 33-3 32.2 32.7 31.9 37.3 23.6 13.9 15.6

also like to a c k n o w l e d g e the efforts o f M r D. A. Williams in assisting with this e x p e r i m e n t and of M s D. A. d e B r u y n e a n d M s R. S. H u i e in c o n d u c t ing the s a m p l e analysis.

ACKNOWLEDGEMENTS T h e authors w o u l d like to a c k n o w l e d g e t h e supp o r t o f Carroll's Foods, Inc. in providing facilities a n d e q u i p m e n t for this experiment. T h e y w o u l d

REFERENCES Beauchamp, E. G., Kidd, G. E. & Thurtell, G. (1978). Ammonia volatilization from sewage sludge applied in the

Loss of nitrogen during sprinkler irrigation of swine lagoon liquid field. J. Environ. Qual., 7 (1), 141-6. Beauchamp, E. G., Kidd, G. E. & Thurtell, G. (1982). Ammonia volatilization from liquid dairy cattle manure in the field. Can. J. Soil, Sci., 62, 11-19. Brunke, R., Alvo, P., Schuepp, P. & Gordon, R. (1988). Effect of meteorological parameters on ammonia loss from manure in the field. J. Environ. Qual., 17,431-6. Crane, S. R., Westerman, P. W. & Overcash, M. R. (1981). Short-term chemical transformations following land application of poultry manure. Trans. ASAE, 24 (2), 382-90. Ernst, J. W. & Massey, H. E (1960). The effects of several factors on volatilization of ammonia formed from urea in the soil. Soil Sci. Soc. Arner. Proc., 24, 87-90. Gordon, R., Leclerc, M., Schuepp, P. & Brunke, R. (1988). Field estimates of ammonia volatilization from swine manure by a simple micrometeorological technique. Can. J. Soil Sci., 68, 369-80. Hoff, J. D., Nelson, D. W. & Sutton, A. L. (1981). Ammonia volatilization from liquid swine manure applied to cropland. J. Environ. Qual., 10 (1), 90-5.

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Lockyer, D. R., Pain, B. E & Klarenbeek, J. V. (1989). Ammonia emissions from cattle, pig and poultry wastes applied to pasture. Environ. Pollut., 56, 19-30. Pain, B. E, Phillips, V. R., Clarkson, C. R. & Klarenbeek, J. V. (1989). Loss of nitrogen through volatilization during and following the application of pig or cattle slurry to grassland. J. Sci. FoodAgric., 47, 1-12. Technicon (1973). Technicon Industrial Methods for the Examination of Water and Wastewater Treatment, Technical Services Bulletin. Piscataway, NJ. Thompson, R. B., Ryden, J. C. & Lockyer, D. R. (1987). Fate of nitrogen in cattle slurry, following surface application or injection to grassland. J. SoilSci., 38,689-700. US EPA (1979). Methods for Chemical Analysis of Waterand Wastes, EPA 600-4-79-020. Environmental Monitoring and Support Lab, US EPA, Cincinnati, OH. Westerman, P. W., Burns, J. C., King, L. D., Overcash, M. R. & Evans, R. O. (1982). Swine lagoon effluent applied to coastal bermudagrass. Final Report of EPA Project R-804608 USEPA.