600S283004 6 1983 NEPIS online LAI 20060912 hardcopy single page tiff rate effluent runoff lagoon soil rates bermudagrass applied irrigation forage medium low subsurface application transport nutrient treatments crop treatment coastal United States Environmental Protection Agency Robert S. Kerr Environmental Research Laboratory Ada OK 74820 Research and Development EPA-600/S2-83-004 Apr. 1983 &EPA Project Summary Swine Lagoon Effluent Applied to Coastal Bermudagrass Philip W. Westerman, Joseph C. Burns, Larry D. King, Michael R. Overcash, and Robert 0. Evans The utilization potential and the envi- ronmental effects of applying swine lagoon effluent to Coastal bermuda- grass were evaluated for six years. Lagoon effluent was applied to 9 m x 9 m plots by weekly sprinkler irrigations during the growing season. A random- ized block design with three application rates based on nitrogen (N) (about 335, 670 and 1,340 kg N/ha/yr) was util- ized. The high rate treatment resulted in application of N. phosphorus (P) and potassium (K) at about five, thirteen, and eleven times, respectively, the normally recommended fertilizer appli- cation rates for high yields of hay. Forage yield and quality, soil nutrient levels and water quality and quantity of runoff and subsurface lateral flow were evaluated. An intake trial with ewes was also conducted to determine ani- mal acceptance of hay from lagoon- irrigated treatments. The results indicated that swine la- goon effluent can be an excellent source of nutrients for Coastal bermudagrass, but water quality considerations, nitrate levels in the forage, and long-term soil effects must be evaluated when deter- mining acceptable maximum applica- tion rates, which is important when land area for application is limiting. This Project Summary was developed by EPA's Robert S. Kerr Environmental Research Laboratory, Ada, OK, to an- nounce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back).* Introduction Swine production systems which utilize anaerobic lagoons usually require a land receiver system for lagoon effluent to avoid lagoon overflow. The ability of a soil-plant receiver system to utilize ap- plied lagoon effluent depends primarily upon the crop and the soil chemical and physical properties. Climate, lagoon ef- fluent application rate, and effluent com- position also affect the utilization. The design of the lagoon and the soil- plant receiver system depends largely on whether the producer's main objective is (1) manure treatment and disposal or (2) utilization of manure nutrients for useful crops. If limited by land, the producer would want maximum lagoon treatment and effluent applied to the soil-plant receiver system at maximum rates. The effluent rates could be sustained without causing toxicity to plants, failure of soil structure, or excessive degradation of ground water and rainfall runoff. Also, if the plants are to be fed to animals, the mineral and metal composition must not reach toxic levels. On the other hand, if land is not limited, and the producer utilizes the lagoon effluent for crop irri- •Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency through grant R- 804608 to North Carolina State University, it has not been subjected to the Agency's required peer and policy review and therefore does not necessarily reflect the views of the Agency, and no official endorsement should be inferred. image: ------- gation and fertilization, the lagoon may be designed to minimize nutrient losses while effluent is applied at rates based on efficient crop utilization of nutrients. Then the producer must decide whether to base application rate on N, P or another element. Typically, if N is the base ele- ment, P and K are applied in excess of plant utilization. However, if P is the base element, additional N must be applied using commercial fertilizer. Thus, depend- ing upon the producer's objectives and the land restrictions, a wide range of nutrient loading rates may be found in practice. Whether the maximum rate is limited by detrimental effects to crop, or soil, or by water quality of ground water and runoff must be determined. One crop which is receptive to irriga- tion of swine lagoon effluent in the Southeast is Coastal bermudagrass (Cyno- don dactylon L Pers). This bermudagrass is a deep-rooted, long-lived perennial which grows well in hot weather and requires a well-drained soil. Also it can remove relatively large amounts of N which is often used as the base element for determining effluent application rates. In this study, the plant-soil receiver system was Coastal bermudagrass grow- ing on a Norfolk sandy loam soil. Lagoon effluent was applied during the crop growing season to replicated plots at three N levels ranging from a fertilization rate normally recommended for high yields to a rate five times higher. Results are presented for six years of monitoring irrigation applications, crop yield and composition, soil cores, and runoff. Also included is a 20-month period of monitoring subsurface flow on three plots. Because most studies of this type have covered only one to three years, the study demonstrates long-term effects which may not be evident in short-term studies, especially in regard to soil accu- mulation and water transport of possible pollutants. Conclusions Weekly irrigation of swine lagoon ef- fluent to Coastal bermudagrass during the growing season resulted in excellent crop response. Yields increased with increased application rates, but there was little advantage in dry matter produc- tion from applying N above the medium rate (670 kg N/ha/yr). Applying N, P, and K up to five, thirteen, and eleven times, respectively, the normal recommended rates for high hay yields under non- irrigated conditions did not result in any significant problem with forage quality or soil physical structure for the six years of the study. The only exception was the possible hazardous animal intake levels of nitrate nitrogen (N03-N) in forage from the highest-rate treatment. Soil sampling results indicated that con- tinued application at the two highest rates could cause some nutrient imbal- ances due to high P accumulation (e.g., reduced iron [fe] uptake), and periodic liming would probably be needed to correct for calcium (Ca) and magnesium (Mg) losses from the topsoil and the decreased pH. The Ca and Mg deficiencies may occur even though large amounts of these and other minor elements are applied with the lagoon effluent. Transport of nutrients in surface runoff was relatively low because of the sandy topsoil and low slope of the plots. Greater transport generally occurred in subsur- face drainage for this layered soil. Be- cause the high nutrient concentrations in surface and subsurface flow and high transport of N03-N in subsurface flow from the highest two treatment rates is apt to be unacceptable in most situations related to water quality, water pollution concerns will probably govern the appli- cation rate for disposal of lagoon effluent. Keeping application rates near the low- rate treatment (near normal crop fertil- ization) would utilize a greater percentage of the nutrients and be more acceptable environmentally. Recommendations After six years of applying swine lagoon effluent to Coastal bermudagrass, no significant detrimental soil effects or nutrient imbalances in plant uptake were evident even when nutrients were applied at several times the normal fertilization rates. However, some trends indicated potential agronomic problems if high-rate applications continued, and the water quality of surface runoff and drainage from the plots receiving high-rate appli- cations was of environmental concern. Some of these trends were not evident after the first two to three years, which is the normal duration of studies of this type. Thus, researchers and research funding agencies should set priorities to allow for some long-term studies of this type. Some recommended research areas are: 1. Studies of ten years or longer dura- tion should be conducted to deter- mine long-term effects of continuing excess applications of nutrients with livestock and poultry manures and lagoon effluent. Various plant-soil receiver systems should be studied * because soil changes, plant nutrient imbalances, and water quality effects will vary with soil type, plant type and hydrologic conditions. Thus, the nu- trient upon which application rates should be based can vary from system to system. 2. The application losses of N by NH3-N volatilization and the soil reduction of NO3-N by denitrification needs fur- ther study, particularly with lagoon effluent irrigation systems. NH3-N losses and mineralization rate of organic nitrogen applied need fur- ther study in order to compare avail- ability rates in these systems with that in agronomic systems using commer- cial inorganic fertilizer. Also, it is difficult to determine how much of the N in the soil is denitrified and how much is transported as N03-N by lateral soil-water flow and deep seepage and thus is a potential water quality problem. 3. Long-term studies of this type should be conducted with other crops, other soils, and other management strate- gies such as year-round irrigation, less frequent irrigation, and basing lagoon effluent application rate on P or K and adding supplemental N in commercial fertilizer. Economics of alternatives should be evaluated. 4. Actual field-size systems should be studied, including evaluation of im- pact on water quality of ground water and nearby streams. Crop Response The Coastal bermudagrass was evalu- ated for dry matter yield, elemental composition, and estimated nutritive value. One major goal was to determine the quantity of N and other constituents that could be deposited in Coastal ber- mudagrass forage without adversely af- fecting stands or forage quality. Dry matter yields are shown in Figure 1. The highest N rate produced the greatest dry matter yields but was not statistically different from the medium rate. Both the high and medium rates produced greater yields than the low rate. The seven-year mean dry matter yields were 10,750, 14,230 and 15,810 kg/ha for the low, medium, and high treatments, respectively. The low N rate with irriga- tion showed about a 25% increase in yield over the non-irrigated plot receiving similar N amounts. Irrigated effluent amounts were approximately 12, 24 and 48 cm/yr for the low, medium, and high image: ------- 20 18 16 a -Medium - Grazed A Irrigated With Lagoon Effluent O Non-Irrigated, Fertilized Year Figure 1. Dry matter yields of Coastal bermudagrass. treatments, respectively, and irrigations were weekly from April through Septem- ber. The simulated hay and grazed plots received 336 and 200 kg N/ha/yr, re- spectively. The yield data indicate little advantage in dry matter production from applying N above the medium rate (670kg N/ha/yr). Also, there was some evidence that bermudagrass plots receiving the medium and high loading rates were more prone to winter injury, and would therefore require more re-sprigging to maintain stands. Concentrations of minerals in the bermudagrass generally increased with increased application rates of effluent. However, the concentration increases were generally nonlinear and showed a plateauing between the medium-rate and high-rate treatments. Elements which showed potential for increased concen- trations with even higher effluent rates were P and manganese (Mn). Nitrogen concentration in the forage averaged 2.24%, 2.77%, and 2.95% for the low, medium and high-rate treat- ments, respectively. However, it was expected that higher concentrations of N (3 to 4%) would result from the high loading rate. The increases in the N concentrations are important because of (1) interest in maximum crop uptake of N and (2) increased use of Coastal ber- mudagrass meal as a source of protein and vitamins in livestock and poultry feeds. The concentrations of elements in the bermudagrass were generally adequate when compared to the requirements for growing and finishing steers. The crude protein values (11 to 20%) were adequate to meet N requirements for most rumi- nants. The nitrate nitrogen (NOa-N) con- centrations, monitored on a limited basis for one year, were in the toxic range on the high-rate treatment. More N03-N data is needed but the limited results indicate that forage from the high-rate treatment would probably need to be blended with other feeds to reduce the NOa-N concentrations. Concerning for- age acceptability, an intake trial with ewes showed no difference in hay intake between the control and the low, medium, and high treatments. The average annual quantities of N and P removed in the bermudagrass are shown in Table 1. Although the amounts of N and P increased with increased effluent rates, the percentage recovery of N and P applied decreased. The amounts not recovered in forage were very high for the high-rate treatment and indicate potential problems with soil accumulation of P and movement of NOa-N to ground- water. Soil Effects Soil levels of NOa-N increased with increased loading rate (Figure 2). The sandy texture of the upper 30 cm of the profile resulted in little N03-N increase in this zone normally, but accumulation occurred in the subsoil. Accumulation of NOa-N in the subsoil has been noted in soils of the Southeastern United States, Table 1. Amounts of N and P in Forage and is thought to be a result of the weak adsorption of NOa-N ions in acid subsoils high in aluminum (Al) and iron (Fe) oxides and a result of non-uniform water movement in the subsoil. However, the amount of N retained in the soil was a relatively small percentage of the N applied. Of approximately 6,800 kg/ha of N applied to the high-rate treatment during the six-year period, only about 12% remained in the soil and most of this was NOa-N. Since crop removal averaged only 34% of the amount applied on the high-rate treatment, a large amount of N is lost by leaching, lateral subsurface flow, and/or denitrification when the application rate is this high. The effect of effluent application rate on concentrations of dilute acid extract- able soil P was generally in the order high rate > medium rate = low rate. By the sixth year, differences were significant in the 30-60 cm layer, indicating a signifi- cant downward movement of P. For this six-year period, application of P in excess of crop removal was about 1,500 kg/ha. Continual application of excess P could cause nutrient imbalance such as re- duced Fe uptake. Irrigation of effluent tended to decrease pH and levels of Ca and Mg inthetopsoil. These changes could be counteracted by periodic additions of dolomitic limestone to the soil. Effluent applications had little or no effect on soil copper (Cu), zinc (Zn) and Mn. Potassium and sodium (Na) accumu- lated in the subsoil on the high-rate treatments. However, the low pH (4.2 - 4.6) and low exchangeable Na (approxi- mately 6% NA saturation) in the zone of Identification Amount applied Amount in harvested forage Amount not recovered Percent recovered in forage Amount applied Amount in harvested forage Amount not recovered Treatment 336 174 162 52 37 16 21 Low N - Irn/ha - 338 247 91 . o/0 73 P kn/hst 78 32 46 % Medium 670 382 288 57 153 43 110 High 1.337 450 887 34 301 52 249 Percent recovered in forage 43 41 28 17 image: ------- ! 30 35 40 45 Figure 2. 15 20 25 Soil NO's-N, Effect of lagoon effluent irrigation rates on soilNO3-N. Treatments with same letter (at same depth) are not significantly different at the 5% level. The control sample (CON) was obtained from adjacent, non-irrigated area fertilized at maintenance levels. highest Na concentration (40 ppm at 210- 240 cm) precluded any loss of soil hydrau- lic conductivity due to Na induced clay dispersion, even though calculation of the ratio of Na and K applied to total salts applied would predict possible dispersion problems. Surface Runoff The sprinkler irrigation system was usually activated each week of the grow- ing season without regard to rainfall. Consequently, some irrigation runoff and irrigation-rainfall mixed runoff occurred, and this runoff was very high in nutrients and oxygen demand. This type of runoff could probably be avoided by withholding irrigation when soil moisture is high or when rainfall is expected. Total runoff (including any irrigation runoff) averaged less than 10% of annual rainfall plus irrigation, which was reason- able for these plots with low slope (1 -3%) and sandy topsoil. However, concentra- tions of nutrients in runoff were high compared to most agricultural runoff. The mean concentrations of total N, NOa-N and P in rainfall runoff (without irrigation runoff) over the six-year period are given in Table 2. Although there was generally an increase in concentration of all nutri- ents with higher effluent rates, only P had a significant increase at the 5% level for the high-rate treatment. Annual mass transport of nutrients in runoff was variable and treatment effects were seldom significantly different. Mass transport by rainfall runoff (no irrigation runoff) was very low compared to nutrient loading rates, e.g. generally less than 1 % forN. The overall potential environmental impact of runoff of the quality measured for the irrigation treatments would de- pend on the particular hydrologic situa- tion and whether concentration or mass transport was the more important. Nutri- ent concentrations were sometimes high Table 2. Nutrient Rainfall Runoff Volume- Weighted Concentrations Concentration, mg/l Low Tmt. Medium Tmt. High Tmt. Total N 7.3 a % NO3-N 2.7 a P 2.0 b 10.2 a 17.3 a 4.2 a 9.8 a 3.4 b 6.0 a %Treatments with same letter are not signifi- cantly different at the 5% level. image: ------- but total runoff and total nutrient mass transport were relatively low. Subsurface Runoff Subsurface lateral flow collected in drain tubes at the interface of the A and B horizons on three plots was much greater in volume than surface runoff for a 20- month period of data. Estimated annual subsurface runoff for a two-year period averaged about 30-45 cm; surface runoff averaged about 1 cm. For layered soils, quality of subsurface lateral flow should be evaluated since it represents a larger flow volume than surface runoff. Duration of individual subsurface run- off events ranged from one to eight days. For a 20-month period, subsurface flow occurred about 15% of the period and volume was about 25% of rainfall plus irrigation during this period. Monthly mean concentrations of NOs-N increased with increased loading rate of effluent. Concentrations from the medium- rate and high-rate treatments were usu- ally between 10 and 30 mg/l. The relative impact of this subsurface flow on quality of water in the surrounding area would depend mainly upon dilution ratios and denitrification rates. Concentrations from the low-rate treatment were less than 10 mg/l. Phosphorus concentrations were usu- ally in the range of 0.1 to 0.3 mg/l for the low-rate and medium-rate treatments, and in the range of 0.3 to 1 mg/l for the high-rate treatment. High applications of effluent promoted P movement in sub- surface flow. Annual mass transport of N03-N, CI" and P in subsurface flow (Table 3) are based upon the 20 months of data. Mass transport of NO3-N was about 8% of applied N for all three treatments. For the high-rate treatment, the estimated an- nual N03-N transport was 115 kg/ha. This represents a high nutrient transport, but the relative water quality impact would depend on the particular hydrologic situation. The P:N ratio in subsurface flow was about 3:100, but was variable. Overall, the nutrient concentrations and mass transport measured for sub- surface drainage from the interface of the A and B horizons indicate that applying swine lagoon effluent at fertilization rates of 670 and 1,340 kg N/ha would likely be detrimental to quality of soil-water inter- flow and ground water in the area. Nitrate nitrogen would probably be the limiting factor, but long-term applications could result in considerable P movement. Philip W. Westerman, Joseph C. Burns, Larry D. King, Michael R. Overcash, and Robert 0. Evans are with North Carolina State University, Raleigh, NC 27650. R. Douglas Kreis is the EPA Project Officer (see below). The complete report, entitled "Swine Lagoon Effluent Applied to Coastal Bermuda- grass," (Order No. PB 83-162 264; Cost: $19.00, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Robert S. Kerr Environmental Research Laboratory U.S. Environmental Protection Agency P.O. Box If98 Ada, OK 74820 Table 3. Annual NOy-N. CI" and P Transport in Subsurface Runoff Estimated Annual Transport kg/ha/yr Nutrient NO3-N cr P Low Tmt. 18 37 0.9 Medium Tmt. 58 60 1.0 High Tmt. 115 108 3.7 •fr U. S. GOVERNMENT PRINTING OFFICE: 1983/659-095/1925 image: ------- United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Postage and Fees Paid Environmental Protection Agency EPA 335 Official Business Penalty for Private Use $300 OQ0032P ^ CHICAGO it image: -------