This study, conducted in the Piedmont of North Carolina, was initiated to determine how reductions in N fertilization and green‐manuring with crimson clover (Trifolium incarnatum L. cv. Tibbee) would affect populations and activities of soil microorganisms. Four continuous corn (Zea mays L.) treatments were used: no‐till (receiving herbicides and soil insecticides) with 0 or 140 kg N ha−1 as NH4NO3; conventionally tilled, receiving 140 kg N ha−1, but no pesticides; and conventionally tilled with a crimson clover green manure, but no fertilizer or pesticides. Populations were determined using selective media for culturable bacteria, gram‐negative bacteria, fungi, actinomycetes, Bacillus spp., and Pseudomonas spp. Microbial activities were estimated by enzyme assays for acid and alkaline phosphatase, arylsulfatase, and β‐glucosidase. Microbial biomass C was determined by a chloroform fumigation‐extraction procedure and levels of available N were measured after anaerobic incubation. Surface soil (0–7.5 cm) from the no‐till treatment receiving 140 kg N ha−1 contained significantly more fungi than did soil from the unfertilized, no‐till treatment. Microbial biomass C and available N were not affected by N addition, but levels of acid phosphatase and β‐glucosidase were significantly higher in the fertilized soil than in the unfertilized soil. Surface soil from a crimson clover‐corn rotation contained significantly larger populations of Bacillus spp. (260% more), actinomycetes (310% more), and culturable bacteria (120% more) than did soil from the well‐fertilized conventionally tilled, no‐pesticide treatment. Also, microbial biomass, available N, and levels of alkaline phosphatase, arylsulfatase, and β‐glucosidase were significantly higher in surface soil from the crimson clover treatment than the nonmanured soil. Although the soil biological properties changed significantly during the year, seasonal variations were similar across treatments. Microbial numbers and activities were high in the spring and fall and low during the late summer.

Swine (Sus scrofa domesticus) confinement systems that use anaerobic lagoons for waste collection in the humid regions require effluent removal during the year. Land area adjacent to the hog facility frequently becomes the site for continuous effluent distribution. The objective of this experiment was to determine the effect of long‐term application of swine lagoon effluent to ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] on dry matter yield, stand persistence, and nutrient concentration and removal. Effluent loading rates of low (L), medium (M), and high (H) approximating 335, 670, and 1340 kg of N ha−1 yr−1, respectively, were evaluated for 11 yr beginning in 1973 through 1983. The experiment was a randomized complete block with three replicates. Dry matter yields in Year 11 were altered by effluent loading rates with greater production from the M (19.0 Mg ha−1) or H (19.6 Mg ha−1) compared with the L (13.1 Mg ha−1). Although fluxes in stands occurred, they recovered completely as indicated by these yields. Higher concentrations of N, P, K, Mg, Cl, and Zn were present in forage in 1983 compared with 1973. Calcium was unchanged and Cu, Fe, and Na were less. In vitro dry matter disappearance of the forage was similar among loading rates (0.634) in 1983 and greater than in 1973 (0.553). Concentrations of NO3‐N were higher in 1978 (1.14 g kg−1) compared with 1973 (0.87 g kg−1), but highest concentrations occurred in 1983 (1.57 g kg−1). By 1983, NO3‐N concentrations of forages from the H loading rate approached or exceeded the toxic threshold in all summer harvests. Only the H loading (1340 kg ha−1) caused unstable stands and eventually produced forage that had NO3‐N concentrations potentially toxic if fed as the sole ration to ruminants. Further, it resulted in disproportionally greater quantities of elements—especially N, P, K, Cl, and Na—that remained in the soil environment to become potential soil and soil‐water pollutants.

Metals in municipal and industrial wastes can cause toxicities in plants and Cd can accumulate to concentrations that pose a health hazard for livestock and humans. Therefore, soil properties important in reducing plant availability of metals must be identified. The capacity of a soil to remove metals from solution is one estimate of the effect of that soil on metal availability to plants. Thirty five milliliter volumes of separate solutions of Cd (0.18 mol m−3), Co (0.34 mol m−3), Cr (0.77 mol m−3), Cu (1.10 mol m−3), Ni (0.34 mol m−3), Pb (0.97 mol m−3), Sb (1.64 mol m−3), and Zn (0.61 mol m−3) were equilibrated for 6 d with 5‐g samples of soil from the A horizons and some B horizons of 10 mineral and three organic soils (21 samples). Total removal from solution (sorption) was determined. The samples then were extracted with 1 M KCl so the quantity of nonexchangeable metal could be determined. The respective ranges of sorbed and nonexchangeable metal, expressed as a percentage of the total quantity of metal in the initial solution, were: Cd 0–90, 0–55; Co 15–93, 1–89; Cr 31–100, 22–100; Cu 36–100, 13–100; Ni 12–95, 5–82; Pb 31–100, 14–98; Sb 50–100, 42–99; Zn 13–98, 5–94. Stepwise multiple regression was performed (on mineral soils only) using sand; silt; clay; pH; cation exchange capacity (CEC); exchangeable cations; organic matter; dithonite‐extractable Al and Fe; and ammonium oxalate‐extractable Al, Fe, and Mn as independent variables and the quantity of sorbed or nonexchangeable metal as the dependent variable. Sorbed and nonexchangeable Cd, Co, Cu, Ni, and Zn were related mainly to soil pH or dithonite‐extractable Fe (Fed). Sorbed and nonexchangeable Cr, Pb, and Sb were related mainly to Fed, ammonium oxalate‐extractable Fe, Sand, or clay. Relative retention of metals by soil was in the order Pb > Sb > Cu > Cr > Zn > Ni > Co > Cd. Although CEC is widely used in regulations governing metal loading rates on agricultural land, the results of this study indicate that Fe oxides and clay content would be better parameters to use for soils of the southeastern USA.

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Application of effluent from animal manure lagoons to cropland is an effective method of utilizing the nutrients in the effluent and minimizing groundwater and surface‐water pollution. The objective of this study was to determine the effect of land application of effluent from a swine (Sus scrofa domenticus) manure lagoon on selected soil chemical properties at the end of an 11‐yr study. Effluent was applied at rates to supply approximately 335, 670, and 1340 kg of N ha−1 yr−1 to ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.) on a Paleudult soil from 1973 through 1983. Soil cores taken to a depth of 210 cm were analyzed for H2O‐extractable NO3‐N and Mehlich 1‐extractable P and cations. Nitrate‐N concentrations (1‐5 mg kg−1) with the two lower rates were similar to concentrations where no effluent was applied. At the high effluent rate, NO3‐N concentrations were elevated, particularly in the subsoil, and 540 kg NO3‐N ha−1 was present in the profile. Phosphorus increased with loading rate and at the high rate, P concentrations (450 mg kg−1) in the 0‐ to 15‐cm zone was 10 times the level above which no response to P fertilization would be expected. Potassium concentration increased with loading rate throughout the profile. Magnesium accumulation was inversely related to effluent loading rate in the 0‐ to 15‐cm zone, but accumulation in the subsoil was directly related to loading rate. Comparison of profile nutrient distributions at the high rate for Years 6 and 11 showed no appreciable accumulation of NO3‐N during the period. Accumulation of other nutrients during this 5‐yr period was P, 210%; K, 200%; Ca, 140%; Mg, 60%; and Na, 10% as compared with Year 6. Soil pH was decreased by the high effluent rate but did increase from 4.2 at Year 6 to 5.0 at Year 11 due to the increased rate of application of basic cations during that period. The high rate poses a groundwater pollution hazard because of the large quantity of NO3‐N present in the profile. In previous years, appreciable NO3‐N was also present at the medium rate, but NO3‐N was low at this rate in Year 11. The high P concentrations in the surface soil increase the potential for runoff transport of P, which might pose a surface‐water pollution problem.