Corn Yield and Nitrogen Uptake in Sandy Soils Amended with Municipal Solid Waste Compost

First year and residual effects of municipal solid waste (MSW) compost application on corn (Zea mays L.) grain yield were evaluated on a Verndale sandy loam (coarse‐loamy, mixed, Udic Argiboroll) at Staples, MN, and on a Hubbard loamy sand (sandy, mixed, Udorthentic Haplaboroll) at Becker, MN. At both locations, compost ‘A’ was applied at 0, 20, 40, and 80 dry tons/acre in 1992, and two other composts, ‘B’ at Staples and ‘C’ at Becker, were applied at 40 tons/acre in the same year. The N fertilizer treatments were 0 or 220 lb N/acre applied each growing year. With the low C:N ratio mature composts ‘B’ and ‘C’, yield was equal to or greater than that of the nonamended control at 220 lb N/acre during the first growing season. Based on the difference between N uptake due to compost and N uptake in nonamended control, about 8% of the total compost N was available from the low C:N ratio composts ‘B’ and ‘C’ the first year while compost ‘A∝, which had a high C:N ratio, reduced stand count and induced N immobilization at Staples. At Becker, there was no response in grain yield with compost ‘A’ without N fertilizer in the first year, however, there was a negative response in grain yield with compost ‘A’ when N fertilizer was applied. In residual years, grain yield with all composts was greater than or equal to that of the nonamended control without N fertilizer. Nitrogen availability from compost 2 to 3 yr after application ranged from 3 to 10% of the total compost N per year and depended on the rate of compost application. The first year, fall soil nitrate N concentrations were elevated with compost ‘B’ and ‘C’, especially with the addition of 220 lb N/acre. In subsequent years, fall soil nitrate N concentrations increased with compost in combination with N fertilizer. Research Question Municipal solid waste (MSW) compost contains a large fraction of organic N that could be potentially beneficial to agricultural soils. A typical MSW compost application of 20 tons/acre can contain from 300 to 500 lb N/acre. Land application of MSW compost has to be managed properly in order to optimize crop growth. Therefore, the objective of this study was to evaluate various MSW compost sources, MSW compost rates, and the interaction of MSW compost with applied inorganic N fertilizer on grain yield, N uptake, and residual soil nitrate N. Literature Summary According to the U.S. Environmental Protection Agency (USEPA, 1993), the estimated annual production of MSW will climb to about 200 million tons by the year 2000 and to 230 million tons by 2010. These projections have prompted interest in composting as an alternative method of managing municipal solid wate. Municipal solid waste compost feedstocks are subject to wide variations and result in variation of the MSW compost chemical and physical properties. Therefore, the beneficial attributes of MSW compost are dependent on a number of factors including: MSW compost maturity, pathogenic, chemical, and inert (plastics) contaminants, and the C:N ratio of the MSW compost. Numerous reports have shown improved soil physical properties due to the addition of MSW compost to soil. Reports have shown improved crop yield in soil amended with MSW compost. However, few studies have evaluated MSW compost and N fertilizer management on crop yield. Study Description Corn yield was evaluated from 1992 to 1994 on a Verndale sandy loam (coarse‐loamy, mixed, Udic Argiboroll) at the Staples Irrigation Center in Staples, MN, and from 1992 to 1995 on a Hubbard loamy sand (sandy, mixed, Udorthentic Haplaboroll) at the Sand Plain Research Farm in Becker, MN. Twelve treatments were evaluated at each site. A control with no compost addition was also included. Compost ‘A’ was applied at: 20, 40, and 80 dry tons/acre at both sites in 1992. Compost ‘B’ was applied at: 40 dry tons/acre at Staples in 1992. Compost ‘C’ was applied at: 40 dry tons/acre at Becker in 1992. N fertilizer treatment applied at: 0 or 220 lb N /acre as urea each growing year. Compost incorporation: 8 in. moldboard plowing at Becker and 4 in. disking at Staples. Applied Questions What is the effect of compost on crop yield? Grain yield response was dependent on the C:N ratio of compost. In the year of compost application, grain yield reduction resulted from an apparent combination of N immobilization and possibly salt toxicity or other toxic effects of immature compost on seed germination. The addition of N fertilizer did not completely overcome the adverse effect of the immature compost. The negative effect of the immature compost was observed only in the first year of application with improved grain yield in the following growing years, especially with the addition of N fertilizer. Conversely, mature compost with C:N ratio less than 20:1 increased grain yield the first year even without the addition of N fertilizer. The addition of N fertilizer with the mature low C:N ratio compost did not increase grain yield significantly compared with the unfertilized mature compost treatment. The mature compost had higher grain yield in subsequent growing years compared with the unfertilized nonamended control, however the addition of N fertilizer resulted in greater or equal grain yield as the fertilized nonamended control. What is compost N availability? There was no N contribution from the immature and high C:N ratio compost the year of application. However, in subsequent growing years, up to 10% of the high C:N ratio (> 30:1) compost N was taken up by plants. Conversely, 8% of the low C:N ratio (< 20:1) compost total N was plant available the first year. In subsequent growing years, 4 to 8% and 3 to 10% of the applied N was available for plants from the low C:N ratio compost and high C:N ratio compost, respectively. What is the effect of compost on soil nitrate N? The first year, the application of the high C:N ratio compost had negligible effect on profile fall soil nitrate N with or without the addition of N fertilizer probably due to N immobilization. However, the low C:N ratio compost increased profile fall soil nitrate N, particularly with the addition of N fertilizer. In subsequent years after compost application, profile fall soil nitrate N was increased only when N fertilizer was applied. Recommendation Refinement of N fertilizer required to maintain yields with added compost is essential to minimize nitrate N leaching potential. Adjustment of N fertilizer application may be required based on the C:N ratio of the compost. Based on compost rates used in this study (20–80 dry tons/acre), a low C:N ratio mature compost application would require less than the recommended rate of N to maintain grain yield the first year. However, when a high C:N ratio immature compost is applied to soil, at least the recommended N rate would be required to supply corn N need the first year.