Effects of biosolids application timing and soil texture on nitrogen availability for corn

Empirical data comparing the effects of different off-season application timings of biosolids are needed to develop recommendations that protect water quality and ensure an accurate estimate of plant-available nitrogen (N) for crop production. The objective of this study was to compare the effects of biosolids application timing and soil texture on the availability of N for corn. Field experiments were conducted on coarse- and fine-textured soil types on each of two farms in the Coastal Plain Physiographic Province of Virginia, in 1996-97 and 1997-98. Factorial combinations of three N source-application timing combinations (winter-applied biosolids, and spring-applied applied biosolids, spring ammonium nitrate fertilizer) and three N rates (0.5X, 1.0X, and 1.5X agronomic rate), plus a non-N fertilized control, were arranged in a randomized complete block design for each soil type. The biosolids applied were anaerobically digested and dewatered from the Chesterfield, VA wastewater treatment facility. Soil samples were collected and analyzed for NO(3)(-) and NH(4)(-)N in March and May of each year. Corn was harvested from a randomly selected 6 m section of row in each plot and yields were expressed on a 15.5% moisture basis after weighing the shelled grain. Loss of nitrogen by leaching was greater and plant available N and crop yields were lower: 1) when biosolids were applied in mid-December to early January than in March, 2) in coarse- than fine-textured soils, and 3) during years with high amounts of precipitation regardless of soil texture. Coarse-textured soils are better suited than fine-textured soils for the land application of biosolids in winter because vehicular traffic and incorporation practices are less likely to destroy soil aggregation of well-drained coarse-textured soils; however, the properties that enable these soils to drain readily also facilitates greater leaching losses of nitrate nitrogen during the winter.