Nitrate Leaching From Fall Applications of Biosolids On Winter Small Grains.

Fall-applied biosolids for small grain production in Virginia poses a nitrate leaching risk if greater amounts of biosolids-borne organic and ammonia N are minerailized and ammonified than the amount that can be assimilated by small grains during the fall and winter. This risk can be exacerbated by moisture retention and infiltration properties of soil. Furthermore, biosolids N from different treatment processes vary in their N fraction composition and, possibly, in N transformation rates. The proposed research has the following objectives: 1. To compare temporal nitrogen mineralization rates of two rates of both lime stabilizer (LS and anaerobically digested (AD) fall-applied biosolids 2. To compare the amounts of plant available nitrogen furnished by two rates of LS and AD fall-applied biosolids 3. To compare the amount of LS, AD and synthetic nitrogen taken up by winter small grains 4. To compare nitrate leaching loss from LS and AD biosolids in various soil types with synthetic fertilizer type. Four field studies were established at four locations in the Virginia Coastal Plain and Valley & Ridge physiographic provinces. The soils were an Altavista fine sandy loam, Bojac loamy fine sand, Frederick-Christian silt loam complex and Frederick & Vertrees silt loam association. Eight N-supply treatments were used, including two rates of each LS (Blue Plains, DC or Arlington, VA) and AD (Alexandria, VA) biosolids, three synthetic fertilizer N rates and a zero control. The biosolids were applied at 50.44 kg/ha and 100.88 kg/ha in the fall. The synthetic N treatments were urea applied at 50.44 kg/ha, 100.88 kg/ha and 151.32 kg/ha. The synthetic fertilizer treatments were split at rates of 1/3 in the fall before planting and the remaining 2/3 applied in late winter. The urea treatments are meant to compare biosolids with conventional fertilizer. The last treatment is a control with no nitrogen fertilization. All treatments were replicated four times. Treatment effects were measured by soil and plant testing. Soil was sampled prior to treatment, immediately before winter application and immediately after harvest. Plant tissue was sampled immediately before application of winter split N and at Growth Stage 58. Yield was measured at harvest. Soil samples will be analyzed primarily for nitrate and plant samples will be analyzed to determine nitrogen uptake. Differences in nitrogen fate between treatments will be tested for statistical significance and any observed statistically significant differences will be deemed as conclusive evidence that the treatments affect nitrate leaching in disparate manners.