Distribution and mineralization of biosolids nitrogen applied to dryland wheat

The greatest challenge in land application of biosolids (sewage sludge) for beneficial use is predicting N-mineralization rates so that managers can amend the soil with an agronomic rate of material. We used 11 yr of field-study information from biosolids addition to dryland hard-red winter wheat (Triticum aestivum L. 'Vona' or 'TAM107') to determine not only the distribution of applied N but also to estimate net N mineralization rates. This stud?, is unique since it involves multiple biosolids application in a dryland summer fallow agroecosystem. We applied five or six applications of biosolids from the cities of Littleton and Englewood, CO (L/E) to Weld loam (Aridic Palenstoll) or Platner loam (Abruptic Aridic Palenstoll) at four locations. This paper focuses on the O (control) and the 56- or 67-kg N ha(-1) fertilizer rate, and the 6.7 and 26.8 dry Mg biosolids ha(-1) rates that we added every crop year, The 6.7 dry Mg biosolids ha(-1) treatment resulted in the following average N distributions: 54% soil residual, 9% grain removal, and 38% unaccounted, At the larger application rate of 26.8 dry Mg biosolids ha(-1) treatment, we found the following average N distributions: 35% soil residual, 2% grain removal, and 63% unaccounted. We estimated a net mineralization of 25 to 57% and a first-gear N net mineralization of 13 to 43% for 6.7 drg Mg ha(-1) and a net mineralization of 62 to 78% and a first-year N net mineralization of 41 to 67% for 26.8 dry Mg ha(-1).