Nitrogen Fertilizer Equivalency of Sewage Biosolids Applied to Dryland Winter Wheat
- K. A. Barbarick * and
- J. A. Ippolito
Determining the N fertilizer equivalency or mineralization rates associated with continuous application of biosolids are paramount in estimating “agronomic rates” for various crops. We used 6 yr of field-study data from sewage biosolids application to dryland hard-red winter wheat (Triticum aestivum L., ‘TAM107’) to estimate the N fertilizer equivalency and mineralization rates of Littleton and Englewood (L/E) biosolids. We made three L/E biosolids and urea applications to two sites (Weld loam soil) using a dryland winter wheat summer-fallow management system. Biosolids rates were 0, 2.2, 4.4, 6.6, 8.8, and 11 dry Mg ha−1 while N fertilizer rates were 22, 44, 66, 88, and 110 kg N ha−1; we replicated all treatments four times. Using N uptake data, we found application of 1 dry Mg of L/E biosolids before each planting delivered an equivalent of about 8.2 kg N fertilizer. By contrast, estimates ranged from 6.2 to 6.7 kg fertilizer N Mg−1 L/E biosolids using the USEPA plant-available N calculations. We also calculated, from our field-study results and USEPA estimations, first-year mineralization rate ranges of 25 to 32%. In a companion greenhouse study, we found that a single application of biosolids provided an N response for only two wheat croppings. These approximations should help managers determine the “agronomic rate” for continuous biosolids additions to dryland winter wheat.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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