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Winter and growing season nitrogen mineralization from fall-applied composted or stockpiled solid dairy manure

Lehrsch, G. A., Brown, B., Lentz, R. D., Johnson-Maynard, J. L., Leytem, A. B.
Nutrient cycling in agroecosystems 2016 v.104 no.2 pp. 125-142
Beta vulgaris, ammonium nitrogen, bags, composts, dairy manure, field experimentation, growing season, mineralization, nitrate nitrogen, nitrogen, nutrient use efficiency, planting, polyethylene, seasonal variation, soil temperature, spring, sugar beet, water quality, winter, Idaho
Adequate characterization of nitrogen (N) mineralization with time from manure and other organic sources is needed to maximize manure N use efficiency, decrease producer costs, and protect groundwater quality. The objective of our 2-year field study at Parma, ID, was to quantify in situ N mineralization with time as affected by a one-time fall application of solid dairy manure, either composted or stockpiled. The experiment included five treatments: a non-N fertilized control, two first-year rates of stockpiled solid dairy manure (21.9 and 43.8 Mg ha⁻¹, dry wt.) and two rates (53.1 and 106.1 Mg ha⁻¹, dry wt.) of composted dairy manure (hereafter termed compost). Net N mineralized (mineralization less immobilization) was determined to a depth of 0.3 m by repeatedly measuring soil inorganic N (NH₄-N + NO₃-N) concentrations in buried polyethylene bags. Overwinter mineralization was measured between amendment incorporation in fall and sugarbeet (Beta vulgaris L.) planting the following spring. In-season mineralization was measured in situ for seven consecutive incubation periods during the c. 220-day growing season for furrow-irrigated sugarbeet. Net N mineralized often varied among amendments and from year to year through mid-season, likely due to seasonal variation in soil temperature, annual differences in amendment properties, and other factors. In early spring 2003 after a warmer-than-normal winter, immobilization exceeded mineralization, regardless of treatment. In-season net N mineralized peaked between mid-August and early September (DOYs 230–251) each year, regardless of treatment. Annual (c. 11-month) net N mineralized in 2003 averaged 52 kg N ha⁻¹, similar among treatments. In 2004, annual net N mineralized was similar between rates within amendments and averaged 250 kg N ha⁻¹ where manure treated, 150 kg N ha⁻¹ where compost treated, and 106 kg N ha⁻¹ where untreated. On average in 2004, 31 % of compost’s annual net N mineralized occurred before the growing season and 69 % during the season while essentially all of manure’s net N mineralized occurred during the season. None of the amendments’ total N was, in net, mineralized in 2003 but in 2004 on average, 2 % of compost’s and 16 % of manure’s total N was mineralized, similar between rates within amendments. When estimating annual net N mineralized from fall-applied organic amendments, one must account for abnormal temperatures, including those overwinter.