摘要
This study aimed to quantify the amount of nitrogen (N) mineralized from the organic fraction of farm manures under field conditions. Nine different farm manures were stripped of their ammonium-N content prior to soil incorporation and establishment of ryegrass at two sites in England. Grass N uptake and nitrate-N leaching were measured for five consecutive seasons and compared with an untreated control, with the sum of N uptake + leaching (net of the control) used as an estimate of the amount of organic N mineralized from the applied manures. The amount mineralized was related to thermal time (cumulative day degrees above 5 degrees C-CDD), with two distinct phases - an initial phase up to 2300 CDD (c.18 months under UK climatic conditions) where mineralization proceeded at rates ranging between 0.005 and 0.027% mineralized/CDD and a slower phase at >2300 CDD, where rates were negligible at <0.001% mineralized/CDD. There was no difference between soil types, both being light-textured (<20% clay), but there were differences between manure types depending on the manure C: organic N ratios. For pig slurry and layer manure (C: organic N = 9-12: 1), up to 70% of the organic N was mineralized, compared to 10-30% mineralization from the cattle slurry and straw-based farmyard manures-FYMs (C: organic N = 10-21: 1). The relationships derived provide a useful tool for predicting both the amount and timing of manure N release, with important implications for both crop N uptake and leaching risk.
- 出版日期2016-6