Nitrogen dynamics in soil amended with manures composted in dynamic and static systems

Abstract

The main objectives of this study were to evaluate the stability of three different composts and to study the N dynamics in soil incubated with the composts under laboratory conditions. The composts were produced from sheep manure processed by static pile composting (C1) and from cattle and sheep manure processed by dynamic pile composting (C2 and C3 respectively). Laboratory incubation assays were carried out at 28 °C to determine the amount of N mineralized and N leached under extreme rainfall conditions in the first 30 days after application of doses of each compost equivalent to 170 and 450 kg ha(-1) of N. There were no differences in the values of these parameters in samples of the composts produced by the static (C1) and dynamic (C3) systems, and both composts behaved in the same way when applied to soil. The chemical characteristics of the three final composts, the respiration rates and the lack of stimulation of total microbial biomass indicated that the composts were stable. However, the final C/N ratio was slightly higher in C2 than in C1 and C3 (14 compared with 10 and 11) as was the respiration rate of the high dose of C2 indicating that C2 was more labile, and thus less stable than C1 and C3. Compost C2 generated the highest N mineralization rates after application of different doses (6.5 and 13.1%), as well as the highest N supplying potential (54.7 and 36.2%), and thus the highest rate of mineral N leaching (16.8 and 16.5 mg L(-1) of NO(3)-N), probably as a result of the slight difference in lability. The N release after compost application was very low and thus the leaching potential was also low, indicating that high doses of mature compost (>170 kg ha(-1) of N) could be applied to soil.