ABSTRACT
An incubation experiment was carried out with the addition of litter filtrate, litter residue and alanine at 25 â for 36 days under 60% and 90%WHC (water holding capacity) conditions. The results showed that alanine was rapidly mineralized in soil, and soil NH4+-N content significantly increased by 5.4%-44.7% and 16.1%-41.3%, respectively under 60% and 90%WHC conditions compared with the control. The soil net nitrogen mineralization and ammonification rates in the two treatments were also higher than those in the control at the early stage of incubation. However, the soil NH4+-N content was reduced by the addition of filtrate and residue, and the reduction degree of residue was greater. During the incubation, soil NO3--N content showed a linear increasing trend with the incubation time, and it was significantly higher under the 60%WHC condition than that under 90%WHC condition at the end of incubation. The mineralization of soil organic matter was limited by higher soil moisture. Therefore, the soil soluble organic carbon (SOC) content under 90%WHC condition was obviously lower than that under 60%WHC, but nitrous oxide (N2O) emission was 1.5-63.0 times higher than that under 60%WHC. Furthermore, N2O emission was induced significantly by the addition of litter residue under 60%WHC condition. These results indicated that there were different effects of soluble matter and litter residue on soil nitrogen transformation, and these differences would change dynamically in the decomposition process.
Subject(s)
Forests , Nitrogen/chemistry , Soil/chemistry , Carbon/chemistry , Minerals , Nitrous Oxide , WaterABSTRACT
The objective of this study was to investigate the influence of L-methionine on nitrification and nitrous oxide emission in a red soil under laboratory incubation experiments. A subtropical broad-leaved forest soil sample was collected from Wanmulin natural reserve in Fujian Province, Southeast China. Five treatments were carried out with three replications, i. e., control (CK), L- methionine addition (M), L-methionine and NH(4+)-N addition (MA), L-methionine and NO(2-)-N addition (MN), L-methionine and glucose addition (MC). The soil moisture was maintained at 60% WHC or 90% WHC. The results indicated that the soil NH(4+)-N content in the M treatment significantly increased by 0.8%-61.3%, while the soil NO(3-)-N content reduced by 13.2%-40.7% compared with CK. Under 60% WHC condition, soil NO(2-)-N content in the MC treatment was higher than in the M treatment, soil NO(3-)-N content in the MA and MN treatments were greater than that in the M treatment, and greater in the MN treatment than in the MA treatment. The soil NO(3-)-N content was lowest in the M treatment after incubation. These results suggested that L-methionine could inhibit nitrosation process of autotrophic nitrification. To some extent, carbon addition as glucose with L-methionine decreased the NH(4+)-N content, inhibited the autotrophic nitrification and their effects were dependent on water level. Under 90% WHC condition, carbon addition improved denitrification more obviously, but the decrease of NO(3-)-N content was not sufficient to prove the inhibition of hetero-nitrification due to carbon addition in the presence of L-methionine. The nitrous oxide emission from soil was increased by L-methionine addition. Compared with 60% WHC condition, the nitrous oxide emission was higher under 90% WHC condition, and the promotion of L-methionine addition on N2O was greater when glucose added.
