[Effects of different amounts of straw return and nitrogen fertilizer application on soil CO2 emission from maize fields.] / ä¸åŒç§¸ç§†è¿˜ç”°é‡å’Œæ°®è‚¥é æ–½å¯¹çŽ‰ç±³ç”°åœŸå£¤CO2排放的影响.

Understanding the effects of different amounts of straw returning and nitrogen fertilizer application on soil CO2 emission from maize field can provide theoretical support for carbon sequestration and CO2 emission reduction and the implementation of black soil region conservation plan. Three rates of straw returning were set up in the semi-arid area of northwest Liaoning Province, China, i.e. 3000 (S1), 6000 (S2) and 9000 kg·hm-2(S3, full amount of straw returned to the field); crossed with three nitrogen fertilizer application rates in the sub-region, respectively, i.e. 105 (N1), 210 (N2, conventional nitrogen application rate) and 420 kg N·hm-2(N3). In addition, there was a control treatment (CK) without nitrogen fertilizer and straw returning. Soil samples were collected after 4 years field experiment with maize plantation. The influence of different treatments on maize field soil CO2 emission and the relationship between CO2 emission and soil dissolved organic carbon (DOC) and microbial biomass carbon (MBC) were investigated in an incubation experiment. The results showed that both of straw returning and nitrogen fertilizer application promoted soil CO2 emission in maize field, which were increased significantly with the increases of straw returning amount and nitrogen application amount. Nitrogen fertilizer application was the most important factor promoting soil CO2 emission in maize field. Straw returning combined with nitrogen fertilizer promoted soil CO2 emission by increasing microbial biomass and increasing DOC consumption. MBC and DOC stimulated soil CO2 emission significantly in maize field, and were mainly affected by their contents in the early stage of incubation. From the perspective of ensuring the fertilization of straw return to the field while reducing CO2 emissions, results from our experiment showed that 210 kg N·hm-2 conventional nitrogen application in combination with 6000 kg N·hm-2 straw returning (N2S2) was the most promising mode in the semi-arid area of northwest Liaoning Province.

[Effects of inhibitors and pig manure on the transformation of urea nitrogen in paddy soil].

With the aim to understand the response of different nitrogen forms in paddy soil under the conditions of urea combined with inhibitors and pig manure, and to explore the nitrogen retention and supply capacity of paddy soil under different management strategy, we conducted a pot experiment with 15N labeled urea. There were six treatments: no nitrogen fertilizer (CK), pig manure (M), urea (N), urea+pig manure (NM), urea+inhibitor (NI), urea+inhibitor+pig manure (NIM). Urease inhibitor (PPD+NBPT) and nitrification inhibitor (DMPP) were used as the inhibitor combination. Soil nitrogen pools, conservation of 15N labeled urea, and rice N adsorption were measured in rice seedling, tillering, and mature stages. Results showed that pig manure significantly increased soil ammonium concentration, soil microbial biomass nitrogen and fixed ammonium, as well as the storage of urea nitrogen in various pools at tillering stage, and significantly increased rice yield. Addition of the inhibitors increased NH4+ fixation by clay minerals and nitrogen immobilization by microorganisms compared with treatment N, and increased urea-derived NH4+ fixation by clay minerals compared with treatment NM. Pathway analysis showed that pig manure increased urea-N assimilation and yield of rice. The urea-derived ammonium fixed by clay minerals was temporarily stored after inhibitors application. NIM treatment stored more N in microbial biomass, and the released ammonium coupled the turnover and mineralization of microbial provided more available nitrogen for the later growth of rice. Both NM and NIM treatments are recommended in paddy fields of north China.

[Effects of stabilized N fertilizer combined with straw returning on rice yield and emission of N2O and CH4 in a paddy field]. / ç¨³å®šæ€§æ°®è‚¥é åˆç§¸ç§†è¿˜ç”°å¯¹æ°´ç¨»äº§é‡åŠN2O和CH4排放的影响.

Based on a two-year field experiment located at Shenyang Applied Ecological Experiment Station of Chinese Academy of Sciences, we examined the effects of stabilized N fertilizer combined with straw returning on rice yield and emission of N2O and CH4 in aquic brown soil. Six treatments were set up, i.e. control (CK), urea(U), urea+urease inhibitor+nitrification inhibitor (U+I), straw (S), straw+urea (S+U), straw+urea+ urease inhibitor+nitrification inhibitor (S+U+I). The results showed that urea application increased rice yield, cumulative N2O and CH4 emission, and global warming potential. The treatment of U+I significantly mitigated cumulative N2O emission. Returning rice straw to the field significantly increased cumulative N2O emission, cumulative CH4 emission, global warming potential, and greenhouse gas emission intensity. The S+U+I treatment had the highest rice yield and greenhouse gas emission intensity. U+I treatment had the the second highest rice yield and the lowest greenhouse gas emission intensity. Rice yield in the S treatment showed no significant difference with CK. Our results indicated that S+U+I and U+I are relatively better agricultural strategies compared with other treatments in paddy fields on aquic soil.