北方稻蟹共作对水体氮素淋溶损失的影响

Effects of rice-crab culture on nitrogen leaching in rice fields in the north of China

为探索稻蟹共作系统水体氮(N)素的淋溶损失,在辽宁省盘锦市开展田间试验。试验采用二因素裂区设计,以养蟹为主因素,施N肥为副因素,设置4个处理,即单作稻不施N肥(R0M),稻蟹共作不施N肥(R0C),单作稻施N肥(施N量为160kg/hm^2,R1M)和稻蟹共作施N肥(160kg/hm^2,R1C)。结果表明:铵态氮(NH4^+-N)是田面水中N素存在的主要形态,占田面水中总N(total nitrogen,TN)含量的50.8%;硝态氮(NO3^--N)是淋溶水N素的主要形态,占TN淋溶量的58.5%。施肥可以显著提高土壤微生物量N(microbial biomass nitrogen,MBN)含量、田面水N素和淋溶水N素含量(P<0.05)。养蟹稻田的土壤MBN含量较单作稻田提高了17.7%。养蟹可以显著降低淋溶水NO3^--N含量(P<0.05),但是对田面水N素、淋溶水铵态氮(NH4^+-N)和可溶性有机氮(dissolved organicnitrogen,DON)含量影响较小。淋溶水NO3^--N含量与田面水NO3^--N含量呈线性正相关(P<0.01),淋溶水DON含量与土壤MBN含量呈线性负相关(P<0.01)。R1M和R1C处理的TN淋溶量分别占当季施肥量的7.6%和6.3%,N淋溶不是肥料中N素损失的主要途径。在施肥条件下,养蟹降低了15.0%的TN淋溶量(P<0.05),而在不施肥条件下,降低了7.2%的TN淋溶量(P>0.05)。说明稻蟹共作模式可以有效地降低稻田肥料N素的淋溶损失。

In order to explore the leaching loss of nitrogen (N) in the rice-crab culture system, a field experiment was carried out in Panjin, Liaoning Province. A split-plot design with two factors was arranged in this experiment, with crab or without crab as main factors, with or without N fertilizer as sub-factors. The treatments included: 1) rice monoculture without N fertilizer (R0M);2) rice- crab culture without N fertilizer (R0C);3) rice monoculture with N fertilization (with N of 160 kg/hm2, R1M);4) rice- crab culture with N fertilizer (with N of 160 kg N/hm2, R1C). The results showed that NH4^+-N was the primary form of N in flooding water, accounting for 50.8% of the total N (TN), while NO3^--N contributed the most to N in leaching water, accounting for 58.5% of TN. Fertilization could significantly increase the concentrations of microbial biomass nitrogen (MBN) in soil, N in flooding and leaching water (P<0.05). The mean concentration of soil MBN in rice- crab field was 17.7% higher than that in rice monoculture. Rearing crab significantly increased the concentration of MBN in soil and reduced leaching losses of NO3^--N (P<0.05), but had little effect on N concentrations in flooding water and leaching losses of NH4^+-N and dissolved organic nitrogen (DON). The concentration of NO3--N in the leaching water showed positive correlation with NO3^--N in flooding water (P<0.01), while the concentration of DON in the leaching water was negatively correlated with the concentration of soil MBN (P<0.01). The cumulative TN leaching of R1M and R1C treatments was 7.6% and 6.3%, respectively, which indicated that the N leaching was not the predominant fertilizer N losses. Rearing crab in rice fields could reduce the cumulative TN leaching by 15.0% at fertilized plots (P<0.05), and 7.2% at no fertilized plots (P>0.05). All in all, the integration of rice and crab cultivation effectively reduces the leaching loss of N fertilizer in rice field.