油菜秸秆还田腐解变化特征及其培肥土壤的作用

为促进油菜秸秆腐解,推进农村作物秸秆的资源化利用,减少秸秆焚烧对环境的负面影响,培养与提高土壤肥力,采用尼龙网袋和田间试验相结合方法,设置了油菜秸秆不同还田量处理和不同还田深度处理,研究了油菜秸秆腐解百分率和腐解速率变化特征,分析了油菜秸秆还田对土壤性质及作物产量的影响。结果表明,油菜秸秆还田的腐解百分率随时间延长而逐渐增大,秸秆腐解速率则早期快后期慢;随秸秆还田量增加,腐解速率降低,表现为全量还田的秸秆腐解速率<2/3量还田秸秆腐解速率<1/2量还田秸秆腐解速率<1/3量还田秸秆腐解速率;在种植水稻条件下油菜秸秆还田深度在10 cm时腐解速度最慢,在表层还田腐解速度最快,20 cm深还田腐解速度居中。相比对照处理来说,油菜秸秆还田降低了土壤容重,增加了土壤有机质含量,一定程度上提高了土壤氮磷钾含量(P<0.05)。油菜秸秆还田对水稻作物有极显著增产作用(P<0.01),增产幅度在6.02%～21.17%之间。本试验对水稻油菜轮作体系下油菜秸秆还田腐解特征进行的研究可为调控油菜秸秆还田腐解速度,改善农业生态环境提供参数依据。

Decomposition characteristics of returned rapeseed straw in soil and effects on soil fertility

The burning of straw in open air, straw stacking or abandoning are not only resource-wasting, but also seriously impact surrounding environments, traffic safety, social production and people lives. Although the promotion of rapeseed straw decomposition and rural crop straw utilization limits the negative impacts of straw burning on the environment and improves soil fertility, so far not much research has been conducted on rapeseed straw decomposition rate of rice-rapeseed rotation system in Jiang-Huai area. Different amounts of rapeseed straw were returned to soil at various buried depths in nylon net bags in the experiment. The decomposition characteristics of the returned rapeseed straws and the effect on soil fertility and crop yield were determined. The results showed that the decomposition ratio of rapeseed straw after being returned to the field increased with time. The decomposition rate of rapeseed straw was faster at the initial stage of decomposition but then slowed down right through the final stage of decomposition. Straw decomposition rate was negatively correlated with the amount of returned rapeseed straw to the field. The order of decomposition rate was entire amount straw returned to soil < 2/3 amount straw returned to soil < 1/2 amount straw returned to soil < 1/3 amount straw returned to soil. The decomposition rate of returned rapeseed straw on surface soil was faster than that in the 20 cm soil depth. Also the decomposition rate of returned rapeseed straw in the 10 cm soil depth was the lowest. Returning straw to soil improved soil physical and chemical properties. Not only did it reduce soil bulk density, but it also enhanced soil organic matter and nutrients in comparison with control treatment (KC) at P < 0.05. Returning rapeseed straw to soils increased rice yield. Yield of CK treatment was 7 725 kg·hm^-2. Also compared with CK, yields of different returned straw-to-soil treatments increased in the range of 6.02%~21.17% (P< 0.01). The study therefore provided the basis for controlling rapeseed straw decomposition rates to promote straw resource utilization and improve agricultural eco-environment.