种植密度与施氮量对麦茬复种饲料油菜土壤微生物活性的影响

通过田间小区试验，研究了不同油菜种植密度与施氮肥对麦茬复种饲料油菜耕层土壤(0～5 cm)微生物活性的影响.结果表明，复种油菜能显著或极显著性提高耕层土壤微生物量碳(C_mic)、土壤微生物量氮(N_mic)、土壤细菌数(SBN)、土壤真菌数(SFN)和土壤放线菌数(SAN)，而显著降低土壤微生物量碳/氮比(C_mic/N_mic).随油菜种植密度的提高，耕层C_mic、C_mic/N_mic、SBN呈逐渐增加态势，而N_mic、SAN呈降低趋势.随着施氮肥梯度增加，耕层SFN显著提高，C_mic和N_mic呈先降低后增加再降低趋势，以1 000 kg·hm^-2施肥处理最高.SFN和收获期SAN为先降低后升高，苗期SAN则为先升高后降低.相同处理油菜收获期各土壤微生物活性指标均高于苗期，而600 kg·hm^-2苗期SAN则相反.SBN和SAN与C_mic、N_mic呈正相关，与C_mic/N_mic呈负相关，SFN与C_mic、N_mic及C_mic/N_mic之间均无明显相关性.

Effects of planting density and nitrogen application rate on soil microbial activity under wheat/forage rape multiple cropping

A field experiment was conducted to study the effects of planting density and nitrogen application rate on the topsoil (0-15 cm) microbial activity under wheat/forage rape multiple cropping. The results showed that multiple-cropping forage rape with wheat could significantly increase soil microbial biomass C (Cmic), soil microbial biomass N (Nmic), soil bacteria number (SBN), soil fungi number (SFN) and soil actinomyces number (SAN), but decrease soil microbial biomass C/N (Cmic/Nmic). The Cmic/Nmic and SBN increased with increasing planting density of forage rape, while Nmic and SAN were in adverse. SFN increased significantly with increasing nitrogen application rate, but Cmic and Nmic decreased first, increased then, and decreased again, with the highest in treatment 1000 kg x hm(-2) N. Also with increasing nitrogen application rate, the SFN and SAN during harvest stage of forage rape decreased first and increased then, while the SAN during seedling stage increased first and decreased then. Soil microbial activities at rape harvest stage were all higher than those at seedling stage, except for SAN in treatment 600 kg x hm(-2) N. SBN and SAN were positively correlated with Cmic and Nmic, but negatively correlated with/Nmic. No significant correlation was observed between SFN and Cmic, and SMBN and Cmic/Nmic.