不同种植模式对甘蔗根际土壤生物学特性的影响

摘要

Ratooning cane monoculture leads to yield decline , but ratooning cane intercropped with legume crops increases the yields .The rhizosphere soils of “Ganzhe 18” newly planted sugarcane , ratooning sugarcane and its intercropping with soybean were used to study the alteration of the microflora and soil enzyme activities , and as well as some agronomic traits indexes .The sugar contents of the canes show no significant difference in different cultivation modes .However , owing to the larger diameter of ratooning cane , the ratooning cane intercropped with soybean has high yield .Furthermore , the soil enzyme activities in the rhizosphere soils under different cultivation modes are significantly different .The intercropping practice increases the enzyme activities , especially the activities of three soil enzymes involved in the cycles of carbon , nitrogen, and phosphorus , i.e., invertase, urease and phosphomonoesterase .The microbial biomass and the ratio of bacteria/fungi are decreased under the ratooning cane monoculture mode but recovered under the intercropping ratooning cane with soybean , suggesting a shift from fungal type to bacterial type in the compositions of microbial communities between two systems .The ratooning practice declines the total microbial biomass and the soil enzyme activities , suggesting that the nutrient cycles mediated by microbes in ratooning cane soil are blocked and thus decreased the yield of sugarcane , whereas, the intercropping mode has a significant improvement on soil microflora , which increases the yield of sugarcane .%甘蔗多年单一化的宿根栽培导致甘蔗产量下降，而套种豆科作物能较明显地提高宿根蔗产量。本研究以“赣蔗18”的新植栽培、宿根栽培和宿根/大豆套种栽培的甘蔗根际土壤为对象，结合土壤微生物区系、土壤酶活性，甘蔗基本农艺性状及其产量、质量指标，揭示宿根蔗套种大豆的增产机制及生物学意义。结果表明，不同种植模式下甘蔗蔗糖含量基本一致，但宿根蔗套种大豆由于茎径粗大而较宿根连作表现出明显的产量优势。不同栽培模式下甘蔗根际土壤酶活性有显著差异，套种明显提高了宿根蔗根际土壤酶活性，尤其是与碳、氮、磷循环相关的蔗糖酶、脲酶、酸性磷酸单酯酶。不同栽培模式下甘蔗根际土壤微生物总量有显著性差异，单一宿根连作甘蔗根际土壤微生物总量和细菌/真菌比例降低，而宿根蔗套种大豆根际土壤微生物总量和细菌/真菌比例提高，使甘蔗根际土壤微生物从“真菌型”向“细菌型”转变。总之，单一的宿根连作可导致根际土壤总微生物量及酶活性下降，引起土壤微生物介导的营养循环受阻，从而使甘蔗产量下降，而宿根蔗套种大豆模式对根际土壤微生物区系具有明显的改善作用，宿根蔗具有明显的产量优势。