Conservation system improves soil microbial quality and increases soybean yield in the Northeastern Cerrado

ABSTRACT The conservation tillage systems is based on the surface protection by crop residue and reduced soil disturbance. These two principles can favor the soil quality and promote sustainable agricultural systems. The study was developed with the objective of measure soil microbial biomass, soil basal respiration, enzymatic activity and soybean yield in conservation systems cultivated with cover crops species in the Northeastern Cerrado. The experiment was carried out in 2016/2017 and 2017/2018 cropping seasons, performed in a randomized blocks design. The treatments were soil tillage systems allocated in the main plots: no-tillage (NT) and minimum tillage (MT) and the cover crops were allocated in the subplots: Pennisetum glaucum (millet), Urochloa ruziziensis (brachiaria), Crotalaria spectabilis (C. spectabilis), Crotalaria ochroleuca (C. ochroleuca), Pennisetum glaucum + Crotalaria spectabilis (millet + C. spectabilis) and spontaneous plants with three replicates. The evaluated variables were dry mass (DM) production and nutrient accumulation in cover crops; soil biological properties, namely microbial biomass carbon and nitrogen (MBC and MBN, respectively), respiration, metabolic quotient (qCO2), dehydrogenase enzymatic activity (DH), fluorescein diacetate (FDA); and soybean yield. The higher production of dry mass and nutrient cycling occurs with the intercropping millet + C. spectabilis and single millet. The highest soybean yield occurs in succession to C. ochroleuca and intercropping of the millet + C. spectabilis. Cover crops in conservation systems improve soil microbial quality and increase soybean yield.

摘要 保护性耕作体系以作物残茬地表覆盖与降低土壤扰动为核心依据，这两大核心原则有助于改善土壤质量，推动农业可持续发展。本研究旨在评估巴西东北部塞拉多地区覆盖作物种植下的保护性耕作体系中，土壤微生物量、土壤基础呼吸、酶活性与大豆产量。本试验于2016/2017与2017/2018两个种植季开展，采用随机区组试验设计。试验设置主区与副区处理：主区为耕作方式，包括免耕（no-tillage, NT）与少耕（minimum tillage, MT）；副区为覆盖作物，分别为狼尾草（Pennisetum glaucum，小米）、鲁兹臂形草（Urochloa ruziziensis，臂形草）、美丽猪屎豆（Crotalaria spectabilis，C. spectabilis）、黄花猪屎豆（Crotalaria ochroleuca，C. ochroleuca）、狼尾草与美丽猪屎豆混播组合（millet + C. spectabilis）以及自生植物组，每组设置3次重复。本试验测定的指标包括：覆盖作物的干物质（dry mass, DM）产量与养分积累量；土壤生物学特性，即微生物量碳（microbial biomass carbon, MBC）、微生物量氮（microbial biomass nitrogen, MBN）、土壤呼吸、代谢商（qCO2）、脱氢酶活性（dehydrogenase, DH）、荧光素二乙酸酯（FDA）酶活性，以及大豆产量。结果显示，狼尾草单播以及狼尾草与美丽猪屎豆混播处理下，覆盖作物干物质产量与养分循环效率更高；当前茬种植黄花猪屎豆，或采用狼尾草与美丽猪屎豆混播时，大豆产量可达最高水平。保护性耕作体系下种植覆盖作物，可改善土壤微生物质量并提升大豆产量。