A short-term study of soil microbial activities and soybean productivity under tillage systems with low soil organic matter

Abstract

Since tillage has an important role in changing soil properties and crop performance, a field experiment was conducted during two growing seasons (2018 and 2019) to assess the possible effects of three prevalent tillage systems (no-tillage, minimum and conventional tillage) on soil microbial activity, nodulation and yield of three soybean (Glycine max) cultivars (Williams 82, Zan and M7) under low content of soil organic matter (~1%). As a result, minimum and no-tillage improved soil basal respiration, metabolic quotient, acid phosphatase and β-glucosidase activities, while decreased soil pH, temperature and NO3-N concentration compared to conventional tillage. Under no-tillage, soil dehydrogenase activity, nodule formation, nitrogen uptake, growth, SPAD values and productivity of soybean cultivars were decreased, and also seedling establishment and day to maturity were delayed in comparison with conventional tillage. Nevertheless, soil microbial biomass carbon and organic matter content were not altered under no-tillage. In contrast, compared to other tillage practices, soil microbial biomass carbon, dehydrogenase activity and nodule formation were increased by minimum tillage resulted in an enhance in nitrogen uptake (~15%), growth, SPAD values, ground cover, grain, protein and oil yields of soybean (~6%). Averaged across tillage and year, the higher nodulation and nitrogen uptake were belonged to M7 and Zan cultivars, which resulted in more grain and protein yields. However, the highest oil yield was recorded in Williams 82. Overall, minimum tillage did not increase the soil organic matter content, but that improved soybean productivity by enhancing soil microbial activities, nodulation and nitrogen uptake; thus, it could be a suitable agronomical practice in the short-term to achieve acceptable yield.