Conservation tillage promotes crop productivity by changing soil aggregation in oasis farming ecosystems

Background Aims Conservation tillage benefited soil aggregate function—essential for soil nutrient cycling and plant growth. Nevertheless, little is known about tillage practices' impact on soil particle aggregation, particularly soil nutrients and distribution of enzymes and microbes among different-sized aggregates, and their possible later influence upon other soil functions and processes. Methods We conducted a long-term experiment with maize ( Zea mays L.) in a region of oasis farming in Northwest China, in which tillage was applied in four treatments: no-tillage, minimal tillage, fold-tillage, and sub-tillage. Soil aggregates were categorized as follow: <0.25 mm (‘micro’), 0.25–2 mm (‘small’), and > 2 mm (‘macro’), whose corresponding nutrient contents, enzymatic activity and stoichiometry were measured, as well as the structure of soil microbial community of those fraction, along with crop productivity. Results The no-tillage treatment increased the amount of N, P, and C in soil, the biomass of microbiota, and the availability P and N within micro-aggregates and bulk soil. It also augmented enzymatic activity for acquiring C- and P as well the enzymatic ratio of C: N but decreased that of N: P in micro-aggregates, and promoted crop productivity compared with conventional tillage. Additionally, microbial community structure differed under the four tillage regimes and between the aggregate fractions, especially under conventional tillage, but the tillage system did not affect alpha diversity. Conclusions Our results showed that no-tillage restructured the soil microbial community composition of aggregate fractions. Thus, long-term conservation tillage promotes soil functioning and crop productivity by changing soil aggregates in oasis farmland ecosystems.