No‐tillage with half‐amount residue retention enhances microbial functional diversity, enzyme activity and glomalin‐related soil protein content within soil aggregates

A 3‐year field tillage and residue management experiment established in North China was used to analyse topsoil (0–15 cm) aggregation, and microbial functional diversity, enzyme activity and glomalin‐related soil protein ( GRSP ) content within aggregates. Compared with conventional tillage ( CT ), no‐tillage ( NT ) alone significantly ( P  <   0.05) increased organic C contents in 50–250 and <2  μ m aggregates and decreased the proportion of C accumulated by 2–50  μ m aggregates and microbial functional diversity indices in <2  μ m aggregates. Regardless of tillage practice, both half‐amount (C50) and full (C100) residue retention tended to increase organic C and GRSP contents, or dehydrogenase and invertase activities, in certain aggregates. Under CT , a poorer performance of C50 than C100 was observed in maintaining Shannon index ( H′ ) and Simpson index ( D ) in >250 and <2  μ m aggregates, and also McIntosh index ( U ) in <2  μ m aggregates, owing to insufficient residue and possible decreases in the distribution of decomposer micro‐organisms. Under NT , however, C50 was more effective than C100 in maintaining/elevating H′ , D and U in all soil aggregates except for 50–250  μ m, suggesting that surplus residue may induce worse soil conditions, decreasing heterotrophic microbial activities. Thus, NT with half‐amount residue retention improved soil physical–chemical–biological properties and could be a useful management practice in North China.