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Soil samples were collected at both jointing and maturing stages of maize and wheat to compare the effects of 4-year no-tillage (NT) and conventional tillage (CT) on seasonal variations of microbial biomass carbon (C), metabolic quotient, and invertase activity in a sandy loam soil in North China. Soil invertase activity significantly increased (P < 0.05) from summer to spring of the next year and then significantly decreased ( P < 0.05) from spring to summer. With a delay of about 3 months, soil microbial biomass C and basal respiration altered in a similar pattern, while microbial metabolic quotient changed on the contrary. Compared with CT, the NT practice significantly increased (P < 0.05) soil organic C content, and tended to result in higher soil microbial biomass C and invertase activity, as well as lower soil microbial metabolic quotient, especially at the jointing stage of maize. Our results indicated that NT might play an important role in the improvement of soil microbial efficiency, especially at the maize seedling season.

The impacts of tillage system (conventional tillage and no-tillage) and residue management (0, 50, and 100%) on soil properties and soil microbial community structure were determined in the Fengqiu State Key Agro-Ecological Experimental Station, North China. The microbial community structure was investigated by phospholipid fatty acid (PLFA) profiles. The results showed that tillage had significant effects on soil properties and soil microbial commu nities. In no-tillage (NT), microbial biomass carbon (MBC), total N, microbial biomass carbon/soil organic carbon (MBC/SOC), total microbes, and arbuscular mycorrhiza fungi increased, while actinomycetes, G + /G – bacteria ratio and monounsaturated fatty acids/saturated fatty acids (MUFA/STFA) decreased, compared with those in conventional tillage (CT). Residue had a significant positive effect on C/N ratio and MUFA/STFA. Canonical correspon dence analysis indicated that tillage explained 76.1%, and residue management explained 0.6% of the variations in soil microbial communities, respectively. Soil microbial communities were significantly correlated with MBC, total N, C/N ratio and MBC/SOC. Among the six treatments, NT with 100% residue application obviously improved soil microbiological properties, and could be a proper management practice in the Huang-Huai-Hai Plain of China.

The effects of tillage and residue input amounts on soil phosphatase (alkaline phosphomonoesterase ALP, acid phosphomonoesterase ACP, phosphodiesterase PD, and inorganic pyrophosphatase IPP) activities and soil phosphorus (P) forms (total P, organic P, and available P) were evaluated using soils collected from a three-year experiment. The results showed that no-till increased soil total and organic P, but not available P as compared to conventional tillage treatments. Total P was increased as inputs of crop residue increased for no-till treatment. There were higher ALP and IPP activities in no-till treatments, while higher PD activity was found in tillage treat ments and tillage had no significant effect on ACP activity. Overall phosphatase activities increased with an in crease of crop residue amounts. Soil total P was correlated negatively with PD activity and positively with other phosphatase activities. Organic P had a positive correlation with ACP activity, but a negative correlation with PD activity. Available P had no significant correlation with phosphatase activities. Our data suggests that no-till and residue input could increase soil P contents and enhance the activities of phosphatase.