Objectives This study compared the effects of different winter green manure crops on comprehensive soil fertility to provide reference for the efficient cropping system in North China.
Methods A field experiment was conducted from 2012 to 2019 in Tianjin under green manure- spring maize rotation system. The treatments comprised four green manure crops arranged in six planting patterns. These were Orychophragmus violaceus (OrV), hairy vetch (HV), rye, ryegrass (RG), planting of hairy vetch and Orychophragmus violaceus (HV + OrV), planting of hairy vetch and rye (HV + Rye), and winter fallow was designated as the control (CK). In 2019, soil samples in 0–15 cm depth were collected to determine soil physicochemical and biological properties. We used the principal component analysis to evaluate the effects of green manure treatment and the soil property indexes that were highly relevant to soil fertility.
Results Compared to CK, the green manure treatments (P<0.05) increased soil organic matter, total N, total P, available P, readily available K, soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), soil saturated water holding capacity and lowered the soil EC value. Compared with CK, the green manure treatments increased the soil bacteria population by 26.67%–75.89%, fungi population by 61.9%–97.9%, actinomycetes population by 51.4%–92.1%, and soil urease activity by 6.59%–20.47%. HV+Rye, Rye and HV (P<0.05) increased the soil phosphatase activity. Soil invertase activity (P<0.05) was increased in Rye and Ryegrass treatments. HV + OrV and HV increased soil catalase activity. Soil polyphenol oxidase activity was increased in HV, Rye, OrV, and RG. The principal component analysis showed that green manure (P<0.05) enhanced soil fertility, especially the combined planting patterns. Soil fertility was in the order of HV + OrV > HV + Rye >HV>OrV>RG>Rye.
Conclusions Planting green manure over the long term improved the physical, chemical, and biological properties of soil and soil fertility. Mixed planting of winter green manures had the highest contribution to soil fertility, followed by unicasting of winter green manure.
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