General patterns of soil nutrient stoichiometry, microbial metabolic limitation and carbon use efficiency in paddy and vegetable fields along a climatic transect of eastern China

Abstract

Soil nutrient stoichiometry and microbial metabolic limitation are crucial factors that regulate the biogeochemical cycling process of carbon (C), nitrogen (N) and phosphorous (P) in diversified agroecosystems. Distinct management patterns between paddy fields and vegetable gardens would possess different soil nutrient stoichiometry and microbial metabolic limitation, thus affecting C sequestration, crop production, and environmental consequences. We explored nutrient stoichiometry, microbial metabolic limitation, and carbon use efficiency in paddy and vegetable soils in temperate, warm temperate, and subtropical climatic zones across eastern China. Our results demonstrated that the soil C:N:P ratios were 36.22:3.12:1.00 for paddy and 21.26:1.72:1.00 for vegetable soils. The contents of soil organic C and total N were similar to the global average for agricultural soils; however, the total P content was low. The microbial C/N was higher in paddy soils than in vegetable soils. The ecoenzymatic C:N:P logarithmic ratios were deviating from the global average ratio of 1.00:1.00:1.00 in both paddy and vegetable soils across three climatic zones. Microbial metabolic limitation varied across climatic zones: In the temperate zone, soil microbes were limited by C and N in paddy soils, while by P in vegetable soils. In contrast, in the warm temperate and subtropical zones, microbial metabolic P limitation was observed in both paddy and vegetable soils, but not C and N. Microbial carbon use efficiency increased along climatic transect for paddy while reversed for vegetable field in eastern China. Thus, microbial C:N:P and metabolic limitation served as better indicators for nutrient cycling and carbon use efficiency.