Contrasting Rhizosphere Soil Stoichiometric Traits and Microbial Nitrogen Limitation between Maize and Peanut under Intercropping and Straw Retention

Aims Extracellular enzyme stoichiometry is a key indicator for assessing resource limitations faced by soil microorganisms. Yet the characteristics of microbial resource limitation in rhizosphere soil under the combined agricultural practices of intercropping and straw retention remain unclear. Methods Here, we conducted a field experiment in the black soil region of Northeast China, to quantify the effects of intercropping and straw retention on soil nutrients, microbial biomass, extracellular enzyme activities, and their C:N:P stoichiometry in the rhizosphere of maize and peanut crops. Results Our results revealed an average vector length (VL) of 1.68 and 1.57 for extracellular enzymes in the rhizosphere soil of maize and peanut, with a vector angle (VA) of 37.80° and 34.67°, respectively. This indicated that soil microorganisms in the rhizosphere of both crops were co-limited by C and N, and the N limitation was more significant in the peanut rhizosphere. Notably, the combined treatment of intercropping and full straw retention increased the VA by 5°, effectively alleviating N limitation in the rhizosphere soil. The extracellular enzyme C:N:P stoichiometry in the rhizosphere soil of maize and peanut was 1.33:1.29:1.00 and 0.89:1.29:1.00, respectively. Microbial biomass nitrogen (MBN) was the primary factor affecting microbial nutrient limitation. Conclusions The extracellular enzyme stoichiometric characteristics of rhizosphere soil differed significantly between the two crops. Intercropping had a stronger impact on rhizosphere microbial nutrient limitation than straw retention, and their synergistic effect could significantly alleviate rhizosphere microbial N limitation by enhancing extracellular enzyme activity.