Based on 11 years of long-term field experiments, the Innovation Team of Fertilizer and Fertilization Technology of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) found that intercropping of maize and leguminous green manure peas maintained maize growth and grain yield under reduced fertilizer N application relative to monoculture with farmers' N inputs. From a temporal and spatial perspective, green manure intercropping significantly reduced soil bulk density and increased subsoil C storage, which was associated with greater belowground C input, dissolved organic matter, and soil microbial biomass C and N. Furthermore, compared with the monoculture with farmers' N input, intercropping green manure peas with maize under reduced N fertilizer application substantially decreased greenhouse gas emissions and nitrate residues, which could be attributed to less N input and downregulated soil denitrification.

The related results were published in the international journal Agriculture, Ecosystems & Environment under the title of "Long-term maize and pea intercropping improved subsoil carbon storage while reduced greenhouse gas emissions".

Cereal-legume intercropping can improve crop productivity and maintain soil health by improving soil's physical, chemical and biological properties. However, the effects of long-term cropping of gramineous and leguminous crops on the soil organic carbon sequestration and the physicochemical properties of soil profiles remain elusive.

The study found that when compared with monoculture under farmers' N inputs, maize and green manure pea intercropping with reduced fertilizer N application maintained the growth and yield of maize. After an 11-year intercropping, soil organic C concentrations increased by 6.7-12.4% in the top 0-20 cm layer and organic C stocks increased by 8.3-17.9%, and bulk density decreased by 6.4-14.2%. Intercropped soils with optimal N application sequestrated 14.8% more organic C in the 0-100 cm soil profile, particularly at depths of 40 cm and below, and the bulk density decreased by 7.0% on average compared with the monoculture with farmers' N practices.

Fig.1. Changes of soil physicochemical properties in one-meter soil profile after 11-year of cultivation

Fig.2. Greenhouse gas emissions (left) and emission intensity (right) under different treatments

Fig. 3. The proposed scheme showing how green manure pea and maize relay planting maintain maize yield and increase soil organic carbon stock in soil profile, while reducing nitrogen loss and greenhouse gas emission

Professor Cao Weidong from the IARRP is the corresponding author. The research was co-funded by the National Key R&D Program of China (2021YFD1700200) and the China Agriculture Research System of MOF and MARA (Green manure)  (CARS-22).

Paper link:

https://www.sciencedirect.com/science/article/abs/pii/S0167880923001032