Response of reactive nitrogen losses and nitrogen fate in the soil-crop system to intercropping regimes

Abstract

Context

Reactive nitrogen (N) loss from cropping systems is strongly influenced by cultivation regimes and microbial activity involved in soil N cycling. Intercropping offers ecological benefits, including enhanced crop yield, improved soil fertility, and increased resource use efficiency, making it a promising strategy for achieving sustainable agriculture.

Research question

However, the complex interspecific interactions and rhizosphere networks in intercropping systems alter N cycling and losses, and the underlying driving factors remain unclear.

Methods

This study employed a meta-analytical approach and a linear mixed-effects model to assess the effects of intercropping on soil reactive N losses (N₂O emissions, NH₃ volatilisation, N leaching, and runoff) and N fate in soil-crop systems (using data from ¹⁵N tracer trials).

Results

The findings indicate that intercropping significantly reduced soil NH₃ volatilisation, N leaching, and runoff while enhancing the recovery of N derived from fertilisers (Ndff) in soil compared to monoculture. The adoption of intercropping in regions with high mean annual precipitation (MAP > 800 mm) or mean annual temperature (MAT > 20 ℃) as well as in soils that are alkaline (pH > 8), low in soil organic carbon (SOC ≤ 10 g kg⁻¹), or moderate in total N (1 < STN ≤ 1.5 g kg^-¹), in conjunction with high N application rates (NAR > 200 Kg N ha^-¹), resulted in relatively lower NH₃ volatilisation, N leaching, and runoff compared to monoculture. Furthermore, cereal–legume intercropping was found to reduce N₂O emissions. Intercropping in soils with low SOC and STN (STN ≤ 1 g kg⁻¹) or using moderate N application (100 < NAR ≤ 200 Kg N ha⁻¹) increased Ndff recovery in soil and the total soil-crop system.

Conclusions

Intercropping has substantial potential to reduce soil reactive N losses and enhance Ndff recovery in soil-crop systems. The selection of suitable intercropping types, N application rates, and soil conditions should be carefully considered to maximise its effectiveness.

Implications

These findings provide robust recommendations for the future adoption of intercropping practices, the mitigation of N pollution, and sustainable management of N in agricultural systems.