Pulses and Soils – promoting symbiosis through crop rotation
The inclusion of pulses in multiple cropping systems, such as intercropping or simple crop rotation, is important for the sustainable management of soil nutrients, for improving soil structure, and overall, it is an important step towards implementing more sustainable agricultural practices. This is of critical importance considering the need to intensify food production while making better use of natural resources and building resilience to climate change.
Through their ability to fix atmospheric nitrogen and solubilize phosphorous, pulses naturally contribute to enriching soils with nutrients and increasing crop yields. This thereby reduces the need for synthetic fertilizers, which in turn reduces greenhouse gas emissions and lowers the risk of soil and water pollution. The inclusion of pulses as part of crop rotation in a farming system reduces the risk of soil erosion by improving soil structure (soil aggregate stability, soil aeration and soil water holding capacity) and supporting soil biodiversity (e.g. roots stimulate microbial activity). Additionally, pulses help to curb pests and diseases when used as green manure or as component crops in intercropping, the practice of growing two or more crops in the same field at the same time.
Reviving the practice of intercropping
Although the inclusion of pulses in crop rotation is sufficient for improving soil health, greater benefits can be obtained by practicing intercropping. Intercropping is a known agricultural practice gaining new momentum thanks to an increasing interest in sustainable agricultural practices. The main advantage of intercropping is the more efficient utilization of available natural resources and an overall increase in crop productivity, compared to single crop harvests.
Critical elements for the practice of successful intercropping are:
- avoiding overlaps in times of peak nutrient demands of crops in the system
- minimizing the competition for light among crops in the system
- growing complementary crops, and
- ensuring that crops have a difference in maturity of at least 30 days.
In general, the combination of two or more crops with different rooting patterns, such as combining a shallow-rooted species with a deep-rooted species, allows for more efficient water and nutrient uptake from the soil.
Pulses and intercropping
Having deeper and more abundant roots, pulse crops can utilize greater amounts of water stored deep within the soil and can withstand drought better than shallow-rooted crops. The deep tap root system of pulse crops, such as pigeon peas, make them more suitable for intercropping with shallow-rooted crops, like coarse cereals and oilseeds, which are often rain-fed.
In India, for example, maize is cultivated both during the rainy season (from April to October) and in the Spring (from mid-November to April/May). Intercropping beans with the maize led to significantly higher yields than growing maize alone.
Pulses can be strategic allies in maintaining and increasing soil health and restoring degraded soils. They can play an important role in achieving the Sustainable Development Goals, thus contributing to food security, better nutrition, climate change adaptation and mitigation and resilience to shocks.
More information on the relationship between pulses and soil health is available in FAO’s publication Soils and pulses: symbiosis for life.