"The practice of inter-cropping — which Chinese farmers have practiced for thousands of years — involves growing two or more crops in alternate rows in the same place and at same time, and can greatly increase grain yields. Li Long, Zhang Fusuo and colleagues at China Agricultural University looked at below-ground biological interactions between faba bean and maize...
They carried out field trials in the western Chinese province of Gansu over four years, and showed that inter-cropping with faba bean increased the maize yield by an average of 43 per cent." Faba bean yield also increased significantly.
"The researchers found that the roots of the faba bean plant released organic acids into the soil, which increases the solubility of inorganic phosphorus, a plant nutrient. Plants take up soluble phosphorus more readily, which explains the increase in the crops' yields.""Shen Qirong, a professor in plant nutrition at Nanjing Agricultural University, told SciDev.Net that by inter-cropping, farmers could cut down on the amount of phosphorous fertilizers they use, as inter-cropped plants have more phosphorous available to them."
The full research paper from the Proceedings of the National Academy of Sciences is available here.
Image caption and credit:: Figure 2, "Visualization of rhizosphere acidification of faba bean (a), soybean (b), and maize (c). The roots were embedded for 6 h in agar gel containing a pH indicator (bromocresol purple) without P supply (Greenhouse Study 2). Yellow indicates acidification, and purple indicates alkalization." National Academy of Sciences.