In the sun-drenched citrus groves of Murcia, Spain, a quiet revolution is taking root. Researchers, led by Margarita Ros from the Centro de Edafología y Biología Aplicada del Segura (CSIC), are exploring how alley cropping—intercropping mandarin trees with legumes and other crops—can transform soil health and boost beneficial bacteria. Their findings, published in the *Journal of Sustainable Agriculture and Environment* (or *Journal of Sustainable Farming and Environment* in English), offer promising insights for the future of sustainable agriculture and, by extension, the energy sector.
For years, monocropping mandarin trees has led to reduced soil biodiversity and functionality. Ros and her team sought to change this by introducing two alley cropping strategies. The first, DIV1, involved diversifying the alley with a sequence of barley/vetch (summer) and fava bean (winter) for three consecutive years. The second, DIV2, repeated the same crops—fava bean, purslane, and cowpea—each year.
The results were striking. While alley cropping didn’t significantly affect alpha-diversity indices, beta-diversity showed significant differences among the three treatments, indicating changes in the bacterial community. “Specific genera such as Haliangium, Microbacterium, Pseudonocardia, Solirubrobacter, and Sphingomonas, known as plant growth-promoting bacteria, showed higher relative abundances in DIV1 and DIV2 than in the monoculture,” Ros explained. “This suggests that alley cropping can enhance the abundance of beneficial bacteria.”
The study also revealed that the genus Novosphingobium showed a higher relative abundance in DIV2, while MND1 showed a higher relative abundance in DIV1. Regarding potential gene abundances related to carbon and nitrogen cycling, only manB (hemicellulose degradation) showed a higher abundance in DIV2 than in the monoculture. However, nifH (nitrogen fixation), amoA, and hao (nitrification) showed higher values in DIV1 and DIV2.
Enzyme activities were lower in the diversified treatments than in the monoculture, but the most significant changes were observed in DIV1, where a sequence of different crops every year proved more effective than repeating the same crops in DIV2.
So, what does this mean for the future of agriculture and the energy sector? Alley cropping strategies like DIV1 and DIV2 could enhance the abundance of beneficial bacteria with increased potential activity related to nitrogen fixation and nitrification. This could lead to more sustainable farming practices, reduced reliance on chemical fertilizers, and improved soil health—all of which are crucial for the energy sector, which increasingly relies on biomass and biofuels.
As Ros noted, “These findings suggest that alley cropping can be an effective strategy to enhance soil health and promote sustainable agriculture.” With further research and implementation, this approach could reshape the agricultural landscape, benefiting both farmers and the energy sector.