Comparison

Soil degradation is a major limitation for food production and is an underlying cause of poverty and malnutrition around the globe. One potential strategy to address these challenges is to increase local-scale crop diversity using legume intercrops, which can form symbiotic relationships with nitrogen-fixing soil bacteria called rhizobia. Through this symbiosis, rhizobia add atmospheric nitrogen to the soil in a form that plants can use, which can increase soil health as well as support crop production. This comparison presents studies that evaluated the impact of legume intercrops on the level of soil nitrogen relative to crop monocultures (i.e., a field planted to only one crop species). Papers included in the comparison were identified through a Web of Science search that included the following search terms: "legum* intercrop*" OR "legum* polyculture" AND ("soil nutrient*" OR phosphorus* OR nitrogen* OR potassium*) AND (effective* OR performance* OR assessment* OR evaluation* OR estimate* OR comparison* OR contrast*). Selected papers include those that were either open access or accessible through the University of Leibniz, Hannover Technical Information Library, and that provided information on soil nitrogen levels in the text or in tables; data presented in figures or plots that required extraction were not included in this comparison. The search yielded 121 papers; data from four papers met the eligibility criteria and were included in the comparison.