Long-term crop diversity improves soil chemical attributes, nutrient cycling and soybean yield

Abstract Cover crops have the potential to reduce agricultural inputs, but the long-term impacts of cover crops on soil chemical properties and nutrient cycling in tropical systems are not fully understood. This study evaluated the impact of different cover crop systems under long-term no-tillage on shoot dry mass (SDM) production, nutrient cycling, soil chemical properties, and soybean yield in succession in the Cerrado region of Mato Grosso State, Brazil. The treatments consisted of different second crops after soybean cultivation: MC (soybean monocropped), fallow; CS1, Crotalaria spectabilis ; CS2, Pennisetum glaucum ; CS3, Urochloa ruziziensis ; CS4, Cajanus cajan ; and MIX, C. spectabilis + P. glaucum + U. ruziziensis + C. cajan . SDM was evaluated at 0, 90, 105, 120, 150, 180, and 210 days after chemical desiccation of the cover crop using herbicides in the crop years from 2014/15 to 2020/21. Soil chemical properties were evaluated after the 2019/20 soybean harvest. MIX increased SDM by approximately 22% compared with CS2 and CS3 and 60% compared with MC. In years 6 and 7, soybean yields were significantly higher in MIX, CS3, and CS4 than in MC, increasing by approximately 840 kg ha −1 . MIX resulted in the greatest long-term improvements in soil cation exchange capacity, pH, nutrient release and concentration, organic matter, and soybean yield. Even when grown individually, U. ruziziensis , C. cajan , and C. spectabilis also had positive effects on these parameters. Thus, crop successions with cover crops promote improvements in soil fertility and are a sustainable long-term strategy to enhance soybean productivity in the Brazilian Cerrado.