No-tillage system combined with cover crops to improve phosphorus availability in the short term

ABSTRACT Phosphorus (P) is an essential macronutrient for plant growth, and its availability is often influenced by management systems adopted over time. Adopting management systems, such as no-tillage, combined with cover crops, can influence soil P availability through factors including soil organic matter accumulation. This study aimed to evaluate how management systems and cover crops influence different P fractions and organic matter. Furthermore, the effect of the time since the implementation of management systems on phosphorus (P) availability and soil organic matter accumulation was assessed. The study was conducted at an organic farm in Seropédica, Rio de Janeiro, Brazil. The soil was classified as Argissolo Amarelo with a sandy texture in the surface layer, corresponding to Ultisols. The experimental design was a randomized complete block design with three replications in a 2 × 6 factorial scheme, with two main plots representing the management systems (no-tillage and conventional tillage) and six subplots within each main plot: monocultures of pearl millet Pennisetum glaucum, sunn hemp (Crotalaria juncea), and jack bean (Canavalia ensiformis), two cover crop mixtures (100 and 50 % seed ratios of the aforementioned species), and a control subplot with spontaneous vegetation. Soil organic matter (SOM) particle size fractionation and P fractionation were analyzed at two-time points: the beginning of the experiment, in 2019, and four years later, in 2023. Four years later, the management systems increased the soluble phosphorus fraction (114-161 % across the evaluated layers) and decreased the occluded fraction (-23 to -43 %). However, within the management systems, higher values were observed for the occluded fraction and organic phosphorus, which may be correlated with the increase in soil organic matter fractions over time. Cover crops did not affect SOM accumulation and P availability. Soil management systems and time since adoption influenced phosphorus availability and soil organic matter accumulation. However, the timeframe was too short to observe the effects of cover crops.