Cover crops affect phosphorus fractions in soybean-based sequences with different phosphorus availability in Mollisols

Abstract

Cover crops (CC) may offer a compelling strategy to increase the availability of nutrients, such as phosphorus (P), in agroecosystems where continuous extractive agriculture has resulted in a depletion of soil fertility. Our objective was to analyse the long-term effect of CC incorporation in soybean-based crop sequences on: i) organic and inorganic P fractions (Pinorg and Porg), ii) extractable inorganic P (PBray), and iii) biochemical soil properties associated with P mineralization (monophosphatase activity and Porg in the coarse fraction (Porg-CF)) in soils with contrasting P availability and under different edaphoclimatic conditions. A factorial design was performed evaluating two sequences (continuous soybean (Sb) or CC/Sb) and two fertilization treatments (with or without P fertilization, +P and 0 P, respectively). In general, the long-term annual implementation of CC tended to decrease inorganic P fractions (Pinorg and PBray), and the magnitude of this effect was more marked when P availability was low (0 P). However, in treatments where P was applied, the use of CC did not modify PBray. The effect of CC on organic P fractions was greater than that of P fertilization. Increases of up to 63 kg Porg ha−1 were determined when including CC, whose magnitude was unrelated with soil texture. Cover crops also increased Porg-CF and monophosphatase activity. Our results demonstrate that, despite decreasing inorganic P fractions, CC have beneficial effects on biochemical variables associated with P mineralization, which is an essential process for crops nutrition.