Residual effects of phosphogypsum rates and machinery traffic on soil attributes and common-bean (Phaseolus vulgaris) yield in a no-tillage system

Abstract

Phosphogypsum (PG) affects many soil attributes, but its long-term effects on soil structure and physical properties remain unclear. We evaluated the residual effects of PG and induced soil compaction on selected soil chemical and physical attributes, and on common bean (Phaseolus vulgaris) yield. The experiment was initiated on a Typic Hapludox soil using a split-plot design with four replicates. In November (2009), PG at rates of 3, 6, 9, 12 Mg ha−1 was broadcast on the soil surface. In November (2012), traffic compaction was applied to the soil and the treatments were wheel-track (WTR), between wheel tracks (BWT) and no traffic/reference (REF) zones. Compaction was applied with a four-wheel-drive tractor with 2.4 and 3.6 Mg on the front and rear axles, respectively, at field water capacity (FC). Common bean was sown in February (2013) and its yield was assessed at physiological maturity. Forty-two months after application of traffic treatments, the 0.0−0.1 and 0.1−0.2 m soil layers were sampled. Phosphogypsum decreased exchangeable acidity and Al3+ concentrations, and increased pH and Ca2+ in both soil layers, as well as SO42- in the 0.1−0.2 m layer. Despite increasing water-dispersible clay (WDC), PG decreased aggregate tensile strength (TS) at the WTR and BWT zones. Phosphogypsum rates increased organic carbon concentrations in soil aggregates. Machinery traffic increased the values of WDC and TS, but also decreased common bean yield. PG application alleviated the negative impacts of wheel traffic on TS. We conclude that the residual effect of PG can positively affect soil chemical and physical attributes and contribute to alleviate the impacts of machinery traffic.