Long‐term effects of lime and phosphogypsum on soil carbon and nitrogen and physical attributes under tropical no‐till

Abstract

AbstractLime and phosphogypsum applications are well‐established practices in weathered soils, and their surface application under no‐till (NT) can affect soil physical attributes and C and N fractions. This study determined the long‐term (10‐yr) effects of lime and phosphogypsum applications to the soil surface on soil C and N fractions of a tropical NT field. The experimental design was a randomized block with four treatments and four replications. The following treatments were applied in October 2002, November 2004, and October 2010, respectively: limestone (2,000 kg ha−1), phosphogypsum (2,100 kg ha−1), and limestone (2,000 kg ha−1) plus phosphogypsum (2,100 kg ha−1). In general, after 10 yr of liming, both alone and when associated with phosphogypsum, the cumulative crop straw inputs were increased at least 20% across the years, and the C fractions increased remarkably at different soil depths. Both treatments improved the SOC stocks by 24% (12.5–15.6 Mg ha−1) at 0.1–0.2‐m soil depths and by 10% (30.6–33.8 Mg ha−1) at 0–0.2‐m soil depths, and in general the soil aggregation at 0–0.4‐m soil depths. However, the particulate C and N fractions were reduced at 0–0.05‐m soil depth, suggesting a slight response to the transitory trend of soil organic C (SOC) depletion. Liming, both alone and when associated with phosphogypsum, overcame the transitory C pool depletion and improved soil aggregation, soil C fractions, and SOC stocks and could be considered an important factor that drives the sustainability of cropping systems under NT.