Changes in carbon and phosphorus storages and humic substances in a Ferralsol, after tillage and animal manures applications

Abstract

The evaluation of the dynamics of storage and loss of soil organic carbon (OC) and available phosphorus, associated with humic substances, in areas under no-tillage (NT) that receive solid or liquid animal manure, has been little reported in the literature. This study aimed to evaluate the effect of different doses of liquid (liquid swine slurry) and solid (poultry manure) animal manures on OC and available phosphorus (PAV.) storages and humic substances (fulvic and humic acids, and humin) of a Ferralsol recently managed under a no-tillage system (four years). The experiment was carried out in a very clay Ferralsol. Two periods were sampled: in 2011, before tillage for incorporation of chemical fertilizer (CF) and start of the NT system, and in 2015, after four years of NT management and animal manure applications. Poultry manure (PM) and liquid swine slurry (LSS) were applied in three rates as follows: 2.00, 5.00, and 8.00 t ha−1 of PM and 45.00, 90.00, and 135.00 m3 ha−1 of LSS semi-annually applied without CF complementation. The CF was used as a reference. The use of LSS recovered the OC content of the 0.00–0.10 m depth at levels similar to those observed in 2011, indicating the interaction of the liquid form with the soil. The similarity of humic substance between CF and animal manures of the 0.00–0.10 and 0.10–0.20 m depths was mainly due to LSS use, which contents of fulvic and humic acids were significantly higher than those observed in the soil that received PM. Although the use of the LSS increased the SOC content, no difference in storage was observed among the treatments. Soil tillage for NT system start and CF use resulted in a PAV storage loss of − 2 kg ha−1 yr−1 in 0.10–0.20 m depth from 2011 to 2015. The LSS promoted PAV. sequestration of up to 33.50 Kg ha−1 yr−1 at 0.00–0.10 m depth and 19.93 Kg ha−1 yr−1 at 0.10–0.20 m depth. The LSS was more effective in increasing PAV. storage at the two soil depths compared to CF and PM. The fulvic and humic acids were more than two times higher in LSS than in the PM applications at 00.00–0.10 and 0.10–0.20 m depths. Thus, the liquid form has a greater potential to recover OC content and PAV storage after short-term of NT start (four years), indicating that it is more suitable for the recovery of Ferralsols recently tillage or degraded.