Microbial activity and carbon rates the soil in response to the application of potassium sources

The continuous use of KCl may not be sustainable in the long term in agricultural systems. High doses used in crops accumulate in the soil and plants, hindering the metabolic processes of soil organisms. This study assessed the soil microbial activity in response to the application of K sources in banana crop and effects on microbial C. The experimental design was completely randomized with four K sources: potassium nitrate (KNO3), potassium chloride (KCl), potassium sulfate (K2SO4), and monopotassium phosphate (KH2PO4) at 200 mg kg-1of K2O, besides the control (without K) and combinations KCl:K2SO4. KCl application increased microbial activity 7 days after incubation, with gradual reduction over time. The isolated application of K2SO4and the combination KCl: K2SO4at the ratio 60: 40% increased total CO2released by the microbiota. K2SO4source had the highest microbial biomass C (MBC), as well as the 60: 40 combinations. Isolated application of K sources, especially with high chloride concentration, reduces the soil microbial activity and MBC.(AU)

Maize yields and carbon pools in response to poultry litter, rock phosphate and P-solubilizing microorganisms

The acid release of phosphates from rock phosphates (RP) and the retention of ammonium by inorganic phosphates have been studied separately in composting; however, there is a gap in the knowledge of combined application of RP with organic residues and microorganisms. The objectives were to evaluate the combined application of fresh poultry litter (PL) with RP and P-solubilizing microorganisms (M) on soil organic matter pools, microbial biomass C (MB-C) and on whole-plant silage maize and grain yields. Two field experiments tested the effects of timing of applications of PL (8 Mg ha–1), RP (4 Mg ha–1) and microorganisms on soil organic matter pools, nutritional aspects and productive components of maize crop whole-plant silage. A second experiment evaluated the effects of RP doses (0, 3, 6 and 9 Mg ha–1) with a fixed dose of PL (8 Mg ha–1) on maize grains. Application of PL+RP decreased soil organic C, while RP alone increased the humin fraction C compared to the control. The MB-C in soil with PL and PL+RP+M increased in comparison to the control and the RP. The application of PL, based on an average of fall and spring, increased leaves + stem dry matter, while in the fall on its own, the highest cob yield was observed in the combination of PL+RP, showing synergistic effects. The best ratio of poultry litter to rock phosphate combination is 2:1 in the anticipated fall application on the maize silage crop or immediate application on the maize grain crops.(AU)

Maize yields and carbon pools in response to poultry litter, rock phosphate and P-solubilizing microorganisms

The acid release of phosphates from rock phosphates (RP) and the retention of ammonium by inorganic phosphates have been studied separately in composting; however, there is a gap in the knowledge of combined application of RP with organic residues and microorganisms. The objectives were to evaluate the combined application of fresh poultry litter (PL) with RP and P-solubilizing microorganisms (M) on soil organic matter pools, microbial biomass C (MB-C) and on whole-plant silage maize and grain yields. Two field experiments tested the effects of timing of applications of PL (8 Mg ha–1), RP (4 Mg ha–1) and microorganisms on soil organic matter pools, nutritional aspects and productive components of maize crop whole-plant silage. A second experiment evaluated the effects of RP doses (0, 3, 6 and 9 Mg ha–1) with a fixed dose of PL (8 Mg ha–1) on maize grains. Application of PL+RP decreased soil organic C, while RP alone increased the humin fraction C compared to the control. The MB-C in soil with PL and PL+RP+M increased in comparison to the control and the RP. The application of PL, based on an average of fall and spring, increased leaves + stem dry matter, while in the fall on its own, the highest cob yield was observed in the combination of PL+RP, showing synergistic effects. The best ratio of poultry litter to rock phosphate combination is 2:1 in the anticipated fall application on the maize silage crop or immediate application on the maize grain crops.