Subsoil-potassium depletion accounts for the nutrient budget in high-potassium agricultural soils.

CORRENDO A; RUBIO G.; GARCIA FO; CIAMPITTI IA

Scientific Reports

Springer Nature

Lugar: Basingstoke; Año: 2021 vol. 11 p. 1 - 10

2045-2322

Continuous potassium (K) removal without replenishment is progressively mining Argentinean soils. Our goals were to evaluate the sensitivity of soil-K to K budgets, quantify soil-K changes over time along the soil profile, and identify soil variables that regulate soil-K depletion. Four on-farm trials under two crop rotations including maize, wheat and soybean were evaluated. Three treatments were compared: i) control (no fertilizer applied); ii) application of nitrogen, phosphorus, and sulfur fertilizers -NPS-; and iii) pristine condition. After nine years, crops removed from 258 to 556 kg K ha-1. Only two sites showed a decline in the exchangeable-K levels at 0-20 cm but not unrelated to K budget. Topsoil exchangeable-K levels under agriculture resulted 48% lower than their pristine conditions, although still above response levels. Both soil exchangeable-K and slowly-exchangeable K vertical distribution patterns (0-100 cm) displayed substantial depletion relative to pristine conditions, mainly concentrated at subsoil (20-100 cm), with 55 to 83% for exchangeable-K, and 74 to 95% for slowly-exchangeable-K. Higher pristine levels of exchangeable-K and slowly-exchangeable-K and lower clay and silt contents resulted in higher soil-K depletion. Soil K management guidelines should consider both topsoil and subsoil nutrient status and variables related to soil K buffer capacity.