Dry matter decomposition and potassium cycling in no-till integrated crop-livestock systems: the effects of tree shading and nitrogen fertilization

Abstract

In integrated crop-livestock systems (ICLS), understanding residue dynamics is crucial to synchronize nutrient release from pasture litter to cash-crop nutrient demands and overcome potential deficiencies using suitable fertilization strategies. The present study evaluated how the inclusion of trees and N availability affected the release rates of K from pasture (black oat + ryegrass) residues to the subsequent maize crop in a no-till ICLS. The experimental design was randomized blocks with treatments set up in split-plots with three replications. Main plots were systems (crop-livestock only and crop-livestock with trees) and sub-plots N levels (90 and 180 kg N ha-1). Litter decomposition and K release from pasture residues were assessed using litterbags, which were installed at maize sowing, for retrieval at 8, 15, 30, 60, 90, 120, 150, and 165 days of incubation. Regardless of N level, shade of 7-year-old trees reduced pasture residue (-30%). Tree residues were unable to offset the shading effect on pasture growth. A faster dry matter decomposition was observed in treeless treatment and with 180 kg N ha-1, with a half-life ranging from 14 to 38 days. Despite no changes in K-release dynamics among treatments, total K released was significantly higher for treeless system (61 kg K ha-1) than in system with trees (40 kg K ha-1), due to changes in the initial amount of residue. These results must be taken into account in fertilization practices. Therefore, a few feasible silvicultural interventions should be considered to avoid losses in soil cover, maximizing nutrient cycling benefits.