Effects of weed control and manure application on nutrient fluxes in the shifting cultivation milpa system of Yucatan

Abstract

Maize (Zea mays L.) cultivation under the shifting cultivation system of Yucatán, Mexico, is normally limited to 2-3 years due to nutrient depletion and weed pressure. This study was undertaken to evaluate the effect of manure application and weed control on partial nutrient budgets for maize, and assess the effect of grain-only or whole-plant harvest on nutrient removal. Two farms were selected near Mérida, Mexico, each including two cultivation years. Maize grain, stem, and leaf fractions were harvested and analyzed for N, P, and K concentrations, and compared to quantities added through manure, to generate partial nutrient budgets. Multiple years of cultivation did not change soil organic matter content while extractable P was reduced (53-62%) at both farms and extractable K was lower (22%) for farm 1. Plant fractions contained similar amounts of N, while P accumulated in grain, and stem and leaf contained the largest K pools. Applied treatments affected crop nutrient removal predominantly through crop yield. Partial nutrient budgets suggested that with stover removal, the lower rate of manure may be sufficient to maintain P, but not N or K; whereas with the higher rate of manure all partial budgets were positive, suggesting nutrient accumulation over time