Effects of foliar nickel (Ni) application on mineral nutrition status, urease activity and physiological quality of soybean seeds

摘要

Meteorological data and light information were collected during a one-year period between 2011 and 2012, under a silvopastoral system (SPS) and an open pasture (OP). The SPS was composed of adult native trees Pterodon emarginatus with a density of 156 trees per hectare and 30-year-old Urochloa brizantha (signal grass) pasture. There were seasonal variations in photosynthetically active radiation (PAR) in both systems: SPS and OP and in leaf area index (LAI) on the SPS. A resource incongruity was verified in the different seasons; whereas there was humidity and heat during summer, the amount of light transmitted under the trees was diminished by the increase in LAI and nebulosity (cloud cover). When there was more sunlight passing through the trees and there was less cloud cover, less humidity was observed and the temperature restricted the growth of tropical grass. Shade tolerance must not be the only criterion by which to choose pasture species to be integrated with trees in SPS. The grass dry matter (DM) yield was 65% less in the SPS than in the OP, with amounts of 97.4 and 149.8 g m-2, respectively. This reduction in yield was similar to the reduction in PAR under the trees, 69%.