Chlorophyll index (SPAD) and macronutrients relation and productive performance of sorghum hybrids in different sowing dates

Abstract

Sorghum is a crop already established for off season planting, in succession to soybeans in the Southeast, Midwest and also in some areas of Northeast in Brazil. Studying new cultivars is necessary for the sorghum development in the country. Therefore, this study evaluated the productive performance of sorghum in different sowing dates and determined the SPAD chlorophyll index, correlating it with macronutrient contents in hybrids in different development stages and sowing dates. Experiments were conducted in contiguous areas in four sowing dates, the first one was sown on February 26 2013 and the others at 17, 30 and 41 days after the first sowing - (DAFS). The experiments were conducted in a randomized block design with nine hybrids and four replications. Each sowing date was considered an individual experiment, and grouped analysis was done to compare characteristics. Macronutrients and indexes content data of Soil Plant Analytical Division value (SPAD) were evaluated at three different stages within the plant cycle, characterizing an experiment in split plot (development stages - subplots), with the factor in the plot (hybrid x sowing time). Pearson’s correlation coefficients for the variables macronutrient and SPAD index were calculated. Production performance of sorghum hybrids varied according to sowing dates. Macronutrient content of sorghum hybrids varied in different development stages evaluated and sowing dates. SPAD chlorophyll index values have positive linear correlations with nitrogen content in the analyzed phenological stages.