Comparação entre métodos para estimar a produtividade de grãos de milho

Abstract

The objective of this work was to evaluate the efficiency of two methods used to estimate the productivity of grains on commercial corn farms. The Reetz method, developed at the University of Illinois, in the United States, and the Emater–MG method, used in productivity contests were appraised. The efficiency of the methods was analyzed in three areas, one being in the UFLA and one in Campo Lindo farm in Lavras–MG, and one in Dutra farm in Itumirim–MG. The productivity estimates and the real productivity being obtained in each local. For obtaining of the estimated productivities, the areas were divided in 4 plots, one portion being harvested per plot. Each portion was made up of 7 sub-samples of 4 m2 with 3 ears of corn each, distributed in 4 lines of 10 m. For the Reetz method, the number of ears of corn in 4m2, the number of rows of grain and the number of grains per row were used in the calculation expression. For the Emater method, the spacing among lines, number of ears of corn in 10 m and the average grain weight per ear of corn was used. With the estimates of the sub-samples, variance analysis were made for each local and for each method. With the variance components of each analysis, variance functions were determined in accordance with the number of portions and sub-samples for subsequent determination of intervals of 95% confidence of the estimated average productivity for the methods, with the intention of verifying if these contained the real productivities of the locals. It is concluded that the Emater method is useful for comparisons among productivities of different areas. The number of ears of corn sampled per portion that has been recommended by the Emater method can be reduced by half. The Emater method tends to overestimate the real productivity with the increase of the number of portions and sub-samples, given the increase of the precision of the estimates. The Reetz method needs to be adapted to hybrid groups with similar characteristics.