Determination of optimum sowing time for black beans in southern Brazil

Abstract

A sowing-time experiment was conducted for 4 years in Pelotas, Rio Grande do Sul, Brazil. Phenological observations, seed yields, seed weights, and stand determinations were made in the experiments. In the early sowings in August and September, soil temperatures were below the requirements for good stands, and heavy rains during the emergence period also reduced stands due to soil crusting. October sowing had the best conditions of soil moisture and soil temperature and resulted in high stands. In later sowings in November to January, soil moisture was too low for good stands. Soil-moisture conditions were found to be an important factor in determining seed yields and seed weights. August sowings produced the highest yields, even though it did not produce the highest stands. August sowing allowed the plant to make best use of the natural climatic conditions of the region and avoid the more detrimental conditions. Soil-moisture conditions in both the vegetative and reproductive periods of the crop were important in determining bean yields. August was recommended as the optimum sowing time for black beans in the region. Where the economic conditions permit, practices which raise the soil temperature during the August sowing times, as well as irrigation, should be considered as a means of increasing bean yields.