Desempenho agronômico e fisiológico de milho em arranjos de plantas, com e sem braquiária, no verão e outono-inverno

Abstract

In intercropping, competition between species can to affect the physiological processes of plants and cause nutritional deficiencies, making the system unfeasible. Spatial arrangements of plants represent an important cultural practice to minimize brachiaria interference on maize. The objective of this work was to evaluate the effect of maize populations and spacings on the characteristics associated with morphology, grain yield and dry matter of maize and Brachiaria plants in crop sole and intercropping in the summer and autumn-winter. The research was realized in Embrapa Western Agriculture, in Dourados city, Mato Grosso do Sul state, in the summer 2015- 2016 and in the autumn-winter 2016. The experimental design was a randomized block with split-split-plot and four replications. The plots were represented by maize cultivation (single and intercropped with Brachiaria brizantha cv. BRS Paiaguás), the subplots by spacings between rows (0.45 m and 0.9 m) and sub-subplots by maize plant populations. In the summer, maize populations were 45, 65, 75 and 85 thousand ha -1 plants, and in autumn-winter 45, 52, 65 and 96 thousand plants ha -1 in 0.45 m spacing and 45, 52, 57 and 65 thousand plants ha -1 in spacing 0.90 m. In the maize flowering, were evaluated the gas exchange and physiological parameters of the plants. In the physiological maturation were evaluated the morphological characters, the yield components and grains yield and dry matter of maize and brachiaria. Data were submitted to analysis of variance (P≤0.05), and means were compared by Tukey test and regression analysis to plant population maize. In the summer, most of the physiological variables of maize not affected by the treatments, whereas in the autumn-winter, the increase maize population and the spacing reduced the CO2 consumption and the photosynthetic activity of the plants. In the largest plant population there was greater light interception of maize-summer, reducing the height and dry mass of the brachiaria, which was also smaller in the spacing 0.45 m. The maize arrangement in autumn-winter the larger population provided forage growth, and intercropped resulted in lower levels of N, P, Ca, S and Cu of maize and, in the 0.45 m spacing, the chlorophyll index too was less. However, in the greater spacing, the soil cover by the brachiaria made it possible to increase the efficiency of the maize water use. Although of affecting the maize productivity components, the increase of the plant population obtained the highest dry mass yields of straw and grains. The intercropping maize with the Brachiaria brizantha cv. Paiaguás does not reduce the grain yield and also allows to increase the straw to cover the soil, independently of the cultivation in the summer or autumn-winter.