Deficit hídrico e produtividade na cultura do milho

Abstract

Resumo -O objetivo deste trabalho foi avaliar o impacto do deficit hídrico, no rendimento de grãos de milho, e a eficácia da irrigação em todo ciclo e, especificamente, no florescimento. Os dados foram obtidos em dez anos de experimentação, durante os quais doses variáveis de irrigação foram aplicadas por um sistema de aspersão, localizado no centro da área experimental. Foram calculados balanços hídricos, tendo como variáveis a água precipitada (chuva e irrigação) e a evapotranspiração máxima do milho. Foram ajustados modelos de regressão para 27 condições hídricas, relacionando-se rendimento de grãos com deficit hídrico e razão evapotranspiração real sobre evapotranspiração máxima (ETr/ETm). A maior redução na produção ocorre em conseqüência do deficit hídrico na polinização, formação do zigoto e desenvolvimento inicial do grão, numa relação quadrática. Nesse período, a razão ETr/ETm explica quase 80% das variações na produção de grãos, que se estabiliza acima de uma razão de 0,7. A irrigação aumenta e estabiliza a produção do milho; doses de rega de aproximadamente 60% daquela necessária para elevar a umidade do solo à capacidade de campo aumentam a eficiência de uso da irrigação.Termos para indexação: Zea mays, período crítico, eficiência de uso. Water deficit and yield in maize cropAbstract -The objective of this work was to evaluate the impact of water deficit on maize grain yield, as well as the irrigation effectiveness, considering all the crop cycle and, specifically, the flowering period. Data were collected during ten years in several experiments, in which variable doses of irrigation were applied by an aspersion system located in the center of the experimental area. Water balances were calculated, and the precipitated water (rainfall and irrigation) and the maximum evapotranspiration of the maize were considered as inputs. Models of regression for 27 water conditions were adjusted, relating grain yield to water deficit and actual evapotranspiration to maximum evapotranspiration ratio (ETr/ETm). The highest reduction on grain production occurred in consequence of the water deficit during pollination, zygote formation and initial development of the grain, with a quadratic relation. For this period, the ratio ETr/ETm explains almost 80% of the variations in grain yields, stabilizing over a ratio of 0.7. The irrigation increases and stabilizes the maize production; doses of irrigation of approximately 60% of that necessary to rise soil moisture up to field capacity increase the efficiency of use of the irrigation.

Simulating maize yield in sub‑tropical conditions of southern Brazil using Glam model

“…Standardized anomalies were calculated by dividing each value by the standard deviation in the time-series. and the atmospheric evaporative demand are high (Bergamaschi et al, 2001(Bergamaschi et al, , 2006Radin et al, 2003). Tasseling occurred between December and January (Table 1).…”

“…The average sowing date for each municipality, obtained from the data of the official extension service in the state (Emater, RS), represents the average date by which at least 50% of the maize crops were sown between 2002 and 2005. Once the sowing data was known, the mean date of tasseling, milky and physiological maturity was obtained from a set of experimental data (Matzenauer et al, 1995;Bergamaschi et al, 2006) for short season maize hybrids (Table 1).…”

“…Great part of the data was obtained from field experiments carried (1) Of at least 50% of the maize crops, according to the official extension service in the state (Emater, RS). (2) Mean date of tasseling, milky and physiological maturity for short season maize hybrids (Matzenauer et al, 1995;Bergamaschi et al, 2006). (Table 2).…”

“…Doorenbos & Kassam (1979) crop yield models have been used to estimate potential and actual yields, as well as to test the sensitivity of maize genotypes to water deficits (Andriolli & Sentelhas, 2009). Several observational studies on soil-plant-atmosphere relations have also been done in recent decades in southern Brazil Bergamaschi et al, 2006). These modeling and observational researches have focused on spatial scales ranging from field (smaller than 10,000 km 2 ) to larger areas (greater than 100,000 km 2 ).…”

Influence of Irrigation Levels and Plant Density on "Second-Season" Maize

“…As such, supplementary water was emphasized as one of the techniques necessary to stabilize the production of maize (MINUZZI; RIBEIRO, 2012). Bergamaschi et al (2006) observed, from a ten-year field experiment in the city of Eldorado do Sul, RS, that total irrigation provided an increase of nearly 70% in maize yield compared with non-irrigated crops. Moreover, Vieira et al (2013) also found a significant increase in irrigated crops compared with non-irrigated plants.…”