Abstract
The influence of corn, bean and wheat crops residues used as soil surface mulching to control the water evaporation demands, for two soils textural classes, was analyzed in the present work. The treatments consisted of three layers of crop residues, corresponding to 0, 50 and 100% of dry matter produced by irrigated cropping systems, and three water evaporative demands of 3, 6 and 8mm d-1, for two soil textural classes, silty sand and heavy loamy soils, with 84% of sand and 76% of clay, respectively. The experiment was carried out in laboratory, with the soil sample conditioned in a 45-cm high and 20-cm nominal diameter PVC pipes columns. The water evaporation rate from the bare soil column presented different behavior for the three water evaporation demands tested. For water evaporative demand of approximately 3mm d-1, the treatments with corn and wheat crops residues, which represented mulching layer of 50 and 100% of dry matter, the water evaporation rate reached only the first evaporation stage. For treatment with 50% of dry matter with residues produced by bean crop, the evaporation stage moved beyond the first evaporation stage. Finally, for mulching with 100% of bean crop dry matter, the rate of soil water evaporation was influenced by the evaporative demand tested. The relationship among evaporation rate for treatment with 100% of dry matter and the water evaporative demands of 7,0, 5,0 and 2,5mm d-1 were 46, 41 and 47%, respectively
Highlights
A taxa de evaporação da água do solo pode ser agrupada em diferentes estádios
The treatments consisted of three layers of crop residues, corresponding to 0, 50 and 100% of dry matter produced by irrigated cropping systems, and three water evaporative demands of 3, 6 and 8mm d-1, for two soil textural classes, silty sand and heavy loamy soils, with 84% of sand and 76% of clay, respectively
For water evaporative demand of approximately 3mm d-1, the treatments with corn and wheat crops residues, which represented mulching layer of 50 and 100% of dry matter, the water evaporation rate reached only the first evaporation stage
Summary
A taxa de evaporação da água do solo pode ser agrupada em diferentes estádios. O primeiro estádio pode durar de um a três dias, conforme a magnitude da taxa de evaporação, que, nesta fase, depende das condições atmosféricas externas, sendo esta de. Com o aumento da demanda evaporativa, a quantidade de água evaporada no primeiro estádio diminuiu. Entretanto, a quantidade de água evaporada nos 25 dias seguintes, após ter cessado o primeiro estádio, aumentou com a elevação da demanda evaporativa. Prihar et al (1996) estudaram o efeito de resíduos da cultura do trigo, utilizados de várias maneiras, nas perdas por evaporação de água em colunas de solos, para três tipos de solos e dois regimes de evaporação. Unger e Parker (1976) trabalharam com resíduos de várias culturas, em diferentes quantidades, e constataram que, para reduzir a evaporação da água de um solo para o mesmo nível de evaporação com resíduos da cultura do trigo de 8.000kg ha-1 foram necessários 32.000kg ha-1 de resíduos de algodão e 16.000kg ha-1 de resíduos da cultura do sorgo. O presente trabalho teve como objetivo analisar a influência dos resíduos das culturas do milho, do trigo e do feijoeiro nas fases de evaporação da água do solo para duas classes texturais de solos
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