Influência dos resíduos vegetais na superfície do solo na dinâmica de evaporação da água e temperatura do solo

Abstract

The availability and proper management of water represent fundamental aspects of the development of sustainable agricultural production systems, since it has direct impact on crop productivity. Maintaining crop residues on the soil surface reduces soil water loss by evaporation and soil temperature changes. Irrigation may be an efficient and safe tool to increase and support crop yields. The accuracy of crop evapotranspiration calculation is important for obtaining satisfactory results, in this context the use of dual crop coefficient allows for the accurate estimation considering separately evaporation soil and crop transpiration. Thus, the objective was to evaluate the influence of plant residues on the surface on the dynamics of water evaporation and soil temperature in the early stages of development of soybean plants. Moreover: (i) quantify plant residues effects on water evaporation, (ii) determine the effect of coverage on soil temperature and (iii) to compare the results obtained under field conditions with simulations performed with the dual crop coefficient methodology. A trial was done on a set of drainage lysimeters installed in a rain-out shelter, located in Las Brujas Experimental Station (34 ° 40 '19''S, 56 ° 20'24''W., altitude 45 m) of the National Research Institute of Agriculture (INIA), Uruguay. Design experimental was completely randomized, factorial with three replications. The factor A was composed of two levels of ground cover (0 and 4 Mg ha-1 of oat straw) and the factor B represented the area of soybean cultivation (with and without plants). Water losses were determined in soil drying cycles based on reference evapotranspiration (ETo). It was estimated by the Penman-Monteith equation.The soil water content was determined with TDR sensors installed at 0-10 cm and 10-30 cm depth. Soil temperature was measured with thermometers installed at 5 and 10 cm depths, records every 30 minutes. The evaporation rate of soil water was reduced 50% by plant residues on the soil surface. The soil cover resulted in maximum temperature 6 º C lower, minimum temperature 2 ° C higher and temperature range 40% lower. The soil water simulations using dual crop coefficient methodology resulted in good agreement with values measured in soil lysimeters without cover and on the ground covered by crop residues.