Tillage effects on the soil water balance and the use of water by oats and wheat in a Mediterranean climate

In the drylands of the Cordillera de la costa of central Chile, the water balance variables are governed by a typical Mediterranean precipitation pattern. In this environment, agronomic management practices are mainly aimed at improving the availability of water in the soil, creating optimal conditions for the crops to effectively use the available water. The aim of this study was to determine the soil water balance and water use efficiency in an oat-wheat crop rotation grown in a duplex soil with two contrasting textural layers. An experiment was conducted during the years 2007-2009 at the Experimental Center Cauquenes located in the inner dryland of the coastal range of central Chile. Conventional tillage (Ct), no tillage (Nt) and no tillage with subsoiling (Nt + Sb) systems were established. The water balance for each year of study and the total biomass, grain yield, harvest index (HI), C-13 discrimination (Delta C-13), crop evapotranspiration (ETc) and water use efficiency (WUE) were determined. The crop evapotranspiration (ETc) varied between 273 and 360 mm, with an overall seasonal average of 300 mm. The conservation tillage systems have a positive effect on SWC; however, the results are related to the annual rainfall. In a dry year, Nt + Sb improved the water use efficiency to 8.10 kg ha(-1) mm(-1), higher than that of Ct and Nt by 40% and 55%, respectively. We have demonstrated how understanding the impact of soil tillage systems on compacted soils with an abrupt contrasting soil texture can improve water use efficiency and consequently reduce water loss.