TILLAGE SYSTEM EFFECTS ON WATER USE AND GRAIN YIELD OF WINTER WHEAT, MAIZE AND SOYBEAN IN ROTATION

The increase of water use efficiency is very important, especially in water-limited conditions. The research project, carried out on cambic chernozem soil at Fundulea, in 2008 and 2009, had as the main objective the evaluation of contribution of the deep sub-soiling, done before the implementation of this experiment, and of certain tillage systems on over-winter soil water storage, water use efficiency (WUE) and water use as well as on the yield of winter wheat (Triticum aestivum L.), maize (Zea mays L.) and soybean [Glycine max. (L) Merr.)], in rotation. The following tillage systems were studied: (1) traditional, with moldboard plough (TS); (2) cizel plough tillage (CS); (3) disc/sweep tillage (DS); (4) strip till, only for row crops (ST); and no till (NT). The over-winter soil water storage estimation was based on calculation of the coefficient of rainfall accumulation during winter (CA), and of capacity of soil water conservation (CC). In the case of maize after wheat, CA was 0.6 on plots with deep sub-soiling, 0.6 on plots without deep sub-soiling, 0.6 with TS, 0.6 with CS, 0.7 with DS, 0.7 with ST, and 0.7 with NT. CC was 85 % on plots with deep sub-soiling, 85 % on plots without deep subsoiling, 82 % with TS, 0.84 % with CS, 86 % with DS, 86 % with ST, and 86 % with NT. For soybean after maize, CA was 0.5 on plots with deep sub-soiling, 0.6 on plots without deep sub-soiling, 0.5 with TS, 0.5 with CS, 0.5 with DS, 0.6 with ST, and 0.6 with NT. CC was 77 % on plots with deep sub-soiling, 79 % on plots without deep sub-soiling, 72 % with TS, 78 % with CS, 78 % with DS, 78 % with ST, and 79 % with NT. Water use and water use efficiency showed non significant differences for all crops under this study on both plots with deep sub-soiling and without deep subsoiling, suggesting that the yield differences were not significantly determined by water supply. The water use average for wheat was: 380 mm with TS, 377 mm with CS, 395 mm with DS, and 382 mm with NT. For maize, water use was 339 mm with TS, 345 mm with CS, 343 mm with DS, 341 mm with ST and 343 mm with NT. For soybean, water use was 320 mm with TS, 315 mm with CS, 317 mm with DS, 314 mm with ST and 319 mm with NT. Water use efficiency from precipitations was: For wheat 13.1 kg hayOPPyO� with TS, 12.1 kg hayOPPyO� with CS, 12.2 kg ha ¹mm�EO with DS, and 13.3 kg hayOPPyO� with NT. For maize 25.6 kg hayOPPyO� with TS, 25.6 kg hayOPPyO� with CS, 25.3 kg hayOPPyO� with DS, 22.9 kg hayOPPyO� with ST, and 26.1 kg hayOPPyO� with NT. For soybean 6.6 kg hayOPPyO� with TS, 5.5 kg hayOPPyO� with CS, 5.8 kg hayOPPyO� with DS, 5.5 kg hayOPPyO� with ST, and 6.0 kg hayOPPyO� with NT. Yield increases due to deep sub-soiling were: 0.1% for wheat, 1.5% for maize, and 7.3% for soybean. The average yields recorded were: For wheat 4948 kg hayO� with TS, 4536 kg hayO� with CS, 4814 kg hayO� with DS, 5048 kg hayO� with NT. For maize 8743 kg hayO� with TS, 8954 kg hayO� with CS, 8792 kg hayO� with DS, 7940 kg hayO� with ST and 9052 kg hayO� with NT. For soybean 2098 kg hayO� with TS, 1812 kg hayO� with CS, 1846 kg hayO� with DS, 1798 kg hayO� with ST and 1941 kg hayO� with NT. The highest yields were obtained with NT for wheat and maize. WUE was strongly correlated with yield, and had the highest values for wheat and maize with NT. In the case of soybean, we consider that a significant yield increase can be obtained with an efficient weed control and soil protection with adequate amounts of residues from the previous crop.