Effect of tillage system on bread wheat yield and grain quality in the temperate semiarid central zone of La Pampa

In the present study the effects of three tillage systems: conventional (CT), vertical (VT) and direct drilling (DD) on three bread wheat varieties of different cycle length, were studied, for yield and yield components. Their influence on grain quality, expressed through thousand kernel weight (TKW, g), test weight (TW, kg/hL), grain protein content (GPC, %) and yellowberry percentage (YBP, %) were also studied. The highest average yield was under CT and DD, while the lowest was under VT. The lowest dry matter accumulation and one third fewer spikes per unit area were determined under VT. Concerning grain quality, a comparatively higher TKW was observed under DD although it showed lower grain protein levels and a higher proportion of YBP. Among varieties, the most consistent grain yield pattern corresponded to the longest cycle material. The largest response to tillage treatments was exhibited by the highest yield potential, middle length cycle variety. Under CT this variety could have been favoured by higher soil nitrate availability. In the case of these two varieties, however, it became evident that in order to acquire high yields and satisfactory protein levels simultaneously, it would have been necessary to correct the N soil levels under SD. The variety sown latest achieved the highest benefits of a more efficient conservation of the water resource. This variety achieved relatively high yields together with an acceptable level of grain quality under DD.