3.3. Grapevine yield and yield components
Grapevine yield responded well to the gradient of soil resources generated by the treatments and a wide range of yields was explored: from 7.2 T ha−1(AL, 2012) to 22.6 T ha−1(IRR, 2012)(Table 3). The AL treatment always gave the lowest yield whereas the irrigated treatments (IRR-FERT and IRR) always had the highest. Soil surface treatments were first applied in 2010, and irrigation and fertilization only started in 2011. As a result, differences between treatments were more pronounced in 2011 and 2012 than in 2010for yield and all yield components (Table 3), except for the shoot number per vine which was manually adjusted to a target of 12shoots per vine a few weeks after budburst. Analysis of the contribution of each component to the yield variation (of Shiraz) yielded the following results: bunch number per plant 55%, berry number per bunch 14%, berry weight 26%, residuals 5%. Bunch number appeared to be the major driver of yield. As the vines were pruned to12 shoots per vine, the number of bunches per shoot (bud fertility) was thus a key yield component.