Fruit thinning in 'Conference' pear grown under deficit irrigation to optimise yield and to improve tree water status

A fruit thinning strategy is introduced for 'Conference' pear to mitigate water stress and to maximise yield. Three irrigation and four thinning treatments were applied. The three irrigation treatments were: full irrigation (FI); deficit irrigation, receiving 50% of the water in FI (DI-50); and deficit irrigation receiving 20% of the water in FI (DI-20). The four fruit thinning treatments were: no thinning (NT); light thinning (LT), leaving more than 80% of the crop load; medium thinning (MT) leaving 50% of the crop load; and heavy thinning (HT) leaving 20% of the crop load. All thinning treatments were combined with DI-20, but only NT and MT were combined with FI and DI-50. Fruit thinning improved fruit size in FI and DI-50, but is not recommended because of the high labour cost and reduction in total fresh-market yield. For DI-20, thinning increased the midday stem water potential (psi(stem)), improved yield (with LT), and increased fruit size (with HT). A three-dimensional regression model was developed to optimise fresh-market yield by fruit thinning, and showed the impact of psi(stem) Using the model, it was also possible to choose, for each value of psi(stem), a suitable crop load to maximise the fresh-market yield.