Pollination can be more important than fertilizer
Missing pollination can reduce the yield of fruit trees in a more critical way than reduced irrigation or fertilization. Almond trees pollinated by hand had the highest fruit set (more than 50%) but produced only very small almonds. Excluding pollination, the fruit set was only 5%, with big and heavy kernels. With insect pollination, the fruit set was over 30% with medium sized fruit. Fertilization and irrigation influenced the yield of the trees only in combination with pollination. However, with insufficient irrigation the trees lost more leaves and without fertilization the leaves yellowed more often. The researchers deduced that almond trees can compensate a short-term lack of water and nutrients by activating reserves in the tree. In contrast to this, insufficient pollination cannot be compensated by the tree itself. The study shows the importance of understanding the interaction of different factors influencing fruit yield and quality as well as the general fruit tree performance.