Nutrition and Irrigation Interactions for a Practical Solution

Fruit cracking in sweet cherries is an economically significant problem for growers world-wide, and is associated with late season rainfall. Building resilience into fruit from an early stage in order to withstand rapid excess water entry without cracking is important. Recent findings from a Tasmanian Institute of Agricultural Research project have broadened the understanding of the fruit cracking phenomenon. It was discovered during the 2010/2011 growing season that higher volumes of irrigation resulted in increased resilience to rain-induced cracking in the sweet cherry variety ‘Sylvia’. Reduced volumes (deficit) of irrigation increased susceptibility to cracking. The assumption that cuticular integrity was maintained under higher irrigation due to lower diurnal variations in fruit size (therefore increasing resilience) was supported by monitoring fruit growth with sensors during the rapid expansion phase of growth. Fruit from trees under reduced irrigation showed high fluctuations. However, given the structural role of calcium in plant cells, and that calcium is xylem mobile, the higher volumes of irrigation may have favoured the uptake and incorporation of calcium into fruit cells, and thus enabled fruit to better withstand rapid uptake of water through the vascular system. The trial is being repeated in the 2011/12 growing season, with calcium levels in fruit monitored at each fruit growth stage and at harvest. In addition, fruit mechanical properties will be assessed at harvest (January 2012). This should provide information about building resilience to cracking in sweet cherry fruit and highlight the importance of both nutrition and irrigation in managing risk, and the application of that knowledge to provide solutions to a very real dilemma. The findings will be important for the development of future cherry fruit cracking management strategies, which may need to be considered early in fruit growth, rather than later in the season when cracking occurs.