The Benefits of Hand Thinning Nules Clementine Mandarin

摘要

Although hand thinning is a common practice in deciduous fruit production, not many citrus growers use this practice due to the fact that it is very labour intensive. An economic premium is paid for larger fruit and the income from the smaller fruit is often less than the picking and transport costs. Previous results indicated that a large proportion of fruit must be removed in order to affect fruit size positively. Fruit thinning usually causes a certain reduction in total fruit yield, although the smaller yield may be of higher commercial value. The objective of this study was to determine if hand thinning results in any benefit, other than an increased fruit size. Nules Clementine trees on Troyer citrange rootstock in the Porterville area were used for the study. On 7 December 2006, 12 single trees in a complete randomized block design were left unthinned or all fruit <21mm were hand thinned from 12 trees, respectively. Hand thinning increased fruit growth and fruit size significantly, but had no significant effect on yield, although it resulted in a 11% yield reduction. The total time taken to thin and harvest was the same for the two treatments, but harvest took longer on the unthinned control trees compared to the thinned trees. Therefore hand thinning, by removing small unmarketable fruit early in the season, reduced the harvest time of a slightly lower crop load of larger, more marketable fruit. This is especially important for harvesting Clementines in the Western and Eastern Cape in South Africa, since these are harvested at the start of the rainy season.