CONTROLLING YIELD AND FRUIT QUALITY IN MAIGOLD APPLE ORCHARDS
A better understanding of the behaviour of an orchard submitted to various management strategies has been reached as a result of a trial carried out at the Centre des Fougères, from 1986 onwards, with the cv. Maigold grafted on M27 rootstock. Four treatments have been tested : three of them combine optimal (long) pruning and three levels of fruit load (minimal, optimal and heavy). The fourth combines severe (short) pruning and heavy load.
The highest and most even yields during the whole experimental period were those obtained while managing the fruit load as suggested in the treatment "optimal pruning and fruit load". However, the initial objective for fruit load proved too generous and should be lowered (5,5 fruits/cm2 of stem cross area, instead of 6,5). The plots with heavy load showed a strong alternance and a break down in yields. Limiting fruit load through excessive thinning (3,5 fruits/cm2 of stem cross area) avoid biennial bearing but results in poor yields and commercial losses due to excessively large fruits which are discarded.
Light pruning and proper load restriction allow for sustained yield of high quality fruits. An excessively severe load restriction results in production of large, commercially discarded fruits. The absence of load restriction results in fruiting alternance and bad fruit quality. An even very severe pruning in not a valuable alternative to load restriction through fruit thinning.