Comparative financial efficiency of training systems and rootstocks for 'Alpine' nectarines (Prunus persica var. nectarine)

[摘要] Most nectarine orchards in South Africa are currently planted at a distance of 4 x1.5 m (2 500 trees/ha). These trees are mainly sylleptically trained to a central leader,although many producers also use the proleptic route. The former produces relativelyhigh yields early in the lifetime of the orchard. A problem with nectarine production inSouth Africa is the lack of efficient rootstocks in terms of aspects such as size-controland the use of nematode-resistant rootstocks. The aim of this study is to evaluate differenttraining systems for nectarine production and to investigate the role of three rootstocksthat play a dominant role in the peach industry in South Africa.'Alpine' nectarines were planted in the winter of 2002 at Lushof near Ceres, WesternCape, South Africa (33º18'S, 19º20'E). The trees were trained according to four differenttraining systems: a four-leader system (5 x 3 m; 667 trees/ha), a two-leader system (5 x1.5 m; 1 333 trees/ha), a proleptically trained central leader (5 x 1 m; 2 000 trees/ha), anda sylleptically trained central leader (5 x 1 m; 2 000 trees/ha). The trees were planted onthree different rootstocks: GF 667; SAPO 778; Kakamas seedling. The time spent per treeon pruning, thinning and picking was recorded. During harvest, the number of fruit andfruit mass per tree were recorded. Light measurements were recorded annually aftersummer pruning. The measurements were taken at different heights and at differentdepths in the canopy. To compare the training systems on an economic basis, the datafrom the trial together with projected data gathered from farmers and advisors were usedto calculate the net present value (NPV) and internal rate of return (IRR) for each trainingsystem.The results showed that rootstock only played a significant role when it came to fruitmass (fruit size). Fruit from trees on SAPO 778 were heavier, indicating bigger fruit, thanfruit from trees on Kakamas seedling rootstocks and this can play a role in packoutpercentage and income. In terms of the training system, the four-leader system took themost time to manage per tree. However, this system took the least time to manage perhectare during the initial years. No differences were found between the two central leaders. They both took the longesttime to manage per hectare. The four-leader system produced significantly less fruit thanany of the other systems during the first two years of production. In the third year ofproduction, there was no significant difference found between the systems.Light penetration seemed to be the poorest at the middle and bottom of the canopy fortrees trained to a central leader. Because of the open centre of the four-leader system,light penetration into the middle of these trees was good, but poor light penetrationoccurred in the upper and outer parts of the canopy underneath the scaffold branches.Poor light penetration occurred in the parts lower than 1.5 m from the ground for all thesystems. This was the area that was measured in this study.The result of an economic comparison showed that according to the IRR rating, the fourleadersystem should be preferred. The final decision should however be made accordingto the NPV rating. Results obtained from NPV calculations did not lead to the sameconclusions as could be made from the IRR calculations. According to the rating of theNPV at five percent discounting rate, the two-leader should be the preferred system,while the proleptically trained central leader system should be preferred at a ten percentdiscounting rate. This implies that when the opportunity cost is low, the two-leadersystem should be preferred, and when the opportunity cost is high, the prolepticallytrained central leader system should be preferred.

[发布机构] Stellenbosch University