馬拉巴栗疏果試驗

Experiment on Fruit Thinning in Malatar Chestnut, Pachira Macrocarpa, Schlecht

馬拉巴栗一年開花四次，放一樹上週年皆有果實存在，但其主要果產期為在四月底至五月下旬間開花，在七月底成熟之第一期，其他三期之產量皆不及之。馬拉巴栗樹分枝疏朗，主枝與地面作水平放射狀伸展，有整齊之層次，每層著生主枝五六枝，側枝亦多水平生長，分枝稀疏不繁。根據作者與傅文吾氏民國40之報告（1），馬拉巴栗之花朵多著生於短枝上，其結果亦以短枝為佳。此項短枝，一次生長僅幾公分（1-6公分），但結實甚為可靠。枝稍長度在10公分以上者帶徒長性，往往祇開花而不能結成果實。因其結果枝甚短，故一枝結三個以上果實者極為罕見，大多數（約84%）枝梢只結一果。

The Malabar chestnut tree flowers four times a year, but the main crop is produced from the flowers of the first, period. Fruits harvested from the other three periods are not only few in number but also containing a lower percentage of well-developed kernels. in addition, typhoons occur frequently during the blossoming and the fruiting seasons of the second and the third, periods and thus decrease the percentage of setting and increase the number of shedding fruits. This test was conducted in the Chiayi Agricultural Experiment Station for six years since 1950 to 1955. The purpose of, which, is to study whether the yield of the Malabar chestnut tree may be increased by thinning those fruits which are unreliable to mature. The trees had been thirteen years old when the experiment was started, Three levels of fruit thinning treatments were used in this test. The first treatment was regarded as a check, no thinning was made to the trees, i.e. all the fruits of four periods on trees of this, treatment was harvested In the second treatment fruits of the second, third and fourth periods were thinned, and only fruits of the first period were harvested. In the third treatment fruits of the second and fourth periods were thinned, and fruits of both the first and third periods were harvested; Fruit thinning was made when the young fruit was as large as or smaller than a walnut. Each treatment consisted of single-tree plots in randomized block design with eight replications. From the results obtained conclusion was drawn as follows: 1. The differences of the number of fruits and the yields of dry kernels produced per tree were smaller between different treatments, but greater between different years. Obviously the Malabar chestnut tree has a tendency of alternate bearing. 2. Thinning may slightly increase the percentage of the well-developed kernels of the first period crop when a great number of fruits of the third period of the before year was thinned. 3. Statistical analyzing the yields of well-developed dry kernels of the three treatment showed that thinning decreased the yield. Through six years experiment, the yield of well-developed dry kernels produced on the non-thinning trees were unvariably higher than on the thinning ones. 4. In the non thinning group, the trees gave the highest yield of well-developed dry kernels is 1953 and lowest in 1954. Differences of yields between different years were largely significant. Obviously it is due to the alternate bearing. In the second group, fruits of the second, third and fourth periods were thinned, the yearly yield of this group is namely the yield of the first period, the differences of which between different years were all insignificant. Evidently even though fruits of these later three periods were thinned it would not increase the yield of its first period, In the third group, fruits of the second and fourth periods were thinned which was regarded as a moderate practice of fruit thinnin showed different responses according to the quantity of fruits of the third period, For example, in 1953 when fruits of the third period were produced profusely, this treatment significantly decresed the total yield in the next year. In other years of the experiment this treatment showed no effect on the total yield. According to the above mentioned, fruit thinning reduced yields of the Malabar chestnut tree, so it is wise to keep the Malabar chestnut tree from fruit thinning.