ผลของการปลูกพืชร่วมต่อการเจริญเติบโตและผลผลิตของปาล์มน้ำมัน

Abstract

Intereropping has been practiced on oil palm farms for a long time especially in Southern Thailand. However, there are few studies related to oil palm intercropping. This research used three studies to investigate the effects of intercropping on oil palm trees. The I" and the 2"' studies determined the effects of intercropped plants with edible leaves, on 3-month-old oil palm seedlings and 2-year-old oil palm trees. Both studies used completely randomized design (CRD) with six treatments including oil palm sole cropping (TI), oil palm intercropped with cashew (T2), sweet leaf bush (T3), cha-om (T4), melinjo (T5), and melientha (T6). Each treatment consisted of three replications. In the I" study, the growth parameters of oil palm seedlings and intercropped plants were measured every month from November 2019 to April 2020, and their biomass parameters were weighed every 2 months: December 2019, February and 'April 2020. In the 2" study, the growth parameters of oil palm trees were measured every 3 months: September and December 2019, March, June, and September 2020. The growth parameters of intercropped plants were measured every month from December 2019 to September 2020. The roots of oil palms and intercropped plants were scanned every month from January to September 2020. The 3"' study determined the effects of woody intercropped plants on 12-year- old oil palm trees. The study was arranged as CRD with eight treatments including oil palm sole cropping (Palm), oil palm intercropped with Borneo teak (Palm-A), iron wood (Palm-B), mahogany (Palm-C), Ternstroemia (Palm-D), Indian walnut (Palm-E), champak (Palm-F), and Ceylon ironwood (Palm-G). Each treatment consisted of ten replications. The growth parameters of oil palm trees and intercropped plants were measured, and yield characteristics of oil palm trees were counted every 4 months: October 2019, February and June 2020. The results showed that, from the I" study, the plant height and diameter, leaf length and width, number of bifurcate and pinnate leaves, leaflet length and width of oil palm seedlings were not significantly different among the treatments in all observed months, excepts for the number of bifurcate leaves in January and the number of pinnate leaves in April 2020 (p < 0.05). The fresh and dry weights of stems, leaves, roots at 0-25 cm, 25-50 cm, and >50 cm, total root, shoot-root ratio, and root lengths of oil palm seedlings were not significantly different among the treatments in all observed months, except for fresh root weights at 0-25 cm and 25-50 cm in December 2019 (p < 0.05). From the 2"d study, the plant height and diameter, petiole width, thickness, and length, rachis width and length, leaflet width and length, number of leaflets, flag leaves, and new leaves, number of male and female inflorescences, and sex ratio of oil palm trees, were not significantly different among the treatments in all observed months, excepts for rachis width in March 2020, and the number of leaflets in March and June 2020 (p < 0.05). The root record reveals that the root weights of sole cropped oil palm trees (T1) were higher than those of intercropped oil palm trees (T2-T6) (p < 0.01) in all observed months. The growth and biomass parameters and growth rates of intercropped cashew, sweet leaf bush, and cha-om showed the most potential plants for intercropping with oil palms in the young stage. From the 3"l study, the plant diameter and height, number of male and female inflorescences, and sex ratio of oil palm trees were not significantly different among the treatments in all observed months, except for the number of female inflorescences in October 2019 and February 2020 and sex ratio in February 2020 (p < 0.05). From the growth parameters and growth rates of intercropped plants, Indian walnut (1. excelsa), mahogany (S. macrophylla), champak (M. champaca), and Ternstroemia (T. wallichiana) showed the most potential for intercropping with oil palm in the mature stage.