Evaluation of the suitability of three weed species as alternative cover crops in smallholder oil palm plantations through plant spacing management

Smallholder oil palm plantations in Indonesia have reached 8.9 million ha, but their role is still not optimal due to low productivity caused by the lack of knowledge of smallholders regarding sustainable oil palm technical culture, such as the use of cover crops. However, it requires appropriate spacing for different species. This study aims to obtain the optimum spacing of 3 weed species planted as cover crops in smallholder oil palm plantations. The research was carried out in 2022 at the smallholder oil palm plantation Naga Rejo village, Galang, Sumatera Utara, Indonesia. The experimental treatments included weed species (Asystasia gangetica, Paspalum conjugatum and Nephrolepis biserrata) as the main plot and spacing (10, 20 and 30 cm) as subplots arranged in a separate plot design with 3 replications. The results showed that the % of 100% land coverage was obtained in plantings of N. biserrata and A. gangetica in 4 WAPs and 10 cm spacing in 3 WAPs independently. The highest leaf area of N. biserrata, P. conjugatum and A. gangetica was obtained at a spacing of 30 cm. The highest dry weight, growth rate and nutrient uptake N and K N. biserrata and P. conjugatum were obtained at a spacing of 10 cm, while A. gangetica at a spacing of 30 cm. This shows that the optimum spacing depends on the weed species. The optimum spacing for A. gangetica (broad leaf) is 30 cm, while for P. conjugatum (grasses) and N. biserrata (ferns) is 10 cm.