Optimization of planting geometry and weed control improves the productivity of potato under poplar-based agroforestry system

Weeds are the major constraint to realize the potential yield of potato crop (Solanum tuberosum) grown under a poplar-based agroforestry system.The objective of the study was to increase the productivity of the poplar-potato intercropping system through the optimization of tree-crop planting geometry with a selection of appropriate weed control measures. Two planting geometries each of poplar (8 m x 2.5 m, 7 m x 3 m paired at 2.5 m) and potato (65 cm x 18.5 cm, 75 cm x 15 cm) with six weed control treatments (atrazine 0.250 kg ha(-1), metribuzin 0.350 kg ha(-1), paraquat 0.300 kg ha(-1), clodinafop + metribuzin 0.270 kg ha(-1), weed free check and weedy check) were investigated for two years (2017-18 and 2018-19). It was observed that these applied herbicides had no phytotoxic effect on the 5 and 6-year-old poplar trees. Broad-leaved weeds dominated the sedges under the poplar-potato based agroforestry system. The potato planting geometry 75 cm x 15 cm recorded a higher weed suppressing ability till 90 days after planting (DAP). Intercropping of potatoes at 75 cm x 15 cm spacing under poplar plantation (8 m x 2.5 m) produced higher tuber weight hill(-1) (343.6 and 281.6 g hill(-1)) and increased tuber yield by 21.8% (averaged over both years) in comparison to other poplar-potato planting geometry with clodinafop + metribuzin 0.270 kg ha(-1). This herbicide recorded a nearly 84.2% decrease in total weed biomass at 90 DAP with an increased tuber yield up to 50% (29.3 and 28.9 Mg ha(-1)) than the weedy check (19.6 and 19.3 Mg ha(-1)). Findings imply that an integrated effect of poplar spacing 8 m x 2.5 m with closer potato planting geometry (75 cm x 15 cm) applied with clodinafop + metribuzin 0.270 kg ha(-1) proved to be the best combination for improving the productivity of potatoes under poplar based agroforestry system.