Weed dynamics, nutrient removal and weed smothering efficiency in pearl millet (Pennisetum glaucum (L.) R. Br.) - based intercropping systems under lowland summer rice fallows

Weed infestation is a major constraint to crop productivity in lowland summer rice fallows. In southern India, high residual soil moisture and nutrient availability during summer fallows favour rapid weed proliferation, leading to nutrient depletion and increased weed pressure in the succeeding rice crop. However, information on weed suppression and nutrient removal in pearl millet-legume-based intercropping under lowland summer rice fallows is limited. A field experiment was carried out during the summer season of 2024–2025 at the Integrated Farming Systems Research Station, Karamana, Thiruvananthapuram, Kerala, to investigate the weed dynamics, nutrient removal and weed smothering efficiency of pearl millet (Pennisetum glaucum (L.) R. Br.) - based intercropping systems in lowland rice fallows. The experiment comprised 13 intercropping treatments involving pearl millet with bush cowpea, fodder cowpea, green gram and black gram in 1:1 and 2:1 planting ratios under an additive series (an intercropping system, where the base crop population is maintained at 100 % and intercrops are added according to main crop geometry), along with their respective sole crops. The treatments were laid out in a randomised block design (RBD) with three replications. The predominant weed flora observed during the crop growth period consisted mainly of broad-leaf weeds at 30 and 60 days after sowing (DAS). Weed growth and nutrient depletion were significantly influenced by the intercropping systems. The lowest total weed dry matter (87.50 g m-2 at 60 DAS) and the highest weed smothering efficiency (56.72 %) were recorded in pearl millet + bush cowpea (1:1). In contrast, the highest weed dry matter (202.15 g m-2) was observed in the sole crop of pearl millet. The inclusion of legumes significantly reduced nutrient depletion by weeds due to complementary resource use and efficient canopy closure. Intercropping systems, pearl millet + bush cowpea (1:1) and pearl millet + black gram (1:1), were more efficient in suppressing weed growth, reducing nutrient losses and improving crop competitiveness compared to sole cropping. The study concluded that legume-based intercropping effectively minimised weed interference, conserved soil nutrients and enhanced ecological weed control in summer rice fallows.