Nutrient management through drip fertigation in polyhouse-grown capsicum

Abstract:

Growing capsicum in a polyhouse should be straightforward, but getting the fertigation recipe right matching nutrient supply to a crop that shifts demand sharply between vegetative and reproductive stages remains a persistent challenge for growers in humid tropical Malaysia. This research tested six nitrogen fertigation rates (75, 100, 125, 150, 175 and 200 kg N ha⁻¹) delivered through drip lines to capsicum (cv. Special Hot) inside a naturally ventilated polyhouse at the Borneo Institute of Agricultural Sciences, Kuching, Sarawak, over two consecutive seasons (2022–23 and 2023–24). A constant P and K base was applied (80 kg P₂O₅ and 120 kg K₂O ha⁻¹) across all treatments. A randomised complete block design with four replications was used. Fruit yield, average fruit weight, number of fruits per plant, plant height, nutrient uptake (N, P, K, Ca, Mg) and apparent nitrogen recovery were measured. Yield responded quadratically to N rate, peaking at 150 kg N ha⁻¹ with a mean of 38.7 t ha⁻¹ and an average fruit weight of 164.3 g. Beyond 150 kg N, yield declined slightly (37.2 t ha⁻¹ at 175 kg, 35.8 t ha⁻¹ at 200 kg), and leaf tip burn appeared in 14–19% of plants. Apparent nitrogen recovery peaked at 125 kg N (67.4%) and dropped to 48.3% at 200 kg N, signalling luxury consumption and potential leaching loss. Nutrient uptake was dominated by K (41.2% of total macronutrient removal) and N (34.7%). These results recommend 150 kg N ha⁻¹ as the economic optimum for drip-fertigated polyhouse capsicum in Sarawak, balancing yield, fruit quality and nutrient efficiency.