Optimum combination of plant spacing and mulching on productivity of red-leaf lettuce

Abstract

Lettuce (Lactuca sativa L.) is increasingly a popular vegetable salad, especially in the tropics where it is reputed for providing health benefits such as lowering cholesterol levels, fighting insomnia, preventing growth of cancerous cells and providing antioxidants. In Uganda, its yields are suboptimal, reportedly due to poor agronomic practices. The objective of this study was to determine the optimum combination of planting density and mulching of red-leaf lettuce under Uganda field conditions. A field experiment was conducted at the Agromax Uganda Limited farm in Kampala in 2018. The study involved two treatments, namely mulching using black polythene and varying intra-row spacing (15, 25 and 35 cm), all against inter-row spacing of 40 cm. The treatments were laid out in a split plot arrangement, in a randomised complete block design, with three replications. The main plot factor was mulching; while the subplot treatment was plant spacing. The interaction effect of plant spacing and mulching with polythene was significant (P<0.05) on plant heights, number of leaves per plant, leaf length and breadth, and fresh weight. Mulching at the widest intra-row spacing (35 cm) resulted in shorter plants (22.9 cm) with the highest leaf numbers per plant (23.6), longest and widest leaves (21.8 and 19.5 cm, respectively); and consequently the highest fresh yield (381.3 g m-2). It is, therefore, prudent that this plant spacing and plastic mulching be on a wider scale to validate the results across the country.