Increasing leaf harvest intensity enhances edible leaf vegetable yields and decreases mature fruit yields in multi-purpose pumpkin.

Abstract

The popular Pumpkin (Cucurbita moschata Duchsene) in Kenya is the multi-purpose type, grown for its edible tender leaves, mature fruits and seeds. It requires appropriate management to realize high yields. Pumpkin is an important crop because most plant parts are rich in nutrients and are edible. Leaves are preferred in African countries. In West Africa, seed consumption is common. In Asian countries, pumpkin seeds have several medicinal applications. Pumpkin is rich in carotenoids that keep the immune system strong and healthy. Its beta-carotene is a powerful antioxidant and antiinflammatory agent that helps prevent build-up of cholesterol in arteries, thus reducing chances of strokes. Its alphacarotene slows down aging, prevents cataract formation and reduces the risk of muscular degeneration that usually results in blindness. Its high fibre improves bowel health, potassium lowers hypertension risk, and zinc boosts immune system and bone density. The high demand for tender pumpkin leaves consumed as a vegetable accompanying the main meal brings about excessive defoliation that terminates the life of the plant prematurely. This research established optimum leaf harvest intensity (LHI) that maximizes either the tender leaf or mature fruit yields. Pumpkin seeds were grown for 3 weeks in a nursery bed followed by transplanting and growing each seedling singly at a spacing of 2 m x 4 m. The layout was completely randomized design with 4 LHI (0, 1, 2 and 3), replicated four times and repeated once. Data collection started when plants had 5-true leaves and it continued for 29 weeks (season 1) and 21 weeks (season 2). Data collection entailed defoliating up to 3 tip-most leaves, with the entire leaf stalk attached, from each vine once per week and then counting. Mature fruits were harvested as their colour started to turn yellowish-brown, counted and weighed. Data were subjected to analysis of variance and regression using Minitab version 15 program. Leaf yield significantly (P<0.05) increased with increase in LHI, but fruit yield significantly decreased. The highest yields were 580 edible leaves for 3-LHI and 20 kg fruits (25 t/ha) for 0-LHI. Fruit yield had a significant (P<0.05) negative relationship with LHI. Thus, the pumpkin leaf and fruit yields depend on leaf harvest intensity. If fruit production is desired, then LHI should be kept to a minimum. If edible leaves are desired then fruit yields should be forfeited. Maximum fruit productivity requires minimum leaf defoliation.