Photosynthetic performance and yield of watermelon grown under biodrainage (Casuarina equisetifolia) vegetation

Abstract

The rise of water table situation, which causes waterlogging in agricultural field, can be controlled with biological drainage in addition to usual engineering drainage measures. The process uses the transpiration properties of trees. The biodrainage species, also known as “phreatophytes”, is able to draw water directly from the groundwater table or from the capillary fringe above it and eventually transpiring it to atmosphere. This causes decline in water table beneath the vegetation bringing waterlogged field to cultivable condition. Under such scenario in post monsoon season watermelon was cultivated as intercrop in a biodrained field under Casuarina equisetifolia plantation. Comparative photosynthesis performance of watermelon in field with and without Casuarina plantation was evaluated. The objective was to physiologically evaluate productivity of intercrops like watermelon under biodrainage vegetation and understanding the tree-intercrop interaction in reclaimed field. The Casuarina plantation on an average caused 21-34% reduction in incident of photosynthetically active radiation (PAR) over watermelon crop in comparison to control. In spite of reduced PAR, photosynthesis rate in two cultivars ‘Mokasa’, Arka Manik and local ‘Sugar baby’ was higher (24.63, 20.36 and 19.43 m mol m-2 s-1) than control (21.80, 19.60 and 18.93 m mol m-2 s-1, respectively). The excess soil water in root zone in control field caused reduction in photosynthesis, stomatal conductance as well as yield, in all the three cultivars. Inside biodrainage vegetation the photosynthesis, stomatal conductance and yield of all the cultivars were better than control. However, cultivars Mokassa and Arka Manik were found better than local ‘Sugar baby’ both in photosynthetic performance as well as yield and therefore, were more suitable cultivar as an intercrop inside Casuarina biodrainage vegetation.