Growth and Yield of Watermelon on Polyethylene Mulch with Different Spacings and Nitrogen Rates

Smiljana Goreta, Slavko Perica, Gvozden Dumicic, Lovre Bucan, and Katja Zanic
Institute for Adriatic Crops, Put duilova 11, Split 21000, Croatia
Additional index words: Citrullus lanatus, ammonium nitrate, fertigation, planting density, fruit size

Abstract. Suggested watermelon planting densities and N rates vary on a large scale, indicating that there is insufficient knowledge about their effects. Therefore, the objective of this study was to evaluate the effects of N rate and planting density on growth, yield and quality of watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] grown on black polyethylene mulch. The field experiments with ‘Crimson Sweet’ watermelon were conducted in two climatologically different growing regions. The treatments were factorial combinations of three in-row plant spacings (1.6, 3.3, and 4.9 ft) and three N rates (102, 174, and 245 lbs/A). Part of the N (31 lbs/ A) was applied preplant and the remainder was fertigated. Vine length increased linearly up to 7 weeks after planting (WAP) as N rate increased from 102 to 245 lbs/A, and up to 9 WAP as plant spacing increased from 1.6 to 4.9 ft. Total marketable yields per acre or per plant did not icrease with N rates above 102 lbs/A. Average fruit weight and fruit size distribution were generally unaffected by N rate. Leaf N concentration increased as N rate increased, although leaf N concentrations at the lowest N rate (102 lbs/A) even at 9 WAP were relatively high (0.68 oz/lb to 0.76 oz/lb). Total and marketable yields per acre were linearly decreased with an increase in plant spacing from 1.6 to 4.9 ft and the same was noticed with the total and marketable number of fruit per acre. With increased plant spacing average fruit weight increased and fruit size distribution shifted to larger categories.