Production functions for the yield of watermelon for different levels of irrigation and nitrogen fertilization in the Curu Valley, CE - Brazil

Soares, J.I.; Costa, R.N.T.; Silva, L.A.C. da; Gondim, R.S.

Revista Brasileira de Engenharia Agricola e Ambiental 6(2): 219-224


ISSN/ISBN: 1415-4366
Accession: 003897946

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The objective of this research was to study the effect of different levels of irrigation and nitrogen fertilizer applied to a watermelon (Citrullus lanatus) crop and to establish a production function aimed at economic optimization of the yield based on the, costs of water and fertilizer. The experimental design consisted of randomized blocks with split plots combining five irrigation water levels (312.1, 288.5, 252.6, 205.2 and 142.5 mm) and four levels of fertilizer application (0, 75, 150 and 300 kg ha-1) with four replications. The watermelon cultivar Crimson Sweet was used and the irrigations were monitored by tensiometers installed at 0.15 m of depth. The irrigation was applied when the soil matric potential reached -30 kPa. The maximum productivity of 64 908.9 kg ha-1 was obtained by the treatment that received 227.3 mm of water and 229.8 kg ha-1 of nitrogen. The substitution of water for nitrogen was found to be not advantageous from the economic point of view. The optimum economic water use was estimated to be 27.2 kg m-3 or 272 kg ha-1 mm-1, corresponding to 242.7 kg ha-1 of nitrogen.