WATERMELON (Citrullus vulgaris Schrad) RESPONSE TO SOIL WATER POTENTIAL

Abstract

The effect of 20, 40 and 60 centibars (cb) of soil water potential (ψ) at irrigation moment, in three phenologyc stages: vegetative (V),
flowering (FL) and fruiting (FR) over the yield of watermelon (Citrullus vulgaris Schrad) was studied in Chontalpa, Tabasco, during the spring Summer cycle of 1998. The research was established in an experimental field using the San Cristóbal experimental design, nested in a completely blocks randomized design. The characters evaluated were: Fruit diameter, length and weight, number of fruits (NF) and yield (R), in the different treatments. There were statistical significant differences among treatments for the variables NF and R, and it was shown that ψ at irrigation had a notorious effect on these variables. These results indicate that during the FL stage this crop is more sensitive to soil water deficit, and that the ψ during this stage is important in defining the magnitud of NF and R. A regression model was determined to relate R with ψ at irrigation, in stages V, FL and FR, which predicts an absolute maximum value within the exploration range studied for ψ. According to the model, during stages V, FL and FR, the crop should be irrigated when ψ reaches values of 40.7, 33.8, and 41.2 cb, in order to obtain maximum fruit yield.