Lysimetric determination of muskmelon crop coefficients cultivated under plastic mulches

A trial was carried out at the lysimeter station in southern Italy on muskmelon crop cultivated with and without plastic mulch during spring-summer in 2001 and 2003. The objective of the experiment was to verify the reliability of the crop evapotranspiration (ETc) estimate by means of the most recent update of the FAO Irrigation and Drainage Paper 56, in comparison with ETc directly measured by two mechanical weighing lysimeters. Crop coefficients (Kc) were determined during different development stages based on lysimetric measures of ETc and of the reference evapotranspiration (ET0) estimated through the Penman Monteith and the Hargreaves methods. On melon crop cultivated without plastic mulch, corrected crop coefficients (Kc) following the last FAO Irrigation and Drainage Paper 56 procedures were well correlated with those measured from lysimeter and were as reliable as the ETc estimate. In contrast, values of Kc proposed by FAO Irrigation and Drainage Paper 56 for crops grown with plastic mulch were meaningfully lowers than those measured from lysimeter, loading to an underestimation of water consumption. On muskmelon, cultivated with and without plastic mulch, it is necessary to adapt development phase duration, suggested by the FAO Irrigation and Drainage Paper 56, to the real phenology of the employed cultivar. An adaptation of the phenology to the real duration of the single phases is essential to avoid error in the estimate of ETc.