Evapotranspiration, crop coefficient and seed yield of drip irrigated pumpkin under semi-arid conditions

Pumpkin (Cucurbita pepo L.) is one of the most important plants in Turkey. A 2-year experiment (2013-2014) was conducted in the Konya Plain of Turkey in order to investigate the response of confectionary pumpkin to irrigation intervals. The experiment was laid out in a randomized block design consisting of three irrigation intervals (I<inf>7</inf>: 7-day, I<inf>14</inf>: 14-day, I<inf>21</inf>: 21-day) with three replications each. Actual evapotranspiration (ET<inf>a</inf>) of irrigation treatments varied from 521.2 to 660.2mm in 2013 and from 493.6 to 629.6mm in 2014. On an average, the ET<inf>a</inf> rate was 4.71mm day^-1 under I<inf>7</inf> and declined by 8% and 21% under I<inf>14</inf> and I<inf>21</inf>, respectively. Crop coefficients (K<inf>c</inf>) varied similar to ET<inf>a</inf> among the different growing stages, i.e., from a mean of 0.56 at the initial stage to 0.95 at mid-season. The mean K<inf>c</inf> was estimated to be 0.74 for the whole season. Irrigation intervals were found to significantly affect the seed yield and the quality of pumpkin in 2013 as well as 2014. No statistically significant differences (P≤0.05) were found between the I<inf>7</inf> and I<inf>14</inf> treatments in both the years although the I<inf>7</inf> treatment was observed to produce the highest seed yield (1275kgha^-1). Hence, in terms of water savings, the irrigation interval could be extended to 14 days without a significant decrease in the seed yield in case of arid and semi-arid areas such as the Konya Plain.