Deficit irrigation is an agricultural practice that can enhance crop water productivity (CWP) when yields are not affected, and be a technique to support crop production under persistent droughts and reduced agricultural water availability. Over two seasons, we evaluated grafted and ungrafted cantaloupe melon (Cucumis melo L.) under three consistent irrigation regimes: 100% of field capacity (FC; full irrigation), and 70% and 50% irrigation volumes of the full irrigation, resulting in moderate and severe deficit irrigation treatments, respectively. Although the deficit irrigation treatments accentuated drought stress through the season, plants in the moderate deficit irrigation (70% FC) maintained their plant water status and slightly lowered stomatal conductance (gs) and photosynthetic rate (Pn) when compared to full irrigation. Under severe deficit irrigation (50%), plants had lower water potential than the full irrigation, and a reduction of 65% in gs and 47% in Pn, when compared to the full irrigation. The yields of the 100% and 70% irrigation treatments were similar in one year and lower for the 70% FC in the second year. The severe deficit irrigation had on average a 40% lower yield than the full irrigation. Overall, the moderate deficit irrigation had a 25% reduction in applied water, and either a similar or a higher CWP, depending on year, when compared to the full irrigation. Melon grafting did not improve yield under deficit irrigation conditions; however, it increased yield under full irrigation and low environmental stress (i.e., year). This study shows that melons can acclimate to lower water availability and sustain yields under a constant, moderate deficit irrigation, which can be an alternative for growers that face long-season droughts and lower irrigation water allocation.
