ENHANCING NITROGEN USE EFFICIENCY IN CUCURBITACEAE CROPS BY GRAFTING

Nitrogen plays a major role in the yield and quality of melon and watermelon plants. Two experiments were carried out to determine if grafting melon and mini-watermelon onto commercial rootstocks could enhance crop performance and nitrogen use efficiency (NUE) of grafted melon and mini-watermelon plants under open field conditions. In experiment 1, melon ‘Proteo’, was used as a scion and ‘P360’ (Cucurbita moschata Duchesne × Cucurbita maxima Duchesne) was used as rootstock, whereas in experiment 2, mini-watermelon ‘Minirossa’, was used as a scion and ‘Vita’ [Lagenaria siceraria (Mol.) Standl.] was used as rootstock. Increasing the nitrogen fertilization rate from 0 to 60 kg ha^-1 increased melon yield by 21%, whereas increasing the nitrogen rate from 60 to 120 kg ha^-1 increased melon production by only 10%. Similarly, increasing the nitrogen fertilization dose from 0 to 50 kg ha^-1 increased mini-watermelon yield by 47%, whereas increasing the nitrogen dose from 50 to 100 kg ha^-1 increased mini-watermelon production by only 5%. When averaged over nitrogen levels, the yield, and NUE were higher by 10%, and 12%, respectively in ‘Proteo’ grafted onto ‘P360’ than in ungrafted ‘Proteo’ plants and by 39%, and 38%, respectively in ‘Minirossa’ grafted onto ‘Vita’ than in ungrafted ‘Minirossa’ plants. Fruit dry matter (DM) and total soluble solids (TSS) contents of grafted melon were slightly inferior to those of ungrafted plants, whereas the fruit DM and TSS contents of grafted mini-watermelon were similar to those of the plants grown on their own roots. Hence grafting melon and mini-watermelon plants onto selected rootstocks can be used as a quick and effective method to improve productivity, NUE, and to reduce environmental pollution.