Oxygation improves yield and quality and minimizes internal fruit crack of cucurbits on a heavy clay soil in the semi-arid tropics

Lack of oxygen due to sustained wetting fronts associated with drip and subsurface drip irrigated crops in heavy clay soil can negatively impacts on yield, fruit quality and water use efficiency of cucurbit crops. This study evaluated the effects of aerated irrigation water (oxygation) with subsurface drip irrigation, employing an in-line air injector (Mazzei venturi to introduce 12% air by volume of water) on fruit yield, quality and water use efficiency of watermelon (Citrullus vulgaris) and pumpkin (Cucurbita maxima) in a heavy clay soil. The fruit yield with oxygation increased from 14.5 t ha-1 to 24.6 t ha-1, and 26.3 t ha-1 to 28.9 t ha-1, for watermelon and pumpkin, respectively. The total soluble solids (TSS) increased by 19% with oxygation (13.2 vs. 11.1%), and internal fruit crack decreased for watermelon, whereas in pumpkin fruit dry matter increased by 4% (40 vs. 38.4%) and TSS by 7% (13.7 vs. 12.8%). Season long water use efficiency was greater with oxygation compared to the control in both crops. The higher yield with oxygation was associated with a more rapid canopy cover, more leaf chlorophyll, and an increase in leaf photosynthetic rate, and leaf transpiration and an increase in fruit number and size. The results suggested that oxygation can ameliorate temporal hypoxia-associated with drip irrigated cucurbit crops in heavy clay soil and also offer yield and fruit quality benefits.