Production and post-harvest quality of mini-watermelon crop under irrigation management strategies and potassium fertilization

ABSTRACT The occurrence of water sources with a high concentration of salts stands out as a limiting factor for production in Northeast Brazil. Thus, the search for strategies that minimize the effect of salt stress on crops is of fundamental importance. In this context, this study was conducted with the objective of evaluating the production and post-harvest quality of Sugar Baby mini-watermelon fruits under different irrigation management strategies with saline water and potassium fertilization. The experiment was conducted in a greenhouse, using a randomized block design, in an 8 × 3 factorial scheme, with three replicates, corresponding to eight saline water irrigation management strategies (No stress throughout the crop cycle; irrigation with saline water in the vegetative, vegetative/flowering, flowering, flowering/fruiting, fruiting, fruiting/maturation and fruit maturation stages) and three doses of potassium (50, 100 and 150% of the recommended dose). The dose of 100% corresponded to 150 mg K2O kg-1 of soil. Water with low and with high electrical conductivity (0.8 and 4.0 dS m-1, respectively) was used. Irrigation with water of 4.0 dS m-1 in the flowering and fruit maturation stages is a promising strategy for the cultivation of mini-watermelon, as it does not compromise production. Fertilization with 50% of K2O recommendation can be used in the cultivation of mini-watermelon without losses in yield. Mini-watermelon plants fertilized with 150% of K2O recommendation and irrigated with water of high salt concentration continuously in the vegetative/flowering and fruiting stages reduced the contents of soluble solids and ascorbic acid in the fruits.

摘要 巴西东北部高盐浓度水源的存在，是制约当地农业生产的突出因素。因此，探寻缓解盐胁迫对作物影响的策略，具有至关重要的意义。在此背景下，本研究旨在评估不同咸水灌溉管理策略与钾肥配施下，‘糖宝宝’（Sugar Baby）迷你西瓜果实的产量及采后品质。本试验在温室中开展，采用随机区组设计（randomized block design），设置8×3因子试验方案，共3次重复。其中8个咸水灌溉管理策略分别为：全生育期无盐胁迫、营养生长期灌溉咸水、营养/开花期灌溉咸水、开花期灌溉咸水、开花/坐果期灌溉咸水、坐果期灌溉咸水、坐果/成熟期灌溉咸水及果实成熟期灌溉咸水；3个钾肥施用量梯度分别为推荐施用量的50%、100%及150%，其中100%推荐施用量对应土壤施入150 mg K₂O·kg⁻¹。试验采用电导率（electrical conductivity）分别为0.8与4.0 dS·m⁻¹的低、高盐度灌溉水。研究结果表明，在开花期与果实成熟期采用4.0 dS·m⁻¹咸水灌溉的策略，对迷你西瓜产量无不利影响，是颇具应用前景的栽培方案。采用50%推荐施用量的钾肥进行施肥，可在不降低迷你西瓜产量的前提下应用于生产。而当迷你西瓜植株采用150%推荐K₂O施用量施肥，且在营养/开花期及坐果期持续采用高盐度水灌溉时，其果实的可溶性固形物与抗坏血酸含量会降低。