调亏灌溉合理滴灌频率提高大棚西瓜产量及品质

Reasonable drip irrigation frequency improving watermelon yield and quality under regulated deficit irrigation in plastic greenhouse

在调亏灌溉条件下,该试验研究了不同膜下滴灌频率对早春大棚西瓜植株生长、果实产量、品质及水分利用效率的影响,从而确定西瓜整个生育期的最佳灌溉频率方案。试验在各生育期设置3个不同的灌溉频率水平,分别为高频(每2 d灌溉1次)、中频(每4 d灌溉1次)和低频(每6 d灌溉1次),并做4因素3水平正交实验设计,共9个处理,各处理总灌水量相等。结果表明:各处理中,苗期中频、开花坐果期高频、果实膨大期中频、成熟期低频灌溉处理植株在生长势上表现最好,该处理植株的叶绿素含量、净光合速率、气孔导度、蒸腾速率以及叶片水分利用效率在全生育期中均能保持较高水平,且该处理植株具有较高的坐果率、单果质量,果实总产量和灌溉水分利用效率最高,分别达到63.72 t/hm2和303.64 kg/(hm2·mm)。品质方面,苗期中频、开花坐果期高频、果实膨大期中频、成熟期低频灌溉处理的果皮最薄,仅有8.30 mm,且具有较高含量的总维生素C和最高含量的可溶性蛋白质和中心边可溶性固形物。综合考虑生长势、产量、品质和灌溉水分利用效率,适用于西北地区早春大棚西瓜调亏灌溉的最佳灌溉频率方案为苗期中频、开花坐果期高频、果实膨大期中频、成熟期低频灌溉。该研究可为实现西北地区早春设施西瓜栽培高效节水灌溉提供理论与技术参考。

In the northwest of China, the area of facility watermelon cultivation continuously expands with popularization. In order to explore an efficient water-saving irrigation system of watermelon growth in plastic greenhouses, the experiment was conducted to investigate the influence of different mulched drip irrigation frequency on growth, yield, quality, and water use efficiency of watermelons in plastic greenhouses during each growth stage under regulated deficient irrigation. According to preliminary study, a diameter of 20 cm evaporating dish was used to measure water surface evaporation so as to control irrigation water. Three different levels of irrigation frequency were designed including high frequency（once every 2 days）, intermediate frequency（once every 4 days）, and low frequency（once every 6 days）. Each treatment was kept at the same total irrigation amount with 0.4 evaporation amount measured by dish（Ep） during the seedling period, 0.8Ep during the flowering fruit-bearing period, 1.6Ep at the fruit enlargement period, and 0.8Ep at the mature period, respectively. The experiment had measured plant morphological index, photosynthetic indexes, fruit quality index, fruit yield, and water use efficiency. The results showed that irrigation with intermediate frequency at seedlings stage, high frequency at flowering fruit-bearing stage, intermediate frequency at fruit enlargement period, and low frequency at the mature stage（T4 treatment） were the best treatment in all of the nine treatments. In the seedling, flowering, fruit enlargement, and mature periods, this treatment displayed the best growth potential in plant height and stem diameter with a relatively high level of chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance, and leaf water use efficiency. This high ability of photosynthesis assimilation in turn contributed to the fruit enlargement and had more advantages against adversity stress early spring. The results of plant height and stem diameter showed that from the stage of seedling to flowering fruit-bearing, the high-frequency irrigation promoted plant height, while intermediate frequency and low frequency irrigation benefited the increase of stem diameter, and because of the different irrigation water during different stages, there were an obvious compensation effect between plant height and stem diameter, in the aspect of quality. T4 treatment had the thinnest peel, which was only 8.30 mm, larger edible part, higher content of total vitamin C, and the highest total center soluble solid content, total edge soluble solid content, as well as soluble protein, which reached 12.85%, 10.80%, 0.35 mg/g respectively. In addition, the fruit sweetness of the T4 treatment was high and had a better quality. In the aspect of fruit production, this treatment also had higher fruit rate, single fruit weight, the highest total fruit production 63.72 t/hm^2, and the highest water use efficiency 303.64 kg/（hm^2·mm）. Therefore, considering the growth potential, yield, quality, and irrigation water use efficiency, the T4 treatment is the best irrigation frequency plan for the whole watermelon growth period, that is, once every 4 days irrigation at seedling stage, once every 2 days irrigation at flowering fruit-bearing stage, once every 4 days irrigation at fruit enlargement stage, and once every 6 days irrigation at the mature stage. T4 is the best treatment in all the nine treatments and the best irrigation frequency scheme for watermelon irrigation in greenhouses under regulated deficit irrigation in early spring of the northwest region. The research could provide valuble information for high efficiency and water-saving irrigation facilities cultivation in the spring of northwest in greenhouse watermelon.