不同水氮供应对小南瓜根系生长、产量和水氮利用效率的影响

Effects of Different Water and Nitrogen Supplies on Root Growth,Yield and Water and Nitrogen Use Efficiency of Small Pumpkin

【目的】针对西北半干旱区温室蔬菜灌水施氮不合理等问题,通过不同灌水施氮水平处理,探讨作物根系生长与分布、产量和水氮高效利用与水氮供应的关系,揭示根系生长分布对灌水施氮模式的响应机制,为提高蔬菜作物产量和水氮利用效率提供科学依据。【方法】采用不同施氮灌水处理的田间试验,以"金童"小南瓜为供试作物,设置3个总灌水量水平:常规灌水(高水W3、1 500 m^3·hm^(-2))、常规灌水减27%(中水W2、1 1 00 m^3·hm^(-2))、常规灌水减54%(低水W1、700 m^3·hm^(-2))和3个施氮量水平:常规施氮(高氮N3,350 kg·hm^(-2))、常规施氮减28.5%(中氮N2,250 kg.hm^(-2))、常规施氮减57%(低氮N1,150 kg·hm^(-2)),试验采用完全随机区组设计,共9个处理,研究膜下滴灌不同水氮供应对温室小南瓜根系生长分布、产量和水氮利用效率的影响。【结果】小南瓜90%根系主要集中在0—40 cm土层,且随土层深度的增加,根系密度呈指数下降;当灌水量相同时,低水(W1)和中水(W2)处理根系长度、产量、水分利用效率(WUE)均随施氮量的增加先增加后减少,而高水(W3)处理根系长度随施氮量的增加而增加,不同施氮量处理小南瓜产量差异不显著;与高氮(N3)处理相比,低氮(N1)和中氮(N2)处理小南瓜根系长度、产量随灌水量增加而增加,当灌水量超过1 1 00 m^3.hm^(-2)时,小南瓜根系长度和产量均有所下降;随着灌水量增多,水分利用效率亦显著下降,低水中氮(W1N2)处理水分利用效率最高,为35.59 kg·m^(-3);灌水量较高(W2和W3)时,氮素利用率(NUE)均随施氮量增加而显著降低,灌水量较低(W1)时,低氮和中氮处理氮素利用率显著高于高氮处理;灌水和施氮对小南瓜总根长作用表现为:氮素作用>水分作用>水氮交互作用;细根(直径小于2 mm根系)根长随灌水量和施氮量增加呈抛物线型变化;小南瓜产量与细根根长和根表面积之间均有显著的线性关系。【结论】灌水和施氮过高或过低均可以导致小南瓜产量、水氮利用效率以及根系各项特征参数显著降低,中水中氮(W2N2)处理小南瓜产量和根系各项特征参数均达到最大值;不同水氮处理主要通过对细根根长的影响进而影响小南瓜的产量。综合考虑产量、水氮利用效率以及根系生长分布,灌水量为1 1 00 m^3·hm^(-2)、施氮量为250 kg·hm^(-2)为小南瓜较优的灌水施氮组合。

【Objective】In order to provide a theoretical support for improving the yield and water and nitrogen use efficiency of vegetable crops in view of the questions of irrigation and nitrogen irrationally in the vegetable greenhouse for semiarid northwest area, the responsive mechanism of root growth and distribution to water and nitrogen supply was studied under the different levels of water and nitrogen treatment by the way of exploring the effects of water and nitrogen supply on crop root, yield and water and nitrogen use efficiency.【Method】 The field experiment was conducted with different N-rate and irrigation treatments. Small pumpkin “Jintong” was chosen as a test cultivar. The treatments consist of three different irrigation levels （W3, 1 500 m3？hm-2; W2, 1 100 m3？hm-2; W1, 700 m3？hm-2） and three different nitrogen rate levels （N3, 350 kg？hm-2; N2, 250 kg？hm-2; N1, 150 kg？hm-2）. There were 9 treatments in total with randomized block design to study the effects of different water and nitrogen supplies on root growth, yield and water and nitrogen use efficiency of small pumpkin. 【Result】 There are 90% of total root length were concentrated in the 0-40 cm soil layer, the root length density decreased exponentially when the soil layer increased. The root length, yield, water use efficiency （WUE） increased with the improvement of N-rate, and decreased by more nitrogen application at the W1 and W2 irrigation level, but the root length increased with increase of N-rate and there were no significant difference in the yield of small pumpkin at the W3 irrigation level. Compared to N3 treatment, the root length, yield and WUE increased with the increase of irrigation amount, they decreased when the irrigation amount was more than 1 100 m3？hm-2. WUE decreased with the increase of irrigation amount and it reached the highest value （35.59 kg？m-3） in W1N2 treatment. Nitrogen use efficiency （NUE） decreased significantly with the increase of N-rate when the irrigation amount was at W2 and W3 levels, and NUE of N1 and N2 treatment increased significantly compared to N3 treatment. The order of irrigation and nitrogen fertilizer effect on total root length of small pumpkin was nitrogen, water, water and nitrogen interactions. The root length of diameter less than 2 mm presented the parabola trend when N-rate and irrigation increased, and had a better linear regression with the yield of pumpkin. A significant linear relationship between yield and root surface area and the root length of root with the diameter less than 2 mm.【Conclusion】Less or more irrigation and nitrogen fertilizer could reduce the yield, water and nitrogen use efficiency and the characteristic parameters of the roots of small pumpkin. The highest values of yield and characteristic parameters of the roots of small pumpkin were obtained when N-rate and irrigation water amount were 1 100 m3？hm-2 and 250 kg？hm-2, respectively. The water and nitrogen treatments were through the way of root length of root with the diameter less than 2 mm to improve the yield of small pumpkin. It was concluded that the optimal pattern of irrigation and nitrogen fertilization is that the irrigation water amount and N-rate are 1 100 m3？hm-2 and 250 kg？hm-2, respectively.