微咸水补灌条件下压砂西瓜叶片氯含量对氮的响应

The response of chlorine content in leaves of watermelon to nitrogen in gravel-mulched field on the condition of brackish water irrigation

为了明确施氮缓解因微咸水补灌引起的西瓜氯离子毒害机制,通过2年田间定位试验,设置5个氮水平,探讨氯在西瓜叶片中的含量、分布及其与氮素的关系。结果表明,在西瓜生长期,适量施氮会增加叶片氯含量,而收获期则表现为抑制作用。与对照(CK)相比,施氮180 kg·hm^(-2)(T4)叶片氯含量在膨瓜期提高10.6%,在收获期则降低21.3%。叶片氯累积量随施氮量增加而增加,在膨瓜期最为明显,T4处理比CK提高107%。氯主要集中在基部叶片和中部叶片,且与施氮量呈正相关,与叶片全氮含量呈负相关,中部叶氯含量与产量呈正相关。可见,在微咸水补灌条件下,适量施用氮肥可提高西瓜叶片氯含量与累积量,基部叶片氯含量与全氮含量互为消长关系。

In order to clarify the mechanism of nitrogen application in alleviating chloride toxicity of watermelon caused by supplementary irrigation with brackish water, two-year field positioning experiment with 5 nitrogen rates was conducted in this study. The results showed that the chlorine ion content and accumulation in leaves were changed with the growth period and the nitrogen application rate. With the development of the plant(from 65 days to 85 days after transplanting),the chlorine concentration in watermelon leaves was increased by appropriate nitrogen application, but it was inhibited in the harvest stage. Compared with the control(CK), the chlorine content in leaves of 180 kg · hm^(-2)(T4)nitrogen rate was increased by 10.6% in the expansion stage and it was decreased by 21.3% in the harvest stage. Meanwhile, the chlorine accumulation in leaves was increased with the increasing of nitrogen rate, especially in the expansion stage, when the cumulative amount of chlorine in leaves was increased by 107% compared with CK. Chlorine was mainly concentrated in basal and middle leaves, and it was increased by proper nitrogen rate. The contents of chlorine in different parts of leaves were positively correlated with nitrogen application rate, and negatively correlated with the total nitrogen content of leaves. Moreover, there was a positive correlation between chlorine content in middle leaves and watermelon fruit yield.In a conclusion, on the condition of brackish water irrigation, the content and accumulation of chlorine ions in watermelon could be significantly increased by a moderate amount of nitrogen fertilization, while it showed a mutual inhibition relationship with the total nitrogen content in basal leaves.