膜下滴灌棉花早衰发生的可能机制研究——从生长与养分的角度

The possible mechanism of cotton premature senescence under drip irrigation below mulch film——From the perspective of growth and nutrient

与漫灌相比,膜下滴灌棉花更易出现早衰问题,而植物养分状况的变化可能是其原因之一。本文在田间试验基础上,以漫灌为对照,分7次采样,对膜下滴灌棉花的生长发育及养分状况进行了研究。结果表明,膜下滴灌棉花在生育后期出现了明显的早衰现象。与漫灌相比,在结铃后期(播种后125 d),膜下滴灌棉花地上部生长量明显高于漫灌,根系正好相反,致使其冠根比较漫灌更高。而从结铃后期至吐絮期(播种后160 d),由于地上部生长量的急剧下降(叶片及蕾铃大量脱落所致)及根系生长的停滞,膜下滴灌棉花冠根比也随之降低。对棉花叶片养分状况进行分析发现,在生长发育后期,无论漫灌还是膜下滴灌,棉株下部叶片氮、磷含量均比中、上部叶片低,但钾含量与此相反;而且膜下滴灌棉花上部叶片钾含量明显低于漫灌,其地上部平均钾含量也较漫灌处理低。以上试验结果说明,膜下滴灌棉花早衰的发生可能是由于过大的地上部生长量及更少的根系造成对钾的供需矛盾引起的。

The premature senescence of cotton under drip irrigation below mulch film （DI） is much more wide- spread than under flooding irrigation （FI） , and the change of plants nutrient under DI has been regarded as a possible influencing factor. In this study, a field experiment was conducted to investigate the cotton growth and nutrient status under DI in comparison to FI. The results indicate that there are severe symptoms of premature senescence at the later growth stages of cotton under DI, while there are not the symptoms under FI. At 125 DAS （late boll stage） , the shoot biomass under DI is significantly higher than that under FI, while root biomasses show the opposite trend, and the shoot/root ratio under DI is significantly higher than that under FI. The shoot dry weight of plants grown under DI is abruptly decreased from 125 DAS （late boll stage） to 160 DAS （harvest stage）. Field observations indicate the main reason for the decrease is the shedding of a large number of leaves, squares and bolls. The shoot to root ratio under DI is also decreased to the same level as that of the FI treatment. To analysis the cotton leaf nutrition, it would be found that the nitrogen and phosphorus concentrations of oldleaves are lower than those of young leaves under both of DI and FI at the later growth stages, whereas the potassium concentration is opposite. The K concentration of young leaves under D! is lower than that under FI, and the K concentration of cotton shoot also shows a same trend. These results indicate that the premature senescence of cotton under DI may be that the K need of the shoots exceeds that K amount of the roots is able to supply.