灌溉水盐度和施氮量对棉花根系分布影响研究

Effects of Water Salinity and Nitrogen Rate on Cotton Root Spatial Distribution under Drip Irrigation with Saline Water

通过田间小区试验，研究了不同灌溉水盐度和施氮量对滴灌棉花根系分布的影响。试验设置3种灌溉水盐度；0．35、4．61和8．04dS·m-2（分别代表淡水、微成水和咸水三种灌溉水类型）；施氮量为0、240、360和480kg·hm-2。结果表明．按质量计．棉花的根主要分布在0-20cm．此部分占根总质量的85％～90％。微成水和成水灌溉棉花根的总质量显著降低，分别较淡水灌溉减少10％和36％，尤其在土壤表层0～20cm和下层60～100cm显著降低；施用氮肥可以显著增加棉花根的质量。以长度计，棉花根集中分布在0～60cm，此部分占总根长的87％～96％；60cm以下根长密度明显降低。微咸水灌溉棉花根长密度最大，其次是成水，淡水灌溉最低；淡水灌溉下，根长密度随施氮量增加显著降低：微成水和咸水灌溉下，根长密度随施氮量增加呈先增后降趋势，其中施氮240kg·hm-2最高。棉花根表面积表现为微成水〉淡水〉咸水，平均根直径为微咸水〉咸水〉淡水，而不同灌溉水处理间根体积的差异不显著。随着施氮量的增加，根表面积、根体积和平均直径均显著降低。

The effect of irrigation water salinity and N application rate on cotton （Gossypium hirsuaun L.） root distribution in a field experiment was investigated, with water salinity levels （EC, electrical conductivity） of 0.35, 4.61 and 8.04 dS. m-I （repre- senting fresh, brackish, and saline water, respectively）. N rates were 0, 240, 360, and 480 kg .hm-2. Results showed that cotton root mass from 0 - 20 cm soil depths made up 85%-90% of the total. The mass under brackish water and saline water treatments significantly decreased; these were 10% and 36% less than that under fresh water treatment, especially in the 0 - 20 cm and 60 - 100 cm soil layers. Cotton root mass increased with N rate. Cotton root length was mainly within 0-60 cm, representing 87% -96% of the total, decreasing significantly below 60 cm. The highest average root length density was observed under brackish water treatment, followed by saline water and fresh water. Under fresh water irrigation, root length density significantly de- creased with N rate increase. Under brackish water and saline water irrigation, root length density showed a trend of initial in- crease and then decrease with increasing N rate. The highest root length density was observed under treatment N rate of 240 kg N. hm-2. Cotton root surface area order was brackish water 〉 fresh water 〉 saline water, but root diameter was brackish 〉 saline 〉 flesh water. No difference was observed in cotton root volume among different irrigation water treatments. Root surface area, volume and diameter declined with N rate increase.