膜下滴灌棉花根系发育特征及其与土壤水盐分布的关系

Characteristics of Cotton Root Development under Mulch Drip Irrigation and Their Relationship with Soil Water and Salt Distribution

为探讨膜下滴灌条件下水分和盐分对棉花根系空间发育的影响,在花铃期选择相同灌溉制度、咸淡水灌溉的两个膜下滴灌处理田块采集距滴灌带不同距离、不同深度上的根系样品144件。用1mm土筛和手拣将棉花根系从土壤中筛分出来,去除死根,冲洗干净后用扫描仪扫描成tif格式图像,再用DT-SCAN软件计算根长密度。对比分析发现膜下滴灌及盐胁迫条件下,咸水灌溉的根系分布范围较大,其总根长密度比淡水大31.69mm/cm3,根系生长深度也远大于淡水灌溉。咸水灌溉根系分布主要受盐分胁迫,淡水灌溉根系分布主要受水分胁迫。水平方向上距滴头40cm以远,水分胁迫对根系发育起主导作用。土壤体积含水率在20%以上、电导率在2000μs/cm以下时可以满足根系的正常生长发育。

In order to understand the impact of water-salt on spatial development of cotton roots under mulch drip irrigation, 144 root samples were collected in the flower and boll stage for two different treatments irrigated with saline groundwater and fresh surface water using same irrigation system. Screening out cotton roots from the soil with 1 mm soil sieve and hand-picking, removing dead roots, scanning into a tif format images after washing, then the root length density was obtained through DT-SCAN software calculation. The results show that the distribution area of roots under mulch drip irrigation with saline water is larger and total root length density （31.69 mm/cm3） is bigger than that with fresh water. The depth of root for saline water irrigation is much greater than that with fresh water because of salt stress. Root distribution is mainly affected by salt stress under saline water irrigation; however, it is affected by water stress under fresh water irrigation. Water stress plays a leading role in root development 40 cm away from the emitter at the horizontal direction. When the volumetric water content of soil is greater than 20 % and the electric conductivity is smaller than 2000 μs/cm, the root can grow and develop normally.