Study On The Layered Distribution Of Winter Wheat Root Water Uptake Under Different Cultivation Methods

For studying the effects of different cultivation patterns and irrigation scheduling on growth,yield and water use of winter wheat,a field experiment with three cultivation patterns（traditional cultivation（TC）,ridge cultivation（RC）,and high and low seed bed cultivation（HLSC））and three irrigation quota levels（90 mm,72 mm,54 mm per irrigation on RC and HLSC pattern,but always 90 mm for TC）was conducted in Dianzi Town,Boxing County,Shandong province.The soil water content,water consumption,and water use efficiency（WUE）of winter wheat under the three cultivation patterns were investigated.Meanwhile,the percents of wheat root water uptake from different soil layers ware analyzed quanitively with stable hydrogen and oxygen isotope technique,and the main factors effected root water uptake and the relationship between infiltrated depth of irrigation water and root water uptake depth also were analyzed.The main results may concluded as followings:（1）The soil water contents of winter wheat at different growth stages were significantly different under different cultivation patterns.The cultivation patterns also had significant effects on the water consumption characteristics and water use efficiency of winter wheat.There was a significant positive correlation between winter wheat yield and water consumption（R²=0.44**）.Compared with RC and TC,wheat on HLSC developed more vigorously,and had finally more panicles per unit land and more grains per panicle.The total water consumption under HLSC pattern was 8.10-14.16%and 7.04-19.90%greater than those under TC and RC respectively,while the grain yield 9.52-22.63%and 13.39-27.37%higher and WUE 1.22-7.69%and 6.41-10.49%higher than those of TC and RC respectively.Overall,the HLSC cultivation pattern improved significantly the yield and water use efficiency of winter wheat,and seems an ideal water-saving and high-yield cultivation pattern in the experimental area.（2）The local meteoric water line（LMWL）,soil water line（SWL）and xylem water line（XWL）were fitted as:δD=6.95*δ¹⁸O+7.16（R²=0.90**）,δD=5.79*δ¹⁸O-14.82（R²=0.85**）and δD=6.54*δ18O-9.53（R²=0.59**）,respectively.The temporal and spatial variations ofδD andδ18O isotopic components in different water supply resources for wheat growth also were analyzed detailedly.The intercept and slope of the LMWL was less than the GMWL and NMWL,which reflected a strong evaporation effect in the experimental area.TheδD andδ¹⁸O abundances in soil water showed an exponential decrease with depth increase in soil profile.Cultivation pattern changed remarkably water infiltration and final distribution,and led to the significant differences ofδD andδ¹⁸O distribution in soil water profile.（3）There were obviously differences in root water uptake under different cultivation patterns:most water uptake was from 0-20 cm soil layer in TC,mainly from 0-20 cm and 20-60 cm of soil layers under RC.In HLSC pattern,wheat plants growing on HLSC-H area showed a better plasticity,i.e.absorbed water mainly from top 0-20 cm soil layer after an irrigation or rain,and from deeper soil layer（20-60 cm）with gradually soil drying.But in HLSC-L area,the root water uptake was mainly from 0-20cm soil layer throughout entire growing season.The top factors affected wheat root water uptake position were root distribution and soil available water content in soil profile.（4）The wheat root water uptake was mainly from 0-60 cm soil layer,but for an irrigation with a 90mm quota,experimental result showed that only 69.07%of the irrigated water was finally stored in 0-60cm of soil layer,which indicated over 30%of irrigated water infiltrated below the main root water uptake depth and will be less available.This result suggested that the planned irrigation wetting depth for winter wheat should be set as less than 60 cm under general situation.