Experimental Study On Subsurface Drainage Criterion To Leakage Strength For Control Targets In Paddy

Suitable soil moisture is one of the necessary conditions for the normal growth of crops, but not the more the better. Therefore, reasonably adjusting to the leakage strength and improving water storage capacity of paddy in the flood season not only ensurea good harvest but also save the cost of drainage and relieve stress of controlling flood. Taking the experimental data from water technology promotion stations in Changshu of Jiangsu Province as basis, in this paper, we analyzedthe effecton rice growth indicators from Surface and subsurface waterloggingfor multi-stage stress, studied the standard on droping the stress of subsurface waterloggingand drainage management indicators of rice fields. The main results were as follows:(1)The stress of subsurface waterlogging has a little effect on the change of plant height, number of tiller and leaf area index for tillering, jointing and booting stage, heading and flowering stage; Cubic Equation simulatethe change trend of tiller number, plant height and leaf area index with time well.(2)Under the stress of subsurface waterlogging, rice chlorophyll content of booting stage decreases with the decreasing of drainage intensity; itnot only increase the chlorophyll content but also ensure rice yield under 3mm/d of drainage treatment for heading and flowering stage.The rate of yield cut increases with drainage intensity decreased for tillering and booting stage.In heading and flowering stage, the rate of yield cut is max underthe drainage intensity with 5mm/d.(3)Under stress of surface and subsurface waterlogging, plant height showesCK>5mm/d> 3mm/d in tillering; in jointing and booting, heading and flowering stage, the effect on plant height from stress of surface and subsurface waterlogging is not obvious stains, and chlorophyll contentreduced with waterlogging increasing.(4) LAI values of three drainage treatment in jointing and booting, heading and flowering stageare lower than CK;resultsof correlation analysis between leaf area index and yield show that increasing the leaf area can promoteunits panicles, each panicle, seed setting rate to form, which can increase the rice yield; length, diameter, number, dry weight and volume of rice root show CK>5mm/d>3mm/d>lmm/d in heading and flowering stage.(5) Rice yield of three stagesdecrease with the decreasing of drainage intensity. The result of correlation analysis between yield component factors and yield by path analysis show that direct effectof grain weight onyield is significant, units panicles and setting rate are following in tillering and heading and flowering stage, direct effectof setting rate onyield is significant, units panicles and grain weight are following in jointing and bootingstage.Indirect effect of units panicles on yield is significant by grain weight in tillering and heading and flowering stage, but jointing and bootingstage show that setting rate has effect on yield by units panicles.(6)To the rate of rice yield cut being no more than 10% target, optimum drainage targets of tillering, jointing and bootingstage are as follows, leakage intensity is 5mm/d, SEW30are respectively 340 and 433.0cm·d, SFEW30 are respectively 164.8 and 229.0cm·d. Besides, the water storage deep of two stages are respectively40 and 60mm, and their storage time are 1 10d. Optimum drainage targets of heading and flowering stage are as follows. leakage intensity is 3mm/d, SE0 is 340～420cm·d and SFEW30 is 207.7cm·d, and the storage deep is 60mm, storage time is1～10d.