Simulation For The Growth And Yield Of Cotton In Response To Drought And Waterlogging

In the context of global warming,in the middle-lower reach of the Yangtze River,total precipitation and precipitation intensity have increased,and precipitation frequency has decreased,which result in an increased the frequency of droughts and floods.Waterlogging,drought,and alternating drought and waterlogging will have marked impacts on agricultural production.Cotton is an important economic crop.Cotton growth is sensitive to soil moisture conditions.Waterlogging and drought might cause substantial yield loss.However,the middle-lower reach of the Yangtze River is one of the three main regions for cotton production in china,and its cultivating areas for cotton is about one third of the total cultivating for cotton areas in china.Thus,studying the effects of water deficit and waterlogging on cotton growth and production and simulating the total dry matter and seed cotton yield is important for farmland water management and can provide data for preventing cotton yield loss under drought and waterlogging.This study is financially supported by state natural science funds named "study on a unified model for crop water production function under drought and waterlogging stress".The experiments were conducted at the Experimental Station of Wuhan University in Wuhan,Hubei Province,China.Based on the observation data under drought and waterlogging stress from 2015 to 2016,the paper analyzed the stomatal conductivity,photosynthetic rate,transpiration rate,intercellular CO2 concentration and light use efficiency of single layer leave under drought and waterlogging stress at flowering and boll opening stage of cotton;the response of cotton growth,yield and yield components under drought and waterlogging stress were discussed and the unified model for crop water production under drought and flood stress was put forward.The main results as flows:(1)Compared to the control,the stomatal conductivity,photosynthetic rate,transpiration rate and light use efficiency decreased under waterlogging alone,drought alone,and alternating drought and waterlogging.Compared to drought alone,the stomatal conductivity,photosynthetic rate,transpiration rate and light use efficiency decreased under alternating drought and waterlogging.The intercellular CO2 concentration decreased under drought alone and that increased under waterlogging alone.In the drought of the alternating drought and waterlogging stress,the intercellular CO2 concentration decreased,in the waterlogging of the alternating drought and waterlogging stress,the intercellular CO2 concentration increased.(2)Compared to the control,the increasing of LAI decreased under waterlogging alone,drought alone,and alternating drought and waterlogging.The dry matter weight of leaf increased under waterlogging alone and that decreased under drought alone and alternating drought and waterlogging;compared to drought alone,the increasing of LAI decreased and the dry matter weight of leaf increased under alternating drought and waterlogging.Compared to the control,the increasing of plant height and the dry matter weight of stem increased under waterlogging alone;the increased of plant height and the dry matter weight of stem decreased under drought alone and alternating drought and waterlogging;compared to drought alone,under alternating drought and waterlogging,after a short drought,the increasing of plant height and the dry matter weight of stem increased;after a long drought,the increasing of plant height and the dry matter weight of stem decreased.Compared to the control,the root length increased and the dry matter weight of root decreased under drought and waterlogging stress;compared to drought alone,under alternating drought and waterlogging,after a short drought,the root length and the dry matter weight of root increased;after a long drought,the root length increased and the dry matter weight of root decreased.(3)Compared to the control,the lint and cottonseed yields decreased under waterlogging alone,drought alone,and alternating drought and waterlogging.In addition,the lint and cottonseed yields under alternating drought and waterlogging were greater than those under drought alone,and drought in the earlier stages led to a reduction in the lint and cottonseed yields,while waterlogging in the later stages had a compensatory effect.There was a significant linear relationship between the lint and cottonseed yields and the number of opening bolls.The decreased number of opening bolls might have been the cause of the observed decrease in the lint and cottonseed yields.(4)Waterlogging alone,drought alone and alternating drought with waterlogging all led to an increase in the proportion of the boll wall biomass and a decrease in the proportion of the fibre biomass of cotton bolls.The proportion of the seed biomass of cotton bolls always decreased,except under alternating drought with heavy waterlogging in 2015.The fibre-to-seed biomass ratio decreased,except under drought alone in 2015.(5)The daily transpiration of cotton under different water stress conditions were well simulated by using P-M method and the root water absorption model based on the soil moisture content.The LAI is the main fact that led to change of potential transpiration.During the whole growing season,the change of mean temperature,wind speed and leaf area index have a great influence on the potential transpiration in the early stage of growth and have a little influence on the potential transpiration in the later stage of growth;the change of plant height has a little influence on the potential transpiration in the early stage of growth and has a great influence on the potential transpiration in the later stage of growth.There was a significant quadratic curve relationship between the actual transpiration and irrigation amount.(6)The influence of stomatal restriction on crop growth can be measured by transpiration,and There was a significant liner curve relationship between the actual transpiration and total dry matter under drought and waterlogging stress.In the improved CROPR model the maximum water use efficiency was revised by the ratio of actual transpiration to potential transpiration.The model efficiency,correlation coefficients of the improved model were greater than the original model and the simulation error of the improved model were less than the original model.Therefore,the improved CROPR model improves the simulation accuracy of total dry matter quality and yield under drought and drought stress and can be used to simulate the quality and yield of crop under drought and waterlogging stress.