Effects Of Increased Precipitation And Nighttime Warming On Cotton Yield In North China Plain

Cotton,an important cash crop,is a leading raw material for the textile industry,which occupies an important position in social economy at national and world scale.With intensifying climate change,population growth and growing planting costs,predicting future changes in cotton production is critical for adaptive management.Global average daily temperature will rise by 1-3.7 ℃ in this century and the increase in night temperature is greater than the day temperature.Crops will show higher sensitivity to nighttime warming than to daytime warming.Increased temperature can regulate plant growth and affect the accumulation of organic matter in plants by affecting photosynthesis and respiration,and thus plant biomass and yield.In addition,with global warming,hydrological cycle will strengthen and further affect precipitation pattern.Water is also an important environmental factor in regulating plant growth.Thus,better understanding of the response of crop yields to environment change in future can help people develop effective crop planting programs and avoid the possible adverse effects of climate change.Models simulations suggest that atmosphere temperature would increase in all regions of China,but precipitation shows a different variation trend in both regional and global scales.It is predicted that the precipitation amount will show an increasing trend in the North China Plain,which is an important food production base in China,and it is the second largest cotton plantation area in China.However,the response of cotton production to climate change and its associated mechanisms remain unclear.This experiment was set up at Henan University’s Research and Teaching Farm in Kaifeng,Henan Province.There were four treatments including control,nighttime warming,increased 30% precipitation,and passive nighttime warming plus increased 30% precipitation.By examining the effects of nighttime warming and increased precipitation on photosynthetic rate,phenology,biomass,yield and harvest index of different cotton varieties in the North China Plain,the study will provide a basis for exploring crop response mechanisms under future climate change scenarios.The analysis of the five-year experimental data shows that:(1)Nighttime warming increased the soil temperature at night and whole day by 0.58 ℃ and 0.57 ℃,respectively,but increased precipitation had no effect on the soil temperature.(2)Neither nighttime warming nor increased precipitation showed effect on leaf photosynthetic rate,but nighttime warming significantly increased water use efficiency of cotton leaves.(3)Further analysis of phenological data in 2016 found that nighttime warming advanced the period of cotton budding and flower bell by 6.04 and 3.7 days,respectively.The decrease in dry matter accumulation during the growing period may cause more dry matter to allocated to the reproductive period.(4)Nighttime warming reduced the aboveground biomass and root biomass by 2.46% and 19.6%,respectively.In addition,nighttime warming stimulated cotton yield and harvest index by 16.65% and 22.09% respectively.Increased precipitation enhanced cotton yield by13.92%.(5)Across 2014 to 2018,two parents of cotton show different sensitivities to nighttime warming and increased precipitation.Under nighttime warming,the yields of parent cotton CT-1 and progeny cotton CT-2 increased by 21.75% and 27.73% respectively,but there was no treatment effect on the second pair of cotton parent and progeny.The increased precipitation enhanced the yield of the second pair of progeny cotton CT-5 by 17.38%,but had no effect on the yield change of the first pair of cotton.(6)Correlation analysis showed that the aboveground biomass and root biomass of cotton had a positive correlation with water use efficiency at leaf level,which explained the change of aboveground biomass and root biomass by 83% and 79%,respectively.Both total cotton yield and yields of CT-2 enhanced with the increasing soil temperature,but the yield of cotton CT-5 increased with enhancing stomatal conductance.The cotton harvest index reduced with increasing aboveground biomass and root biomass,but it improved with increasing cotton yield.The results of multiple stepwise regression analysis showed that cotton root biomass contributed 90% of changes in cotton harvest index.The results of decreases in aboveground biomass and root biomass under the nighttime warming treatment suggest that the amount of organic matter accumulated in vegetative growth stage may be mostly contributed to the reproductive phase,which favor for growth of cotton fruit and finally increase harvest index.At the same time,the study found the different sensitivities in varieties of cotton to nighttime warming and increased precipitation.The findings in this study reveal that the effect of nighttime warming and increased precipitation on cotton production can help to understand the impact of climate change on agricultural production in the future,and highlight that the importance of developing new crop varieties that can adapt to future climate change,and provide basic data and theoretical support for future agricultural production policies.