Spatial Pattern of Cotton Yield Variability and Its Response to Climate Change in Cotton Belt of Pakistan

Cotton is a revenue source for cotton-producing countries;as the second-largest crop in Pakistan,it significantly contributes to its economy.Over the past few decades,cotton productivity has become unstable in Pakistan,and climate change is one of the main factors that impact cotton yield.Due to climate change,it becomes very important to understand the change trend and its impact on cotton yield at the regional level.Here,we investigate the relationship of standardized cotton yield variability with the variability of climate factors using a 15-yr moving window.The piecewise regression was fitted to obtain the trend-shifting point of climate factors.The results show that precipitation has experienced an overall decreasing trend of–0.64 mm/yr during the study period,with opposing trends of–1.39 mm/yr and 1.52 mm/yr before and after the trend-shifting point,respectively.We found that cotton yield variability increased at a rate of 0.17%/yr,and this trend was highly correlated with the variability of climate factors.The multiple regression analysis explains that climate variability is a dominant factor and controlled 81%of the cotton production in the study area from 1990 to 2019,while it controlled 73%of the production from 1990 to 2002 and 84%from 2002 to 2019.These findings reveal that climate factors affact the distinct spatial pattern of changes in cotton yield variability at the tehsil level.

Attribution of Maize Yield Increase in China to Climate Change and Technological Advancement Between 1980 and 2010

Crop yields are affected by climate change and technological advancement.Objectively and quantitatively evaluating the attribution of crop yield change to climate change and technological advancement will ensure sustainable development of agriculture under climate change.In this study,daily climate variables obtained from 553 meteorological stations in China for the period 1961-2010,detailed observations of maize from 653 agricultural meteorological stations for the period 1981-2010,and results using an Agro-Ecological Zones（AEZ） model,are used to explore the attribution of maize（Zea mays L.） yield change to climate change and technological advancement.In the AEZ model,the climatic potential productivity is examined through three step-by-step levels：photosynthetic potential productivity,photosynthetic thermal potential productivity,and climatic potential productivity.The relative impacts of different climate variables on climatic potential productivity of maize from 1961 to 2010 in China are then evaluated.Combined with the observations of maize,the contributions of climate change and technological advancement to maize yield from 1981 to 2010 in China are separated.The results show that,from 1961 to 2010,climate change had a significant adverse impact on the climatic potential productivity of maize in China.Decreased radiation and increased temperature were the main factors leading to the decrease of climatic potential productivity.However,changes in precipitation had only a small effect.The maize yields of the 14 main planting provinces in China increased obviously over the past 30 years,which was opposite to the decreasing trends of climatic potential productivity.This suggests that technological advancement has offset the negative effects of climate change on maize yield.Technological advancement contributed to maize yield increases by 99.6%-141.6%,while climate change contribution was from-41.4%to 0.4%.In particular,the actual maize yields in Shandong,Henan,Jilin,and Inner Mongolia increased by 98.4,90.4,98.7,and 121.5 kg hm^（-2） yr^（-1） over the past 30 years,respectively.Correspondingly,the maize yields affected by technological advancement increased by 113.7,97.9,111.5,and 124.8 kg hm^（-2） yr^（-1）,respectively.On the contrary,maize yields reduced markedly under climate change,with an average reduction of-9.0 kg hm^（-2） yr^（-1）.Our findings highlight that agronomic technological advancement has contributed dominantly to maize yield increases in China in the past three decades.

Cotton flooding and drought analysis regarding growth stages in Hubei,China,using a daily agrometeorological index

Cotton yield is restricted worldwide by flooding and drought that occur across various growth stages.In this study,cotton flooding and drought in Hubei(a major cotton-production province in China)from 1961 to 2019 were analyzed regarding growth stages through a daily index named the standardized antecedent precipitation evapotranspiration index(SAPEI).In addition,the impacts of flooding and drought on cotton climatic yield were quantified using multiple regression models.The results showed that the temporal trends of cotton flooding and drought intensities were generally smooth,except for an obvious downward trend for cotton drought intensity at the flowering and boll-forming stage.Additionally,cotton drought intensity varied more drastically than that of flooding over the years.Cotton-flooding proneness was much greater than cotton-drought proneness at all growth stages,and the most flooding-prone and drought-prone periods were identified as the flowering and boll-forming stage and the budding stage,respectively.In terms of spatial distribution,northeastern Hubei and southwestern Hubei were most prone to flooding and drought,respectively.The SAPEI-based regression model(R2=0.490,p<0.001),obviously outperforming the SPEI-based model(R2=0.278,p<0.05),revealed that both cotton flooding and drought exhibited negatively significant effects on cotton climatic yield and that the yield-reducing effect of cotton flooding was much greater than that of drought.Moreover,when growth stages were further considered using regression analysis,only the flowering and boll-forming stage was detected with a significant yield-reducing effect of cotton flooding.In conclusion,the SAPEI can effectively assist in monitoring cotton flooding and drought;cotton flooding,especially during the flowering and boll-forming stage and that occurring in northeastern Hubei,is the key issue for cotton field water management in Hubei.