Adaptation to climate change through the choice of cropping system and sowing date in sub-Saharan Africa

Multiple cropping systems provide more harvest security for farmers, allow for crop intensification and furthermore influence ground cover, soil erosion, albedo, soil chemical properties, pest infestation and the carbon sequestration potential. We identify the traditional sequential cropping systems in ten sub-Saharan African countries from a survey dataset of more than 8600 households. We find that at least one sequential cropping system is traditionally used in 35% of all administrative units in the dataset, mainly including maize or groundnuts. We compare six different management scenarios and test their susceptibility as adaptation measure to climate change using the dynamic global vegetation model for managed land LPJmL. Aggregated mean crop yields in sub-Saharan Africa decrease by 6–24% due to climate change depending on the climate scenario and the management strategy. As an exception, some traditional sequential cropping systems in Kenya and South Africa gain by at least 25%. The crop yield decrease is typically weakest in sequential cropping systems and if farmers adapt the sowing date to changing climatic conditions. Crop calorific yields in single cropping systems only reach 40–55% of crop calorific yields obtained in sequential cropping systems at the end of the 21st century. The farmers’ choice of adequate crops, cropping systems and sowing dates can be an important adaptation strategy to climate change and these management options should be considered in climate change impact studies on agriculture.     

Growth and yield of rainfed wheat on the seasonally dry Aegean Islands

Summary The effects of water regime on the rate of growth, the growing period and the yield of a winter wheat crop in the summer-dry climate of Aegean Islands are examined. It is shown that wheat growing period is significantly restricted by either, unfavourable weather conditions at planting (coinciding with the start of rains), or by early soil moisture depletion at the end of the wet season. The probability of a successful early planting, which is conditional on a considerable pre-planting rainfall not being following by a long (10-day) dry spell, is estimated by recurrence relationships. Farmers on the driest (south) islands will have a 25% risk for unsuccessful planting before November 14. Evapotranspiration rates, estimated by the Penman-Monteith equation, are optimum for crop growth for about two months after wintering. The growing season on average comes to an end by the end of spring (soon after anthesis), when the available soil moisture. (estimated by a simple water balance equation) drops to zero.The water shortage, especially during the grains-filling period, may reduce yields by up to 75%, depending on the length and severity of the soil moisture deficit at the site. Reliability and distribution of rainfall suggest that the risks of water deficits in rainfed cropping vary across the region. In order to minimise yield losses from crop failures, farmers should adjust areas sown each year according to the date when the wet season starts.With 10 Figures     

气候变化对我国农作物种植结构的影响

气候变化引起水热条件的变化,从而影响到我国农业生产的方方面面,人们采取不同措施以适应气候变化带来的各种影响。为了清楚地认识气候变化对我国主要粮食作物生产的影响以及适应措施,利用《中国农业统计年鉴》1980-2007年资料和1961-2007年全国逐日平均温度观测数据及前人的研究成果,分析了气候变化对我国三大粮食作物布局和种植结构的影响。结果表明,由于气候变暖,粮食作物种植比例变化明显。小麦种植比例对气候变化最为敏感,波动大;水稻种植比例变化南北方反向,且变化幅度趋缓;玉米种植比例持续增加,增幅加大。三大粮食作物种植结构变化均以2000年为分界点,呈现不同增减趋势。而作物熟制、复种指数也发生明显变化,种植北界持续北推。黑龙江地区大面积扩种水稻,原来的玉米优势种植区为水稻所替代。     

北方农牧交错带春小麦生育期对气候变化的响应——以内蒙古武川县为例

北方农牧交错带是气候变化的敏感地带,研究气候变化对农业生产的影响规律与农业生产的响应特征,对促进北方农牧交错带的农业可持续发展具有重要意义。以北方农牧交错带代表性站点--武川县为例,基于1960-2009年气象观测数据和1992-2010年春小麦农业气象观测数据,研究了气候变化与春小麦生育期变化之间的相互关系。结果表明,武川县1960-2009年年平均气温每10年升高0.43℃,春季稳定通过0℃的初日每10年提前0.98 d,当地满足春小麦播种温度的日期有提前的趋势,秋季稳定通过0℃的终日每10年推迟0.24 d,生长季具有延长趋势;1992-2010年作物生长季（4-8月）0～10 cm、10～20 cm土壤相对湿度有明显下降趋势,平均每10年分别下降18%和13%;播种期与0～10 cm和10～20 cm土壤相对湿度呈现显著负相关关系,表现为土壤相对湿度每降低1%,播种期分别推迟0.2 d和0.3 d;各生育期与播种期一样,受温度与水分综合作用的影响,不同生育期与二者之间关系不同,各生育期之间持续日数与二者呈正相关关系。研究得出,春小麦生育期的变化是各气侯因素综合作用的结果,在北方农牧交错带,水分对农作物生长发育具有较大影响,直接影响着春小麦的各个生育过程。     

Contributions of individual variation in temperature, solar radiation and precipitation to crop yield in the North China Plain, 1961–2003

An understanding of the relative impacts of the changes in climate variables on crop yield can help develop effective adaptation strategies to cope with climate change. This study was conducted to investigate the effects of the interannual variability and trends in temperature, solar radiation and precipitation during 1961–2003 on wheat and maize yields in a double cropping system at Beijing and Zhengzhou in the North China Plain (NCP), and to examine the relative contributions of each climate variable in isolation. 129 climate scenarios consisting of all the combinations of these climate variables were constructed. Each scenario contained 43 years of observed values of one variable, combined with values of the other two variables from each individual year repeated 43 times. The Agricultural Production Systems Simulator (APSIM) was used to simulate crop yields using the ensemble of generated climate scenarios. The results showed that the warming trend during the study period did not have significant impact on wheat yield potential at both sites, and only had significant negative impact on maize yield potential at Beijing. This is in contrast with previous results on effect of warming. The decreasing trend in solar radiation had a much greater impact on simulated yields of both wheat and maize crops, causing a significant reduction in potential yield of wheat and maize at Beijing. Although decreasing trends in rainfed yield of both simulated wheat and maize were found, the substantial interannual variability of precipitation made the trends less prominent.     

Understanding the causes and consequences of differential decision-making in adaptation research: Adapting to a delayed monsoon onset in Gujarat,India

Weather variability poses numerous risks to agricultural communities, yet farmers may be able to reduce some of these risks by adapting their cropping practices to better suit changes in weather. However, not all farmers respond to weather variability in the same way. To better identify the causes and consequences of this heterogeneous decision-making, we develop a framework that identifies (1) which socio-economic and biophysical factors are associated with heterogeneous cropping decisions in response to weather variability and (2) which cropping strategies are the most adaptive, considering economic outcomes (e.g., yields and profits). This framework aims to understand how, why, and how effectively farmers adapt to current weather variability; these findings, in turn, may contribute to a more mechanistic and predictive understanding of individual-level adaptation to future climate variability and change. To illustrate this framework, we assessed how 779 farmers responded to delayed monsoon onset in fifteen villages in Gujarat, India during the 2011 growing season, when the monsoon onset was delayed by three weeks. We found that farmers adopted a variety of strategies to cope with delayed monsoon onset, including increasing irrigation use, switching to more drought-tolerant crops, and/or delaying sowing. We found that farmers’ access to and choice of strategies varied with their assets, irrigation access, perceptions of weather, and risk aversion. Richer farmers with more irrigation access used high levels of irrigation, and this strategy was associated with the highest yields in our survey sample. Poorer farmers with less secure access to irrigation were more likely to push back planting dates or switch crop type, and economic data suggest that these strategies were beneficial for those who did not have secure access to irrigation. Interestingly, after controlling for assets and irrigation access, we found that cognitive factors, such as beliefs that the monsoon onset date had changed over the last 20 years or risk aversion, were associated with increased adaptation. Our framework illustrates the importance of considering the complexity and heterogeneity of individual decision-making when conducting climate impact assessments or when developing policies to enhance the adaptive capacity of local communities to future climate variability and change.     

Increased yield potential of wheat-maize cropping system in the North China Plain by climate change adaptation

In the North China Plain, the grain yield of irrigated wheat-maize cropping system has been steadily increasing in the past decades under a significant warming climate. This paper combined regional and field data with modeling to analyze the changes in the climate in the last 40 years, and to investigate the influence of changes in crop varieties and management options to crop yield. In particular, we examined the impact of a planned adaptation strategy to climate change -“Double-Delay” technology, i.e., delay both the sowing time of wheat and the harvesting time of maize, on both wheat and maize yield. The results show that improved crop varieties and management options not only compensated some negative impact of reduced crop growth period on crop yield due to the increase in temperature, they have contributed significantly to crop yield increase. The increase in temperature before over-wintering stage enabled late sowing of winter wheat and late harvesting of maize, leading to overall 4–6% increase in total grain yield of the wheat-maize system. Increased use of farming machines and minimum tillage technology also shortened the time for field preparation from harvest time of summer maize to sowing time of winter wheat, which facilitated the later harvest of summer maize.     

Winter crop sensitivity to inter-annual climate variability in central India

India is predicted to be one of the most vulnerable agricultural regions to future climate changes. Here, we examined the sensitivity of winter cropping systems to inter-annual climate variability in a local market and subsistence-based agricultural system in central India, a data-rich validation site, in order to identify the climate parameters to which winter crops – mainly wheat and pulses in this region – might be sensitive in the future. We used satellite time-series data to quantify inter-annual variability in multiple climate parameters and in winter crop cover, agricultural census data to quantify irrigation, and field observations to identify locations for specific crop types. We developed three mixed-effect models (250 m to 1 km scale) to identify correlations between crop cover (wheat and pulses) and twenty-two climate and environmental parameters for 2001-2013. We find that winter daytime mean temperature (November–January) is the most significant factor affecting winter crops, irrespective of crop type, and is negatively associated with winter crop cover. With pronounced winter warming projected in the coming decades, effective adaptation by smallholder farmers in similar landscapes would require additional strategies, such as access to fine-scale temperature forecasts and heat-tolerant winter crop varieties.     

北方冬小麦冬季冻害及播期延迟应对

全球变暖背景下, 我国北方冬麦区冬季冻害是否仍是主要气象灾害,冬小麦播期延迟是否能作为应对气候变化的措施,成为当前亟待解决的科学问题。研究表明：1981—2000年北方冬麦区偏北地区冬季冻害指数与冬小麦减产率相关系数为0.62(达到0.001显著性水平),即2000年前冬季冻害是冬小麦减产的主要气象灾害之一;2000年后冻害与冬小麦减产率相关不显著,即冬季冻害已不再是冬小麦减产的主要影响因子。2018—2021年的冬小麦分期播种试验分析表明：山东泰安和陕西咸阳主栽的冬小麦品种播期推迟,冬前积温和生长季积温明显减少,导致冬小麦植株高度、地上总干重和叶面积指数减小;播期推迟对产量结构造成不利影响,有效穗数、穗粒数和千粒重均分别减少,导致减产,播期推迟10 d平均减产22%,推迟20 d平均减产40%。因此,冬小麦推迟播期并未产生积极效应, 可能原因是当前冬小麦播期和主栽的冬小麦品种已适应当地气候变化。     

CERES-Wheat模型在我国小麦区的应用效果及误差来源

气候模型与作物模型耦合是评价未来气候变化对作物生产影响的常用方法之一, 但当两者结合时, 存在着空间和时间尺度差异问题, 将作物模型升尺度到区域是解决该差异的一种方法。将CERES-Wheat模型升尺度进行区域模拟, 利用区域校准后的CERES-Wheat模型, 模拟了1981—2000年全国各网格小麦产量, 与同期农调队调查产量相比较, 以探讨CERES-Wheat模型在我国小麦区的模拟效果及误差来源。结果表明:全国小麦产量的区域模拟值与农调队调查产量的相对均方根误差为27.9%, 符合度为0.75, 全国59.2%的模拟网格相对均方根误差在30%以内, 其中相对均方根误差小于15%的占26.3%;各区的效果不同, 种植面积最大的小麦种植生态2区, 模拟效果最好。总体来说, CERES-Wheat的区域模拟, 可以反映产量变化规律, 能为宏观决策提供相应信息, 尤其是在主产区; 但区域模拟中还存在一系列误差, 今后还需进一步研究。     

Thermal Climate Variations and Potential Modification of the Cropping Pattern in Bangladesh

Summary Changes in the thermal climate due to inter-annual climatic variability can potentially modify existing cropping pattern by forcing farmers to rearrange transplanting and harvesting dates. In the present study, a crop climate model, the YIELD, has been applied to 12 meteorological stations located in major rice growing regions in Bangladesh to estimate the effect of thermal climate variations on the transplanting and harvesting dates of boro rice and the resultant potential changes in cropping pattern and spatial shift. The abnormal thermal climate scenarios have been created by synthetically perturbing mean air temperatures (T_air) up to −5 °C to +5 °C with an interval of 1 °C for each of these stations. Historical meteorological records of air temperature in Bangladesh have been used to prepare these scenarios. The study finds that under abnormally cool conditions transplanting dates will be pushed well into February to avoid plant injury and harvesting dates will be moved into the monsoon. The growing seasons will be longer under cooler than normal thermal conditions. Under abnormally warm conditions harvesting dates will be established well into March and will cause reduction of yield due to a shorter growing season. These conditions will also cause spatial shift in crop potential and changes in the cropping pattern. Due to a longer boro rice growing season farmers will lose a significant amount of cropping land which is usually used for low and deep water rice cultivation. New crops will need to be introduced during the beginning of a year to overcome the loss of production under abnormally cool conditions. Wheat and potato can be good options for the farmers for such conditions. New aus rice variety needs to be introduced after the boro harvesting under warmer than the normal conditions to overcome the loss of yield due to a shorter growing season. Received September 16, 1996 Revised September 8, 1997     

The impacts of climate change on the winter hardiness zones of woody plants in Europe

The potential impacts of climate change on potatoes cropping in the Peruvian highlands (Altiplano) is assessed using climate projections for 2071–2100, obtained from the HadRM3P regional atmospheric model of the Hadley Centre. The atmospheric model is run under two different special report on emission scenarios: high CO₂ concentration (A2) and moderate CO₂ concentration (B2) for four locations situated in the surroundings of Lake Titicaca. The two main varieties of potato cultivated in the area are studied: the Andean potato (Solanum tuberosum) and the bitter potato (Solanum juzepczukii). A simple process-oriented model is used to quantify the climatic impacts on crops cycles and yields by combining the effects of temperature on phenology, of radiation and CO₂ on maximum yield and of water balance on yield deficit. In future climates, air temperature systematically increases, precipitation tends to increase at the beginning of the rainy season and slightly decreases during the rest of the season. The direct effects of these climatic changes are earlier planting dates, less planting failures and shorter crop cycles in all the four locations and for both scenarios. Consequently, the harvesting dates occur systematically earlier: roughly in January for the Andean potato instead of March in the current situation and in February for the bitter potato instead of April. Overall, yield deficits will be higher under climate change than in the current climate. There will be a strong negative impact on yields for S. tuberosum (stronger under A2 scenario than under B2); the impact on S. juzepczukii yields, however, appears to be relatively mixed and not so negative.     

郯麦98对播种期变化的响应

播种期调整被广泛用于作物适应气候变化, 但播种期调整对作物生长发育过程的影响仍需探讨。基于2017—2022年华北平原北部冬小麦郯麦98的播种期调整大田试验资料, 分析播种期变化对郯麦98的生长发育、产量形成和品质影响。结果表明: 播种期推迟使郯麦98的生长季缩短、有效穗数和籽粒产量减少, 9月30日—10月30日播种期的籽粒产量减少率达569.71 kg·hm-2·(10 d)-1, 但对穗粒数、穗粒重无显著影响。播种期推迟还影响郯麦98成熟期地上干物质分配, 茎秆随播种期推迟呈减少趋势, 为2.44%·(10 d)-1; 而穗部呈增加趋势, 为2.44%·(10 d)-1。播种期变化对郯麦98的叶片光合特性和籽粒品质影响不显著。研究结果可为华北平原北部冬小麦播种期调整提供依据。     

中、高温室气体排放情景下2069~2098年中国冬小麦气候适宜种植分区对比北大核心CSCD

基于温度、降水、光照等指标,通过利用区域气候模式所预估的分辨率为1°(纬度)×1°(经度)的未来气候预估数据,对1981~2005年的基准期和RCP4.5、RCP8.5两排放情景下2069~2098年中国热量资源以及冬小麦种植界限、理论生育期和气候适宜种植分区的空间分布特征进行了对比分析。研究主要结论为:与基准期相比,两未来气候变化情景下我国热量资源、冬小麦种植条件与气候适宜性差异显著。且相比于RCP4.5情景,在RCP8.5情景下中国2069~2098年多数地区热量资源增加、冬小麦种植北界和南界北移东扩、可种植面积扩大,多数区域理论适宜播种期推迟、理论成熟期提前、潜在生长季缩短,且潜在生长季内的光—温—水配置使得冬小麦气候适宜性有所提高。但由于冬小麦为喜凉作物,对高温胁迫非常敏感,RCP8.5情景下更多的极端高温天气和不对称增温等因素带来的负面影响很可能抵消前述光—温—水配置所带来的有利影响,从而降低冬小麦的种植适宜性。因此,未来研究工作仍应致力于减缓气候变化,以保障我国粮食生产的安全。     

Quantifying the effects of climate trends in the past 43 years (1961–2003) on crop growth and water demand in the North China Plain

This paper explores changes in climatic variables, including solar radiation, rainfall, fraction of diffuse radiation (FDR) and temperature, during wheat season (October to May) and maize season (June to September) from 1961 to 2003 at four sites in the North China Plain (NCP), and then evaluates the effects of these changes on crop growth processes, productivity and water demand by using the Agricultural Production Systems Simulator. A significant decline in radiation and rainfall was detected during the 43 years, while both temperature and FDR exhibit an increasing trend in both wheat and maize seasons. The average trend of each climatic variable for each crop season from the four sites is that radiation decreased by 13.2 and 6.2 MJ m^?2 a^?1, precipitation decreased by 0.1 and 1.8 mm a^?1, minimum temperature increased by 0.05 and 0.02°C a^?1, maximum temperature increased by 0.03 and 0.01°C a^?1, FDR increased by 0.21 and 0.38% a^?1 during wheat and maize season, respectively. Simulated crop water demand and potential yield was significantly decreased because of the declining trend in solar radiation. On average, crop water demand was decreased by 2.3 mm a^?1 for wheat and 1.8 mm a^?1 for maize if changes in crop variety were not considered. Simulated potential crop yields under fully irrigated condition declined about 45.3 kg ha^?1 a^?1 for wheat and 51.4 kg ha^?1 a^?1 for maize at the northern sites, Beijing and Tianjin. They had no significant changes in the southern sites, Jinan and Zhengzhou. Irrigation, fertilization development and crop variety improvement are main factors to contribute to the increase in actual crop yield for the wheat–maize double cropping system, contrasted to the decline in the potential crop yield. Further research on how the improvement in crop varieties and management practices can counteract the impact of climatic change may provide insight into the future sustainability of wheat–maize double crop rotations in the NCP.     

Combined Impact of Climate Change,Cultivar Shift,and Sowing Date on Spring Wheat Phenology in Northern China

Distinct climate changes since the end of the 1980 s have led to clear responses in crop phenology in many parts of the world. This study investigated the trends in the dates of spring wheat phenology in relation to mean temperature for different growth stages. It also analyzed the impacts of climate change, cultivar shift, and sowing date adjustments on phenological events/phases of spring wheat in northern China(NC).The results showed that significant changes have occurred in spring wheat phenology in NC due to climate warming in the past 30 years. Specifically, the dates of anthesis and maturity of spring wheat advanced on average by 1.8 and 1.7 day(10 yr)~(-1). Moreover, while the vegetative growth period(VGP) shortened at most stations, the reproductive growth period(RGP) prolonged slightly at half of the investigated stations. As a result, the whole growth period(WGP) of spring wheat shortened at most stations. The findings from the Agricultural Production Systems Simulator(APSIM)-Wheat model simulated results for six representative stations further suggested that temperature rise generally shortened the spring wheat growth period in NC.Although the warming trend shortened the lengths of VGP, RGP, and WGP, the shift of new cultivars with high accumulated temperature requirements, to some extent, mitigated and adapted to the ongoing climate change. Furthermore, shifts in sowing date exerted significant impacts on the phenology of spring wheat.Generally, an advanced sowing date was able to lower the rise in mean temperature during the different growth stages(i.e., VGP, RGP, and WGP) of spring wheat. As a result, the lengths of the growth stages should be prolonged. Both measures(cultivar shift and sowing date adjustments) could be vital adaptation strategies of spring wheat to a warming climate, with potentially beneficial effects in terms of productivity.     

Quantifying sources of uncertainty in projected wheat yield changes under climate change in eastern Australia

Future climate projections and impact analyses are pivotal to evaluate the potential change in crop yield under climate change. Impact assessment of climate change is also essential to prepare and implement adaptation measures for farmers and policymakers. However, there are uncertainties associated with climate change impact assessment when combining crop models and climate models under different emission scenarios. This study quantifies the various sources of uncertainty associated with future climate change effects on wheat productivity at six representative sites covering dry and wet environments in Australia based on 12 soil types and 12 nitrogen application rates using one crop model driven by 28 global climate models (GCMs) under two representative concentration pathways (RCPs) at near future period 2021–2060 and far future period 2061–2100. We used the analysis of variance (ANOVA) to quantify the sources of uncertainty in wheat yield change. Our results indicated that GCM uncertainty largely dominated over RCPs, nitrogen rates, and soils for the projections of wheat yield at drier locations. However, at wetter sites, the largest share of uncertainty was nitrogen, followed by GCMs, soils, and RCPs. In addition, the soil types at two northern sites in the study area had greater effects on yield change uncertainty probably due to the interaction effect of seasonal rainfall and soil water storage capacity. We concluded that the relative contributions of different uncertainty sources are dependent on climatic location. Understanding the share of uncertainty in climate impact assessment is important for model choice and will provide a basis for producing more reliable impact assessment.     

Combined impact of climate change,cultivar shift,and sowing date on spring wheat phenology in Northern China

Distinct climate changes since the end of the 1980s have led to clear responses in crop phenology in many parts of the world. This study investigated the trends in the dates of spring wheat phenology in relation to mean temperature for different growth stages. It also analyzed the impacts of climate change, cultivar shift, and sowing date adjustments on phenological events/phases of spring wheat in northern China (NC). The results showed that significant changes have occurred in spring wheat phenology in NC due to climate warming in the past 30 years. Specifically, the dates of anthesis and maturity of spring wheat advanced on average by 1.8 and 1.7 day (10 yr)^?1. Moreover, while the vegetative growth period (VGP) shortened at most stations, the reproductive growth period (RGP) prolonged slightly at half of the investigated stations. As a result, the whole growth period (WGP) of spring wheat shortened at most stations. The findings from the Agricultural Production Systems Simulator (APSIM)-Wheat model simulated results for six representative stations further suggested that temperature rise generally shortened the spring wheat growth period in NC. Although the warming trend shortened the lengths of VGP, RGP, and WGP, the shift of new cultivars with high accumulated temperature requirements, to some extent, mitigated and adapted to the ongoing climate change. Furthermore, shifts in sowing date exerted significant impacts on the phenology of spring wheat. Generally, an advanced sowing date was able to lower the rise in mean temperature during the different growth stages (i.e., VGP, RGP, and WGP) of spring wheat. As a result, the lengths of the growth stages should be prolonged. Both measures (cultivar shift and sowing date adjustments) could be vital adaptation strategies of spring wheat to a warming climate, with potentially beneficial effects in terms of productivity.