Characterizing patterns of seasonal drought stress for use in common bean breeding in East Africa under present and future climates.

Common bean (Phaseolus vulgaris L.) is the second most important source of dietary protein and the third most important source of calories in Africa, especially for the poor. In East Africa, drought is an important constraint to bean production. Therefore, breeding programs in East Africa have been trying to develop drought resistant varieties of common bean. To do this, breeders need information about seasonal drought stress patterns including their onset, intensity, and duration in the target area of the breeding program, so that they can mimic this pattern during field trials. Using the Decision Support for Agrotechnology Transfer (DSSAT) v4.7 model together with historical and future (Coupled Model Inter-comparison Project 6, CMIP6) climate data, this study categorized Ethiopia, Tanzania, and Uganda into different target population of environments (TPEs) based on historical and future seasonal drought stress patterns. We find that stress-free conditions generally dominate across the three countries under historical conditions (50-80% frequency). These conditions are projected to increase in frequency in Ethiopia by 2-10% but the converse is true for Tanzania (2-8% reduction) and Uganda (17-20% reduction) by 2050 depending on the Shared Socioeconomic Pathway (SSP). Accordingly, by 2050, terminal drought stresses of various intensities (moderate, severe, extreme) are prevalent in 34% of Uganda, around a quarter of Ethiopia, and 40% of the bean growing environments in Tanzania. The TPEs identified in each country serve as a basis for prioritizing breeding activities in national programs. However, to optimize resource use in international breeding programs to develop genotypes that are resilient to future projected stress patterns, we argue that common bean breeding programs should focus primarily on identifying genotypes with tolerance to severe terminal drought, with co-benefits in relation to adaptation to moderate and extreme terminal drought. Little to no emphasis on heat stress is warranted by 2050s.

Optimization of sowing date and irrigation levels for white oats using the CERES-Barley model.

Studies on the use of deficit irrigation and application of models for estimating agronomic performance of crops can help in more sustainable agricultural managements. The objective of this study was to evaluate the effect of irrigation levels on the agronomic performance of white oat (Avena sativa L.) and accuracy of the CERES-Barley model in simulating white oat growth and yield, as well as performing long-term simulation to identify the best sowing time for each irrigation management. The experiment consisted of five irrigation levels (11%, 31%, 60%, 87%, and 100%), being conducted in two agricultural years in southeastern Brazil. The model was calibrated with data of the treatment without water deficit (100%) of the first year and validated with the data of the other treatments in the 2 years. Long-term analyses, with a historical series of 16 years, were performed to recommend the best sowing dates for each irrigation management. Deficit irrigation linearly reduces the agronomic performance of white oat. The high accuracy of white oat yield estimation (R2 = 0.86; RMSE = 616 kg ha-1) using the CERES-Barley model allowed the long-term simulation for establishing the best sowing date for each irrigation level. For higher irrigation levels, sowing in periods with lower temperature (May and June) is more appropriate, as the 1 °C increment in the average temperature before flowering reduces crop yield by 600 kg ha-1. At irrigation levels with higher deficit, sowing in periods with higher rainfall (March and April) promotes higher crop yield.

Importance of genetic parameters and uncertainty of MANIHOT, a new mechanistic cassava simulation model.

We identified the most sensitive genotype-specific parameters (GSPs) and their contribution to the uncertainty of the MANIHOT simulation model. We applied a global sensitivity and uncertainty analysis (GSUA) of the GSPs to the simulation outputs for the cassava development, growth, and yield in contrasting environments. We compared enhanced Sampling for Uniformity, a qualitative screening method new to crop simulation modeling, and Sobol, a quantitative, variance-based method. About 80% of the GSPs contributed to most of the variation in maximum leaf area index (LAI), yield, and aboveground biomass at harvest. Relative importance of the GSPs varied between warm and cool temperatures but did not differ between rainfed and no water limitation conditions. Interactions between GSPs explained 20% of the variance in simulated outputs. Overall, the most important GSPs were individual node weight, radiation use efficiency, and maximum individual leaf area. Base temperature for leaf development was more important for cool compared to warm temperatures. Parameter uncertainty had a substantial impact on model predictions in MANIHOT simulations, with the uncertainty 2-5 times larger for warm compared to cool temperatures. Identification of important GSPs provides an objective way to determine the processes of a simulation model that are critical versus those that have little relevance.

Simulated Optimum Sowing Date for Forage Pearl Millet Cultivars in Multilocation Trials in Brazilian Semi-Arid Region.

Forage production is primarily limited by weather conditions under dryland production systems in Brazilian semi-arid regions, therefore sowing at the appropriate time is critical. The objectives of this study were to evaluate the CSM-CERES-Pearl Millet model from the DSSAT software suite for its ability to simulate growth, development, and forage accumulation of pearl millet [Pennisetum glaucum (L.) R.] at three Brazilian semi-arid locations, and to use the model to study the impact of different sowing dates on pearl millet performance for forage. Four pearl millet cultivars were grown during the 2011 rainy season in field experiments conducted at three Brazilian semi-arid locations, under rainfed conditions. The genetic coefficients of the four pearl millet cultivars were calibrated for the model, and the model performance was evaluated with experimental data. The model was run for 14 sowing dates using long-term historical weather data from three locations, to determine the optimum sowing window. Results showed that performance of the model was satisfactory as indicated by accurate simulation of crop phenology and forage accumulation against measured data. The optimum sowing window varied among locations depending on rainfall patterns, although showing the same trend for cultivars within the site. The best sowing windows were from 15 April to 15 May for the Bom Conselho location; 12 April to 02 May for Nossa Senhora da Gloria; and 17 April to 25 May for Sao Bento do Una. The model can be used as a tool to evaluate the effect of sowing date on forage pearl millet performance in Brazilian semi-arid conditions.

Assessing high-impact spots of climate change: spatial yield simulations with Decision Support System for Agrotechnology Transfer (DSSAT) model.

Drybeans (Phaseolus vulgaris L.) are an important subsistence crop in Central America. Future climate change may threaten drybean production and jeopardize smallholder farmers' food security. We estimated yield changes in drybeans due to changing climate in these countries using downscaled data from global circulation models (GCMs) in El Salvador, Guatemala, Honduras, and Nicaragua. We generated daily weather data, which we used in the Decision Support System for Agrotechnology Transfer (DSSAT) drybean submodel. We compared different cultivars, soils, and fertilizer options in three planting seasons. We analyzed the simulated yields to spatially classify high-impact spots of climate change across the four countries. The results show a corridor of reduced yields from Lake Nicaragua to central Honduras (10-38 % decrease). Yields increased in the Guatemalan highlands, towards the Atlantic coast, and in southern Nicaragua (10-41 % increase). Some farmers will be able to adapt to climate change, but others will have to change crops, which will require external support. Research institutions will need to devise technologies that allow farmers to adapt and provide policy makers with feasible strategies to implement them.

Número de gerações de um percevejo e seu parasitoide e da severidade da ferrugem asiática em soja, simulados em cenários de clima e manejo no norte do RS / Number of generations of a stink bug and its parasitoid and severity of soybean rust, simulated under climate and crop management scenarios in northern RS State, Brazil

Objetivou-se simular o número de gerações do percevejo Euschistus heros e seu parasitoide Telenomus podisi e da severidade da ferrugem causada por Phakopsora pachyrhizi na cultura da soja em função da data de semeadura, cultivar e momento de ocorrência desses organismos. A simulação foi feita em dois locais representativos de duas importantes regiões produtoras de soja no Estado do Rio Grande do Sul. Modelos bioclimáticos dos insetos e da doença foram integrados a um modelo de simulação da cultura da soja (DSSAT) e rodados para uma série temporal de dados meteorológicos diários para Passo Fundo (52 anos) e Santa Rosa (34 anos). Independente do grupo de maturação, quanto mais antecipada foi a data da semeadura e o estádio de ocorrência de E. heros na cultura, maior o número de gerações (de 2 a 3) até a maturação fisiológica da soja. Para T. podisi, um maior número de gerações (5 a 6) foi simulado para semeadura antecipada e cultivares de ciclo tardio. Para a ferrugem asiática não foram observadas tendências de redução nos níveis médios de severidade com o uso de práticas preconizadas, como plantio antecipado e cultivares de grupos mais precoces de maturação.

The objective of this study was to simulate the number of generations of a soybean insect pest (Euschistus heros) and its parasitoid (Telenomus podisi) and a fungal disease (soybean rust caused by Phakopsora pachyrhizi) as influenced by sowing date, cultivar and time of occurrence of the pest and the disease. Bioclimatic models that predict development of the organisms and severity of the disease were integrated into a crop simulation model of soybean (DSSAT) that predicted phenological stages of the crop for scenarios of sowing data and cultivar maturity group in a long time series of daily meteorological data to Passo Fundo and Santa Rosa, Rio Grande do Sul State, Brazil. The results showed that regardless of the maturity group, the earlier the sowing date and the time of occurrence of E. heros in the field, the greater its number of generations (2 to 3) until physiological maturity. For T. podisi, a higher number of generations (5 to 6) was estimated for the earlier sowing dates and late-maturing cultivars. For soybean rust no significant trends of reduction in the mean disease severity was observed when advocated practices such as early sowing and early-maturing cultivars were used.

Número de gerações de um percevejo e seu parasitoide e da severidade da ferrugem asiática em soja, simulados em cenários de clima e manejo no norte do RS

The objective of this study was to simulate the number of generations of a soybean insect pest (Euschistus heros) and its parasitoid (Telenomus podisi) and a fungal disease (soybean rust caused by Phakopsora pachyrhizi) as influenced by sowing date, cultivar and time of occurrence of the pest and the disease. Bioclimatic models that predict development of the organisms and severity of the disease were integrated into a crop simulation model of soybean (DSSAT) that predicted phenological stages of the crop for scenarios of sowing data and cultivar maturity group in a long time series of daily meteorological data to Passo Fundo and Santa Rosa, Rio Grande do Sul State, Brazil. The results showed that regardless of the maturity group, the earlier the sowing date and the time of occurrence of E. heros in the field, the greater its number of generations (2 to 3) until physiological maturity. For T. podisi, a higher number of generations (5 to 6) was estimated for the earlier sowing dates and late-maturing cultivars. For soybean rust no significant trends of reduction in the mean disease severity was observed when advocated practices such as early sowing and early-maturing cultivars were used.

Objetivou-se simular o número de gerações do percevejo Euschistus heros e seu parasitoide Telenomus podisi e da severidade da ferrugem causada por Phakopsora pachyrhizi na cultura da soja em função da data de semeadura, cultivar e momento de ocorrência desses organismos. A simulação foi feita em dois locais representativos de duas importantes regiões produtoras de soja no Estado do Rio Grande do Sul. Modelos bioclimáticos dos insetos e da doença foram integrados a um modelo de simulação da cultura da soja (DSSAT) e rodados para uma série temporal de dados meteorológicos diários para Passo Fundo (52 anos) e Santa Rosa (34 anos). Independente do grupo de maturação, quanto mais antecipada foi a data da semeadura e o estádio de ocorrência de E. heros na cultura, maior o número de gerações (de 2 a 3) até a maturação fisiológica da soja. Para T. podisi, um maior número de gerações (5 a 6) foi simulado para semeadura antecipada e cultivares de ciclo tardio. Para a ferrugem asiática não foram observadas tendências de redução nos níveis médios de severidade com o uso de práticas preconizadas, como plantio antecipado e cultivares de grupos mais precoces de maturação.

Número de gerações de um percevejo e seu parasitoide e da severidade da ferrugem asiática em soja, simulados em cenários de clima e manejo no norte do RS

The objective of this study was to simulate the number of generations of a soybean insect pest (Euschistus heros) and its parasitoid (Telenomus podisi) and a fungal disease (soybean rust caused by Phakopsora pachyrhizi) as influenced by sowing date, cultivar and time of occurrence of the pest and the disease. Bioclimatic models that predict development of the organisms and severity of the disease were integrated into a crop simulation model of soybean (DSSAT) that predicted phenological stages of the crop for scenarios of sowing data and cultivar maturity group in a long time series of daily meteorological data to Passo Fundo and Santa Rosa, Rio Grande do Sul State, Brazil. The results showed that regardless of the maturity group, the earlier the sowing date and the time of occurrence of E. heros in the field, the greater its number of generations (2 to 3) until physiological maturity. For T. podisi, a higher number of generations (5 to 6) was estimated for the earlier sowing dates and late-maturing cultivars. For soybean rust no significant trends of reduction in the mean disease severity was observed when advocated practices such as early sowing and early-maturing cultivars were used.

Objetivou-se simular o número de gerações do percevejo Euschistus heros e seu parasitoide Telenomus podisi e da severidade da ferrugem causada por Phakopsora pachyrhizi na cultura da soja em função da data de semeadura, cultivar e momento de ocorrência desses organismos. A simulação foi feita em dois locais representativos de duas importantes regiões produtoras de soja no Estado do Rio Grande do Sul. Modelos bioclimáticos dos insetos e da doença foram integrados a um modelo de simulação da cultura da soja (DSSAT) e rodados para uma série temporal de dados meteorológicos diários para Passo Fundo (52 anos) e Santa Rosa (34 anos). Independente do grupo de maturação, quanto mais antecipada foi a data da semeadura e o estádio de ocorrência de E. heros na cultura, maior o número de gerações (de 2 a 3) até a maturação fisiológica da soja. Para T. podisi, um maior número de gerações (5 a 6) foi simulado para semeadura antecipada e cultivares de ciclo tardio. Para a ferrugem asiática não foram observadas tendências de redução nos níveis médios de severidade com o uso de práticas preconizadas, como plantio antecipado e cultivares de grupos mais precoces de maturação.

Calibration and test of the cropgro-dry bean model for edaphoclimatic conditions in the savanas of Central Brazil

Simulation models are important tools for the analysis of cultivated systems to estimate the performance of crops in different environments. The CROPGRO- model (DSSAT) was calibrated and validated using Carioca bean (Phaseolus vulgaris L.) to estimate yield and the development of the crop, sown in three row spacings (0.4, 0.5, and 0.6 m) and two fertilization rates (300 and 500 kg ha-1 of 4-30-16 N-P-K), in Santo Antônio de Goiás, GO, Brazil. To calibrate the model a combination of the genetic coefficients that characterize the phenology and morphology of the dry bean crop was used to obtain the best possible fit between predicted and observed anthesis and physiological maturity dates, leaf area index (LAI), total dry matter (TDM), yield components, and grain yield for the 0.6 m row spacing. To test the model the experimental records of the 0.4 and 0.5 m row spacings were used. In both, calibration and test, the performance of the model was evaluated plotting observed and predicted values of LAI and TDM versus time, using the r², and the agreement index (d) as statistical criteria. In relation to yield and yield components the percent difference between the observed and predicted data was calculated. The model appeared to be adequate to simulate phenology, grain yield and yield components for the Carioca bean cultivar, related to different levels of fertilization and row spacing, either during calibration or the testing phase. During the test, the grain yield was overestimated by less than 15.4%, indicating a potential use for the calibrated model in assessing climatic risks in this region.

Modelos de simulação são importantes ferramentas na análise de sistemas cultivados para estimar a performance da cultura em diferentes ambientes. O modelo CROPGRO- foi calibrado e testado, utilizando-se o cultivar Carioca para estimar a produtividade e o desenvolvimento do feijoeiro (Phaseolus vulgaris L.) sob três espaçamentos (0,4, 0,5 e 0,6 m) e duas doses de adubação (300 e 500 kg ha-1 de 4-30-16 de N-P-K), em Santo Antônio de Goiás, GO. A calibração consistiu na modificação dos coeficientes genéticos característicos da fenologia e morfologia do feijoeiro, visando obter os melhores ajustes possíveis entre os dados simulados e os observados a campo das datas de antese e maturação fisiológica, índice de área foliar (IAF), massa de matéria seca total (MMST), componentes de produção e produtividade de grãos para o espaçamento de 0,6 m. Para o teste do modelo foram utilizados os dados experimentais correspondentes aos espaçamentos de 0,4 e 0,5 m. Em ambos, calibração e teste, a aferição da performance do modelo foi efetuada plotando-se os valores observados e simulados do IAF e MMST ao longo do tempo (dias após semeadura), e utilizando-se o r² e o índice de concordância (d) como critério estatístico. Para produtividade de grãos e componentes de produção determinou-se a diferença percentual entre os valores observados e simulados. O modelo simulou satisfatoriamente a fenologia, a produtividade de grãos e os componentes de produção, para as diferentes doses de adubação e espaçamentos, tanto na fase de calibração como na de teste. Durante o teste, a produtividade de grãos foi superestimada, no máximo, em 15,4%, indicando o potencial do modelo calibrado em futura análise de riscos climáticos.

Calibration and test of the cropgro-dry bean model for edaphoclimatic conditions in the savanas of Central Brazil

Simulation models are important tools for the analysis of cultivated systems to estimate the performance of crops in different environments. The CROPGRO- model (DSSAT) was calibrated and validated using Carioca bean (Phaseolus vulgaris L.) to estimate yield and the development of the crop, sown in three row spacings (0.4, 0.5, and 0.6 m) and two fertilization rates (300 and 500 kg ha-1 of 4-30-16 N-P-K), in Santo Antônio de Goiás, GO, Brazil. To calibrate the model a combination of the genetic coefficients that characterize the phenology and morphology of the dry bean crop was used to obtain the best possible fit between predicted and observed anthesis and physiological maturity dates, leaf area index (LAI), total dry matter (TDM), yield components, and grain yield for the 0.6 m row spacing. To test the model the experimental records of the 0.4 and 0.5 m row spacings were used. In both, calibration and test, the performance of the model was evaluated plotting observed and predicted values of LAI and TDM versus time, using the r², and the agreement index (d) as statistical criteria. In relation to yield and yield components the percent difference between the observed and predicted data was calculated. The model appeared to be adequate to simulate phenology, grain yield and yield components for the Carioca bean cultivar, related to different levels of fertilization and row spacing, either during calibration or the testing phase. During the test, the grain yield was overestimated by less than 15.4%, indicating a potential use for the calibrated model in assessing climatic risks in this region.

Modelos de simulação são importantes ferramentas na análise de sistemas cultivados para estimar a performance da cultura em diferentes ambientes. O modelo CROPGRO- foi calibrado e testado, utilizando-se o cultivar Carioca para estimar a produtividade e o desenvolvimento do feijoeiro (Phaseolus vulgaris L.) sob três espaçamentos (0,4, 0,5 e 0,6 m) e duas doses de adubação (300 e 500 kg ha-1 de 4-30-16 de N-P-K), em Santo Antônio de Goiás, GO. A calibração consistiu na modificação dos coeficientes genéticos característicos da fenologia e morfologia do feijoeiro, visando obter os melhores ajustes possíveis entre os dados simulados e os observados a campo das datas de antese e maturação fisiológica, índice de área foliar (IAF), massa de matéria seca total (MMST), componentes de produção e produtividade de grãos para o espaçamento de 0,6 m. Para o teste do modelo foram utilizados os dados experimentais correspondentes aos espaçamentos de 0,4 e 0,5 m. Em ambos, calibração e teste, a aferição da performance do modelo foi efetuada plotando-se os valores observados e simulados do IAF e MMST ao longo do tempo (dias após semeadura), e utilizando-se o r² e o índice de concordância (d) como critério estatístico. Para produtividade de grãos e componentes de produção determinou-se a diferença percentual entre os valores observados e simulados. O modelo simulou satisfatoriamente a fenologia, a produtividade de grãos e os componentes de produção, para as diferentes doses de adubação e espaçamentos, tanto na fase de calibração como na de teste. Durante o teste, a produtividade de grãos foi superestimada, no máximo, em 15,4%, indicando o potencial do modelo calibrado em futura análise de riscos climáticos.