IXIM: A new maize simulation model for DSSAT v4.5.

The Decision Support System for Agrotechnology Transfer (DSSAT) is a suite of crop simulation models and associated tools for simulating growth, development, and yield of 25 crops. The maize simulation model in DSSAT is CSM-CERES, the modular version of CERES-Maize, which was first published in 1986. The newest release of DSSAT, version 4.5, provides users with the opportunity to run an alternative maize simulation model. IXIM (eeh-sheem), the Mayan language for maize, is a new, more mechanistic, maize simulation model fully compatible with DSSAT. The purpose of this work is to compare seasonal simulations of maize growth and N uptake using CSM-CERES and IXIM

Coupling DSSAT and HYDRUS-1D for simulations of soil water dynamics in the soil-plant-atmosphere system

Abstract Accurate estimation of the soil water balance of the soil-plant-atmosphere system is key to determining the availability of water resources and their optimal management. Evapotranspiration and leaching are the main sinks of water from the system affecting soil water status and hence crop yield. The accuracy of soil water content and evapotranspiration simulations affects crop yield simulations as well. DSSAT is a suite of field-scale, process-based crop models to simulate crop growth and development. A “tipping bucket” water balance approach is currently used in DSSAT for soil hydrologic and water redistribution processes. By comparison, HYDRUS-1D is a hydrological model to simulate water flow in soils using numerical solutions of the Richards equation, but its approach to crop-related process modeling is rather limited. Both DSSAT and HYDRUS-1D have been widely used and tested in their separate areas of use. The objectives of our study were: (1) to couple HYDRUS-1D with DSSAT to simulate soil water dynamics, crop growth and yield, (2) to evaluate the coupled model using field experimental datasets distributed with DSSAT for different environments, and (3) to compare HYDRUS-1D simulations with those of the tipping bucket approach using the same datasets. Modularity in the software design of both DSSAT and HYDRUS-1D made it easy to couple the two models. The pairing provided the DSSAT interface an ability to use both the tipping bucket and HYDRUS-1D simulation approaches. The two approaches were evaluated in terms of their ability to estimate the soil water balance, especially soil water contents and evapotranspiration rates. Values of the d index for volumetric water contents were 0.9 and 0.8 for the original and coupled models, respectively. Comparisons of simulations for the pod mass for four soybean and four peanut treatments showed relatively high d index values for both models (0.94–0.99)

Crop and soil organic matter simulation models – A brief review of their basic features and application in sub-Saharan Africa

Over the past decades, numerous crop-soil models have been developed to represent dynamic processes in cropland systems, including soil organic carbon (SOC) dynamics (Campbell and Paustian, 2015). These models use mathematical equations that determine carbon allocation in the vegetation and biomass and soils to represent biogeochemical processes, such as photosynthesis, respiration and decomposition. Furthermore, a range of crop management practices are represented in most of the models, enabling an assessment of their impacts on SOC in agricultural systems. Although models were initially developed for research purposes, they are increasingly becoming important in many aspects of environmental policies (Manlay et al., 2007). Extensively tested models provide effective tools that can be used in identifying sustainable land management practices across different agroecological conditions. Compared to field experiments, which are time and resource consuming, models are more effective for making predictions and understanding crop and SOC dynamics on large scales and different time scales. However, the choice of the model depends on the ability of the model to simulate key processes in the region of interest. We conducted a survey to identify the features of the commonly used crop-soil models in order to inform the choices for application in sub-Saharan Africa. The survey was administered online to the model developers. In addition, we also conducted a literature search to assess the usage of the different models in different parts of sub-Saharan. In this brief, we provide a basic summary of the information from the survey and literature review

Managing Crop Production Risk with Crop Index Insurance Products

Index crop insurance products can eliminate the asymmetric information problem inherent in farm-level multiple peril crop insurance. Purchasers of index insurance products are, however, exposed to basis risk. This study examines the feasibility of various index insurance products for corn farms in southern Georgia. Index insurance products considered are based on county yields, cooling degree days, and predicted yields from a crop simulation model.Risk and Uncertainty,

Evaluating the Efficiency of Crop Index Insurance Products

Index crop insurance products can eliminate the asymmetric information problem inherent in farm-level multiple peril crop insurance. Purchasers of index insurance products are, however, exposed to basis risk. This study evaluates the efficiency of various index insurance products to reduce farm yield loss for representative corn farms in southern Georgia. Index insurance products considered are based on county yields, cooling degree days, and predicted yields from a crop simulation model.Crop Production/Industries, Risk and Uncertainty,

Impact of climate change on first generation biofuels production in the 21st century

This study assessed the potential (near, medium, and long term) impacts of climate change on first generation corn bioethanol and soybean biodiesel production in Gainesville, Florida, USA. The Decision Support System for Agrotechnology Transfer-Cropping System Model (DSSAT-CSM) was used to simulate biomass and grain yield under climate change scenarios in the 21st century with direct effect of CO2. Weather projection was made for each scenario using the 10 year weather data for the baseline period (1981–1990). Precipitation is projected to increase by +20, +10, -10, and -20% every month throughout the growing season. Daily minimum and maximum air temperatures are projected to increase by +1.5, +3, and +5oC. Atmospheric CO2 is projected to increase by +70 and +350ppm. Simulated yields (grains/seeds and by-products) were then used as inputs into the LCA models. Results show that while bioethanol from corn and biodiesel from soybean offers some potential for GHG emissions savings per cultivated ha of set-aside land, this is tempered by rising air temperature. However, increased atmospheric levels of CO2 relative to current condition would reduce the severe impact of warming. Only soybean biodiesel will be positively affected by climate changes

Global and local economic impacts of climate change in Syria and options for adaptation:

There is broad consensus among scientists that climate change is altering weather patterns around the world. However, economists are only beginning to develop tools that allow for the quantification of such weather changes on countries' economies and people. This paper presents a modeling suite that links the downscaling of global climate models, crop modeling, global economic modeling, and subnational-level computable equilibrium modeling. Important to note is that this approach allows for decomposing the potential global and local economic effects on countries, including various economic sectors and different household groups. We apply this modeling suite to Syria, a relevant case study given the country's location in a region that is consistently projected to be among those hit hardest by climate change. Despite a certain degree of endogenous adaptation, local impacts of climate change (through declining yields) are likely to affect Syria beyond the agricultural sector and farmers and also reduce economy-wide growth and incomes of urban households in the long term. The overall effects of global climate change (through higher food prices) are also negative, but some farmers can reap the benefit of higher prices. Combining local and global climate change scenarios shows welfare losses across all rural and urban household groups of between 1.6 – 2.8 percent annually, whereas the poorest household groups are the hardest hit. Finally, while there is some evidence that droughts may become more frequent in the future, it is clear that even without an increase in frequency, drought impacts will continue to put a significant burden on Syria's economy and people. Action to mitigate the negative effects of climate change and variability should to be taken on the global and local level. A global action plan for improving food security and better integration of climate change in national development strategies, agricultural and rural policies, and disaster risk management and social protection policies will be keys for improving the resilience of countries and people to climate change.Climate change, Development, drought, Growth, Poverty,

Changes in Management Can Improve Returns from Cambodian Upland Crops

Farming systems research for wet-season non-rice upland crops in Cambodia is being conducted with the overall aim of poverty reduction and food security for farmers in the Provinces of Battambang and Kampong Cham. Some of these cash crops exhibit low and variable incomes, especially when grown in the early wet season. Cambodian farmers may borrow money to buy crop inputs and often sell their produce to companies and traders from neighbouring countries, hence they are price takers. Some new crop technologies are evaluated which relate to soil and crop fertility management interacting with climatic factors. The DSSAT crop simulation model is used to predict outcomes from alternative management strategies. Bio-economic analyses are conducted to assess the likely appeal of these technologies to Cambodian farmers in a return-on-investment context. The results show that management to adjust the nitrogen fertility available to corn, the use of rhizobium in soybean, and a delay in planting early-wet-season corn may all show substantial financial benefits. Further research and an associated farmer demonstration program involving local extension officers are recommended.Upland crops, Cambodia, technology, economics, simulation, risk, Crop Production/Industries,