Capability of APSIM-Oryza to stimulate lowland rice-based farming systems under nitrogen treatments in a tropical climate

Rice is the most important crop in Asia and the staple food for most of the world’s population. Due to the overwhelming importance of this crop, modelling rice-based farming systems will provide valuable help to compare experimental research findings across regions, extrapolate field experimental data to wider environments, develop management recommendations and decision-support systems, explore effects of climate change and adaptation options, and prediction of crop yield. There is an increasing demand for the capability to simulate rice-based cropping systems, especially in Asia. Such a system capability will allow expanded investigation of nitrogen dynamics, crop sequencing, intercropping, crop residue management and soil and water management. Incorporation of the ORYZA2000 rice model(Bouman and van Laar, 2006) into APSIM (Agricultural Production Systems Simulator (APSIM-Oryza) together with recent work on carbon and nitrogen dynamics in transitional flooded/non-flooded systems(Gaydon et al., 2009) has facilitated long-term simulation of lowland rice-based farming systems scenarios. However, the capability of APSIM-Oryza to simulate rice-based crop sequences involving other crops has undergone limited testing to this point and under a variety of crop management practices and cropping systems. In this paper, we detail testing of the APSIM-Oryza simulation model against an experimental dataset involving lowland rice-rice-soybean crop rotation in West Nusa Tenggara Province(NTB) Indonesi

Nitrogen dynamics in flooded soil systems: an overview on concepts and performance of models

Extensive modelling studies on nitrogen (N) dynamics in flooded soil systems have been published. Consequently, many N dynamics models are available for users to select from. With the current research trend, inclined towards multidisciplinary research, and with substantial progress in understanding of N dynamics in flooded soil systems, the objective of this paper is to provide an overview of the modelling concepts and performance of 14 models developed to simulate N dynamics in flooded soil systems. This overview provides breadth of knowledge on the models, and, therefore, is valuable as a first step in the selection of an appropriate model for a specific application. © 2017 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry

How we used APSIM to simulate conservation agriculture practices in the rice-wheat system of the Eastern Gangetic Plains

Examples of how to simulate performance of conservation agriculture (CA) and conventional tillage (CT) practices using cropping systems models are rare in the literature, and from the Eastern Gangetic Plains (EGP). Here we report a comprehensive evaluation of the capacity of APSIM for simulating the performance of CA and CT cropping practices under a diverse range of tillage (CT vs zero tillage (ZT)), crop establishment options (puddled transplanted rice vs unpuddled transplanted rice), residue, N rates, and irrigation practices from two sites in the EGP that differed in soil type, water table dynamics, and agro-climatic conditions. We followed a robust procedure of model parameterisation, calibration, and validation, then undertook statistical analyses to evaluate model performance. We have demonstrated that when different values for key model input parameters are employed (i.e. change in soil properties (Ks, BD)), crop rooting parameters (xf- root hospitality, kl- root extraction efficiency) and soil microorganism activity (Fbiom- fraction of soil organic matter present as microbial biomass and Finert- the inert fraction of soil organic matter), the model performed well in simulating the different performances of CA and CT management practices across the environments in the EGP. Model performance was markedly better in the full-N than in zero-N, but both are still considered acceptable. In addition to well-watered and fertilised treatments, the model was able to capture an observed crop failure in rainfed unpuddled transplanted rice accurately, illustrating an ability to capture crop response under a wide range of water stress environments. As demonstrated by robust statistical criteria, APSIM was able to capture the effect of cropping system, irrigation, tillage, residue, and N-application rate within the bounds of experimental uncertainty, hence is now deemed a suitable tool for scenario analyses around the relevant practices

Performance of rice on a coarse sandy loam soil in response to water-saving irrigation practices in lowland eastern Indonesia

Rapid increase in world population and a corresponding increase in demand for water and land from industrial and municipal have forced the agricultural sector to use marginal land and irrigation water more efficiently by using less water to produce more food. Coarse-textured and porous soils of the tropical regions are increasingly used for growing both upland and lowland rice. In porous soils under rice, continuous flooding cannot be maintained due to high water percolation rates. Development of appropriate planning and management strategy to improve available water resources for the agricultural sector is a high national and global priority. Increased efficiency in water use is essential for future food security in Asia where rice production needs to increase by 70% over the current production by the year 2025 (Tuong and Bhuiyan 1999). However, experimental evidence for the hydrological and environmental conditions of coarse soils under which current rice-based cropping systems are practiced is limited. Such studies will become more important as porous soils are increasingly used for irrigated rice-based cropping systems. In this paper, we evaluate the effectiveness of alternately submerged and non-submerged (ASNS) over continuously submerged (CS) irrigation practices using three years of field experimental data on a coarse soil in the tropical region of eastern Indonesia

Farmers’ perceptions and management of risk in rice-based farming systems of south-west coastal Bangladesh

Farmers in coastal Bangladesh face significant production and market risks as well as uncertainty about trends in the farming environment. Understanding farmers’ perceptions of the risks they currently experience and the farming and livelihood strategies they adopt to mitigate risk is important to inform policies designed to safeguard coastal livelihoods in the future. In this paper, we draw on a case study of typical village in the coastal zone to explore (1)farmers’ perceptions of the cropping risks they face, (2)the implications of risk for the choice of cropping strategies within different farm types, and (3)the role of other farm and non-farm activities in mitigating risk to household livelihoods. Quantitative and qualitative farm-level data were collected through a reconnaissance survey, a village census, a household survey, and household case studies. Farmers saw the shortage of irrigation water in the dry season and uncertain weather patterns as the major sources of production risk. The main source of market risk was the fluctuation in farm-gate demand and prices for dry-season cash crops. Representative budgets were constructed for the major cropping systems practised by small, medium, and large farm households. The riskiness of these systems was simulated, based on farmers’ estimates of yield and price variability, and a stochastic efficiency analysis was undertaken. The current systems appeared economically viable given the typical range of yields and prices. While some were riskier than others, farm households were largely able to balance their livelihood portfolios to offset the risks. Major risk management strategies included adoption of stress-tolerant rice varieties, staggering the sale of rice, using early wet season rice as a buffer, switching from rice to non-rice crops in the dry season, and undertaking off- or non-farm employment within and outside the village. The dominant trend was to farm and livelihood diversification, contributing to household resilience. However, at the village level, public policy to safeguard the agricultural environment will be crucial to sustaining household risk management strategies

Bio-economic evaluation of cropping systems for saline coastal Bangladesh: II. Economic viability in historical and future environments

The objective of this study was to assess the impacts of climate change and salinity on the economic viability of rice-based cropping systems under farmers' current management across current and future climate and salinity scenarios in south-west coastal Bangladesh. Detailed case studies were conducted in two contrasting coastal villages in Dacope Sub-district, Khulna District. Enterprise budgets were developed using APSIM-simulated and extrapolated yields together with crop management, cost, and price data obtained from the villages and estimated from various sources. The projected impact of climate change and salinization on the economic viability (profitability and riskiness) of most cropping systems was not pronounced. Thus rice-based cropping systems are likely to remain viable in both optimistic and pessimistic climate scenarios in coming decades, even allowing for salinization, because some of the positive effects of climate change were projected to offset the sizeable losses due to salinity. Moreover, where small yield declines were projected these were often offset by higher future prices. Sustainably-managed rice/shrimp cropping systems are likely to remain the most profitable option in locations with access to tidal saline water. In other sites, given adequate freshwater for irrigation in the dry season, rice/non-rice cropping systems were projected to be the most viable options, especially incorporating newer crops such as sunflower and maize. Dry-season rice and wheat were not projected to be viable options

Bio-economic evaluation of cropping systems for saline coastal Bangladesh: I. biophysical simulation in historical and future environments

Climate change, increased climate variability, extreme weather events, and increasing salinization pose a serious challenge to the sustainability of crop production in coastal Bangladesh. This study assessed yield performance of rice and non-rice crops under farmers’ current practices across five climate and three salinity scenarios in the south-western coastal zone. Representative village case studies in Khulna District were used to obtain data on current cropping practices and yields. A validated biophysical crop simulation model (APSIM) was used to simulate performance of crops within 10 cropping systems, representing both existing and potential future cropping patterns. The salinity impact on rice crops was simulated directly using an improved APSIM model, capable of simulating both soil salinity dynamics and the resulting rice crop response. The salinity impact on maize, wheat and sunflower was assessed by developing crop salinity response functions and applying these post-simulation to the crop yields simulated in the absence of salinity. The future performance of some existing crops, namely, watermelon, and pumpkin were extrapolated from data available in the literature and expert knowledge. Climate change is projected to have both positive and negative impacts on crop yields but growing salinity is projected to have substantial negative effects. Allowing for uncertainties inherent in the modelling process, the results indicate that loss of crop production would be negligible under projected 2030 conditions for climate and salinity, even with farmers’ current practices. Under 2060 conditions, the adverse impacts on wet-season rice, dry-season rice, and wheat remained negligible, while sunflower experienced notable yield decline. However, the effects of 2060 conditions on early wet season rice and dry-season maize were positive. Climate change in itself does not pose a major risk to crop production and aquaculture in south-west coastal Bangladesh over the next 15–45 years but increasingly salinity will have an unambiguously negative influence

Bio-economic evaluation of cropping systems for saline coastal Bangladesh: III Benefits of adaptation in current and future environments

Climate change and salinisation present substantial challenges to the sustainability of cropping systems in south-west coastal Bangladesh. This is the third paper in a series reporting a study to assess the impacts of climate change and salinity on the productivity and economic viability of ten current and potential rice-based cropping systems in two coastal villages in Khulna District. In this paper, possible adaptations are assessed, including novel dry-season crops, changed fertilizer use, and changed sowing dates, across five climate and three salinity scenarios. Farmers’ estimated, APSIM-simulated, and extrapolated yield distributions were incorporated in budgets for the ten cropping systems, using current and projected salinity levels. Current and projected future prices and costs were used to estimate different measures of profitability. Estimated variability in yields and prices was used to generate probability distributions for these profitability measures, permitting comparison of cropping systems based on profitability and risk. Adaptation through changed fertilizer use (higher or lower, depending on the crop) was projected to give higher returns for some cropping systems. However, larger improvements were obtainable with changes in sowing dates to avoid the worst stresses imposed by climate change and salinity. The loss of production of all crops except watermelon and pumpkin due to salinity was more than offset with changed sowing dates for 2030 and 2060 conditions, irrespective of season. With such adaptations, and allowing for risk, the rice/shrimp system maintained the top ranking in terms of net income per hectare in 2030 and 2060 and the rice/sunflower system maintained the second ranking. The rice/pumpkin/rice system ranked third for 2030 and fourth in 2060 while the rice/maize system moved up to third in 2060

Corrigendum to “Describing the physiological responses of different rice genotypes to salt stress using sigmoid and piecewise linear functions” (Field Crops Research (2017) (S0378429017307578)(10.1016/j.fcr.2017.05.001)

The authors regret some mistakes in the published highlights and in the legend of the Highlights • Rice crop responses to soil salinity can be fitted using a logistic function with three parameters.• Tolerant genotype, BRRI Dhan 47 presented 50% reduction in leaf net photosynthesis and transpiration at soil salinity levels higher than 14 dS m.• Growth of tolerant genotype as BRRI Dhan 47 was significantly reduced at soil salinities higher than 5 dS m.____________________________ DOI of original article: http://dx.doi.org/10.1016/j.fcr.2017.05.00