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Highlights • ORYZA v3 and APSIM-Oryza models were improved to account for salinity effects on rice production. • Variability of soil salinity was represented by a simple linear relationship between salt concentration and electrical conductivity. • The derived salinity parameters captured response differences between tolerant (BRRI Dhan47) and non-tolerant variety (IR64). • An increase in salinity parameters of 5 % above the value for IR64 would result in a 3 % increase in simulated yield. Abstract Development and testing of reliable tools for simulating rice production in salt-affected areas are presented in this paper. New functions were implemented in existing crop models ORYZA v3 and the cropping systems modelling framework APSIM. Field experiments covering two years, two different sites, and three varieties were used to validate both improved models. We used the salt balance module in the systems model APSIM to simulate the observed daily soil salinity with acceptable accuracy (RMSEn <35%), whereas ORYZA v3 used measured soil salinity at a given interval of days as a model input. Both models presented similarly good accuracy in simulating aboveground biomass, leaf area index, and grain yield for IR64 over a gradient of salinity conditions. The model index of agreement ranged from 0.86 to 0.99. Variability of yield under stressed and non-stressed conditions was simulated with a RMSE, of 191 kg ha−1 and 222 kg ha−1 , respectively, for ORYZA v3 and APSIM-Oryza, corresponding to an RMSE n of 14.8% and 17.3%. These values are within the bounds of experimental error, therefore indicating acceptable model performance. The model test simulating genotypic variability of rice crop responses resulted in similar levels of acceptable model performance with RMSE n ranging from 11.3 to 39.9% for observed total above ground biomass for IR64 and panicle biomass for IR29, respectively. With the improved models, more reliable tools are now available for use in risk assessment and evaluation of suitable management options for rice production in salt-affected areas. The approach presented may also be applied in improving other non-rice crop models to integrate a response to soil salinity − particularly in process-based models which capture stage-related stress tolerance variability and resource use efficiency. [ABSTRACT FROM AUTHOR]

Resource shortages, driven by climatic, institutional and social changes in many regions of Asia, combined with growing imperatives to increase food production whilst ensuring environmental sustainability, are driving research into modified agricultural practices. Well-tested cropping systems models that capture interactions between soil water and nutrient dynamics, crop growth, climate and farmer management can assist in the evaluation of such new agricultural practices. One such cropping systems model is the Agricultural Production Systems Simulator (APSIM). We evaluated APSIM’s ability to simulate the performance of cropping systems in Asia from several perspectives: crop phenology, production, water use, soil dynamics (water and organic carbon) and crop CO 2 response, as well as its ability to simulate cropping sequences without reset of soil variables. The evaluation was conducted over a diverse range of environments (12 countries, numerous soils), crops and management practices throughout the region. APSIM’s performance was statistically assessed against assembled replicated experimental datasets. Once properly parameterised, the model performed well in simulating the diversity of cropping systems to which it was applied with RMSEs generally less than observed experimental standard deviations (indicating robust model performance), and with particular strength in simulation of multi-crop sequences. Input parameter estimation challenges were encountered, and although ‘work-arounds’ were developed and described, in some cases these actually represent model deficiencies which need to be addressed. Desirable future improvements have been identified to better position APSIM as a useful tool for Asian cropping systems research into the future. These include aspects related to harsh environments (high temperatures, diffuse light conditions, salinity, and submergence), conservation agriculture, greenhouse gas emissions, as well as aspects more specific to Southern Asia and low input systems (such as deficiencies in soil micro-nutrients). [ABSTRACT FROM AUTHOR]

Abstract: For irrigation farmers, the deregulation of water markets and consequent emergence of water as a tradeable commodity calls for a method of comparing traditional on-farm water options (growing crops) with off-farm market options (selling water seasonally, or selling water licences permanently). The option to diversify farm income in this way is a desirable future adaptation strategy in response to decreased and more variable water supplies. We demonstrate a method for comparing such options based on their risk-return characteristics. A framework commonly used in the finance sector is adapted to agricultural water decisions, and illustrated using a case-study farm from Australia''s Riverina region. In our example, a range of potential farm management practices are examined for several future water availability scenarios, and then compared with a fixed-return option (selling water entitlements to the Australian Government''s current water buy-back scheme). We demonstrate how the attractiveness of the scheme for farmers depends on future water availability levels. For any future allocation level, the best way to use water on-farm varies with the value of the fixed-return option. The farmer''s decision on what portion of their water entitlement to sell provides them with the opportunity to tailor their operation''s risk-return performance. This method is universally applicable wherever there is a mix of variable and fixed-return options, and offers a framework to assist farmers in conceptualizing comparisons between traditional on-farm uses for water and newer, market-based options. [Copyright &y& Elsevier]

Abstract: Photosynthetic aquatic biomass (PAB – algae and other floodwater flora) is a significant source of organic carbon (C) in rice-based cropping systems. A portion of PAB is capable of fixing nitrogen (N), and is hence also a source of N for crop nutrition. To account for this phenomenon in long term simulation studies of rice-based cropping systems, the APSIM modelling framework was modified to include new descriptions of biological and chemical processes responsible for loss and gain of C and N in rice floodwater. We used well-tested algorithms from CERES-Rice, together with new conceptualizations for algal dynamics, in modelling the contribution of PAB to maintenance of soil organic C and soil N-supplying capacity in rice-based cropping systems. We demonstrate how our new conceptualization of PAB growth, turnover, and soil incorporation in flooded rice systems facilitates successful simulation of long-term soil fertility trials, such as the IRRI Long Term Continuous Cropping Experiment (35+ years), from the perspectives of both soil organic carbon levels and yield maintenance. Previous models have been unable to account for the observed maintenance of soil organic C in these systems, primarily due to ignoring inputs from PAB as a source of C. The performance of long-term rice cropping system simulations, with and without inclusion of these inputs, is shown to be radically different. Details of our modifications to APSIM are presented, together with evidence that the model is now a useful tool to investigate sustainability issues associated with management change in rice-based cropping systems. [Copyright &y& Elsevier]

Abstract: Water shortages in many rice-growing regions, combined with growing global imperatives to increase food production, are driving research into increased water use efficiency and modified agricultural practices in rice-based cropping systems. Well-tested cropping systems models that capture interactions between soil water and nutrient dynamics, crop growth, climate and management can assist in the evaluation of new agricultural practices. The APSIM model was designed to simulate diverse crop sequences, residue/tillage practices and specification of field management options. It was previously unable to simulate processes associated with the long-term flooded or saturated soil conditions encountered in rice-based systems, due to its heritage in dryland cropping applications. To address this shortcoming, the rice crop components of the ORYZA2000 rice model were incorporated and modifications were made to the APSIM soil water and nutrient modules to include descriptions of soil carbon and nitrogen dynamics under anaerobic conditions. We established a process for simulating the two-way transition between anaerobic and aerobic soil conditions occurring in crop sequences of flooded rice and other non-flooded crops, pastures and fallows. These transitions are dynamically simulated and driven by modelled hydraulic variables (soil water and floodwater depth). Descriptions of floodwater biological and chemical processes were also added. Our assumptions included a simplified approach to modelling O2 transport processes in saturated soils. The improved APSIM model was tested against diverse, replicated experimental datasets for rice-based cropping systems, representing a spectrum of geographical locations (Australia, Indonesia and Philippines), soil types, management practices, crop species, varieties and sequences. The model performed equally well in simulating rice grain yield during multi-season crop sequences as the original validation testing reported for the stand-alone ORYZA2000 model simulating single crops (n =121, R 2 =0.81 with low bias (slope, α =1.02, intercept, β =−323kgha−1), RMSE=1061kgha−1 (cf. SD of measured data=2160kgha−1)). This suggests robustness in APSIM''s simulation of the rice-growing environment and provides evidence on the usefulness of our modifications and practicality of our assumptions. Aspects of particular strength were identified (crop rotations; response to applied fertilizers; the performance of bare fallows), together with areas for further development work (simulation of retained crop stubble during fallows, greenhouse gas emissions). APSIM is now suitable to investigate production responses of potential agronomic and management changes in rice-based cropping systems, particularly in response to future imperatives linked to resource availability, climate change, and food security. Further testing is required to evaluate the impact of our simplified assumptions on the model''s simulation of greenhouse gas emissions in rice-based cropping systems. [Copyright &y& Elsevier]

Abstract: Around the globe farmers managing irrigated crops face a future with a decreased and more variable water supply. To investigate generic adaptation issues, a range of on-farm strategies were evaluated for apportioning limited water between fields and enterprises using a typical case-study farm from Australia''s Riverina region. These strategies are compared for a range of seasonal water availability levels. The analysis did not address investment in new irrigation technologies or new crops, but focussed on irrigation intensity and crop choice amongst existing enterprises. Participatory engagement and whole-farm simulation modelling were our primary tools of research. The adaptation options found to best suit irrigation farming in years of high water availability were substantially different to those when water supplies were low. This illustrates strategic differences between irrigation farming in land-limited circumstances and water-limited circumstances. Our study indicates that the cropping and irrigation strategy leading to greatest farm returns changes on a season-by-season basis, depending primarily on the water availability level. [Copyright &y& Elsevier]

Abstract: With increasing interest in retaining crop residues on the soil surface, there is a need to evaluate their short- and long-term effects on crop yield and water and fertilizer requirements. Therefore, research on the interactions between residue and irrigation management on wheat crop performance and water use was initiated, using the dual approach of field experiments and crop modelling. This paper presents the results of a comprehensive evaluation of the APSIM model for its ability to simulate the effects of mulch and water management, and their interactions, for wheat in Punjab, India. The model was evaluated for its ability to predict crop development, grain yield, biomass production over time, soil water dynamics, daily soil evaporation (Es), total evapotranspiration (ET) and water productivity (WPET kgha−1 mm−1), using two years of data from field experiments at Ludhiana, Punjab. The model predicted grain yield adequately, with coefficients of determination (r 2) of 0.91 and 0.81 with and without mulch, respectively, and prediction of total biomass was even better, with r 2 of 0.99 and 0.92. The corresponding absolute RMSE values were 433 and 550kgha−1 for grain yield (means 4100 and 3800kg ha−1) and 300 and 800kgha−1 for total biomass (means 10,200 and 9300kgha−1). However, grain yield was underpredicted (by 600–1000kgha−1) in treatments where the crop was subjected to water deficit stress, even though simulation of soil water dynamics, and the effect mulch on soil water content, was generally very good. The model accurately predicted total crop seasonal evaporation and the effect of mulch; however, daily Es was poorly simulated. APSIM does not attempt to capture the soil temperature driven effect of mulch on crop phenology. The evaluation shows that APSIM is suitable to use for wheat under the conditions of north-west India. However, additional model processes that capture the effects of mulch on crop development and growth, as driven by soil temperature, are needed to help design intensive cropping systems to optimise land and water productivity. The ability to better simulate crop performance under conditions of water deficit is also needed to help determine irrigation management strategies that minimise irrigation input while maintaining yield. [Copyright &y& Elsevier]

Abstract: The majority of rice grown in south-east Australia is continuously flooded for much of its growing season, but reduced irrigation water availability brought about by a combination of drought and environmental flow legislation has presented a need to maintain (or even increase) rice production with less irrigation water. Delaying the application of continuous flooding until prior to panicle initiation can increase input water productivity by reducing non-beneficial evaporation losses from free water and the soil. A field experiment was conducted over two growing seasons, 2008/9 and 2009/10, comparing a conventional dry seeded treatment (the control – continuous flooding from the 3 leaf stage) with delayed continuous flooding (10–20 days prior to panicle initiation) with several irrigation scheduling treatments prior to flooding commencement. In the first year, the delayed water treatments were irrigated at intervals of 40, 80 and 160mm of cumulative reference evapotranspiration (ETo) prior to delayed continuous flooding, thereby imposing differing degrees of crop water stress. In year 2, the 80 and 160mm treatments were modified by use of a crop factor (Kc) when the plants were small and the 40mm treatment was replaced with a continuously flooded treatment throughout the crop duration. Decreases in net water input (irrigation+rain−surface drainage) and increases in input water productivity were achieved by reducing the flush irrigation frequency during the pre-flood period. Savings of 150 and 230mm (10 and 15%) were achieved in Year 1 from the 80 and 160mm cumulative ETo irrigation frequency treatments, respectively, in comparison to the control. In the second year, net water input savings of 230 and 330mm (15 and 22%) were achieved with the 80/Kc and 160/Kcmm treatments, respectively. Input water productivity of the 160mm treatment was 0.06kg/m3 (8%) higher than the control in Year 1, while in Year 2 a 0.15kg/m3 (17%) increase in input water productivity above the control was achieved by the 160/Kcmm treatment. Delaying the application of continuous flooding in the second year greatly extended the period of crop growth suggesting the need for earlier sowing (by 7–10 days) to ensure pollen microspore still occurs at the best time to minimise yield loss due to cold damage. Nitrogen fertiliser management is an important issue when delaying continuous flooding, and nitrogen losses appeared to increase with the frequency of irrigation prior to continuous flooding. This was likely due to increased denitrification from alternate wetting and drying of the soil. Further research is required to determine the most appropriate nitrogen management strategies, and to also better define the optimal pre-flood irrigation frequency. [Copyright &y& Elsevier]

• We evaluated options for increasing Boro rice production at Satkhira, Bangladesh. • Earlier sowing offers higher grain yields with increased cropping area due to better utilisation of fresh river water. • Increases in Boro rice production of up to 4x are possible. • Constraints with late-maturing monsoon rice crops and ineffective sluice gate management must be solved. • Potential problems associated with increased salinization of polder soils need to be investigated. Increasing Boro (irrigated dry season) rice production in the saline coastal zone (CZ) is part of the Bangladesh Government strategy for meeting its Sustainable Development Goals (SDG's). However salinity and fresh water shortages during the Rabi (dry) season result in large areas of land remaining uncropped and under-utilised in the CZ, with crop yields below potential. We evaluated a range of options for increasing Boro rice production and farmer profit in this region. These included changes to sowing dates in combination with different polder sluice-gate management strategies aimed at increasing irrigation water supply and cropping area. We employed a case-study approach, using a combination of field experimentation, APSIM cropping systems modelling, and economic analysis, focussing on Satkhira District, Khulna Division. We found the most profitable strategies were to establish Boro rice crops in mid-November, around a month earlier than current farmer practice, on larger portions of land irrigated using river water supplied via the polder canal network. This offers significant increases in both farmer profit and regional production (up to 4x). The reasons for the gains are dual – (1) potential rice yields are higher; and (2) early sowing unleashes the potential of extensive fresh-water availability to greatly increase cropping area, because at that time river salinity levels are low and unlimited amounts of suitable irrigation water are available. Under current practices with later sowing dates (around mid-December), these early-season water resources are hardly used. To achieve the advantages of early-sowing, certain system changes are necessary. Firstly, farmers must adopt early-maturing transplanted Aman (T. Aman) rice cultivars in the monsoon season. Secondly, they must synchronise agronomic timings with fellow farmers in polder sluice-gate management zones to allow efficient gate operation and timely drainage of stagnant monsoon waters from fields in October, followed by early-season establishment of Boro rice crops. The applicability of our findings will vary geographically in the CZ, as a function of prevailing dynamics of river salinity, water tables, soils and climate. To understand the economics at a national scale, our analysis should be extended on a regional basis to estimate regional production gains possible, as well as to assess environmental health risks – particularly related to increased salinization of polder soils. Our analysis suggests that substantial investment in further research and achieving the required social and agronomic changes may be warranted. [ABSTRACT FROM AUTHOR]

Machinery for sowing wheat directly into rice residues has become more common in the rice-wheat systems of the north-west Indo-Gangetic Plains of South Asia, with increasing numbers of farmers now potentially able to access the benefits of residue retention. However, surface residue retention affects soil water and temperature dynamics, thus the optimum sowing date and irrigation management for a mulched crop may vary from those of a traditional non-mulched crop. Furthermore, the effects of sowing date and irrigation management are likely to vary with soil type and seasonal conditions. Therefore, a simulation study was conducted using the APSIM model and 40 years of weather data to evaluate the effects of mulch, sowing date and irrigation management and their interactions on wheat grain yield, irrigation requirement (I) and water productivity with respect to irrigation (WP I ) and evapotranspiration (WP ET ). The results suggest that the optimum wheat sowing date in central Punjab depends on both soil type and the presence or absence of mulch. On the sandy loam, with irrigation scheduled at 50% soil water deficit (SWD), the optimum sowing date was late October to early November for maximising yield, WP I and WP ET . On the clay loam, the optimum date was about one week later. The effect of mulch on yield varied with seasonal conditions and sowing date. With irrigation at 50% SWD, mulching of wheat sown at the optimum time increased average yield by up to 0.5 t ha −1 . The beneficial effect of mulch on yield increased to averages of 1.2–1.3 t ha −1 as sowing was advanced to 15 October. With irrigation at 50% SWD and 7 November sowing, mulch reduced the number of irrigations by one in almost 50% of years, a reduction of about 50 mm on the sandy loam and 60 mm on the clay loam. The reduction in irrigation amount was mainly due to reduced soil evaporation. Mulch reduced irrigation requirement by more as sowing was delayed, more so on the sandy loam than the clay loam soil. There was little effect of mulch on irrigation requirement for late October sowings. There were large trade-offs between irrigation input, yield, WP ET and WP I on the sandy loam with regard to the optimum irrigation schedule. Maximum yield occurred with very frequent irrigation (10–20% SWD) which also had the greatest irrigation input, while WP I was highest with least frequent irrigation (70% SWD), and WP ET was highest with irrigation at 40–50% SWD. This was the case with and without mulch. On the clay loam, the trade-offs were not so pronounced, as maximum yield was reached with irrigation at 50% SWD, with and without mulch. However, both WP ET and WP I were maximum and irrigation input least at the lowest irrigation frequency (70% SWD). On both soils, maximum yield, WP ET and WP I were higher with mulch, while irrigation input was slightly lower, but mulch had very little effect on the irrigation thresholds at which each parameter was maximised. [ABSTRACT FROM AUTHOR]

The irrigated rice–wheat system of north west India is not sustainable, as currently practised, due to over-exploitation of groundwater, soil degradation, labour scarcity, high fuel and labour costs, and air pollution from stubble burning. Labour and water scarcity are driving farmers to change from puddling and manual transplanting of rice to mechanised dry seeding. The introduction of dry seeding to the rice–wheat system brings with it the potential to adopt conservation agriculture (CA), with reduced or zero tillage for all crops, and surface residue retention. This would further reduce fuel and labour costs for crop establishment, and air pollution, and also bring benefits for soil structure and nutrient cycling. However, whether conversion to CA rice–wheat systems would help solve the problem of groundwater depletion is less well-understood. In this region, evapotranspiration (ET) must be reduced to reduce groundwater depletion. We used the APSIM cropping system model to examine whether conversion from recommended farmer practice (rFP, comprising puddled transplanted rice, alternate wetting and drying rice water management, rice straw removal, tillage for wheat) to a CA rice–wheat system would reduce ET in Punjab, north west India. We also used the model to identify the optimum system management taking into account effects on total cropping system rice equivalent yield (REY), components of the water balance and water productivity. Maximum REY (mean 14.6 t ha −1 ) occurred in systems with 5 June sowing of a popular long duration rice variety, with similar yield for rFP and CA. Irrigation input with CA was much lower (by 390 mm) than with rFP, resulting in slightly higher irrigation water productivity (increased from 11.3 to 11.7 kg ha −1 mm −1 ). However, changing to CA only reduced ET of the highest yielding system by 4% (55 mm), and of other current practices (late May and early June sowing of medium and long duration varieties) by less than this. The only way to achieve a substantial reduction in ET was by growing short duration rice varieties in both the rFP and CA systems. However, with current short duration varieties, this came at the cost of both rice and system yields (system yield reduced by an average of about 1.8 t ha −1 ). This could be overcome by intensification to 3 crops per year in a CA rice–wheat–mung system (with short duration rice varieties), while still providing a substantial but smaller decrease in ET. This system also had considerable flexibility in rice sowing date, with similar system yields for sowings from 5 June to 15 July. These findings suggest that greater effort to increase the yield potential of short duration rice varieties is warranted. Field experimentation is needed to test the improved systems as suggested by the model simulations, particularly in terms of cropping system yield and ET, and alternatives to rice and wheat should also be evaluated. At the same time, spatial hydrological studies are needed to determine the sustainable level of ET from cropping systems that will allow matching of groundwater depletion and recharge. [ABSTRACT FROM AUTHOR]

Rainfed rice production in Lao PDR is critical to national food security; under traditional transplanting methods farmers are exposed to climate risks at both the onset and the conclusion of the wet season. Production of the annual crop has a high labour requirement especially during transplanting and harvesting. We engaged with smallholder farmers to investigate the feasibility of one form of dry seeding of rice, i.e. mechanised dry drill seeding, which in this paper we refer to as “dry seeding”. We hypothesised that dry seeded rice crops will be established earlier in the wet season and will produce a comparable yield while requiring less water and labour than transplanted rice. Field trials, supported by scenario modelling using the APSIM model, indicated average dry seeded rice yields are comparable to average transplanted yields over the longer term but with reduced risk of crop failure, under both current (1971–2011) and near-future (2021–2040) climates, for two common soil types. Net overall labour savings reduce the cost of rice production under mechanised dry seeding, better positioning households against fluctuations in labour costs and rice prices. Mechanised dry seeding requires different crop management to traditional methods and will not be appropriate for all farmers. Performance of DSR under future climate scenarios is projected to be as good as or better than under current climate conditions. [ABSTRACT FROM AUTHOR]

Crop and water productivities of rice-based cropping systems and cropping patterns in the irrigated lowlands of Sri Lanka have not been researched to the degree warranted given their significance as critical food sources. In order to reduce this knowledge gap, we simulated the water requirement for rice, maize, and mungbean under rice-based cropping systems in the Dry Zone of Sri Lanka. We evaluated the best combinations of crops for minimum water usage while reaching higher crop and water productivities. We also assessed the risk of cultivating mungbean as the third season/sandwich crop (i.e. rice-mungbean-rice) in different regions in Sri Lanka. In the simulation modelling exercise, APSIM-Oryza (rice), APSIM-maize and APSIM-mungbean modules were parameterised and validated for varieties grown widely in Sri Lanka. Moreover, crop productivities and supplementary irrigation requirement were tested under two management scenarios i.e. Scenario 1 : irrigate when plant available water content in soil fell below 25% of maximum, and Scenario 2: irrigate at 7-day intervals (current farmer practice). The parameterised, calibrated and validated model estimated the irrigation water requirement (number of pairs of observations (n) = 14, R 2 > 0.9, RMSE = 66 mm season −1 ha −1 ), and grain yield of maize (n = 37, R 2 > 0.95, RMSE = 353 kg ha −1 ) and mungbean (n = 26, R 2 > 0.98, RMSE = 75 kg ha −1 ) with a strong fit in comparison with observed data, across years, cultivating seasons, regions, management conditions and varieties. Simulated water requirement during the cropping season reduced in the order of rice (1180–1520 mm) > maize and mungbean intercrop = maize sole crop (637–672 mm) > mungbean sole crop (345 mm). The water productivity of the system (crop yield per unit water) could be increased by over 65% when maize or mungbean extent was increased. The most efficient crop combinations to maximise net return were diversification of the land extent as (i) 50% to rice and 50% to mungbean sole crops, or (ii) 25%, 25% and 50% to rice, maize and mungbean sole crops, respectively. Under situations where water availability is inadequate for rice, land extent could be cultivated to 50% maize and 50% mungbean as sole crops to ensure the maximum net return per unit irrigation water (115 Sri Lankan Rupees ha −1 mm −1 ). Regions with high rainfall during the preceding rice cultivating season are expected to have minimum risk when incorporating a third season mungbean crop. Moisture loss through evapotranspiration from the third season mungbean crop was similar to that of a fallowed site with weeds. [ABSTRACT FROM AUTHOR]

The APSIM–Oryza model has been used worldwide to evaluate the impact of diverse management practices on the growth of rice ( Oryza sativa L.). Despite its importance, the crop productivity (kg ha −1 ) and water productivity (kg ha −1 mm −1 ) of rice under moisture-limited (i.e. rainfed or rainfed with supplementary alternate wetting-and-drying (AWD) irrigation) farmer-field conditions in tropical South-Asia has received little attention in modelling exercises. Benefits of aligning crop establishment with the onset of rainfall to reduce dependency on supplementary irrigation and improve crop and water productivities have not yet been quantified in Sri Lanka. Therefore, we parameterised and evaluated the APSIM–Oryza model for two widely grown Sri Lankan short- and medium-duration rice varieties. The model estimated the grain yield of rice under moisture-limited farmer-field conditions with a strong fit ( n = 24, R 2 > 0.97, RMSE = 484 kg ha −1 ), across cultivation year, season, time of establishment (i.e. with rainfall onset or date-specific planting), variety and/or water management practice (i.e. totally rainfed or rainfed with supplementary irrigation). A climatic analysis indicated that the farmers regularly establish rice crops 2–4 weeks after the rainfall onset. This is a consequence of the current practice of setting the date for crop establishment at pre-season cultivation meetings without a scientifically-validated rainfall forecast. The same analysis revealed that an early onset to the rainy season resulted in longer seasons with more rain than late onset. When the onset of rainfall is delayed, crop modelling scenarios using the validated APSIM model showed an increased dependence on supplementary irrigation for rice cultivation. Alternatively, in years when an early onset was observed, late planting in the season reduced the use of rain water by 95% while increasing the irrigation water requirement by 11% compared with planting at rainfall onset. Access to supplementary with AWD irrigation increased the stability of grain yield, and crop and water productivity, irrespective of the onset of rainfall or time of crop establishment. [ABSTRACT FROM AUTHOR]

The irrigated rice–wheat (RW) systems of north-west India are critical for food security. However, these systems are not sustainable due to over-exploitation of the groundwater resource on which they largely rely. Current farmer practice (FP) involves manual transplanting of rice into heavily tilled/puddled soil from 10 June to early July, prolonged periods of flooding, rice residue burning, and heavy tillage prior to sowing wheat. Inclusion of a short duration mungbean crop between wheat harvest and rice transplanting has also been promoted at times. Options for reducing irrigation input to the RW system include delaying transplanting until after the monsoon rains start (late June), switching to shorter duration rice varieties, and alternate wetting drying (AWD) water management for rice. However, the effect of such practices on groundwater depletion is not well-understood. Examining the effects of these options on cropping system yield and components of the water balance and water productivity is highly complex because of the need to consider the interactions between each crop in the system. Therefore, we used a cropping system model (APSIM) to compare the performance of RW systems with a range of rice transplanting dates (4 dates from 10 June to 10 August) and rice variety durations (long – 158 d, medium – 144 d, short – 125 d), with and without mungbean in the system. The results suggest that changing from long to short duration varieties would reduce ET by around 250 mm, more than enough to halt the groundwater decline, but with a reduction in rice-equivalent system yield of about 2.5 t ha −1 compared with current FP. On the other hand, inclusion of mungbean into the RW system results in much higher system yield than recommended farmer practice (by over 3 t ha −1 ), but the tradeoffs are much higher ET (by 250–300 mm) and irrigation requirement (by 300–450 mm). The results of this study suggest that more effort should be directed towards the development of higher-yielding, short duration rice varieties to reduce groundwater depletion of the RW system while maintaining yield, and that inclusion of short duration summer crops such as mungbean should not be recommended. [ABSTRACT FROM AUTHOR]

Abstract: World population growth, changing diets and limited opportunities to expand agricultural lands will drive agricultural intensification in the decades ahead. Concerns about the reliance of past agricultural intensification on non-renewable resources, about its negative impacts on natural resources both on and off farm and on greenhouse gas emissions, provide an imperative for future agricultural intensification to become ecologically efficient. We define ecological intensification of agriculture (EIA) as: producing more food per unit resource use while minimising the impact of food production on the environment. Achieving it will require increased precision in the use of inputs and reduction in inefficiencies and losses. It will also require a more holistic view of farming, going beyond efficiencies of single inputs into a single field in a single season to consideration of efficiencies of whole systems over decades. This paper explores the ecological intensification issues facing agricultural production in Australia where opportunities for agricultural intensification are centred on more efficient use of limited and unreliable water resources in both dryland and irrigated agriculture. Ecological efficiencies can be achieved by better matching the supply of nutrients to crops’ requirements both temporally and spatially. This has the added benefit of minimising the opportunities for excessive nutrients to impact on soil health (acidity and dryland salinity) and water quality (pollution of groundwater and eutrophication of lakes and rivers). Opportunities for ecologically efficient intensification are also identified through better integration of crop and livestock enterprises on mixed crop–livestock farms. We define nine desirable attributes of an EIA system: (1) increased agricultural production; (2) efficient use of limited resources; (3) minimal impact on global warming; (4) minimal negative on-site impacts; (5) minimal negative off-site impacts; (6) minimal risk and maximum resilience; (7) preservation of biodiversity in agriculture; (8) preservation of biodiversity in nature and; (9) positive social outcomes. We focus on four technologies and production systems emerging in Australian agriculture: climate risk management; precision agriculture; crop–livestock integration and deficit irrigation. For each of these systems we identify how well they are likely to match the nine desirable attributes of an EIA system. While it seems unlikely that any single technology can satisfy all nine desirable attributes, there is hope that in combination emerging and future technologies will progress Australian agriculture towards greater productivity and ecological efficiency. [Copyright &y& Elsevier]

• ZT uses less water & reduces fuel costs in rice-maize systems. • ZT increases maize yields and crop resilience to climate variability. • Irrigation frequency can be reduced with introduction of ZT for no yield loss. • Fewer irrigations increases gross margins and water use efficiency. In the Eastern Gangetic Plain of South Asia, cropping systems under conventional crop management are frequently unprofitable due to the inefficient use of resources, particularly irrigation water and energy. Across the Eastern Gangetic Plain, farmers generally produce a wet-season rice crop followed by an irrigated dry season crop: maize has been recently introduced as the dry-season crop and is rapidly growing in popularity. Irrigation water is commonly applied using diesel-powered pumps and fluctuating fuel prices are a major factor affecting cropping system profitability. We hypothesised that the adoption of zero tillage crop establishment in a rice-maize system would reduce irrigation requirements compared to a conventionally-established rice-maize system, while maintaining comparable crop yields. Thus, higher water use efficiency and economic profitability would be achieved under the improved crop management compared to conventional practice. Field experiments over two years in Sabour, Bihar, demonstrated that early sowing of maize resulted in 8% higher maize grain yields, while zero tillage establishment produced 7% higher maize grain yields than conventionally established maize. Using the APSIM cropping systems model we tested our hypothesis over 49 years, from 1969 to 2018. Over the longer-term, zero-till maize grain yields were 9% higher than those of conventionally established crops. Under these improved management practices fuel savings of 8–15 % and labor savings of 34–43 % were achieved compared to conventionally managed crops, leading to higher water use efficiency in all treatments under improved management. Overall, gross margins in rice-maize systems under improved management practices were 20–39 % higher than rice-maize systems under conventional management. In rice-maize cropping systems in the Eastern Gangetic Plain, improved crop management practices can improve the efficiency of water use and thus increase farming households' profitability and incomes. [ABSTRACT FROM AUTHOR]