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Agricultural eco-efficiency is promoted as a means of increasing agricultural production and improving the security of food systems in response to climate change. The rationale is that economic and environmental resources will be used more efficiently, enabling increased amounts of food to be produced from the same amount or fewer inputs. We used (i) a quantitative literature analysis to examine current usage of the eco-efficiency concept to assess strategies aimed at improving food security under climate change, and (ii) a wheat (Triticum aestivum L.) simulation experiment to consider possible tradeoffs between economic benefits of agricultural intensification, environmental performance, and social impacts. Two issues were highlighted from this. First, the relationship between economic and environmental outcomes is regularly assumed, leading to potentially erroneous conclusions and unintended outcomes. Second, the lack of any consideration for the social dimensions of food security ignores variability in incomes generated from agricultural production, and the potential for reduced quantities of food to be produced as a rational response to maximizing gross margins. We suggest the eco-efficiency concept explicitly include social as well as economic and environmental criteria if it is to avoid poor rates of uptake of eco-efficiency technologies, the promotion of practices that reduce the effectiveness of hunger-reduction efforts, and unintended environmental degradation. doi: 10.2135/cropsci2009.10.0566

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: 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]

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]

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]