The economics of irrigating wheat in a humid climate - A study in the East of England

In the UK, wheat is the most important cultivated cereal, grown extensively as a rainfed crop. Irrigation of wheat has previously been considered uneconomic, but increases in world wheat prices and recent droughts have led to some farmers revising their views. Widespread adoption of wheat irrigation would have major implications for wheat production, the irrigation industry and water resources in regions that are already water scarce. This study investigated the financial viability of irrigating winter wheat grown on a sandy loam soil in the East of England. Long-term climate data (1961–2011) for Silsoe (Bedfordshire) was used to drive a biophysical crop model to assess irrigation water requirements and yield response. Modelling assumed a typical irrigation schedule to maximise yield and quality, and average reported wheat prices for 2007 to 2012. Irrigation costs were calculated assuming an overhead mobile hosereel–raingun system applying river water, abstracted either in summer and used directly, or abstracted in winter and stored in an on-farm reservoir. The results suggest that the yield benefit would justify supplemental irrigation by farmers who have unused irrigation equipment and unused summer water, although irrigation of higher-value field vegetable crops later in the season would normally take precedence – the Added Value of Water (AVW) usefully applied to milling winter wheat under these conditions ranged between 0.24 and 0.32 £ m−3. Investment in new irrigation schemes could also be marginally viable if unused summer river water was available for direct abstraction (AVW = 0.08 £ m−3). Investments in new farm reservoirs for irrigating wheat are currently not profitable (AVW = –0.23 £ m−3). Sensitivity analysis suggests that in the longer term, the expected increase in world wheat prices and the impacts of climate change are likely to make the financial benefits stronger, particularly in the drier catchments further east and on low moisture retentive soils, but competing demands for water would still make extensive wheat irrigation unlikely

Water and energy footprint of irrigated agriculture in the Mediterranean region

Irrigated agriculture constitutes the largest consumer of freshwater in the Mediterranean region and provides a major source of income and employment for rural livelihoods. However, increasing droughts and water scarcity have highlighted concerns regarding the environmental sustainability of agriculture in the region. An integrated assessment combining a gridded water balance model with a geodatabase and GIS has been developed and used to assess the water demand and energy footprint of irrigated production in the region. Modelled outputs were linked with crop yield and water resources data to estimate water (m3 kg−1) and energy (CO2 kg−1) productivity and identify vulnerable areas or 'hotspots'. For a selected key crops in the region, irrigation accounts for 61 km3 yr−1 of water abstraction and 1.78 Gt CO2 emissions yr−1, with most emissions from sunflower (73 kg CO2/t) and cotton (60 kg CO2/t) production. Wheat is a major strategic crop in the region and was estimated to have a water productivity of 1000 t Mm−3 and emissions of 31 kg CO2/t. Irrigation modernization would save around 8 km3 of water but would correspondingly increase CO2 emissions by around +135%. Shifting from rain-fed to irrigated production would increase irrigation demand to 166 km3 yr−1 (+137%) whilst CO2 emissions would rise by +270%. The study has major policy implications for understanding the water–energy–food nexus in the region and the trade-offs between strategies to save water, reduce CO2 emissions and/or intensify food production

Climate change impacts on rain-fed and irrigated rice yield in Malawi

There is extensive scientific evidence on climate impacts and adaptation in rice (Oryza sativa L.) but the majority relates to production in south Asia and China. Only a handful of studies have been conducted in Sub-Saharan Africa and none in Malawi. In this paper, the climate impacts on rain-fed and irrigated rice yield have been assessed by combining the downscaled outputs from an ensemble of general circulation models (GCM) (HADCM3, INCM3 and IPCM4) with data from the LARS-WG weather generator to drive the CERES-Rice crop model. This was calibrated and validated using 10 years (2001-2010) field data from three rice schemes to simulate the baseline (1961-90) yield (t ha-1) and then model future yield changes for selected (B1 and A2) emissions scenarios for the 2050s. Although relatively small increases in average yield were projected (+8% and +5% for rainfed and irrigated rice, respectively) there was large uncertainty (-10% to +20% yield change) when considering different GCMs and emission scenario. Farmer responses to cope with the projected impacts include both autonomous and planned adaptation strategies, such as modifying planting dates to maximise crop growth calendars and available soil moisture, increased use of on-farm water conservation measures and land levelling to improve water efficiency in rice schemes dependent on surface irrigatio

Modelling irrigation and fertiliser use for chlorophyll production

Chlorophyll is a natural coloring extract used extensively in the food and pharmaceutical industries. In Europe, most chlorophyll is produced commercially from rainfed grassland production in eastern England. This paper describes a biogeochemical modeling study to assess the potential yield benefits associated with switching from rainfed to irrigated production. The research is in response the impacts of recent summer droughts on yield coupled with risks regarding climate change, rainfall reliability and long-term viability of rainfed production. The Denitrification-Decomposition model was calibrated and validated using multiple field data (n = 47) from 2000 to 2009 for a tall fescue grass (Festuca arundinacea) to simulate a range of irrigation and fertilizer management regimes on yield (annual and individual yield per cut). For chlorophyll production, a schedule combining 300 mm year−1 irrigation with 300 kg N ha−1 was shown to provide the highest average yield (an uplift of +62% above current levels). Switching from rainfed to irrigated production could also potentially halve (54%) current levels of fertilizer application. The implications for reducing environmental impacts from nitrate leaching are discussed

The impact of changing food choices on the blue water scarcity footprint and greenhouse gas emissions of the British diet: The example of potato, pasta and rice

Food production is a major contributor to a country's environmental burden. However, the burdens associated with individual foods vary significantly due to differing agricultural systems and locations, post-harvest storage, manufacturing and transport requirements. Dietary choices can therefore have a significant impact on the overall burdens associated with food consumption. Previous studies have generally considered changes in the proportion of animal-based foods in the diet or changes to a vegetarian, or a vegan diet. Using a life cycle assessment approach and data from published sources supplemented by original analysis, we estimated the blue water scarcity footprint and greenhouse gas emissions associated with the production, manufacture and distribution of three popular starchy carbohydrate foods as consumed in the United Kingdom – British fresh potatoes, Italian dried pasta and Indian dried basmati rice. Although similar to pasta in terms of greenhouse gas emissions per unit carbohydrate, when considered on the basis of typical portion size, potatoes have lower greenhouse gas emissions than pasta or basmati and the blue water scarcity footprint of basmati is two orders of magnitude greater than potatoes or pasta. The increasing preference for pasta and rice and reduction in household purchases of fresh potatoes in the United Kingdom over the period 1981–2010 has resulted in an increase in blue water scarcity footprint and a transfer of burdens from the United Kingdom to Italy and India, however the increased greenhouse gas emissions associated with rice and pasta has been, more or less, compensated by a reduction in emissions associated with purchases of potatoes. This paper has shown that dietary choices within food groups (in this case starchy carbohydrates) have a significant impact on an individual's contribution to greenhouse gas emissions and blue water scarcity footprint. The life cycle assessment approach is useful for understanding where the impacts of dietary choices occur and can inform the supply chain about where efforts should be targeted to reduce those impacts

Meta-analysis of climate impacts and uncertainty on crop yields in Europe

Acknowledgments This research was conducted as part of the FACCE Knowledge Hub: Modelling European Agriculture with Climate Change for Food Security (MACSUR1 and 2). The authors acknowledge funding support provided by the UK Research Council BBSRC (Grant BB/K010301/1 and BB/N00485X/1) and the preliminary assessment and literature searches conducted by Benson Sumani. Any enquiries for access to the data referred to in this article should be directed to [email protected] reviewedPublisher PD

Simulating impacts of irrigation heterogeneity on onion (Allium cepa L.) yield in a humid climate

This paper reports on a study combining experimental field data with biophysical crop modelling to assess the impacts of irrigation heterogeneity on onion yield. The AquaCrop model was calibrated and validated for brown onion (cv Arthur) and used to simulate yield variability under a set of contrasting soil and agroclimatic conditions assuming perfect (100% uniform) irrigation. The impacts of non-uniform irrigation as measured on-farm under two overhead systems (mobile hose reel fitted with boom and a linear move) were then evaluated using scenario analysis and multi-model runs. Stochastic modelling confirmed that the lowest yield (8.6 t DM/ha) occurs on the lowest moisture retentive soils under the driest agroclimatic conditions with non-uniform irrigation. There is much greater yield variability in dry years compared to wet years. In wet years, rainfall reduces the scheduled number of irrigation events and buffers the effects of irrigation non-uniformity on yield. Yields were more variable under the mobile hose reel system fitted with the boom compared to the fixed linear move system. The modelled yield variability under non-uniform was similar to the observed yields reported by growers based on an industry survey. The study highlights the importance of achieving high irrigation uniformity in dry years on light soils to maximise yield and provides useful data for evaluating the potential yield benefits that might accrue from precision irrigation

Assessing the financial and environmental impacts of precision irrigation in a humid climate

Precision agriculture is increasingly used where in-field spatial variability exists; however, the benefits of its use in humid climates are less apparent. This paper reports on a cost-benefit assessment of precision irrigation with variable rate technique (VRI) versus conventional irrigation, both compared to rainfed production, using a travelling hose-reel irrigator fitted with a boom on onions in eastern England. Selected environmental outcomes including water savings and CO2e emissions are evaluated. The modelled precision irrigation system, which responds to soil variability, generates better environmental outcomes than the conventional system in terms of water savings and reduced CO2e emissions (22.6% and 23.0% lower, respectively). There is also an increase in the ‘added value’ of the irrigation water used (£3.02/m3 versus £2.36/m3). Although precision irrigation leads to significant financial benefits from water and energy savings, these alone do not justify the additional equipment investment costs. However, any changes in yield or quality benefits, equipment costs or greater soil variability than on this site would make investment in precision irrigation more viable

Essential irrigation and the economics of strawberries in a temperate climate

Strawberries are a high value crop in the UK soft fruit sector, with the majority of production grown at field-scale and under protected (polytunnel) conditions. Despite its importance to the rural economy, there is surprisingly little published scientific evidence on the economics of irrigated strawberry production and the value of water in this horticultural sector. A survey of growers, supplemented by secondary data and industry sources, shows considerable variation in key physical and financial performance indicators, both within and between different strawberry production systems, as well as evidence of good practice. Water application depths ranged widely from 800 to over 2000 m3 ha−1 according to grower and crop variety. Irrigation costs typically range between £1.30 and £2.50 m−3 of water applied, highest where storage reservoirs and public water supplies are used. The average value of irrigation water for strawberry net of costs was about £6 m−3, much higher than for field crops such as potatoes. The importance of a reliable water supply to support irrigated strawberry production is highlighted. Climate change and growing pressures on water resources are likely to force a greater interest in irrigation economics in the soft fruit sector, especially in the face of restrictions on summer abstraction and rising competition and charges for using public water supply

Modelling impacts of precision irrigation on crop yield and in-field water management

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/),Precision irrigation technologies are being widely promoted to resolve challenges regarding improving crop productivity under conditions of increasing water scarcity. In this paper, the development of an integrated modelling approach involving the coupling of a water application model with a biophysical crop simulation model (Aquacrop) to evaluate the in-field impacts of precision irrigation on crop yield and soil water management is described. The approach allows for a comparison between conventional irrigation management practices against a range of alternate so-called ‘precision irrigation’ strategies (including variable rate irrigation, VRI). It also provides a valuable framework to evaluate the agronomic (yield), water resource (irrigation use and water efficiency), energy (consumption, costs, footprint) and environmental (nitrate leaching, drainage) impacts under contrasting irrigation management scenarios. The approach offers scope for including feedback loops to help define appropriate irrigation management zones and refine application depths accordingly for scheduling irrigation. The methodology was applied to a case study in eastern England to demonstrate the utility of the framework and the impacts of precision irrigation in a humid climate on a high-value field crop (onions). For the case study, the simulations showed how VRI is a potentially useful approach for irrigation management even in a humid environment to save water and reduce deep percolation losses (drainage). It also helped to increase crop yield due to improved control of soil water in the root zone, especially during a dry season