Combining the simulation crop model AquaCrop with an economic model for the optimization of irrigation management at farm level

Water resources used in irrigated agriculture are increasingly scarce, particularly in many countries where irrigation has undergone recent expansion. To optimize the limited resources available, optimization models provide useful tools for technical and economic analyses. One of the key inputs of these models is the yield response to water which is often simulated with empirical water production functions. At present, dynamic crop simulation models, such as AquaCrop (Steduto et al., 2009) offer alternative predictions of crop responses to different irrigation strategies as inputs to economic optimization. A model at farm scale was developed and applied to an area in South-western Spain to assist farmers in pre-season decision making on cropping patterns and on irrigation strategies. Yield predictions were obtained from the AquaCrop model which was validated for four different crops. The model simulated the impact on farm income of: (a) irrigation water constraints; (b) variations in agricultural policies; (c) changes in product and water prices; and, (d) variations in the communication to farmers of the specific level of irrigation water allocation. The applications of the models to the study area showed that currently, the changes in cropping patterns induced by the agricultural policy will encourage water savings more than an increase in water prices. Under water restrictions, the best strategy combines planting of low water use crops in part of the area to release water to grow more profitable crops with greater water needs. The model predicted a strong negative impact on farm income of delaying a decision on the level of seasonal water allocation by the water authority, reaching up to 300 € ha⁻¹ in the case of the study area.     

Understanding effects of multiple farm management practices on barley performance

Because of the complexity of farming systems, the combined effects of farm management practices on nitrogen availability, nitrogen uptake by the crop and crop performance are not well understood. To evaluate the effects of the temporal and spatial variability of management practices, we used data from seventeen farms and projections to latent structures analysis (PLS) to examine the contribution of 11 farm characteristics and 18 field management practices on barley performance during the period 2009–2012. Farm types were mixed (crop-livestock) and arable and were categorized as old organic, young organic or conventional farms. The barley performance indicators included nitrogen concentrations in biomass (in grain and whole biomass) and dry matter at two growing stages. Fourteen out of 29 farm characteristics and field management practices analysed best explained the variation of the barley performance indicators, at the level of 56%, while model cross-validation revealed a goodness of prediction of 31%. Greater crop diversification on farm, e.g., a high proportion of rotational leys and pasture, which was mostly observed among old organic farms, positively affected grain nitrogen concentration. The highest average grain nitrogen concentration was found in old organic farms (2.3% vs. 1.7 and 1.4% for conventional and young organic farms, respectively). The total nitrogen translocated in grain was highest among conventional farms (80 kg ha⁻¹ vs. 33 and 39 kg ha⁻¹ for young and old organic farms, respectively). The use of mineral fertilizers and pesticides increased biomass leading to significant differences in average grain yield which became more than double for conventional farms (477 ± 24 g m⁻²) compared to organic farms (223 ± 37 and 196 ± 32 g m⁻² for young and old organic farms, respectively). In addition to the importance of weed control, management of crop residues and the organic fertilizer application methods in the current and three previous years, were identified as important factors affecting the barley performance indicators that need closer investigation. With the PLS approach, we were able to highlight the management practices most relevant to barley performance in different farm types. The use of mineral fertilizers and pesticides on conventional farms was related to high cereal crop biomass. Organic management practices in old organic farms increased barley N concentration but there is a need for improved management practices to increase biomass production and grain yield. Weed control, inclusion of more leys in rotation and organic fertilizer application techniques are some of the examples of management practices to be improved for higher N concentrations and biomass yields on organic farms.     

Does the recoupling of dairy and crop production via cooperation between farms generate environmental benefits? A case-study approach in Europe

The intensification of agriculture in Europe has contributed significantly to the decline of mixed crop-livestock farms in favour of specialised farms. Specialisation, when accompanied by intensive farming practices, leaves farms poorly equipped to sustainably manage by-products of production, capture beneficial ecological interactions, and adapt in a volatile economic climate. An often proposed solution to overcome these environmental and economic constraints is to recouple crop and livestock production via cooperation between specialised farms. If well-managed, synergies between crop and livestock production beyond farm level have the potential to improve feed and fertiliser autonomy, and pest regulation. However, strategies currently used by farmers to recouple dairy livestock and crop production are poorly documented; there is a need to better assess these strategies using empirical farm data. In this paper, we employed farm surveys to describe, analyse and assess the following strategies: (1) Local exchange of materials among dairy and arable farms; (2) Land renting between dairy and arable farms; (3) Animal exchanges between lowland and mountainous areas; and (4) Industrially mediated transfers of dehydrated fodder. For each strategy, cooperating farm groups were compared to non-cooperating farm groups using indicators of metabolic performance (input autonomy, nutrient cycling and use efficiency), and ecosystem services provision. The results indicate that recoupling of crop and dairy production through farm cooperation gives farmers access to otherwise inaccessible or underutilised local resources such as land, labour, livestock feed or organic nutrients. This in turn leads to additional outlets for by-products (e.g. animal manure). Farmers’ decisions about how to allocate the additional resources accessed via cooperation essentially determine if the farm diversifies, intensifies or expands operations. The key finding is that in three of the four crop-livestock integration strategies assessed, these newly accessed resources facilitated more intensive farming practices (e.g. higher stocking rate or number of milking cows per hectare) on cooperating dairy farms relative to non-cooperating, specialised dairy farms. As a consequence, cooperation was accompanied by limited environmental benefits but helped to improve resource use efficiency per unit of agricultural product produced. This article provides a critical step toward understanding real-world results of crop-livestock cooperation beyond the farm level relative to within-farm crop-livestock integration. As such, it brings practical knowledge of vital importance for policy making to promote sustainable farming.     

Assessment of irrigation scenarios to improve performances of Lingot bean (Phaseolus vulgaris) in southwest France

In the context of climate change, producing the same amount of food with less water has become a challenge all over the world. This is also true for the Lingot bean production in the area of Castelnaudary of southwest France where market competition with imported bean has made it crucial to achieve high yields to maintain production in the area. The use of an appropriate and robust crop model can help to identify crop management solutions to face such issues. We used SSM-legumes, a crop model generic to legume species, as well as field observations recorded over five years on eight farms of the Castelnaudary area to assess the effect of different irrigation scenarios on bean yield and water consumption. First, it was demonstrated that the SSM-legumes model is robust in simulating the development and growth of Lingot bean in non-stressed or moderately stressed conditions of this region regarding water and nutrient availability. Then, the use of the model to compare irrigation scenarios provided guidance on how to improve irrigation management for Lingot bean production. These results showed that farmers could achieve slightly higher yields with less water by basing irrigation decisions on the water content of the soil.     

Evaluating irrigation strategies for lettuce by simulation: 1. Water flow simulations

Among crop systems, vegetable crops with high inputs of fertilizer and water represent an important threat to the quality of the water. To give guidelines to growers and decision-makers for crop management, numerous fertilization and irrigation practices in various situations should be evaluated with regard to their production and pollution effects.

Here, we used a model of water flow and solute transport (Lafolie, 1991) to compare three irrigation strategies with regard to their effects on the water balance. The model was run for a lettuce crop for two growing periods (summer and autumn) and over 100 years in French Mediterranean conditions. The three strategies were (1) the current strategy based on the occurrence of rainfall, (2) a strategy based on a simplified modelling of the soil water balance and (3) a strategy based on tensiometer readings.

As expected, strategy 1 was very water and time-consuming. Compared with strategy 2, strategy 3 appeared as a good choice, minimizing the waste of water: it involved less irrigation and less drainage loss. The crop was also less stressed by this strategy.     

A field study of the impact of different irrigation practices on herbicide leaching

Agricultural practices, such as subsurface drainage, irrigation and tillage, may significantly affect pesticide leaching and, consequently, the risk of groundwater contamination. The aim of the present study was to investigate the impact of different irrigation systems on herbicide leaching to shallow groundwater through direct monitoring at the field scale in northern Italy over a 3-year period. Concentrations of the herbicide terbuthylazine (TBA) and its metabolite desethylterbuthylazine (DES) were monitored on 10 farms cropped with maize and irrigated by sprinkler, basin and border systems. Considering the results grouped according to the different irrigation systems, the mean TBA and DES concentrations was lower than the arbitrary non-health based legal limit of 0.1 μg/L using sprinkler and border systems, while it was 0.19 and 0.30 μg/L respectively for TBA and DES using basin systems.However, since many factors other than the irrigation systems can contribute to pesticide leaching and in a field study it is impossible to discriminate between all the different variables, the concentrations of both compounds were simulated with and without irrigation using the model MACRO 5.1 in order to gain a deeper understanding of the role of irrigation on leaching. First, the groundwater table depth, which was measured daily in all fields, was used to calibrate the model and thus achieve a good soil hydrology calibration. To assess the performance of the model the root mean squared error (RMSE) was used. RMSE ranged from 0.2 to 0.5 m, showing that a satisfactory hydrology calibration was obtained. Afterward, the solutes were modelled and the results showed that under non-irrigated conditions, concentrations of both compounds would be very low. These findings validate the hypothesis that careful selection of agricultural practices, such as the type of irrigation, can reduce pesticide leaching.     

Yield and water consumption characteristics of wheat/maize intercropping with reduced tillage in an Oasis region

Higher irrigation quota for conventional farming causes substantial conflicts between water supply and demand in agriculture, and wind erosion near soil surface is one of the major causes of farmland degradation and desertification in arid areas. This research investigated the effect of the amounts of irrigation in combination with tillage practices on soil evaporation (E), water consumption (ET) characteristics, and grain yield performance and water use efficiency (WUE) for wheat (Triticum aestivum L.) intercropped with maize (Zea mays L.) in strip planting in an Oasis region. The field experiment, conducted at Wuwei station during 2008–2010, had two tillage systems (reduced tillage with wheat stubble retention vs. conventional tillage without stubble retention), and three (low, medium, and high) levels of irrigation, in a randomized complete block design. Averaged across three years, soil evaporation with medium and high levels of irrigation was 6.8% and 5.4% greater than that with low level of irrigation, respectively. Total water consumption of wheat/maize crops under the medium and high irrigation levels was 8.5% and 18.5% greater, respectively, than that under low irrigation. However, grain yields were similar under the medium and high levels of irrigation, so was WUE. The effect of tillage on the wheat/maize intercropping was inconsistent across years or among treatments: soil moisture at harvest was 3.0–7.6% greater in the fields with reduced tillage compared with those with conventional tillage in 2008 and 2009, but no difference was found in 2010; the E/ET ratio of reduced tillage was 9% lower than the ratio under conventional tillage in 2008, 3% higher in 2010, but no difference between the two tillage systems in 2009. Across three years, there was a general trend that the WUE of the wheat/maize intercropping system with reduced tillage was greater (by 4–11%) than that with conventional tillage. We conclude that a medium level of irrigation is sufficient to achieve crop yields and WUE equivalent to those under high level of irrigation, provided that a reduced tillage practice is applied to the wheat/maize intercropping in Oasis areas.     

Effects of corn deficit irrigation and soil properties on water use efficiency. A 25-year analysis of a Mediterranean environment using the STICS model

This study analyses the role of variability induced by climate and soil properties (texture and total available soil water in the root zone, TAW) on the “corn deficit irrigation–water use efficiency” relation over a 25-year period, between 1981 and 2005, in three different sites located in the South of Italy. The analysis of water use efficiency was carried out by means of three indexes: crops water use efficiency (WUE_ET and WUE_T) and irrigation water use efficiency (IWUE). These indexes can be obtained by calculating the ratio between the yield and the seasonal values of evapotranspiration (ET), transpiration (T) and irrigation volume (I). After its validation, the STICS model was retained to simulate the variables required to determine these indexes.Climatic variability affected the three indexes in different ways during the 25-year period studied. The dispersion around the mean values of the water use efficiency is 17% on average for the WUE (ET or T) indexes, whereas it could reach 54% for the IWUE index. This last index is only poorly reliable due to the high variability of rainfall during the corn growing season in the Mediterranean region.For the same level of soil water deficit, TAW led to an improvement (the case of the site with a high TAW and loam–clay soil texture), a stabilisation (the case of the site with a high TAW and clay soil texture) or a decrease (the case of the site with a poor TAW and clay soil texture) in WUE_ET and WUE_T values. For the same conditions of soil water deficit and TAW, crops water use efficiency was higher in loam textured soil than in clay soil.The results derived by analyzing three indexes (WUE_ET, WUE_T and IWUE) converge to the same conclusions on the “corn deficit irrigation–water use efficiency” relation observed at the three different sites.The hypotheses which may explain the differences observed in the different sites studied in terms of water use efficiency are discussed, with the presentation of some suggestions devised for corn irrigation practices.     

水肥耦合条件下间作小麦光合特性的响应

本试验在河西绿洲灌区进行,研究水肥耦合条件下间作小麦灌期浆光合特性对其的响应。结果表明,间作小麦灌浆期的肥水组合以灌溉量370m3/亩、N肥28kg/亩,370m3/亩、42kg/亩和450m3/亩、28kg/亩这3个肥水组合的光合特性表现较为突出。不同的水肥处理其中,370m3/亩的灌溉水平与其他肥料水平相结合或28kg/亩（N肥）的肥料水平与其他灌溉水平相配合具有一定的节水性且光合特性也良好。     

Analysis of maize growth for different irrigation strategies in northeastern Spain

Water availability is the key factor determining maize yields in NE Spain. Irrigation is needed to obtain economic yields but it is costly and water supply is sometimes insufficient. The aim of this research was to test a simple simulation model for evaluating different irrigation strategies, especially under water-limited conditions. The LINTUL model was adapted and parameterized using experimental data from the 1995 season. Most parameters were obtained from experiments, although some were taken from the literature. This model is based on the concept of light use efficiency, incorporates a soil water balance and simulates phenology, crop leaf area, biomass accumulation and yield. It was tested on independent data from the 1995 and 1996 seasons under different irrigation treatments. The model predicted the flowering date within ±5 days of the observed values. Leaf area index was predicted satisfactorily, except under extreme water-stress conditions, where it was overestimated. In general, soil moisture content and yield were accurately predicted. In the 1996 experiment measured yields ranged from 6.4 to 13.6 t ha⁻¹ and simulated yields from 6.5 to 12.2 t ha⁻¹. These results show that the LINTUL model can be used as a tool for exploring the consequences on maize yields of different irrigation strategies in NE Spain. Analysis of the model identified a process that strongly affects yield loss due to drought, but for which present understanding is still insufficient: the effects of drought on leaf senescence and canopy architecture.     

Evaluation of Best Management Practices for N fertilisation in regional field vegetable production with a small-scale simulation model

Assessing the environmental impact of field vegetable production on a regional basis is a challenging task, since vegetable farms are often scattered. In order to use a soil–plant–environment–economics model as an assessment tool, a method is suggested that allows Best Management Practices (BMPs) for N-efficient field vegetable production to be tested and evaluated on different spatial entities. The model farm concept was exemplarily demonstrated on field vegetable production in the region of Baden-Wurttemberg, Germany. Two scenarios using different fertiliser strategies illustrate how the implementation of BMP can be evaluated at regional, sub-regional and farm level. Simulated results show how the area-wide enforcement of the N_min method in Baden-Wurttemberg, as the first step to implement BMP, would lower the N leaching potential of field vegetable production by 66%. At sub-regional level, the results reveal that current targets stipulated by German legislation may still not be achieved in smaller areas with intensive field vegetable production.     

An empirical analysis of risk in conventional and organic arable farming in The Netherlands

This paper assesses and compares risk in conventional and organic arable farming in The Netherlands with respect to family farm income and underlying price and production variables. To investigate the risk factors the farm accountancy data network was used containing unbalanced panel data from 196 conventional and 29 organic representative Dutch arable farms (for the period 2002 up to and including 2011). Variables with regard to price and production risk were identified using a family farm income analysis scheme. Price risk variables are input and output prices, while yield volatility of different crops is the main production risk variable. To assess risk, an error components implicit detrending method was applied and the resulting detrended standard deviations were compared between conventional and organic farms. Results indicate that the risk at the level of family farm income is higher in organic farming. The underlying variables show higher risk for organic farms in crop yields, crop prices and variable input costs per crop.     

锡林河流域紫花苜蓿需水规律与灌溉定额优化研究

为了确定锡林河流域紫花苜蓿生育期内不同阶段的需水量、需水规律和合理的灌溉定额。采用非充分灌溉试验,研究了紫花苜蓿的需水规律、产量与灌溉定额间的关系以及合理灌溉定额。结果表明：第1 茬紫花苜蓿需水高峰值出现在6 月下旬—7 月初,其需水强度最大可达5.09 mm/d;第2 茬紫花苜蓿需水高峰值出现在8 月上旬—8 月中旬,其需水强度最大可达5.23 mm/d。根据紫花苜蓿产量与灌溉定额间表现为二次抛物线型关系,以追求单位面积产量、灌溉水生产效率和生产弹性系数最大为目标,确定紫花苜蓿的合理灌溉定额,该成果为节水灌溉制度的制定和灌溉预报等提供了科学依据。     

气候变化下水肥及CO2对冬小麦生长的影响模拟

从机理上研究冬小麦最优水肥管理措施及其对大气CO2浓度变化的适应性,对保障粮食安全、促进农业可持续发展有重要意义。基于DSSATv4.5 模型中的CERES-Wheat 模块,模拟开封市冬小麦2001—2010 年气象条件变化对冬小麦开花期、成熟期的影响;设定42 种水肥组合方式,分析水肥因素对冬小麦产量的影响,同时选取出最优水肥组合方式;在最优水肥组合方式支持下,模拟不同大气CO2浓度水平下冬小麦的生长状况,分析CO2的施肥效应。研究结果表明：冬小麦开花期、成熟期随降水量的增加有所提前;生长期平均温增加能够明显促进冬小麦开花期、成熟期提前;灌溉量、施肥量的增加对冬小麦产量带来先快速增长后趋于稳定的增产效果,但过量施肥或灌溉均会导致不同程度的减产;大气CO2浓度增高对冬小麦有明显的增产效果,同时其各项生产指标也随CO2浓度增高而表现出平稳增长的趋势。可得出结论：冬小麦开花期、成熟期较晚的年份其生长期平均温均在11.0℃以下;控制施肥量300 kg/hm2、灌溉量200 mm左右的水肥组合能够达到理想的冬小麦高产节约种植效果;未来40 年的大气CO2浓度增高会对冬小麦种植带来明显的增产效应。     

基于WIN ISAREG模型的紫花苜蓿灌溉制度优化研究

为了探索锡林河流域紫花苜蓿高效节水的最优灌溉制度,在田间灌溉试验基础上,研究了锡林河流域滴灌条件下紫花苜蓿的灌溉制度。利用WIN ISAREG模型对紫花苜蓿的实际灌溉制度进行了评价,在此基础上根据紫花苜蓿需水特性进行了多种灌水方案设计和模拟。研究表明:紫花苜蓿在现蕾期土壤水消耗比率最低,作物系数、产量反应系数和腾发量最大,为紫花苜蓿的需水关键期。紫花苜蓿生育期内共灌水10次,总灌水量在250 mm,产量下降率为6.0%。因此,研究结果为流域内紫花苜蓿的灌溉预报,以及当地灌溉人工草地建设提供参考。     

基于GIS的辽宁省农田水利管理信息系统研究

为改善辽宁省农田水利长期以来传统的管理方法,应用先进的科技手段3S技术提高灌区管理水平是现代农业发展的必然趋势。从辽宁省管理部门的实际出发,设计开发了基于GIS的农田水利管理信息系统,系统由灌溉子系统模块、排涝子系统模块、农村饮水子系统模块、报表系统模块和权限管理模块组成,具有一定的智能水平,大大改善了辽宁省农田水利的全方位管理。     

Crop-livestock integration,from single practice to global functioning in the tropics: Case studies in Guadeloupe

Agricultural systems will have to produce more and better in a changing world. Mixed crop livestock systems (MCLS) are sound alternative ways to progressively achieve these goals through crop-livestock integration (CLI). CLI exploits the synergies between cropping and livestock systems, for example, through organic fertilization and the use of crop residues to feed livestock, and offers many opportunities to improve productivity, as well as to increase resource use efficiency and improve the resilience of the whole farming system. In the scientific literature, authors advocate the interest of MLCS and CLI, based on theoretical considerations, modelling and empirical evidence from local case studies. But these studies do not clearly identify the respective roles of the diversity of activities and CLI management practices in improving performances at the level of the whole farming system. The aim of this study was thus to assess CLI at farm scale in a range of MCLS and to explain farm performances by analyzing the combination of activities and the level of integration. This study was conducted in Guadeloupe, (French West Indies), where MCLS and CLI are complex but important challenges for local agricultural. Ecological network analysis was used to study the structure, functioning and performance of agrosystems. To this end, a range of eight farms was selected to characterize CLI as practices, and as a network of nitrogen flows at farm level. The land and labor productivity were then assessed along with the resilience, efficiency, productivity and self-sufficiency of the network of flows. Results show that CLI only applies to certain types of production, including feeding pigs with a wide range of crop residues (crop residues provide from 16 to 45% of the N supply to pigs) or organic fertilization of small market gardens and plots used to grow tubers (manure provides 24–100% of the N supply to plots). But at whole system level, CLI remains low: in seven cases, the N circulating within the system – ICR- represent only between 0.7 to 3.5% of the total N circulating through the system; only one farm presents a higher intensity of CLI, with an ICR of 18.9%. Consequently, performances and especially efficiency and productivity, depend more on the nature of the activity than on CLI management practices.     

灌溉定额和施氮量对机采棉田水分运移及硝态氮残留的影响

水资源短缺和土壤环境污染严重是制约农业可持续健康发展的瓶颈,迫使农民开发和采用可持续的农业生产技术。水分运动机理和氮肥残留行为是评价干旱地区农业水肥管理水平的依据,提高水氮利用效率是降低环境污染这一重要科学问题的重要途径。本研究采用裂区试验设计,以灌溉量为主区,设2250(低灌溉量,W1)、3450(传统灌溉量,W2)和4650 m~3 hm–2 (高灌溉量, W3) 3个灌溉量;设0 (空白, N1)、300 (传统施肥量, N2)和600 kg hm–2 (高施氮量, N3) 3个纯氮投入量,在干旱的中国西北内陆棉区开展2年的田间试验,评估灌溉和施氮策略对水氮运移、籽棉产量、水氮生产效率的影响。结果表明,灌溉量及水氮耦合效应是影响籽棉产量及灌溉水生产力的影响因素,其中灌溉量是主效应。2年均值表明,灌溉量为W1时,施肥量由N1增加至N3,生育期0～80 cm平均土壤含水量呈先显著上升后显著下降的趋势, N2和N3处理较N1处理籽棉产量分别提高13.8%和7.6%,水分利用效率分别提高13.6%和6.8%;灌溉量为W2和W3时,施肥量由N1增加至N3,生育期0～80 cm土层平均含水量...