Bio-economic assessment of climate change impacts on managed grassland production

In order to analyze impacts of climate change on managed grassland systems and to project potential changes in farmers’ management practices in response to altered climatic conditions, we develop a modeling approach that integrates a process-based grassland model into an economic model. This economic model describes farmers’ decision making with respect to input use and accounts for production levels, production risks, fodder quality as determined by the grassland composition, and environmental protection. We apply the bio-economic model to an intensively managed grassland system with a geographic focus on the Swiss Plateau. Our results show an increase of future production risks in grassland production due to climate change. Projected changes in yield levels, grassland composition and optimal responses of risk-averse farmers are dependent on the assumptions concerning cross-compliance obligations, forage quality and particularly on the assumed effect of elevated CO₂ concentrations: Grasslands yields will increase under future climatic conditions only if the benefits of rising atmospheric CO₂ concentrations are taken into account. Without this potential benefit, climate change will lead to less intensive input use and lower grassland yields.     

Towards using a thermal infrared index combined with water balance modelling to monitor sugarcane irrigation in a tropical environment

In humid regions, the timing and quantity of a complementary irrigation regime is challenging because of the irregularity of rainfalls events. In this study, we tested the use of a thermal infrared derived empirical crop water stress index (CWSI_e) as an in situ measurement of the water status of sugarcane, to better monitor the irrigation scheduling. To do this, we set up a 2-year experiment in Reunion Island, on a trial with plots under different water conditions (rainfed and irrigated). Crop surface temperature was measured daily with infrared radiometers (Apogee Instruments) installed above the canopy, and soil moisture and drainage measurements were used to derive the ratio between actual and maximum evapotranspiration (AET/MET) values that were then averaged on “hydrically homogeneous” time periods (between 7 and 25 days). Only the thermal data acquired on clear days and 1 h after noon in 2007 were used to define the empirical lower and upper baselines required for the calculation of empirical CWSI. The data set acquired in 2008 was used to test the robustness of the method as we used the upper and lower baselines defined in 2007 to calculate CWSI_e. The linear regression between AET/MET and (1 − CWSI_e) averaged on the same periods (values ranging between 0.4 and 1) showed a significant correlation for both experimental years (global R² = 0.75 and RMSE = 0.12). This result indicates the effectiveness of the CWSI_e to measure the water status of the sugarcane crop, even in humid conditions with a vapor pressure deficit (VPD) between 0.5 and 2.1. We conclude the study by discussing the complementarity of this remote water stress index (CWSI_e) with OSIRI water balance modelling tool currently used in Reunion Island for monitoring sugarcane crop irrigation.     

Effects of different emitter space and water stress on yield and quality of processing tomato under semi-arid climate conditions

The objective of the study was to determine the effects of different emitter spaces and water stress on crop yield, such that the tomatoes would be suitable for processing and paste output (Lycopersicon esculentum Mill cv. Shasta). Such variables were also analyzed with respect to crop quality characteristics (e.g., mean fruit weight - MFW, fruit diameter - FD, penetration value of fruit - PV, pH, total soluble solids - TSS, and ascorbic acid contents - AA). The experiment was conducted under ecological conditions typical of the Konya Plain, a semi-arid climate, in 2004 and 2005. Drip irrigation laterals were arranged in such a way that every row had one lateral. Emitters were spaced at 25, 50, and 75 cm intervals in the main plots, while four levels of water supply, irrigation at 7-day intervals with enough water to fill the soil depth of 0-60 cm until capacity was reached (I₁), and 25, 50, and 75% decreased water supply levels were applied as subplots of the experiment. Results of the field experiments showed that yield suitable for processing (68.7-72.7 t ha⁻¹) and paste output (12.2-12.9 t ha⁻¹) were obtainable under conditions of I₁ application (p < 0.01). MFW, FD, PV, and TSS were significantly affected from treatments (p < 0.05). High stress resulted in the highest soluble solids. The total irrigation water amount and water consumptive use of the mentioned application (I₁) were determined as 426 and 525 mm in 2004. In 2005, the total irrigation water amount and water consumptive use of the same treatment were 587 and 619 mm, respectively.     

Estimating the impacts of water pricing on smallholder irrigators in North West Province, South Africa

Worldwide growing water scarcity has increased the call for economic instruments to stimulate rational water use in agriculture. Furthermore, cost-recovery is now widely accepted as a cornerstone of sustainable water management. In many developing countries, where agricultural water use is often still subsidised, water pricing policies are developed for allocating water efficiently and achieving sustainability of water systems. However, the impacts of water pricing policies on irrigation water use and on farm production systems is mostly unknown. We introduce an innovative two-stage methodology that allows estimating these effects at farm level. Applying the method to small-scale irrigators in South Africa, we show that water demand is quite responsive even to small changes in water price. In addition, the introduction of a water price significantly decreases farm profit. This appears to be a problem primarily for the poorer farmers.     

Economic impacts on farm households due to water reallocation in China's Chaobai watershed

Our study area in the Chaobai watershed, upstream of Miyun Reservoir, has been undergoing agricultural water transfers to downstream municipal uses in Beijing. We examine the impacts of water reallocation on crop production and farmers’ income and discuss issues relating to current compensation mechanisms. We use data from a survey of 349 farm households and their farm plots in the upper Chaobai watershed within Hebei province. Water reallocation from upstream to downstream areas has reduced agricultural water supply and the area irrigated. Regression results show that in plots deprived of irrigation, maize yields decrease by 21% and crop revenues decline by 32%. On average, losing irrigation on one hectare of cultivated land reduces net crop income by 2422 yuan. We examine compensation arrangements and social equity for the major policies implemented in the region and we identify gaps between current compensation levels and farmers’ income and production losses. The current compensation received by farmers is generally lower than the losses incurred due to reduced irrigation. A more appropriate compensation mechanism is called for in future water transfers.     

GIS tools applied to the sustainable management of water resources: Application to the aquifer system 08-29

The sustainable exploitation of water resources requires planning and control methods that allow the incorporation of a great number of spatial and temporal variables. Because of its features, a Geographic Information System (GIS) seems the most suitable tool to aid in the management of available hydric resources. In this study, we have developed a specific GIS within the GESMO Project in order to better manage the 08-29 aquifer system (Mancha Oriental). This tool is intended for use by the JCRMO: Junta Central de Regantes de la Mancha Oriental (General Board of Irrigation Users of Eastern La Mancha), the organism responsible for aquifer management.This system is designed to integrate information from different sources, such as remote sensing, fieldwork data or administrative files with the cadastral subplot as a common reference. One of its functions is to expedite the control and monitoring, in real time, of the exploitation plans, which constitute the legal instrument to regulate water extractions. It will allow us to estimate the spatial and temporal distribution of water extractions needed for crops and their irrigation systems. These estimates will be highly valuable for aquifer modelling. The system also permits display of information on maps for easy handling. This visualisation allow users to more readily participate in decision-making processes.     

Effects of nutrition systems and irrigation programs on tomato in soilless culture

A research has been carried out to determine the effects of nutrition systems and irrigation programs on soilless grown tomato plants under polyethylene covered unheated greenhouse conditions. Two nutrition systems (open and closed) and three irrigation programs (high, medium and low) based on integrated indoor solar radiation triggering thresholds (1 MJ m⁻² [0.4 mm], 2 MJ m⁻² [0.8 mm] and 4 MJ m⁻² [1.6 mm]) in both nutrition systems have been tested. Applied and discharged nutrient solution, evapotranspiration, total and marketable yield have been measured and water use efficiency has been calculated. The highest total yield has been obtained from the open system with respectively 11% and 7.2% increases in autumn and spring. Applied nutrient solution volume and seasonal ET have been modified between 47.8-180.4 l plant⁻¹ and 41.7-145.5 l plant⁻¹ respectively during both growing seasons. As average of two growing seasons, respectively 826.5 and 330.6 m³ ha⁻¹ nutrient solutions have been discharged from the greenhouse in the open and closed systems. WUE of treatments varied between 33-55 kg m⁻³ in autumn and 26-35 kg m⁻³ in spring. Highest WUE values have been determined in 4 MJ m⁻² and in the closed system in both growing seasons. Results showed that the closed system and infrequent irrigations increased water use efficiency while decreasing yield and discharged nutrient solution.     

提高藏东地区节水灌溉水平的几点思考

灌区渠道渗漏、坍塌现象突出,致使过水能力、灌溉水利用系数低的问题在藏东地区十分严重,,主要原因既有地质条件等客观因素,也有规划建设和营运管理相对落后等主观原因。要解决这一问题,除了采用管理和技术手段维护好现有的灌溉工程外,更重要的是还要在解决农牧区新灌区规划设计及灌溉节水的工作思路上有所突破。     

Regional assessment of evaporation from agricultural irrigation reservoirs in a semiarid climate

The aim of this study was to assess the magnitude of evaporation loss from the agricultural water reservoirs (AWRs) for irrigation at a regional scale and to analyze its impact on water storage efficiency. To this end, we identified the extant AWRs for irrigation in the Segura River Basin (SRB) in southeastern Spain, and calculated the water loss from each AWR per month and year. In order to accomplish this, we determined the monthly and yearly values of the pan coefficient, K_p, taking into account the geometric dimensions (area and depth) of the AWRs and local climate conditions through a function of air vapour pressure deficit (VPD). AWR areas were identified by interpreting aerial images, while climate conditions were assessed using daily meteorological data obtained from 74 automated agro-meteorological stations located in irrigated areas. Regional evaporation losses were estimated using aggregation GIS techniques. A total of 14,145 AWRs covering 4901 ha were identified, which represents 0.26 and 1.81% of the total area of SRB and the irrigated land, respectively. Results indicated that annual water loss at a basin scale reaches 58.5 × 10⁶ m³, which corresponds to 1.404 m of water depth over the flooded area and to 8.3% of irrigation water use in the basin. This quantity is higher than the industrial demand and similar to the environmental demand, and is equivalent to 27% of the domestic water use in a region with approximately two million inhabitants. The method used, based on annual K_p, appears the most straightforward to assess regional evaporative losses from AWRs, and can be extended to other regions and climates, provided that the VPD-dependent function that gives the pan coefficient is available.     

Seasonal climate change impacts on evapotranspiration, precipitation deficit and crop yield in Puerto Rico

The purpose of this study was to estimate precipitation (P), reference evapotranspiration (ET_o), precipitation deficit (PD = P − ET_o) and relative crop yield reduction (YR) for a generic crop under climate change conditions for three locations in Puerto Rico: Adjuntas, Mayagüez, and Lajas. Reference evapotranspiration was estimated by the Penman-Monteith method. Precipitation and temperature data were statistically downscaled and evaluated using the DOE/NCAR PCM global circulation model projections for the B1 (low), A2 (mid-high) and A1fi (high) emission scenarios of the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios. Relative crop yield reduction was estimated from a water stress factor, which is a function of soil moisture content. Average soil moisture content for the three locations was determined by means of a simple water balance approach.Results from the analysis indicate that the rainy season will become wetter and the dry season will become drier. The 20-year average September precipitation excess (i.e., PD > 0) increased for all scenarios and locations from 121 to 321 mm between 2000 and 2090. Conversely, the 20-year average February precipitation deficit (i.e., PD < 0) changed from −27 to −77 mm between 2000 and 2090. The results suggest that additional water could be saved during the wet months to offset increased irrigation requirements during the dry months. The 20-year average relative crop yield reduction for all scenarios decreased on average from 12% to 6% between 2000 and 2090 during September, but increased on average from 51% to 64% during February. Information related to the components of the hydrologic water budget (i.e., actual evapotranspiration, surface runoff, aquifer recharge and soil moisture storage) is also presented. This study provides important information that may be useful for future water resource planning in Puerto Rico.     

Modeling wheat yield and crop water productivity in Iran: Implications of agricultural water management for wheat production

In most parts of Iran, water scarcity has been intensifying and posing a threat to the sustainability of agricultural production. Wheat is the dominant crop and the largest irrigation water user in Iran; hence, understanding of the crop yield-water relations in wheat across the country is essential for a sustainable production. Based on a previously calibrated hydrologic model, we modeled irrigated and rainfed wheat yield (Y) and consumptive water use (ET) with uncertainty analysis at a subbasin level in Iran. Simulated Y and ET were used to calculate crop water productivity (CWP). The model was then used to analyze the impact of several stated policies to improve the agricultural system in Iran. These included: increasing the quantity of cereal production through more efficient use of land and water resources, improving activities related to soil moisture conservation and retention, and optimizing fertilizer application. Our analysis of the ratio of water use to internal renewable water resources revealed that 23 out of 30 provinces were using more than 40% of their water resources for agriculture. Twelve provinces reached a ratio of 100% and even greater, indicating severe water scarcity and groundwater resource depletion. An analysis of Y-CWP relationship showed that one unit increase in rainfed wheat yield resulted in a lesser additional water requirement than irrigated wheat, leading to a larger improvement in CWP. The inference is that a better water management in rainfed wheat, where yield is currently small, will lead to a larger marginal return in the consumed water. An assessment of improvement in soil available water capacity (AWC) showed that 18 out of 30 provinces are more certain to save water while increasing AWC through proper soil management practices. As wheat self-sufficiency is a desired national objective, we estimated the water requirement of the year 2020 (keeping all factors except population constant) to fulfill the wheat demand. The results showed that 88% of the additional wheat production would need to be produced in the water scarce provinces. Therefore, a strategic planning in the national agricultural production and food trade to ensure sustainable water use is needed. This study lays the basis for a systematic analysis of the potentials for improving regional and national water use efficiency. The methodology used in this research, could be applied to other water scarce countries for policy impact analysis and the adoption of a sustainable agricultural strategy.     

Effects of irrigation regimes on yield and water productivity of safflower (Carthamus tinctorius L.) under Mediterranean climatic conditions

A field study was carried out in order to determine the effect of deficit irrigation regimes on grain yield and seasonal evapotranspiration of safflower (Carthamus tinctorius L.) in Thrace Region of Turkey. The field trials were conducted on a loam Entisol soil, on Dincer, the most popular variety in the research area. A randomised complete block design with three replications was used. Combination of four well-known growth stages of the plant, namely vegetative (V_a), late vegetative (V_b), flowering (F) and yield formation (Y) were considered to form a total of 16 (including rain fed) irrigation treatments. The effect of irrigation and water stress at any stage of development on grain yield per hectare and 1000 kernels weight was evaluated. Results showed that safflower was significantly affected by water stress during the sensitive late vegetative stage. The highest yield was obtained in V_aV_bFY treatment. Seasonal irrigation water use and evapotranspiration were 501 and 721 mm, respectively, for the non-stressed treatment. Safflower grain yield of this treatment was 5.22 Mg ha⁻¹ and weight of 1000 kernels was 55 g. The seasonal yield-water response factor value was 0.87. The total water use efficiency was 7.2 kg ha⁻¹ mm⁻¹. Irrigation schedule of the non-stressed treatment may be as follows: the first irrigation is at the vegetative stage, when after 40-50 days from sowing/elongation and branching stage, that is the end of May; the second irrigation is at the late vegetative stage, after 70-80 days from sowing/heading stage, that is in the middle of June; the third irrigation is at the flowering stage, approximately 50% level, that is the first half of July; and the fourth irrigation is at the yield formation stage, seed filling, that is the last week of July.     

Adapting to climate change: Agricultural system and household impacts in East Africa

The East African region exhibits considerable climatic and topographic variability. Much spatial and temporal variation in the response of different crops to climate change can thus be anticipated. In previous work we showed that a large part of this variation can be explained in terms of temperature and, to a lesser extent, water effects. Here, we summarise simulated yield response in two crops that are widely grown in the region, maize and beans, and investigate how the impacts of climate change might be addressed at two levels: the agricultural system and the household. Regionally, there are substantial between-country and within-system differences in maize and bean production responses projected to 2050. The arid-semiarid mixed crop-livestock systems are projected to see reductions in maize and bean production throughout most of the region to 2050. Yields of these crops in the tropical highland mixed systems are projected to increase, sometimes substantially. The humid-subhumid mixed systems show more varied yield responses through time and across space. Some within-country shifts in cropping away from the arid-semiarid systems to cooler, higher-elevation locations may be possible, but increased regional trade should be able to overcome the country-level production deficits in maize and beans caused by climate change to 2050, all other things being equal. For some places in the tropical highlands, maize and bean yield increases could have beneficial effects on household food security and income levels. In the other mixed systems, moderate yield losses can be expected to be offset by crop breeding and agronomic approaches in the coming decades, while more severe yield losses may necessitate changes in crop types, movement to more livestock-orientated production, or abandonment of cropping altogether. These production responses are indicative only, and their effects will be under-estimated because the methods used here have not accounted for increasing weather variability in the future or changes in the distribution and impacts of biotic and other abiotic stresses. These system-level shifts will take place in a context characterised by high population growth rates; the demand for food is projected to nearly triple by the middle of this century. Systems will have to intensify substantially in response, particularly in the better-endowed mixed systems in the region. For the more marginal areas, the variability in yield response, and the variability in households’ ability to adapt, suggest that, even given the limitations of this analysis, adaptation options need to be assessed at the level of the household and the local community, if research for development is to meet its poverty alleviation and food security targets in the face of global change.     

Tuber yield, water and fertilizer productivity in early potato as affected by a combination of irrigation and fertilization

Excessive amounts of irrigation water and fertilizers are often utilized for early potato cultivation in the Mediterranean basin. Given that water is expensive and limited in the semi-arid areas and that fertilizers above a threshold level often prove inefficacious for production purposes but still risk nitrate and phosphorous pollution of groundwater, it is crucial to provide an adequate irrigation and fertilization management. With the aim of achieving an appropriate combination of irrigation water and nutrient application in cultivation management of a potato crop in a Mediterranean environment, a 2-year experiment was conducted in Sicily (South Italy). The combined effects of 3 levels of irrigation (irrigation only at plant emergence, 50% and 100% of the maximum evapotranspiration - ETM) and 3 levels of mineral fertilization (low: 50, 25 and 75 kg ha⁻¹, medium: 100, 50 and 150 kg ha⁻¹ and high: 300, 100 and 450 kg ha⁻¹ of N, P₂O₅ and K₂O) were studied on the tuber yield and yield components, on both water irrigation and fertilizer productivity and on the plant source/sink (canopy/tubers dry weight) ratio. The results show a marked interaction between level of irrigation and level of fertilization on tuber yield, on Irrigation Water Productivity and on fertilizer productivity of the potato crop. We found that the treatments based on 50% ETM and a medium level of fertilization represent a valid compromise in early potato cultivation management. Compared to the high combination levels of irrigation and fertilization, this treatment entails a negligible reduction in tuber yield to save 90 mm ha⁻¹ year⁻¹ of irrigation water and 200, 50 and 300 kg ha⁻¹ year⁻¹ of N, P₂O₅ and K₂O, respectively, with notable economic savings for farmers compared to the spendings that are usually made.     

Empirical assessment of water management institutions in northern China

We examine the development of irrigation management in northern China using data from village and household panels. During the past decade, reform-oriented institutions, such as water user associations and contracting, have largely replaced the traditional institution of collective management in village-level irrigation systems. A feature unique to China is that water user associations and contractors are provided with monetary incentives to save water. Water user associations have not yet achieved the broad-based participation of farmers that some advocates consider as a primary goal for forming the associations. Many village leaders serve also as the leaders of water user associations, thus possibly reducing opportunities for receiving operational input and policy direction from farmers. However, we observe improved performance of irrigation systems managed by water user associations, relative to collective management, in terms of maintenance expenditures, the timeliness of water deliveries, and the rates of fee collection. Performance has improved also in systems managed by contractors, although not as substantially as in the case of water user associations.     

Agro-environmental evaluation of irrigation land: I. Water use in Bardenas irrigation district (Spain)

Non-point agrarian contamination makes its allocation to a specific territory difficult. This first part of the study seeks to analyze contamination resulting from water use in 54,438 ha of Bardenas irrigation district included in the Arba basin (BID-Arba). To this end, water balances were carried out in BID-Arba by means of measuring or estimating the main inputs, outputs and water storage between 1 April 2004 and 30 September 2006. Also, the spatial-temporal variability in water use was analyzed.The semester error balances were acceptable (between 11% and −6%), which permits the attribution of the mass of pollutants exported in drainage to the irrigation area evaluated, the objective of the second part of the study. Irrigation efficiency (IE) in BID-Arba was high (90%) despite the fact that Irrigation Sub-District VII (ISD-VII), with considerable flood irrigation drainage (27%), and ISD-XI with considerable losses due to evaporation and wind drift in sprinkler irrigation systems (15%), brought down the average (IE_VII = 73%; IE_XI = 83%). Irrigation management was inadequate as there was a water deficit (WD) of 9%, partly affected by the 2005 drought (WD_{Apr-05/Sep-05} = 21%) and the low irrigation doses applied in ISD-XI (WD_XI = 12%).To sum up, intense re-use of water caused a water use index (percentage of water used by the crops) of 85% which surpassed 90% in periods of drought. Nevertheless, irrigation management should be improved in order to annul the water deficit and to maximize the productivity of the agrarian system.     

柳州市郊县灌溉水养分元素含量

本文研究了柳州市郊柳江、柳城和来宾三县的灌溉水养分元素含量和pH值。含氮0.52～0.87mg/L,磷0.003～0.024mg/L,钾0.81～1.19mg/L,钠0.99～1.52mg/L,钙29.44～73.28mg/L,镁5.14～17.20mg/L,硫1.02～1.60mg/L,氯2.68～7.40mg/L和氟0.15～0.24mg/L。pH8.33～8.44。在9种元素中,硫随季节变化比较明显。钾、钠、镁和硫、氯随流程增长含量增加。     

OSIRI: A simple decision-making tool for monitoring irrigation of small farms in heterogeneous environments

A new decision-making software tool for sprinkler or drip irrigation scheduling and monitoring, was developed at the request of small scale sugarcane (Saccharum spp.) farmers in Reunion Island (France) facing variable climate and soil conditions. Based on a simple water balance simulation model coupled with a comprehensive set of decisions rules, OSIRI was designed to provide farmers with targeted advices on discrete units of irrigation and for simulating scenarios of irrigation systems to optimize their performance. An optional procedure of direct adjustment by farmers and a system of controlled irrigation rationing are proposed. To meet the producer needs, the number of input parameters is adapted to the rather limited data availability, and the recommendation sheet is user-friendly oriented. Field data confirmed that OSIRI simulates very reasonably well actual evapotranspiration and drainage below the sugarcane root zone. Also, OSIRI allowed to save about 30% of irrigation delivery on a 140-day period as compared to the currently used crop water requirement method (respectively, 165 and 240 mm of water), without significant decrease in yield (respectively, 102 and 101 T ha⁻¹).     

Yield and quality response of drip irrigated broccoli (Brassica oleracea L. var. italica) under different irrigation regimes, nitrogen applications and cultivation periods

The experiment aimed at evaluating the yield and quality response of broccoli (Brassica oleracea L. var. italica) to applied irrigation water and nitrogen by drip irrigation method during the spring and autumn cultivation periods of 2007. Irrigation water was applied based on a ratio of Class A pan evaporation (k_cp = 0.50, 0.75, 1.00 and 1.25) with 7 days interval. Also, the effect of four nitrogen levels (0 kg ha⁻¹, 150 kg ha⁻¹, 200 kg ha⁻¹ and 250 kg ha⁻¹) was compared with each treatment. The seasonal evapotranspiration in the treatments varied from 233 mm to 328 mm during the spring period and from 276 mm to 344 mm during the autumn period. The highest broccoli yield was obtained in the spring period as 11.02 t ha⁻¹ and in the autumn period as 4.55 t ha⁻¹. In general, there were statistical differences along nitrogen does with respect to yield and yield components while there were no statistically significant differences in the yield and yield components among irrigation regimes. Both yield and yield parameters in the spring period were found to be higher than that of the autumn period due to the low temperature and high rainy days in autumn. Irrigation water use efficiency (IWUE) ranged from 3.78 kg m⁻³ to 14.61 kg m⁻³ during the spring period and from 1.89 kg m⁻³ to 5.93 kg m⁻³ during the autumn period. On the other hand, nitrogen use efficiency (NUE) changed as 37.32-73.13% and 13.08-22.46% for spring and autumn season, respectively.     

发展我国设施农业节水灌溉技术的对策研究

大力推广农业节水灌溉，是从根本上解决我国农业缺水问题的重要措施。在设施农业上大力推广现代节水灌溉技术，将更有利于我国节水农业的稳步发展。本文分析了我国农业的特点和面临的水资源短缺的严峻状况；回顾了国内外设施农业的发展形势和节水灌溉技术与设备的应用现状；提出设施农业实施节水灌溉的重要性和今后大力发展设施农业节水灌溉技术的对策。