Modeling nitrogen cycling in tomato–safflower and tomato–wheat rotations

The use of crop models to simulate the nitrogen (N) cycle in crop rotations is of major interest because of the complexity of processes that simultaneously interact. We studied the performance of the Erosion Productivity Impact Calculator (EPIC) model in simulating the N cycle in two different rotations under irrigation: tomato (Lycopersicon esculentum Mill.)–safflower (Carthamus tinctorius L.) and tomato–wheat (Triticum aestivum L.). Processing tomatoes were grown on raised beds and furrow irrigated in 1994 in the Sacramento Valley of California, USA. Safflower and wheat were grown in 1995 and 1994–95, respectively, after the previous tomato crop. A data set from safflower grown on different plots in 1994 was used to calibrate the model for this crop. The model accurately predicted the yield, biomass and N uptake of the crops in the rotation. Soil inorganic N was also accurately simulated in the two rotations. The model predicted important amounts of N leached during the winter period of 1994–95 due to the heavy rainfall. The model was used to explore the influence of rotation type (tomato–safflower or tomato–wheat) and irrigation type (fixed amounts and dates or flexible automatic irrigation). Simulation results of the two rotations during 10 years (1986–95) predicted average losses by leaching higher than 200 kg N ha⁻¹ for each rotation period, irrespective of the rotation type. Losses were more important during the fall–winter and increased as rainfall increased above a threshold rainfall of 300 mm. The flexible automatic irrigation resulted in lower N leached during the tomato crop season. Simulation results indicated that a fallow period during the fall–winter following processing tomatoes should be avoided because of the high risk of N leaching losses. The introduction in the rotation of a deep-rooted crop, such as safflower, grown with low irrigation, drastically reduced the risk of N leaching during the following fall–winter period, without substantial yield reductions.     

Analysis of several discharge rate–spacing–duration combinations in drip irrigation system

In order to study the use of water irrigation in a rational way, several combinations of discharge rate, irrigation duration and inter-emitter distances were tested. For instance, three dripper spacings of 30, 50 and 70 cm which delivered water volumes of 4, 8 and 16 l per dripper, respectively, and three discharge rates of 2, 4 and 8 l/h for each spacing, were applied.An overlapping of the wetted bulbs was observed at the end of the different irrigation experiments. The inter-dripper root-zone had an average water content of 45% and a coefficient of uniformity of 90%.The discharge rate of 2 l/h applied to a 70 cm dripper spacing was characterised by water losses of 15% due to the significant irrigation duration (8 h).From this study, we reach the following conclusions, specific to the soil type and practical culture.

• 1.The maximum irrigation duration does not exceed 4 h.
• 2.Two hours durations can be used for the different spacings, each of which was characterised by its own discharge rate.

     

Tank performance and multiple uses in Tamil Nadu,South India–comparison of 2 time periods (1996–97 and 2009–10)

Irrigation tanks in India are common property resources. Tanks provide not only for irrigation, but also forestry, fishing, domestic water supply, livestock, and other uses. Using empirical results from a study of tank performance from 80 tanks in Tamil Nadu, South India in two time period: 1996-97 and 2009-10, this paper evaluates tank irrigation system performance in terms of economic output and revenue generation forirrigation and other uses. The results indicate that irrigation and other productive uses put together raised the total value of output at tank level by 12 % in 1996-97 and just 6 % in 2009-10. This may suggest that tank multiple use values are small and getting smaller, and therefore not worth consideration. However, it was also found that, while declining in absolute terms, non-irrigation uses provided the majority of tax revenues and still more than cover government's operation and maintenance expenditure (O&M) budget. This finding provides another reason to consider multiple use values and their linkage with overall system viability.     

A GIS-based approach for up-scaling capillary rise from field to system level under soil–crop–groundwater mix

Capillary rise represents an often neglected fraction of the water budget that contributes to crop water demand in situations of shallow groundwater levels. Such a situation is typical in irrigated areas of Central Asia where water from capillary rise is exploited by farmers to meet production targets in Uzbekistan under uncertain water supply. This leads to higher water inputs than needed and creates a vicious cycle of salinization that ultimately degrades the agricultural land. In this study, capillary rise is quantified at different spatial scales in the Shomakhulum Water Users Association (WUA), situated in the southwest of Khorezm, Uzbekistan. The mathematical model HYDRUS-1D was used to compute the capillary rise at field level for three major crops (cotton, wheat and vegetables) on six different hydrological response units (HRUs). These six HRUs having homogenous groundwater levels (1–2 m beneath the soil surface) and soil texture were created using GIS and remote-sensing techniques. Capillary rise from these HRU was then up-scaled to WUA level using a simple aggregation approach. The groundwater levels simulated by FEFLOW-3D model for these HRUs in a parallel study under four improved irrigation efficiency scenarios (S-A: current irrigation efficiency or business-as-usual, S-B: improved conveyance efficiency, S-C: increased application efficiency and S-D: improved conveyance and application efficiency) were then introduced into HYDRUS-1D to quantify the impact of improved efficiencies on the capillary rise contribution. Results show that the HRUs with shallow groundwater-silt loam (S-SL), medium groundwater-silt loam (M-SL) and deep groundwater-silty clay loam (D-SCL) have capillary rise contribution of 28, 23 and 16 % of the cotton water requirements, 12, 5 and 0 % of the vegetable water requirements and 9, 6 and 0 % for the wheat water requirements, respectively. Results of the scenarios for the whole WUA show that the maximum capillary rise contribution (19 %) to the average of all crops in the WUA was for the S-A scenario, which reduced to 17, 11 and 9 % for S-B, S-C and S-D, respectively. Therefore, it is recommended that before any surface water intervention or drainage re-design, water managers should be informed about the impacts on groundwater hydrology and hence should adopt appropriate strategies.     

Comparing Penman–Monteith and Priestley–Taylor approaches as reference-evapotranspiration inputs for modeling maize water-use under Mediterranean conditions

A comparison between experimental and simulated data, considering the Priestley–Taylor (PT) and Penman–Monteith (PM) reference-evapotranspiration (ET₀) approaches was carried out. Experimental data, obtained from an irrigation assessment, conducted during the 1995 and 1996 maize growth-seasons at Zaragoza, Spain, was compared to the mechanistic-model SWAP simulation-results, considering each of the ET₀ calculation approaches in the model input. Soil hydraulic properties, meteorological data, seeding and harvest dates, crop water management and other experimental data were used as SWAP input. As corresponding to the windy and dry conditions found in many Mediterranean landplanes, PT-ET₀ values were significantly lower than PM-ET₀ calculations. Furthermore, simulated actual evapotranspirations considering the PT approach (PT-ET_c) were lower than those found in the simulations that consider the PM approach (PM-ET_c). Correspondingly, simulated drainage flux and soil water contents were higher when the PT-ET₀ approach was used. The correlation coefficients between simulated and measured actual maize evapotranspirations and soil water contents were statistically significant, but the same for both ET₀ calculation approaches. Mean and median differences between actual and simulated maize water-use were not statistically different from zero for both considered ET₀ calculation approaches. Experimental data variability was significantly higher than simulated variability. The comparisons among the evaluated irrigation options, made with the experimental water-use data, lead almost to the same conclusions than those achieved from the simulated maize water-use. Considering PM-ET_c rather than PT-ET_c yields no statistical difference in the modeling-based conclusions. According to the obtained results, the PT approach could be used under Mediterranean conditions for comparative assessments aimed to support irrigation decision-making.     

Assessment of the parameters of a mechanistic soil–crop–nitrogen simulation model using historic data of experimental field sites in Belgium

Intensification of the agricultural sector and the increase in quantity and decrease in quality of municipal and industrial wastewater, in particular during the past decades, resulted in many industrial countries, such as Belgium, in a sharp degradation of surface water and groundwater. To control the current degree of contamination and reduce the environmental impact of the agricultural sector, the Flemish government recently introduced a number of regulations aiming at controlling the use of nitrogen fertilisers. To facilitate the implementation and the control of the new regulations, threshold values of allowable doses of organic and inorganic nitrogen fertilisers, and their spreading in time were made soil independent. As the soil physical, chemical and biological response depends on the geohydrology of the site and the past fertilisation practice, fertiliser standards applied on different soil–crop systems result in different leaching patterns.To assess the effect of the soil on the nitrogen leaching, a number of past experimental field trials were analysed using the WAVE model as modelling tool for the reconstruction of the nitrogen dynamics. As a first step in the study, the historic data of the field experiments were used to calibrate and validate the WAVE model. The deterministic calibration and validation of the WAVE model yielded a set of model parameters for the examined soil–crop–fertiliser practice conditions. The bottlenecks in the calibration were the nitrogen mineralisation parameters and the initialisation and subdivision of the soil organic matter over the different organic pools. The model validation, being the second step in the study, revealed the power of the WAVE model to predict the evolution and transformations of nitrogen in the soil profile and the leaching of nitrate at the bottom of the root zone. In a third step, the WAVE model was used in a scenario-analysis exercise to examine the factors effecting the amount of nitrate leached at the bottom of the root zone. This analysis revealed that the nitrate leached out of the soil profile is controlled by the fertiliser practice, the rainfall depth and its distribution, the soil texture, the soil mineralisation capacity and the past fertilisation practice.     

Crop–animal interactions in mixed farming systems in Asia

The integration of crop and animal production is well developed in the farming systems of Asia, particularly those in small-scale agriculture. There is marked complementarity in resource use in these systems, with inputs from one sector being supplied to others. Specific examples of the main crop–animal interactions are given for different countries, and reference is made to the results of a number of case studies. These have demonstrated the important contribution that animals make to increased production, income generation, and the improved sustainability of annual and perennial cropping systems.     

Crop–animal systems in Asia: implications for research

The importance of crop–animal systems in Asia, the multiple roles played by animals and the opportunities for increasing their contribution to these systems justifies continued research effort. An assessment of the role of livestock in mixed farming systems in 14 countries has identified priority systems, technical constraints and weaknesses in the national organisations. Future research needs to focus on the rain-fed production systems, where most of the livestock are found. There is an overriding need for a farming systems perspective to the research agendas that involves inter-disciplinarity and community-based participation. Such an approach will be more complex, require concentrated effort and more efficient resource use, but will be associated with considerable benefits due to a greater integration of effort.     

基于OKR–KPI模式的电网企业绩效管理探索

正党的十九大提出"培育具有全球竞争力的世界一流企业",没有一流的管理就没有一流的企业,建设世界一流企业必须加快提升企业管理水平。地市级电网企业深入贯彻党的十九大精神,加快推动企业高质量发展,全力创建世界一流电网企业的战略目标,创新企业绩效管理模式,将体量规模优势转化为高质量发展优势,用高质量电网支撑服务地区建设。本文开展电网企业组织绩效管理     

Environmental–economic decision-making in lowland irrigated agriculture using multi-criteria analysis techniques

The continuing debate on sustainability has raised wide concerns towards integration of environmental and economic aspects into the development decision-making process. This paper develops a framework for environmental–economic decision making that includes the environmental and economic sustainability criteria, and local people's preferences in the context of a lowland irrigated agriculture system using multi-criteria decision-making techniques. Several criteria, such as land capability/suitability, energy input/output ratio, water demand and environmental costs, are considered as environmental sustainability criteria. Economic sustainability is measured from farmers', governments and societal viewpoints using extended cost-benefit analysis. The Geographic Information System (GIS) technique has been used to evaluate spatial sustainability criteria. The involvement of local people at various levels of the decision- making process is emphasized and their opinions are sought in the decision-making process using a two-stage field survey. The results of the multi-criteria analysis combining both environmental and economic sustainability criteria are discussed, and economic incentives for sustainable intensification of lowland irrigated agriculture are outlined.     

Availability and use of feed resources in crop–animal systems in Asia

Feed resources and nutrition constitute the principal technical constraints to ruminant production in Asia. Four main categories of feed resources are potentially available for use in smallholder crop–animal systems. These are pastures (native and improved grasses, herbaceous legumes and multi-purpose trees), crop residues, agro-industrial by-products (AIBPs), and non-conventional feed resources (NCFRs). Priorities for the use of crop residues in terms of nutrient potential and animal species are indicated. Of the technologies developed to improve the nutritive value of crop residues, more attention has been given to chemical treatment of cereal straws than to supplementation. However, a failure to demonstrate cost-effectiveness has discouraged on-farm adoption. The production of fodder from food crop systems and the establishment of multi-purpose trees and shrubs are potentially important for insuring adequate feed supplies for ruminants and improving soil fertility, but there has been limited adoption on small farms to date. Equally, there is significant potential for the more effective use of locally-produced AIBPs and NCFRs, all of which are under-utilised currently.     

Water–yield relations and optimal irrigation scheduling of wheat in the Mediterranean region

Crop yield is primarily water-limited in areas of West Asia and North Africa with a Mediterranean climate. Ten years of supplemental irrigation (SI) experiments in northern Syria were conducted to evaluate water–yield relations for bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L.), and optimal irrigation scheduling was proposed for various rainfall conditions. The sensitive growth stages of wheat to water stress were from stem elongation to booting, followed by anthesis, and grain-filling. Water stress to which crop subjected depends on rainfall and its distribution during the growing season; the stress started from early March (stem-elongation stage) or even in seedling stage in a dry year, and from mid-April (anthesis) in an average or wet year. Crop yield linearly increased with increase in evapotranspiration (ET), with an increase of 160 kg for bread wheat and of 116 kg for durum wheat per 10 mm increase of ET above the threshold of 200 mm. Water-use efficiency (WUE) with a yield ≥3 t ha⁻¹ was ca. 60% higher than that with yield <3 t ha⁻¹; this emphasises the importance of that to achieve effective use of water, optimal water supply and relatively high yields need to be ensured. Quadratic crop production functions with the total applied water were developed and used to estimate the levels of irrigation water for maximizing yield, net profit and levels to which the crops could be under-irrigated without reducing income below that which would be earned for full SI under limited water resources. The analysis suggested that irrigation scenarios for maximizing crop yield and/or the net profit under limited land resource conditions should not be recommended. The SI scenarios for maximizing the profit under limited water resource conditions or for a targeted yield of 4–5 t ha⁻¹ were recommended for sustainable utilization of water resources and higher WUE. The time of irrigation was also suggested on the basis of crop sensitivity index to water stress taking rainfall probability and available soil water into account.     

Crop–animal systems in Asia: socio-economic benefits and impacts on rural livelihoods

Traditionally, small farmers in Asia have practiced mixed farming. To improve crop and animal productivity, increase farm incomes and maintain the ecological balance, several technology options have been developed through on-station and on-farm research by international organisations and national agricultural research systems. However, a review of the research reveals a paucity of information, particularly in South Asia, on the socio-economic benefits and impacts of these technologies and interventions for poor farming households. This paper presents the few case studies available which document the benefits of new technologies to improve crop–animal systems. Additionally, the paper suggests reasons for the neglect of socio-economics in these studies, and ways to strengthen this dimension.     

Sustaining rice–wheat system productivity in the Indo-Gangetic plains: water management-related issues

The Indo-Gangetic plains constitute the most important agricultural region in south Asia. From early 1960s to late 1980s, the area under rice–wheat cropping systems in the Indian portion of the plains has grown rapidly and the crop yields have increased resulting in large production gains. The gains were particularly significant in the north-western region covered by the states of Punjab, Haryana, and western Uttar Pradesh although, of late, growth rates have slowed. In comparison productivity levels and growth rates in the eastern region represented by eastern Uttar Pradesh, Bihar and West Bengal have remained low. Water management-related issues pose a major concern to the sustainability of production systems across the region. In the eastern region flooding is widespread, groundwater resources have not been adequately developed and water availability to crops from surface irrigation systems is unreliable and poorly distributed. Over exploitation of groundwater resources and quality degradation are major concerns in sustaining high productivity in the north-western region. Suggestions are made on areas which call for enhanced research efforts.