‘Microbigation’: delivery of biological control agents through drip irrigation systems

The uniform and precise application of microbial particles close to the target organism and to the plant to be protected can increase the success of a biological control treatment. The use of systems or technologies which are usually available in agriculture could influence the acceptability of biocontrol agents by farmers, and enlarge the market. A pilot system was realized using dripper lines, drippers, filters and other tools commonly used in irrigation and precision agriculture in the greenhouse to evaluate their suitability for applying and distributing microbial biocontrol agents. Conidial suspensions of marketed or marketable agents were used, i.e. Fusarium oxysporum, F. solani, Trichoderma harzianum and Paecilomyces lilacinus. The experiments carried out demonstrated that conidial suspensions (10⁶ conidia ml⁻¹) can pass through the drippers without causing clogging, regardless of their size, and remained viable. The term ‘microbigation’ is here proposed for this kind of microbial application technique.     

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.     

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.     

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.     

Coordination in irrigation systems: An analysis of the Lansing–Kremer model of Bali

Farmers within irrigation systems, such as those in Bali, solve complex coordination problems to allocate water and control pests. Lansing and Kremer’s [Lansing, J.S., Kremer, J.N., 1993. Emergent properties of Balinese water temples. American Anthropologist 95(1), 97–114] study of Balinese water temples showed that this coordination problem can be solved by assuming simple local rules for how individual communities make their decisions. Using the original Lansing–Kremer model, the robustness of their insights was analyzed and the ability of agents to self-organize was found to be sensitive to pest dynamics and assumptions of agent decision making.     

A conceptual model for analysing input–output coefficients in arable farming systems: from diagnosis towards design

Environmental legislation is forcing a rethink about desirable crop production systems. The development of new production systems that meet economic and environmental objectives demands knowledge about which input–output combinations are feasible and optimal in practice. A review of concepts in agronomy and in farm and behavioural economics leads to a conceptual model with a division into production levels and accompanying production restricting factors. The highest production level can be defined by merely agronomic growth factors; the next production level is restricted by a mixture of economic and other agronomic factors. The two lowest levels are further restricted by taking into account the socio-psychological factors. With the production restricting factors of the conceptual model the differences in agronomic efficiency of actual and theoretical input–output combinations will be analysed in order to find out which input–output combinations will be feasible and optimal in practice.     

Forage options for smallholder crop–animal systems in Southeast Asia: working with farmers to find solutions

Most research and development involving forages in Southeast Asia has been directed towards impacts in commercial farming systems. Little adoption of forages has occurred in smallholder livestock systems, which account for the vast majority of the livestock in the region. The main reason for this lack of adoption is the linear processes that have been used to develop forage technologies on research stations leading to the extension of ‘finished' technology packages. This paper describes existing uses of forages in Southeast Asian farming systems and, using a recent case study, describes the potential for developing smallholder forage systems using participatory approaches to technology development.     

Simulation of peak-demand hydrographs in pressurized irrigation delivery systems using a deterministic–stochastic combined model. Part I: model development

This study describes a model named HydroGEN that was conceived for simulating hydrographs of daily volumes and hourly flow rates during peak-demand periods in pressurized irrigation delivery networks with on-demand operation. The model is based on a methodology consisting of deterministic and stochastic components and is composed of a set of input parameters to reproduce the crop irrigation management practices followed by farmers and of computational procedures enabling to simulate the soil water balance and the irrigation events for all cropped fields supplied by each delivery hydrant in a distribution network. The input data include values of weather, crop, and soil parameters, as well as information on irrigation practices followed by local farmers. The resulting model outputs are generated flow hydrographs during the peak-demand period, which allow the subsequent analysis of performance achievable under different delivery scenarios. The model can be applied either for system design or re-design, as well as for analysis of operation and evaluation of performance achievements of on-demand pressurized irrigation delivery networks. Results from application of HydroGEN to a real pressurized irrigation system at different scales are presented in a companion paper (Part II: model applications).     

Simulation of peak-demand hydrographs in pressurized irrigation delivery systems using a deterministic–stochastic combined model. Part II: model applications

A deterministic–stochastic combined model named HydroGEN was developed, as described in a companion paper (Part I: Model development), to enable the simulation of demanded daily volumes and hourly flow rates during peak periods in pressurized irrigation delivery networks. The model was applied to a pilot large-scale irrigation system located in southern Italy for calibration and for testing its reliability in analyzing the operation of large-scale pressurized delivery systems through the simulated flow configurations. Daily input data on rainfall, temperature, solar radiation, wind speed and relative humidity were gathered from a meteorological station located within the study area, whereas information on local irrigation management practices were collected through interviews with farmers and from extension specialists. The model was tested at different management levels, from district to sector and hydrants. The model testing was supported by the use of high-resolution remote-sensing imagery acquired on a single overpass date in 2006 and then classified and recoded following a ground-truthing campaign conducted during the same year. Simulations were performed to identify the 10-day peak-demand period and to generate the hydrographs of daily volumes and of hourly flow rates. Results from the different simulations were compared with historical datasets of irrigation volumes and discharges recorded during the 2008 and 2009 seasons at the upstream end of the irrigation network under study, at a sector level during the 2007 season and at selected delivery hydrants during the 2005 season. Some discrepancies between simulated and recorded data were noted that can be related to small errors in estimating crop and soil parameters, application efficiency at field level, as well as to large variability in irrigation management practices followed by local farmers. Overall, the results from testing showed that the model is capable of forecasting with good accuracy the timing of peak-demand periods, the irrigation volumes demanded during the season, as well as the hydrographs of daily volumes and hourly flow rates withdrawn by farmers during these peak-demand periods, especially when it is applied to large multi-cropped command areas.     

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.     

Estimating in situ soil–water retention and field water capacity in two contrasting soil textures

A priori knowledge of the in situ soil field water capacity (FWC) and the soil-water retention curve for soils is important for the effective irrigation management and scheduling of many crops. The primary objective of this study was to estimate the in situ FWC using the soil-water retention curve developed from volumetric water content (θ), and water potential (ψ) data collected in the field by means of soil moisture sensors in two contrasting-textured soils. The two study soils were Lihen sandy loam and Savage clay loam. Six metal frames 117 cm × 117 cm × 30 cm high were inserted into the soil to a depth of 5–10 cm at approximately 40 m intervals on a 200 m transect. Two Time Domain Reflectrometry (TDR) sensors were installed in the center of the frame and two Watermark (WM) sensors were installed in the SW corner at 15 and 30 cm depths to continuously monitor soil θ and ψ, respectively. A neutron probe (NP) access tube was installed in the NE corner of each frame to measure soil θ used for TDR calibration. The upper 50–60 cm of soil inside each frame was saturated with intermittent application of approximately 18–20 cm of water. Frames were then covered with plastic tarps. The Campbell and Gardner equations best fit the soil–water retention curves for sandy loam and clay loam soils, respectively. Based on the relationship between soil ψ and elapsed time following cessation of infiltration, we calculated that the field capacity time (t _FWC) were reached at approximately 50 and 450 h, respectively, for sandy loam and clay loam soils. Soil-water retention curves showed that θ values at FWC (θ _FWC) were approximately 0.228 and 0.344 m³ m⁻³, respectively, for sandy loam and clay loam soils. The estimated θ _FWC values were within the range of the measured θ _FWC values from the NP and gravimetric methods. The TDR and WM sensors provided accurate in situ soil–water retention data from simultaneous soil θ and ψ measurements that can be used in soil-water processes, irrigation scheduling, modeling and chemical transport.     

The origin and hazard of inputs to crop protection in organic farming systems: are they sustainable?

Sustainability is defined as the ability of a system to ‘continue’. In view of this definition, several aspects of the crop protection activity in organic farming are reviewed according to their ability to ‘continue’. As no absolute measure of sustainability is available, this analysis takes the form of a comparison between organic and conventional crop protection methods. Two elements of crop protection are considered: one being the source of the inputs to crop protection and the other being the environmental hazard of the chemicals used in crop protection. In addition, the sustainability of some of the wider issues related to crop protection methods in organic farming are discussed. It is concluded that organic farming systems are not sustainable in the strictest sense. Considerable amounts of energy are input to organic farming systems, the majority of the compounds utilised in crop protection are derived from non-renewable sources and incur processing and transport costs prior to application. Further, these compounds are not without toxicological hazards to ecology or humans. Despite these problems, it is concluded that organic farming is probably more sustainable than conventional farming in a bio-physical sense. However, an assessment of the overall sustainability of farming systems may depend upon the valuation given by society to their inputs and outputs, and in this sense it is extremely difficult to assess which farming system is most sustainable.     

Is IWRM achievable in practice? Attempts to break disciplinary and sectoral walls through a science-policy interfacing framework in the context of the EU Water Framework Directive

The word ‘integrated’ is prone to different interpretations in relation to various disciplines and sectors. When approaching operational water management, one would dream that integration would encompass effective links between scientific disciplines and technical features, with a good knowledge of interactions among different environmental compartments (land/water, terrestrial/coastal, surface/groundwater etc.), of pollution pathways, of various pressures and impacts (including from climate change) etc. The world of management effectively involves many different actors, representing different economic sectors (e.g. agriculture, industry), the civil society, stakeholder organisations, including the representation of citizens, and it is often (wrongly) thought that any kind of decision-making is carried out in an agreed and harmonious way. The theory is at least paved through IWRM principles as they are conceived within the framework of the EU Water Framework Directive (WFD), so we might say that we have actually no choice but to make it work!! But what is the reality in practice? The difficulty is to consider mandatory policy obligations on the one side, technical feasibility and scientific knowledge on the other side, and reflect whether and how these can be properly interfaced. This has been the subject of dynamic discussions within the past 6 years in the framework of EU-funded research projects aiming to support policy WFD developments and implementation. One of the key conclusions of these discussions among scientists, policy-makers and stakeholders underlined the need to develop a conceptual framework for a science-policy interface related to water, which would enable to gather various initiatives and knowledge. This paper discusses on-going developments in this field with an European perspective.     

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.     

Intensive versus low-input cropping systems: What is the optimal partitioning of agricultural area in order to reduce pesticide use while maintaining productivity?

Pesticide use should be reduced for sustainable agriculture. Low-input cropping systems, centered on hardy varieties that maintain their yield in the presence of pests, allow pesticide use to be reduced. Since yield potential is generally lower for hardy varieties than for high-yielding varieties, a balance must be found between production and pesticide reduction. In order to compute the optimal partitioning of agricultural area between intensive and low-input cropping systems, we present a model that allows yield and gross margins to be computed at the landscape scale, as a function of the proportion of the area under intensive and low-input systems. The model shows that two cases must be distinguished, depending on inoculum production by each of the coexisting systems. If the low-input system produces less inoculum (e.g. because resistant varieties are used), coexistence can be optimal, whereas if the low-input system produces more inoculum (e.g. because tolerant varieties are used), it is best to devote the whole area to a single system. The model gives the gross margin for each cropping system as a function of the proportion of low-input systems - and so predicts the proportion to which the farmers’ choices will lead - and illustrates the use of different (simplified) policies that would ensure that the optimum proportion is reached.     

Application of confined aquifer theory for verification of solutions of water flow towards a drain in saturated–unsaturated soil

The method for verification of numerical solution of water flow towards a drain in homogeneous soil under steady rainfall or steady irrigation recharge is presented in the paper. In 1979, Zaradny and Feddes proved that the accuracy of the numerical result depended, among other things, on the size and pattern of discretization applied. Ibidem, a partly verification of numerical solution was presented. It was based on the Thiem–Dupuit well formula and on the hodograph solutions given by Van Deemter [Van Deemter, J.J., 1950. Versl. Landb. Onderz. 56 (7), 1–67] and Childs [Childs, E.C., 1959. J. Soil Sci. 10 (1), 83–100]. Up till now, there was no full verification of this solution. The proposed method which depends on replacement of the drain by horizontal ‘well’ in a confined aquifer of a constant thickness, the geometry of which in the x–z plane is compatible, in shape and size, with saturated zone in the numerical solution gives the possibility of such verification. For this problem groundwater flow can be described by the Laplace equation. The analytical solutions for the hydraulic head φ and the stream function ψ, specification of boundary conditions for the considered problem and the method of determination of the Fourier series constants are given in the paper. Presented results confirm the correctness of numerical solution given by Zaradny and Feddes [Zaradny, H., Feddes, R., 1979. Agric. Water Manage. 2, 37–53] and they also show that when verification with respect to observed and measured data is impossible, such tests should be performed.