Project Summary

Soil acidity and nutrient deficiencies limit crop yields in most under developed countries. The consequences of poor yields include food insecurity, economic hardship, further deforestation, and increased soil exposure, erosion and downstream pollution. Upon overcoming soil acidity and nutrient constraints new cropping strategies are possible, products and services are diversified, vegetative soil protection increases and off-site nutrient transport is minimized. This project seeks to integrate and disseminate decision aid tools that will reduce acidity and nutrient limitations to food production and quality by facilitating the process for diagnosing soil constraints and selecting the appropriate management practices for location-specific conditions.

Our strategy is to develop globally applicable, largely computer-assisted, integrated decision aids that will both diagnose and prescribe appropriate solutions to soil nutrient constraints. Tools varying from guides to assist in management decisions at a regional level to those that provide site-specific diagnoses and recommendations will be available for users to select as appropriate to their local conditions. Prior to final release, the capabilities of these integrated decision aids will be tested and refined with the assistance of user groups.

Project activities will be conducted by a multi-disciplinary team of 16 scientists from four U.S. universities in close collaboration with investigators from NARES, IARCS, PVOs, NGOs, agri-business and other CRSP projects. Developmental research will be conducted in selected testing areas, consisting of a representative farming community in each of three agroecological zones. Testing areas provide real life situations that allow joint team efforts in assembling information for knowledge gaps, testing and refining products, and interaction with ultimate beneficiaries of project activities. During the first year social, economic, cultural and resource assessments will be performed in each testing area. Similar assessments in the third and fifth years will help document project impact.

A second type of collaborative effort, extensive evaluation, will focus on a global network of collaborators to evaluate refined products under a variety of conditions. Once suitable product performance is achieved in the testing areas, the extensive evaluators will help clarify the global extent of remaining knowledge gaps and potential adjustments needed for widespread application of products. Collaborators in both testing areas and extensive evaluation will participate in workshops planned for years 1, 2, 4 and 5. The initial workshop will serve as a coordination and planning meeting. Subsequent workshops will focus on obtaining collaborator feedback on performance of product prototypes when applied to their local conditions.

Project Description

General Overview

Soil acidity and nutrient deficiencies limit crop yields in most under developed countries. The consequences of poor yields include food insecurity, economic hardship, further deforestation, and increased soil exposure, erosion and downstream pollution. Upon overcoming these soil nutrient constraints new cropping strategies are possible, economic infrastructure is diversified, vegetative soil protection increases, and off-site nutrient transport is minimized.

The knowledge requirements to properly diagnose and prescribe best management alternatives for location-specific soil acidity and nutrient problems throughout the world exceed the capacity of any human expert. Numerous combinations of crops, social, political, economic and resource conditions must be considered. Scarcity and cost of experts can be alleviated if the required knowledge is organized in a manner accessible to inexperienced personnel. When combined with local data and observations, decision support systems (DSS) make this knowledge available for agriculturalists to choose appropriate management strategies.

This five-year project seeks to integrate and disseminate decision aid tools that facilitate the diagnosis of soil nutrient constraints and the selection of appropriate management practices for location-specific conditions. Once decision-makers have access to tools that make it easier to properly diagnose and manage soil acidity and nutrient constraints, the expected outcome is increased food production and quality.

Objectives

• improve the diagnosis and recommendations for soil acidity and nutrient problems by identifying and resolving knowledge gaps through extensive literature reviews and, when necessary, developmental research;
• develop an integrated computerized knowledge base for diagnosing and recommending practical solutions to soil acidity and nitrogen and phosphorus problems, which considers location-specific differences in resource availability, soil, climate, crop and management factors;
• develop auxiliary tools to the integrated knowledge base to enable agriculturalists to diagnose and solve soil acidity and nutrient problems that predominate within the social, economic and agronomic conditions of their regional domains;

Strategy

A range of decision aids will be available for users to select as applicable to their local conditions. These tools vary from guides to assist in nutrient management at a regional level to those that provide site-specific nutrient diagnoses and prescriptions. The integrated nutrient management decision support system will serve as the core knowledge base from which information is extracted to build auxiliary tools for different purposes and groups.

We perceive the process of developing the integrated core knowledge base and auxiliary tools as a continuous feedback loop among developmental research and outreach activities. Upon the synthesis of existing knowledge the team will gather to formulate options and refine research needs. Prototypes will be assembled, tested, and the team will critique/discuss/improve the prototypes. With each repetiton of this cycle the product approaches desired performance.

Both research and outreach activities are distributed among the two following levels of collaborative effort:

Intensive testing sites are a selected farming community in each of three agroecological zones (semi-arid, wet-dry and humid tropical) where there is significant potential for decision aid tools to be used in addressing soil acidity, nitrogen and phosphorus constraints. Testing sites are real life situations where developmental research will be conducted. The first activity at each site will be a baseline assessment of social, economic and cultural conditions, infrastructure, and nutrient needs. Subsequent activities in research and outreach will be tailored to address the particular soil acidity, nitrogen and phosphorus problems of each site. Decision aid tools will be tested at these sites and refined to provide satisfactory performance.

Extensive evaluation provides the opportunity to test the decision aid tools among a network of collaborators under a variety of global conditions. Although this effort will be concentrated towards the end of the 5-year project, a modest level of interaction with network collaborators is planned for the initial years. Early and continued interaction with network collaborators will clarify the global extent of knowledge gaps and potential adjustments needed for application of products beyond the intensive testing sites.

Decision Support System Development

Team members of this project participated in prior development of individual decision support systems for soil acidity (ADSS), nitrogen (NDSS) and phosphorus (PDSS). These computer-based systems allow users to diagnose individual nutrient problems and evaluate different solutions. With user replies to questions about soils, crops, available nutrient-supplying materials and input-output prices, the programs recommend best management strategies. Feedback from users have identified weaknesses in the knowledge assemblies and information gaps in the knowledge base of these single-constraint systems.

A major challenge in achieving an integrated DSS for soil nutrient magement will be how to address nutrent interactions when prescribing management solutions to the combination of location-specific constraints. An integrated DSS needs to account for conditions wherein economics or availability of lime and fertilizers prevents correction of one or more of the targeted nutrient constraints.

Our DSS development efforts will address two major areas simultaneously:

• Component research- to synthesize, analyze and assemble knowledge required to overcome recognized information gaps in the current ADSS, NDSS and PDSS; and

• DSS integration- to merge the single-constraint DSS into an integrated system.

DSS Component Research

Investigations will address existing information gaps in the DSS knowledge base for the acidity, nitrogen and phosphorus components. Each of these tasks will involve extensive reviews and assembly of existing knowledge in the literature and prior research of the Soil Mangement Collaborative Research Support Program (CRSP) in Africa, Asia and Latin America during the last 10 years. Experiences and recommended practices of our collaborators at both the intensive testing sites and among the extensive evaluation network are of special importance. They often are an important source of unpublished or 'grey literature'. Some of the tasks will involve linkages with commodity research teams at international agriculture research centers and other CRSPs. Once existing information is assembled, it may need to be verified through additional laboratory and field work in both the intensive testing sites and the extensive evaluation network.

Each of the existing DSS prototypes, tasks planned for their improvement and a timiline are briefly described in the following:

Acidity

ADSS diagnoses acidity problems for a targeted crop by comparing the existing ratio between exchangeable aluminum and other exchangeable cations in the soil (Al saturation) with a table of Al saturation values above which there is negligeable crop response to lime. A modified version of the equation developed by Cochrane et al. (1980) is used to estimate lime needs:

CaCO₃ (in t ha^-1) = 1.8[cmol_c kg^-1 of (Al - [TAS(ECEC)/100])

where 1.8 = original empirical factor of 1.5 plus corrections for the average weight-to-volume ratio;

Al = aluminum extracted from the soil with 1 N KCl;

TAS = the critical aluminum saturation for 95% relative yield of the targeted crop; and

ECEC = the sum of exchangeable Al, Ca, Mg and K in the soil.

Users can use default soil data from a database in the program if no site-specific data is available. In recommending lime applications ADSS adjusts the rate for additional factors: depth of incorporation, soil bulk density, use of organic inputs, and lime quality.

A financial analysis of liming the crop is based on a partial budget analysis that includes the cost of lime, transportation and spreading. Costs associated with liming can be applied to a single crop or prorated across subsequent crops. The value of increased crop yield with liming is calculated from estimates of high and low yields for the region. ADSS allows users to evaluate lime needs of a given soil and financial implications for a variety of scenarios with different cropping sequences and available lime materials.

The following areas will be addressed to improve ADSS performance:

• selection of indicators for prediction of Ca and Mg movement from lime applied to surface layers and alleviation of subsoil acidity;
• improved diagnosis and recommendations for soil conditions where crop growth is limited by Ca and Mg deficiencies or excess Mn; and

Timeline for tasks on ADSS

Nitrogen

NDSS estimates the N fertilizer needed for a given crop yield through the following equation:

N needed = [Plant N - (Soil + Manure + Atmospheric N - N loss)]/ N uptake efficiency

where Plant N = the total aboveground plant N requirement for the targeted yield. There is no unifying concept for crop N use efficiency. Rather it is a function of crop, soil, climate, soil mineralization rates and timing, and crop cultural management practices. Similarly, N inputs from soils, organic inputs (green and animal manures) and atmospheric deposition are highly variable as are losses of N (leaching, volatilization, denitrification, and fixation). It is, therefore, difficult to assign transfer coefficients to these processes since there is no effective soil index to measure the quantity of N potentially available to the crop in most tropical regions. As a consequence, transfer coefficients must be calibrated for each new set of conditions or N management decisions must be inferred from cropping history, crop yield potential, climate, soils, and N source.

From calibrated or inferred transfer coefficients, nitrogen recommendations are made for each cropping system. Overlain on this recommendation for optimal nitrogen is a financial analysis to determine the most economical rate of nitrogen given the type of nitrogen fertilizer available, transportation, and spreading costs. Since non-organic nitrogen amendments are rarely available from one cropping season to the next, the analysis is based on application for one cropping season.

Developmental research for NDSS will focus on the following areas:

• acquisition and refinement of coefficients for crup uptake efficiency and mineralization transfer between soil N source compartments under a variety of soils and climate conditions;
• predictions of biologically fixed N contributions by legume crops and its recovery by nonleguminous crops;

• legume management recommendations for efficient use of biologically fixed N in subsequent crops; and
• predictions of losses in N supply through leaching, denitrification and volatilization.

Timeline for tasks on NDSS

Phosphorus

PDSS is in a younger stage of development than DSSs for acidity and N. Diagnostic information is incomplete for many food crops and tree species. For many situations, predicted P requirements are uncertain or undetermined. The present algorithm for resolving a soil P constraint requires three coefficients and two measurements. The coefficients are

1. the proportion of P added to the soil that remains available, as measured by extractable P (buffer coefficient);
2. the critical extractable soil P above which no yield response is expected for the crop under consideration (critical P level); and
3. the rate of decline in extractable soil P with time.

Required measurements are the current level of extractable P in the soil and clay content. Since various solutions are used to measure available soil P, relationships among these extractants are used to convert measured data to a standard value.

Developmental research for PDSS will cover the following areas:

• diagnosis and recommendations for soil and crop conditions where rock P is a preferable source to other P-containing materials;
• diagnosis and prescription of P requirements for tree crops;

• refinement of soil P coefficients used to prescribe P requirements to encompass a broader range of soil and crop conditions; and
• improve recommendations for localized placement of prescribed P.

Timeline for tasks on PDSS

DSS Integration

Nutrient interaction problems are of such complexity that they need to be addressed simultaneously to activities focusing on the individual nutrient modules. A prototype of the integrated DSS will be assembled by the end of the first year, using the existing knowledge base in ADSS, NDSS and PDSS. The initial prototype will be evaluated with location-specific data sets at the intensive testing sites and among a select group of extensive network collaborators. Feedback from this testing will identify weaknesses in the DSS integration process which need refinement.

Intermediate prototype releases are planned for the second and third project years, with incorporation of planned refinements plus additional information synthesized for the acidity, N and P components. The process of prototype evaluation will be repeated with each prototype release. The final version of the integrated soil nutrient management DSS, with incorporation of all developmental research, is planned for the end of the fifth project year.

The integrated DSS software will be complemented by auxiliary tools for local use of the knowledge base under conditons where computers are not available or user interest is in recommended management alternatives and economic analyses for prevailing crop, cultivar, lime and fertilizer materials, and soil conditions for a given region. Format of these tools can include printed materials, decision-making structures, map overlays, GIS, or spreadsheet templates. Feedback from collaborators, upon evaluation of tool prototypes, will determine the most desirable formats.

A series of four workshops will be held in project years 1, 2, 4 and 5 involving both U.S. team members and collabortors from intensive testing sites and the evaluation network. The initial workshop will serve as a coordination and planning meeting. Collaborators will consider whether planned products are relevant to their local needs and suggest modifications or additions. Workshops in years 2, 4 and 5 will focus on collaborator feedback to evaluations of the integrated DSS prototype and auxiliary tools, when applied to their local conditions. Collaborators will be instructed on use of software and auxiliary tools, as well as desirable make-up of local data sets to be used in evaluating these products.

Developmental research for several information gaps in nutrient management will be addressed in conjunction with DSS integration tasks, because they are common to more than one nutrient constraint. The primary tasks are as follows:

• prediction of the value organic amendements to soils as lime and P-supplying materials and the duration of these effects;
• improved prediction of the residual management effects and long-term economic value of lime and fertilizer P applications in cropping sequences; and

• diagnosis of potential nutrient pollution conditions and management recommendations to minimize or remedy such situations.

Timeline for Integrated DSS tasks