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Chapter 1
Introduction

The ‘Agro-ecological Land Resources Assessment for Agricultural Development Planning’, is a study concerned with the development and implementation of national level methodology for the determination of land use potentials of land resources of individual districts for policy formulation and development planning. This Kenya case study has been carried out by FAO and IIASA in collaboration with the Government of Kenya (FAO 1984).

The complete work is described in a main report entitled: Resources Data Base and Land Productivity.

This main report are supported by technical annexes which deal with relevant methodological details and analysis.

This report, Technical Annex 8, presents quantitative results of the crop productivity assessment for Kenya, carried out at the International Institute for Applied Systems Analysis (IIASA) in the context of the above mentioned work programme. The climatic and soil resources inventory upon which the analysis rests is described in Technical Annex 1. The paper is subdivided into three chapters. Chapter 1 will give a brief overview of the software package. Then, in Chapter 2, the methodology and the resource data base underlying the crop productivity assessment is summarized. Chapter 3 begins with an illustrative example of the computations involved, and briefly discusses and presents crop suitability results at the national level. Additional information regarding the coding schemes used in the presentation can be found in Appendix A. Estimates of rainfed arable land and production potential by crop, according to three sets of assumptions, at national, province and district level are contained in Appendixes B to D.

1.1 Overview of the AEZ-CCS Software Package

The software package to be applied in detailed AEZ Country Case Studies (AEZ-CCS) consists of a set of five central computer programs which are required for applying the various steps of the AEZ methodology, accompanied by a suite of supplementary computer programs related to various aspects of data preparation, scenario analysis and graphical presentation of results.

The first program, AEZCCS01, converts the coded country specific productivity assessment rules, e.g. soil unit rating, fallow requirement tables, etc., from a format adequate for human use into a file format more suitable for rapid access and processing by computer.

FIGURE 1
Overview of AEZ-CCS Software Package

Figure 1

Then, program AEZCCS02 sets up tables of constraint-free attainable potential crop yields in relation to the parameters of the climatic resource inventory, length of growing period zone and pattern of growing period zones. This approach has been chosen to guarantee flexibility and to allow for refinement and adaptation of the methodology when such need arises.

Program AEZCCS03 processes the records of the land inventory and calculates for each location (agro-ecological cell) production potential by primary crop as well as crop combinations according to the AEZ land productivity assessment principles. Application of these rules yields an average productivity factor relative to the maximum attainable yield of a particular crop. For each crop/crop combination and each location a productivity loss factor, accounting for water erosion hazard and soil degradation, is quantified. The program generates an intermediate data file, containing cell information and crop combination records, which forms the basis for assessing district/regional and nation-wide policy scenarios.

Program AEZCCS04 reads the intermediate output file from the land productivity assessment (program AEZCCS03) and generates the input file for a linear program according to the specifications given in a scenario control file. The LP specification file is generated in standard MPS file format.

Finally, program AEZCCS05 re-reads the output file from the AEZ land productivity assessment (program AEZCCS03) and the LP solution file generated by a standard LP package to print out summary tables at a level of detail as indicated in the control file. The LP package is assumed to be available on the respective installation. In our tests of the AEZ-CCS software package a slimmed ‘LP only’ version of MINOS, a large scale non-linear programming system (see Murtagh and Saunders, 1977), was used to solve for an optimal cropping pattern in relation to the specified scenario objectives and constraints. Formulating and running scenarios using the optimization modules is a subject for a separate report. Figure 1.1 provides an overview of the information flow in the AEZ-CCS software package.

In addition to the above mentioned computer programs there is a growing number of utility programs of various kinds related to :

-   compilation of the land resources inventory from GIS

-   statistical analysis and cross tabulation of the resource inventory

-   aggregation of district level results to province and national level

-   crop suitability assessment and production potential

-   back-transformation of district/national scenario results to spatial representation (GIS)

-   color display of results and resource data base in map form

Before turning to more complex tasks as implied by national policy planning, valuable information about the resource endowment of a country regarding agricultural production potential can be obtained by assessing the extents of land and their average suitability to producing individual crops. To this effect, all included crop types, grasses and fuelwood species are evaluated in each of the more than 90000 agro-ecological cells, thereby quantifying potential arable extents in terms of five quality classes and corresponding minimum, average and maximum production. Where possible and relevant, sequential (mono) cropping sequences are constructed to assess the full production potential in areas with long growing periods. In each agro-ecological cell a ‘reasonable’ agricultural land use is determined, considering crop suitability and production stability, to derive district level estimates of rainfed arable land. Hence, this Technical Annex is concerned with the fourth item in the above list of utility programs surrounding the AEZ-CCS package, crop productivity assessment and production potential.


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