24 LAND EVALUATION FOR AGROFORESTRY: THE TASKS AHEAD Anthony Young August 1984 - i - CONTENTS Page ABSTRACT 1 I OBJECTIVE 2 2 THE NATURE AND PURPOSE OF LAND EVALUATION 3 2.1 What is land evaluation? 3 2.2 Procedures of land evaluation 4 2.3 Results of land evaluation 7 3 THE DEVELOPMENT OF LAND EVALUATION METHODOLOGY 8 3.1 Introduction 8 3.2 Rainfed crop production 9 3.3 Forestry 10 3.4 Irrigated agriculture 11 3.5 Livestock production 11 3.6 Scales of survey and kinds of application 12 4 LAND EVALUATION FOR AGROFORESTRY 14 4.1 The need 14 4.2 What is already known? 16 4.3 Problems 18 4.4 Comparison with the diagnosis and design 19 methodology 5 STAGES IN THE DEVELOPMENT OF A METHODOLOGY 24 5.1 An environmental data base 25 5.1.1 General 25 5.1.2 The sites file 26 5.1.3 The requirements file 28 5.2 Land utilization types 31 5.3 Land use requirements 35 5.4 Biophysical models of interactions 43 5.5 Environmental impact and sustainability 45 5.6 Method for comparison between agroforestry 46 and non-agroforestry land utilization types 5.7 Case studies 47 5.8 An international workshop 48 6 THE TASKS AHEAD 48 6.1 Progress to date 49 6.2 Relations with concurrent research 49 6.3 Estimates of productive potential 50 6.4 What can land evaluation offer to agro­ forestry? 51 REFERENCES 53 LIST OF TABLES Page Table 1. The ICRAF environmental data base: example 29 of output from the sites file, to the Summary Level. Table 2. The ICRAF environmental data base: example of 32 output from the requirements file. Table 3. Land qualities relevant to agroforestry: 37 summary. Table 4. Check list of land qualities for agroforestry. 38 LIST OF FIGURES Figure 1. Outline of procedures of land evaluation. 5 Figure 2. Relations between environmental conditions 15 and land utilization types. Figure 3. Simplified structure of the ICRAF environmental 27 data base. LAND EVAI UATION LOR AGR(tIORST'RY: 'IIL TASKS AIILAD Anthony Young AISI RACT The objectives and procedures of land evaluation and the natur'e of the restults obt ained are out,­ lined. The pr'esent st ate of c evelopmenit uf evalua­ tion methodlogy is re'iewed for kinds of land use related to agrororestry: crop product ion. forest,ry and liv'estock production. The stages in1 tihe develop­ ment of a methodology of land evaluation for agro­ forestry are described, namely: arn environmental data base, formulation of appropriate agroforestry land utilization types, determination of land tse require­ ments, construction of biophysical models, assessment of environmental impact and sustainability, method for comparison between agroforestry and non-agro­ forestry land utilization types, and testing through case studies. Land evaluation cizaws upon data from, and interacts with, many other ICRAF projects in ag toforestyIres earch. "lhe pr'incipal outputs ftrot a land evaluation research proglamme will be: (i) a systematic assessment of the en'ironmental suit­ abilities of specified agroforest ry land ut ilization types; (ii) a method for comparison of the suit­ ability, including environmental, economic and social aspects, of land utilization types, both agroforestry and non-agrofo'estry, on different land units. The results will permit qiantitative estimates of the potential contribut ion of agroforestry to sustainable production over specified areas of land. 1 . OBJECT] VF The ob)j('Cti\'e or this paper is to formu late a means by which the approach and methods oF land evaluat ion can be applied to agro­ forestry. It commences with a review of land eva 1uation, first. in its geneva] aspects and secondly as it has been ap)l ied to the component land use elemenits of agroforest ry: crop product i on, forestry and l ivestock product ion. Next comes discussion of the need for land evaluation in ag oforestry and the problems which arise in it.s appl]ication. These accounts lead to the formulation of a set of related activ ities which it,appears practicable to undertake, and which, if successful. will converge towards a methodology for the appli.­ cation of land evaluation to agroforestry. An important element is how the various current activities in agroforestry research in general, and the work of ICRAI: ,iparticular, can contriL ute to the land evaluation activities; and,conversely, how land evaluation fits into the broader sphere of agroforestry research and its application to practical land development. -3­ 2. THE NATURE AND PURPOSE OF LAND EVALUATION 2.1 What is land evaluation? Land evaluation is the process of assessment of land perfor­ mance when used for specific purposes, in order to identify and compare promising kinds of land use. Essentially it is a procedure for comparing land with land use, where land refers to all the factors of the physical environment, including climate, landforms, soils and vegetation. More precisely, land evaluation involves comparison between the environmental requirements of various kinds of land use and the properties possessed by different areas of land. Take, as a simplified example, the growth of a single tree or crop species. Clearly, what grows well in a semi-arid environment will not do so in the rain forest zone, and vice versa. For each plant species there is a range of conditions which are highly favour­ able for its growth, a wider range within which it will grow but not so well, and sets of conditions (e.g. too wet or too dry, too acid or too alkaline) in which it will not grow at all. In the terminolog of land evaluation, these sets of environmental conditions are, res­ pectively, highly suitable, suitable and not suitable for the tree or crop. Many environmental properties, e.g. temperature, moisture availability, soil reaction, drainage, need to be assessed in this way, and account taken of their interactions. There is a second way of looking at the comparison between land use and land, that of taking a specific area of land as the basis. Any given area of land possesses a distinctive set of proper­ ties, of climate, soils, vegetation, etc. Under such conditions there will be some trees or crops which grow very well, some which grow satisfactorily, and othe-swhich fail and die. That is, taking a specific area, it will be found that different plant species are highly suitable, suitable, or not suitable for the environment of that area. The same approach to that outlined above for a tree or crop species considered in isolation can be applied to cropping systems (rotations, intercropping, etc.); to crops grown under specified management conditions (e.g. with or without fertilizer); or to com­ biinat ions bet weeln t ie.., . crops and past ii .. Anty lanid use systlm, descried in as much detail as the int ensi t y or the stcuyv .qui res can e evaluated as to its suitability in different environments. The term employed to 'efer to a def'ined land use system, taken as the sublject of land evaluat ion. is a l andc t i lizat ion type. These simplif'ied examples illu.istrate the potent ial of' land evaluation for answenri og que. t ions of two kinuds: i. For a gi ven kincl olf land use, where are tlie areas to which it is best suited- Hi. For a given area of land, what is the most suitable use? 2.2 Procedures ofr land evaluation The procedures of a land evaluation study are shown in simpli­ fied Form in -ig. 1. They commence with formulation of the objective of the study, frequently within the framework of a land development project. Two parallel sets of activities are then initiated: studies of promising kinds of land use, and surveys of the land. The studies of land use lead to the ident.ification of a range of alternative land use svstems which appear to meet t he objectives and to be rele­ vant bothh to the physical and to tihe social and economic context, of the area. Ihese systems are progressively amplified and refined, leading to their descript.i on as land utilization types. Next, the land use requirements of each land utilization type are identifled; requirements. for example, for temperature regime, moisture, nutrients, so!] erosion hazard, or absence of pests and disease... Each land utilization type has di fferent requirements: for examp]e, each crop reqiui res clifferent climatic and soil con­ dit ions, the soil nutrient requiremeit"s differ according to whether mechanized ori manual harvesting is specified. Parallel with the activities directed towards land use come surveys and specialized studies of the land. The first task is to identiffy and survey relatively homogeneous areas of land, called the land units. This term refers not to a particular scale or type of mapping unit, !ut to any area of" land taken as the basis for - 5 Figurv 1. Outline of' Pi'oc-chives in Land Evaluatinm. Sou'ce: FAO (198ja, p. 27). PLAN ING TIC. EVALUATION - Objectives - Constraints - Data & assumptions - Programme of work LAND IRILIZATION TYPES| ECONOMIC & SOCIAL LAND UNITS ON DATA - Identification - Collection - Identification & - Descrip.ion - Analysis description -Surveys LAND USE REQUIREI-TS LAND QUALITIES & CHAR.ACTERI STICS For specified purposes - !;election as required by land - 3urvsys and speci­ utilization typeG alined studies COMPARI SOI OF LAND USE WITH LAND - Matching - Environmental impact - Economic & social analysi a - Land suitability classification 'RFSETATION OF REULTS - Descriptions of land utilization types (Lurs) - Land suitability classification - yannement specifications for LUTa on land units - vironmental impact - :'unumic and social analysis of alternatives - i)ata from basic surveys and specialized studies land evalunation: rpr examle, in broad reconnai ssancv. surveys, land systems might fiorm the mapping unit. whilst in more dietaied su evevs they might consist of' land facets, soil seri,.s or vegetat ion communities. Hayving iglntitfied an(l mapped each ar'ea. t.he rel ev'ant propert ies o" the lanld tunits are surve('(lyed and recorded: for example moisture availability, soil depth, soil nutrient availabil ity. eros ion hazard. plre.('ltC(e or pests arnd diseases, or terrlain ii1 tL1i (illS which atfect meclantiziat ion. Ihese two sets of activit ies are lnoiglht togpther in the com­ parison of land usp withi land. ilhen first stage of comparison Ks matching , in which the requirements of' each kind oI and use are compareI with t. he properties of each area of landt. Thus moisture requirements of a crop or land use system ale compared with the moi st urie avai I abi li ty of each land unit, nut ri ent requi rements with nut.rient availalbiliLy, the suscept ibility of the land use to erosion with the erosion hazard, etc.. Matching leads to a first "pproxi­ mation of' land suitability, in terms of physical land use require­ ments only. These provisional suitabilities are then subjected to further st ages of analysis, .in terms of environmental impact, economic ana­ ly..is, and social conseqtences. Some combinations of land use wit h laiid which appeared .,nitablp in physical terms may be rejected on groti ds or ad verse en \'1 ronment al conseeltences , negat i ve economic return or linacceptable social Pffects. TIhese further stages of analysis lead to land suitability classif.i1cation. giving the suitability of' each surveyed land tinit for eac def'ined land utiization type. In the land slitbt ilit y classificat ion normally employed there are two suitability o;ders, S Suitable and N Not Suitable, divideld into fie'suitability classes as follows: SI Highly suitabie NI Currently not suitable (physically possible, but S2 Moderately suitable no economically viablh) S3 Marginally suitable 2N2 Permanent.ly not stitable Further sul)livision is possible, into land suitability sub­ classes and units. Subclasses show the type of' limitation, e.g. 7 ­ moisture deicidn.y, salinity, ad\verse conditiou for mechanization. Land suitability units consist of f'pt ter suIdi vision into areas. with relatively urniform manlragement reqtuir'emenits anid a specified range or p'oduct vv c'apac itv. 2.3 Re.suits o 1Ilnd eval a t'ion The principal results of a standard land evaluat. ion survey ape: i. De-criptions of lnid ut ilizat ion tyvpes relevant to the area. ii. An assessment, or the suitab ilitie.s of each land util izat ion type fop each of thc mapp..,d larid uhiLs, Logethe' with reasons for this assessment. iii . Management. specifications, for land utilization types on each of the land units for which they are suitable. iv. An account of the consequences of each land utilization type on each land unit: including required inputs, ex­ pect Cd output s (prco(licts, services and other bnerits) environment tal i mpactl. soci IalI consequienrces, and econom c alia ysi s. These result.s are presented as one or more land suitability maps, together with a report.