Improving adoptability of farm forestry in the Philippine uplands: a ...

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Key words: Adoption, Farm forestry, Linear programming, Timber trees, Tree farming, Tree hedgerow. Abstract ..... children in Claveria go to school or work-off farm when they are older (Stark ..... Department of Trade and Industry. (DTI)-Region ...
 Springer 2006

Agroforestry Systems (2006) 68:81–91 DOI 10.1007/s10457-006-0005-7

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Improving adoptability of farm forestry in the Philippine uplands: a linear programming model M. Bertomeu1,*, M. Bertomeu2 and J.C. Gime´nez2 1

World Agroforestry Center (ICRAF), ICRAF-Philippines, 2/F College of Forestry and Natural Resources Admin. Building, 4031 College, Laguna, Philippines; 2Ingenierı´a Te´cnica Forestal (Universidad de Extremadura), Centro Universitario de Plasencia, Avenida Virgen del Puerto 2, Plasencia 10600, Ca´ceres, Spain; *Author for correspondence (e-mail: [email protected]; phone: +63-49-5362925) Received 17 November 2004; accepted in revised form 16 January 2006

Key words: Adoption, Farm forestry, Linear programming, Timber trees, Tree farming, Tree hedgerow

Abstract In the Philippines, smallholder farmers have become major timber producers. But the systems of timber production practiced have several limitations. In intercropping systems, the practice of severe branch and/ or root pruning reduces tree-crop competition and increases annual crop yields, but is detrimental to tree growth and incompatible with commercial timber production. In even-aged woodlots, lack of regular income and poor tree growth, resulting from farmers’ reluctance to thin their plantations, are major constraints to adoption and profitable tree farming. In the municipality of Claveria, Misamis Oriental, the recent practice of planting trees on widely spaced (6–8 m) contour grass strips established for soil conservation suggests ways to improve the adoptability (i.e., profitability, feasibility and acceptability) of timber-based agroforestry systems. Assuming that financial benefits are the main objective of timber tree farmers, we develop a simple linear programming (LP) model for the optimal allocation of land to monocropping and tree intercropping that maximizes the net present value of an infinite number of rotations and satisfies farmers’ resource constraints and regular income requirements. The application of the LP model to an average farmer in Claveria showed that cumulative additions of widely spaced tree hedgerows provides higher returns to land, and reduce the risk of agroforestry adoption by spreading over the years labour and capital investment costs and the economic benefits accruing to farmers from trees. Therefore, incremental planting of widely spaced tree hedgerows can make farm forestry more adoptable and thus benefit a larger number of resource-constrained farmers in their evolution towards more diverse and productive agroforestry systems.

Introduction During the 1960s and 1970s in the Philippines, the forestry sector was one of the major income earners contributing 12.5% to the gross domestic product (GDP) (ADB 1994). Forestry activities began to decline in the 1980s due to overexploi-

tation of rapidly diminishing timber resources. The country is now a net importer of timber (ITTO 1996), and importation is draining its foreign currency reserves. Since the virtual disappearance of its natural forests, increasingly larger amounts of commercial timber are being produced in agroforestry systems

82 on small farms. Compared with large-scale forest plantations, smallholder farmers possess several unique advantages in timber production: (i) intensive management which ensures tree survival and growth; (ii) minimal tree establishment and management costs as weeding and fertilisation are charged to the intercrops; and (iii) reduced risk of fire since cropped alleys act as firebreaks (Garrity and Mercado 1994). Consequently, farm forestry has been proposed as an alternative approach to conventional, government-driven tree planting and small upland farms as land management units for reforestation (Pasicolan et al. 1997). Tree planting extension programs in the Philippines have typically recommended the establishment of even-aged, closely spaced (e.g., 2 · 2 m or 3 · 2 m) plantations (Agpaoa et al. 1976; Valdez 1991; Gacoscosim 1995; DENR-ERDB 1998), regardless of whether the objective was plantation forestry or smallholder farm forestry. Thus many farmers have established woodlots on small portions of their farms (0.2–1 ha), intercropping for 1 or 2 years while trees are small, using these areas for grazing household’s cattle once intercropping is no longer possible and eventually, beginning a new cycle by coppicing tree stumps after tree harvest. This system of timber production, also practiced in many of the Pacific islands, has been described as sequential cropping or improved timber fallows (Magcale-Macandog et al. 1999; Elevitch and Wilkinson 2000). Farmers perceive that the short period in which intercropping is feasible and the lack of a regular intermediate income from the tree crop are major limitations of even-aged woodlots (Predo 2003). Therefore, they have developed management practices, such as intensive tree branch and root pruning (by deep ploughing close to the trees), to reduce tree-crop competition and prolong the period of intercropping. But these management practices are detrimental to tree growth (Watanabe 1992; Miah 1993; Gonzal 1994; Roshetko et al. 2004) and thus are incompatible with profitable timber production. Moreover, many timber traders and sawmill owners are dissatisfied with poor diameter growth due to farmers’ reluctance to thin immature trees (Bertomeu 2004). Staggered planting of timber trees at wide spacing may be the best way to generate short- and long-term benefits from trees and crops combined in the same land unit. In Central America and the

Caribbean, continuous or incremental small-scale adoption of tree planting has been reported to be more appropriate for smallholder farmers (Current et al. 1995). In hedgerow intercropping systems in the Philippines, Shively (1998) reported that when the spacing of tree hedgerows is narrower than approximately seven meters, yield reduction outweights the benefits of more hedgerows. According to Santiago (1997), in the ‘‘line planting system’’ (LPS) (i.e., 1 · 10 m) promoted in the tree farming scheme of The Paper Industries Corporation of the Philippines (PICOP), trees grow faster and farmers are able to plant annual crops in between the trees at a commercial scale. Recently in the upland municipality of Claveria, Misamis Oriental, smallholders began to gradually incorporate trees on six- to eight-meter spaced contour grass strips they had previously established to control soil erosion (Stark 2000). Subsequent research on smallholder timber production systems showed that trees planted in hedgerows 10 m apart provide higher returns to land than trees in woodlot (2 · 2.5 m), and higher returns to labour than maize monocropping (Bertomeu 2004). Building on the practices of widely spaced trees lines and staggered planting, we propose in this paper cumulative additions of widely spaced in1 tercropped tree hedgerows as a more adoptable system of timber production for smallholder farm forestry. Incremental planting of widely spaced tree hedgerows has several advantages over evenaged tree woodlots: (i) longer periods of intercropping as trees are planted at wider distance; (ii) provision of income on a more regular basis since once the system is established there would be trees of different ages; (iii) higher feasibility and reduced risk since investment costs are spread over several years; (iv) lower production costs because of lower tree density and faster tree growth because of the more favourable light regime of widely-spaced trees; (v) higher carrying capacity for the household’s livestock because of the increased

1 According to Franzel et al. (2002), to be adoptable agroforestry technologies must be profitable, feasible and acceptable. Feasibility refers to farmers’ ability to plant and maintain an agroforestry technology, which depends on farmers’ available resources (land, labour and capital), information and skills, and their ability to cope with any problem that arises. Acceptability includes profitability, feasibility, risk, compatibility with farmers’ values and farmers’ valuation of benefits.

83 production of under-storey groundcover between widely spaced trees. Linear programming (LP) is a powerful analytical tool that can be used to determine an ‘‘optimal’’ combination of several production systems while considering farmers’ constraints and requirements (Betters 1988). LP has been used in the planning and evaluation of agroforestry systems involving the optimisation of a single objective under a set of management constraints (Raintree and Turray 1980; Verinumbe et al. 1984). Assuming income generation as the main objective of farmers interested in commercial timber production, we develop a simple LP model for the optimal allocation of land to monocropping and tree intercropping that maximises the net present value of these farm enterprises and satisfies farmers’ labour constraints and regular income requirements. Here, for demonstration purposes, the model is applied to the case of an average smallholder farmer of Claveria with an interest to grow Gmelina arborea R. Br. (hereafter referred to as gmelina), a timber tree commonly planted throughout the Philippines. By illustrating how the apparently mutually exclusive monocropping and tree farming enterprises can be gradually integrated into the same land unit, we aim to assist farmers’ decisions in their evolution towards more diverse and productive agroforestry systems and to help farm forestry extensionists to facilitate this transition.

2004). Consequently, the LP model here presented has been developed to find out an optimal land allocation to the most common land use systems practiced by these farmers, maize monocropping and tree intercropping, that maximises total income. An important feature of the model is that it incorporates farmers’ practice of staggered tree planting, resulting in what in forestry is called a fully regulated tree plantation (Davis and Johnson 1987), or a tree-based system that once fully established generates income continually. The linear programming model with continuous decision variables developed assigns portions of the farm to monocropping and intercropping without specifying the exact location and arrangement of the monocropping and intercropping units as an integer programming (IP) or mixed-integer programming (MIP) model with binary (0–1) decision variables would do. In this sense, a spatially explicit programming model would be more desirable. However, it is well known in forest management planning (specifically in timber harvest scheduling problems) that the combinatorial nature of IP and MIP models causes computational difficulties, thus requiring from heuristic solution methods in order to approximate an optimal solution at a reasonable computational cost, without being able to guarantee optimality or even feasibility (Snyder and ReVelle 1996; Brumelle et al. 1998; Borges et al. 1999).

Materials and methods Justification of the approach Given the multiple ecological and socio-economic benefits derived from agroforestry and that LP techniques are used in the optimisation of a single objective under a set of management constraints, LP has been considered inadequate for planning and evaluating agroforestry systems. Instead, multi-objective programming (MOP) can be used to optimise several objective functions simultaneously Mendoza et al. (1986). Although smallholders in the study site have been undertaking farm forestry for various reasons (e.g., cash and savings, erosion control, aesthetics, shade and shelter and others), capital accumulation and income generation are the primary concern of commercially oriented tree farmers, considering other benefits as by-products (Predo 2003; Bertomeu

Description of the site and farming systems under study Research on smallholder timber production systems began in October 1997 at the World Agroforestry Center (ICRAF) research site in Claveria, Misamis Oriental, The Philippines. Claveria is an upland municipality located 42 km northeast of Cagayan de Oro City, in northern Mindanao. It covers an area of 112,175 ha and has a mountainous topography, with 62% of the land area having slopes of 18% or greater and elevation ranging from 390 to 2000 m (DTI and PKII Engineers 1996). Soils are derived from volcanic parent material and classified as deep acidic (pH 3.9 to 5.2) Oxisols with texture ranging from clay to silty clay loams, with low available P, low CEC,

84 high Al saturation and low exchangeable K+ (Magbanua and Garrity 1988). Average rainfall is 2500 mm with a wet season from June to December (>200 mm rainfall per month) and a short dry season from March to April (