B. Land clearing and development

Land clearing or removal of TRF vegetation is the first step toward bringing new land under cultivation. Improper and incompatible methods of deforestation and subsequent land development can lead to soil degradation and a rapid decline in crop yields (Weert, 1974; Seubert et al., 1977; Lal, 1981a, b; Hulugalle et al., 1984; Lal et al., 1992). The severity of soil degradation depends on the intensity and speed of mechanized methods of land clearing. The heavier and quicker the equip mental the more the degradation of soil structure. Different types of equipment and attachments used for manual and mechanized clearing techniques are shown in Plates 11-15.

Fig. 10 Natural resource assessment for an appropriate land use

Technological options for different methods of deforestation, land development, and trees, pastures, and crop management are outlined in Fig. 11. These technological options for land clearing are based on the following assumptions:

- The food production capacity of most potentially available soils of the humid tropics (especially Oxisols and Ultisols) is low and inferior to areas already producing food crops. Therefore, it is important to adopt improved soil and crop management practices to improve production on existing lands rather than clear new land.

- If deforestation for developing new land is deemed absolutely necessary, it must be done with careful planning after land evaluation and assessment of all natural resources.

- Whenever possible, manual clearing is preferable to mechanized clearing. If burning fell biomass is necessary, it must be done in situ. Indiscriminate use of heavy machines is to be discouraged.

- If mechanized clearing is inevitable, the use of front-mounted shear blades is preferred over tree pushers/tree crushers and other equipment that causes severe soil disturbance. Root rakes are to be avoided.

- Soil and water conservation measures are installed and the cleared land is immediately sown with an aggressively growing cover crop.

Guidelines for land clearing and development were outlined in the symposium held at IITA (Lal et al., 1986), and some important dos and donuts of land clearing are listed in Table 12. These guidelines are based on the assumption that locale-specific packages of cultural practices for improved cropping and farming systems are available. It is difficult to sustain productivity on newly cleared lands if these cultural practices are not known. If not available, these cultural practices are to be developed on the basis of the following research information available for site-specific ecological conditions:

- the comparative economics of land clearing by different methods (e.g., manual vs. mechanized);

- permissible slope limits for different land uses (e.g., arable, pastoral. silvicultural, and mixed farming systems);

- restorative technologies for compacted soils and those with low soil pH;

- nutrient management techniques based on soil test values;

- appropriate cover crops, woody perennials, and herbaceous shrubs for use in innovative farming/cropping systems; and - mulch farming techniques, including ways to procure mulch and grow crops through it.

Fig. 11 Options for methods of forest conversion for different land uses

Table 12 Some dos and don'ts of land-clearing methods in the humid tropics

Dos	Don'ts
Increase production from existing land to reduce the need for clearing new land	Clear steep lands > 5% slope
Use shear-blade clearing where possible	Construct windrows too far apart
Burn biomass in situ rather than in windrows	Drag trees over long distances
Sow cover crops soon after clearing land clearing with untrained operators	Use construction equipment for
Adopt conservation tillage with residue mulch	Remove litter roots and stumps
Use multiple cropping systems to provide ground cover implement soil and water conservation measures	Scrape off or disturb the top soil
Adopt controlled grazing with low stocking rate on pasture land	Follow plow tillage and equipment that cause soil disturbance
Use science-based inputs for soil, crop. trees, and pasture management	Follow productivity mining techniques and resource-based methods