Steps to follow in designing a conservation plan

As in the implementation of any technology, the best results are usually obtained when each situation and pertinent details are carefully examined. The following list of steps has been found useful in both designing conservation plans and in teaching students about soil conservation.

a. Select lot, subdivide if necessary
b. Study lot, find out problems with respect to erosion, drainage, drought.
c. Select suitable drainage site if necessary
d. Decide on position of "linea madre"
e. Calculate slope
f. Select conservation strategy
g. Decide on appropriate distance between structures
h. Place marker stakes along the "linea madre" at the appropriate intervals
i. Survey and mark contour lines
j. Realign stakes along contour lines if necessary
k. Carry out conservation practice
l. Plant protective barriers if necessary
m. Plant desired crop(s) along the contour
n. Periodically review structures and carry out any needed maintenance practices.

a. Select lot, subdivide if necessary. (Fig. 22)

This step includes choosing the parcel of land to work on, noting if it should be subdivided into separate management units, each of which should be conserved separately following the rest of the steps. Subdividing the lot into separate units, each of which has a relatively uniform slope, allows the design of a conservation plan far each of the simpler units separately, rather than the difficult task of designing a single plan for a complicated, convoluted area. It should be noted here that most soil conservation techniques are only practical if maintained over a long period of time. Therefore the lot selected should be owned by or permanently available to the involved farmer.

Fig. 22. Select and subdivide lot

Fig. 23. Investigate erosion, drainage, and/or drought problems

b. Study lot, find out problems with respect to erosion, drainage, and drought (Fig. 23)

This involves asking the farmer about previous years problems; whether flooding or drought are serious problems, the point of entry of runoff water from upper slopes, and sites of serious erosion or drainage problems. It should also include investigating the types of crops, cultivation method used, fallow periods, pests or diseases, etc.

Example: In this cornfield, sections 1 and 2 are characterized by rapid rainfall runoff, causing small gullies to form. This is followed by excessive soil drying between rains. Section 3 on the other hand, is relatively level, but experiences flooding due to poor soil drainage and the runoff received from Sections 1 + 2.

c. Select suitable drainage site if necessary. (Fig. 24)

This is an often neglected step which can result in serious problems such as gully formation, flooded roads, or angry neighbors if not considered carefully. If ditches will be constructed to divert excesses of water from a lot, care must be taken to divert the water to a well-vegetated area, a retention well, or to a grass or rock lined waterway. In deciding where to divert excess water, one should also consider the positions of neighboring fields, roads, or houses in order to avoid flooding these areas. If necessary' the construction of drainage ditches or terraces should be delayed until an adequate-site for runoff water can be constructed and thoroughly protected against erosion. (See section on Waterways for draining excess water from fields") Meanwhile, other conservation practices which do not result in concentrations of runoff water, such as the use of contour barriers, maintaining a dense ground cover, etc., can be employed.

Fig. 24. Select suitable drainage site if necessary

Fig. 25. Decide on position of "linea madre"

d. Decide on position of "linea madre". (Fig. 25)

This is is the imaginary line which best represents the average slope on a unit of land. It will be used as the reference line from which to measure the distance between successive soil conservation structures. It should be positioned so that contour lines will be perpendicular to it.

e. Calculate Slope. (Fig. 26)

The slope of the terrain should be measured at 5-10 randomly selected sites per hectare and then averaged. The slope can be measured using a string and a small line level as illustrated, or by using an A-frame level m e slope of the terrain is important in planning soil conservation strategies. Ideally, flat or gently sloping areas should be used for the production of annual crops, while more steeply sloping areas (35% or more) should be used for perennial crops such as fruit trees or forage, and in very steeply sloping areas (50% or more) the natural vegetation should be maintained. The slope of the terrain is also used when deciding on the distance between successive contour structures, as described in other sections.

Fig. 26. Calculate slope

f. Select conservation strategy

No strict guidelines are presented here for selecting soil conservation techniques due to the tremendous number of variables influencing the decision. However, the following points should be considered as the extensionist and the farmer(s) work out the most appropriate design for an area.

1. Identify resources and constraints which will affect the process. These include the availability of labor, rocks, and live barrier plants; presence of water sources for irrigation; the acceptability of a more longterm investment (perennial crop); the presence of cattle during the fallow period; etc.

2. Select as many complementary soil conservation techniques as possible which are appropriate to the desired cultivation system.

EXAMPLE 1: Plant fruit trees on individual terraces protected by contour infiltration ditches and live barriers of king grass. Plant a green manure crop inbetween the trees and mulch around the tree bases.

EXAMPLE 2: Intercrop corn and beans to form a dense ground cover, Construct contour discontinuous narrow terraces with a live barrier of Guatemala grass. Plant a green manure crop such as Velvet bean, during the fallow season. Plant fruit trees on the terraces.

3. Design all structures along carefully measured contour lines (Usually 0%-i% slope).

4. Carefully maintain all contour structures, protective barrier plantings, and drainageways to endure proper functioning.

5. Review Table 6, "Advantages and disadvantages of different soil conservation techniques"- and Appendix 2, "Dichotomous key to the selection of soil conservation practices".

TABLE 6 Advantages and Disadvantages of Different Soil Conservation Techniques

TABLE 6. (Continued)

g. Guidelines in determining the distance between soil conservation structures

The most simple rule to follow when placing a series of barriers or ditches in a field is that of locating one structure with every vertical drop of approximately 1.5 m. By standing at the site of one structure and sighting along an extended arm, one can determine the position of the next highest structure. (Fig 27)

Fig. 27. Visual method for determining the distance between successive contour structures.

Technical tables prescribing distances based on the slope of the terrain should be used whenever possible to insure an optimum placement of structures. Simple tables are included in the section on soil Conservation and Water Management Practices" (Tables 2-5). Soil texture, soil structure, and rainfall intensity may also affect the optimum placement distance of structures but for simplicity these affects are usually ignored. If the farmer(s) considers the amount of work required to place these structures excessive, then it may be necessary to limit the first seasons work to the placement of every other structure planning to finish the work at a later date.

Fig. 28. Place marker stakes along the "linea madre" at the appropriate intervals.

h. Place marker stakes along the "linea madre" at the appropriate intervals. (Fig. 28) m e first stake should be placed along the upper edge of the lot or at the highest convenient place where a structure will be located, subsequent stakes are placed below.

i. Survey and Mark contour lines. (Fig. 29)

This can be done using an A-frame or other type of level. The construction of two types of levels is described in Appendix 4. Care should be taken to carefully calibrate the level and to orient it in the proper direction if surveying lines for drainage ditches.

Fig. 29. Survey and Mark contour lines

Fig. 30. Carry out conservation practices.

j. Realign stakes along contour lines if necessary.

If the contour lines result in an extreme zig-zag pattern which may cause difficulties, for example in plowing a plot, the lines may be straightened somewhat by slightly moving some of the stakes. It should be noted that realigning stakes means that they no longer lie along measured contour lines and that this will have to be corrected for if digging sort of ditches to drain or retain water.

k. Carry out conservation practice(s). (Fig. 30)

These are described in detail in the Section on "Soil Conservation Strategies" .

l. Plant protective barriers if necessary (Fig. 31)

If not protected by barriers; terraces, ditches, and drainages tend to fill in and cease to fulfill their function as conservation structures. A live barrier planted above these structures acts as a filter to keep soil particles from filling them in and lessens their maintenance requirements.

Fig. 31. Plant protective barriers

m. Plant desired crop(s) along the contour (Fig 32,33)

Planting along the contour with closer spacing within rows and more distance between rows forms a partial live barrier with each crop furrow. Care should be taken to plant well selected seeds in order to ensure a more complete germination.

On irregular terrain with varying slope, successive contour lines will not be parallel. Point rows are used in the wider intervals in order to fill up the land space and still maintain contour oriented furrows. (Fig. 33)

Plant desired crop(s) along the contour

Fig. 33. Use of point rows to maintain contour furrow orientation on irregular terrain.

Fig. 34. Periodic review and maintenance of structures

n. Periodically review structures and carry out any needed maintenance practices.

Common maintenance practices include replanting of open spaces in live barriers and replanting grass on terrace walls.