**6. Conservation agriculture technologies for soil fertility management in Ghana**

Conservation Agriculture (CA) is described as a set of practices or procedures carried out that ensure higher agricultural productivity and profitability whilst improving soil health and environment. It is known to be hinged on three basic principles which are (i) Little or no disturbances of the soil, (ii) The soil should have a cover all year round and (iii) the crops should be in rotation from season to the other or in intercropping situations.

Conservation Agriculture was introduced into Ghana in the early 1970s, mostly through donor funded Agricultural projects. Even though results in terms of crop yields from the various onfarm experiments have been found to be higher than the yields from the traditional slash and burn method of farming, it has not been easy to convince farmers to adopt the practice holistical‐ ly. Generally the adoption of CA by farmers in Ghana is therefore low and those who are said to have adopted CA may either be practicing one or two of the principles of CA such as no-till, notill with intercropping but not all the three principles of the practice. Comparatively, climatic and weather conditions in the southern part of the country favour the adoption of some of these principles. For example, the rainfall system in the south is bi-modal with only a dry period of less than three months. This allows the growth and development of vegetation all year round and therefore not prone to bush fires. The decay of these vegetative matter when killed by weedicide, will go a long way to enrich the soil with its nutrients.

On the other hand, the northern part of Ghana has only one rainy season which commences in late May and ends in early November with a dry period of about five months which is characterized by the Hamattan winds. During the dry season, the vegetative matter is dried up and therefore prone to bush fires. The occurrence of bush fires either accidentally or in‐ tentionally, clears up all the dry vegetative cover exposing the soil to the Harmattan winds in the dry season and the running water during the rainy season which robs the soil of its nutrients. It is therefore not surprising to know that farmers in the northern part of the coun‐ try consider any technology that conserves soil and water such as soil bunding as a CA tech‐ nology. Table 4 shows the results of a survey that was carried out to identify technologies related to CA practiced by farmers in the northern part of Ghana. Comparatively, among the districts covered, East Mamprusi recorded a higher percentage of farmers practicing some of these technologies than Lawra or Bawku which according to Ekekpi and Kombiok (2008) could be indicative of better extension services in that district.


Number of respondents = 32

cropping seasons, maize is planted in the major season (April-June) and an edible legume

A legume as a candidate crop in intercrop systems is again being encouraged because of the same reason as above. In the northern part of Ghana where the soils are low in both organic matter and essential nutrients, farmers intercrop cereals with legumes. The most common intercropping systems in this area are maize/cowpea, millet/cowpea, and maize/soybean. In some cases, both in the north and south of Ghana cover crops such as *Mucuna or Callopogoni‐ um* is planted in maize at the latter part of its growth cycle (6 weeks after planting maize). In southern Ghana, maize is harvested earlier and the cover crop (*Mucuna*) is left to grow into the minor season (August to March) until the next major season (April to August). In the northern savanna zone however, the cover crop dries when the rains end in October and the residue forms mulch protecting the soil. The incorporation of the residue in the soil after two years of cropping increased both the soil nitrogen and maize grain yield significantly

One approach that has proved to be inherently attractive to farmers and is standard practice in most parts of northern Ghana is intercropping maize or sorghum with the grain legume cowpea or groundnut. If cowpea is sown between maize rows, the plant population and yield of maize can be maintained, whilst reaping the advantage of yield from the cowpea harvest. There is high labour requirement in the practice of intercropping because more than one crop is being planted at a time. So, labour is required for planting the component crops and for the careful control of weeds in the system. Insecticides are needed for the control of

Pigeon pea is an ideal legume for intercropping with cereals. Its slow initial growth affords little competition with the cereal for light or water, and it continues growing into the dry season after the maize crop has been harvested. The leaves that fall from pigeon pea before harvest provide a mulch and can add as much as 90 kg N/ha to the soil that then mineralizes relatively slowly during the subsequent season, releasing N for the next maize crop (Adu-Gyamfi et al., 2007). Thus a substantial rotational benefit, although not a perfect soil cover,

**6. Conservation agriculture technologies for soil fertility management in**

Conservation Agriculture (CA) is described as a set of practices or procedures carried out that ensure higher agricultural productivity and profitability whilst improving soil health and environment. It is known to be hinged on three basic principles which are (i) Little or no disturbances of the soil, (ii) The soil should have a cover all year round and (iii) the crops

Conservation Agriculture was introduced into Ghana in the early 1970s, mostly through donor funded Agricultural projects. Even though results in terms of crop yields from the various on-

should be in rotation from season to the other or in intercropping situations.

insect pests on the legume component either being rotated or intercropped.

such as cowpea or a cover crop (*Mucuna*) is planted in the minor season.

(Kombiok Clottey, 2003).

10 Soil Fertility

can be achieved for the next season.

**Ghana**

Source: Ekekpi and Kombiok, 2008

**Table 4.** Percentage of farmer respondents on CA technologies in the savanna zone

## **6.1. Direct seeding**

Direct seeding of crops is carried out without tilling the land in most parts of Ghana. In the southern part of the country (forest zone) where vegetation exists all year round, the vegeta‐ tion is slashed using a cutlass and the residue instead of burning, is left as mulch on the farm. However, in the north, the crops (maize, sorghum and millet) are planted directly on the bare soil since all vegetative matter would have been burnt during the dry season. In both cases, the crops are planted using a dibbling stick or cutlass to create holes either on the bare soil (North) or inside the mulch as in the case of the South. This is advantageous in the South since the farmer will benefit from the mulch as it will conserve soil water and eventu‐ ally decay with time to add nutrients to the soil within the season. Under such a situation, the physical and biological properties of the soil are also expected to improve after the mulch decomposes. In the north however, weeding should be carried out within three weeks after planting after which fertilizer or manure would be applied to the farm since the soil is devoid of vegetative cover at planting. This is to be sure that the crops are supplied with enough nutrients and to avoid heavy weed infestation on the farm which can reduce crop yields.

since tillage activity before planting the crop is avoided and this helps to maintain the struc‐

Enhancing Soil Fertility for Cereal Crop Production Through Biological Practices and the Integration of Organic...

http://dx.doi.org/10.5772/53414

13

In some cases, the application of pre-emergent weedicides such as Atrazine for maize pro‐ duction can also help to delay or avoid the use of hand hoe to remove weeds after planting of the crop. Comparing the north and south, not much fertilizer is applied in the south prob‐ ably because the fertility of the soil is always improved after the mulch decomposes in the subsequent seasons. For high yields of crops in the north, application of higher rates of fer‐

Alley cropping is not widely practiced in Ghana but this is found in few places in the southern part of Ghana. It is similar to agro-forestry systems where fast growing shrubs or trees such as pigeon pea is planted in alleys while cover crops such as *Mucuna* or *Cal‐ apogonium* spp are planted to protect the soil from erosion and for weed control. Afetr harvesting the pigeon pea in the alleys, the biomass is harvested and used as mulch on the cover crops where maize is planted directly in the mulch. In this system, nitrogen is fixed in the soil from atmosphere by both the pigeon pea and the cover crops. Also, the decay of the biomass from the pigeon pea goes to enhance the N status of the soil which goes to improve the yield of the maize. Soil water is conserved and weeds are controlled

The planting of alternating strips of several crops aligned on the contour in the field is known as strip cropping. It is an effective conservation measure on slope between 5 and 10%. In this case, erosion is largely limited to the row crop strip and soil removed from these is trapped in the next strip down slope which is generally planted to close grow‐

Strip cropping involving pigeon pea has many additional advantages especially in a mixed farming situation. In northern Ghana, almost every farm family raises livestock (goats, sheep and cattle) as well as poultry in addition to crop production (SARI, 1995). It is therefore common to find strips of pigeon pea on most fields where the grain is har‐ vested and cooked on the farm as lunch for the family. Studies have shown that the bio‐ mass of pigeon pea can be pruned over three times within a year and shade-dried to feed livestock during the dry season. Among the three pruning heights of pigeon pea at 30, 60 and 90 cm in the trial, it was found that pruning at 90 cm height for livestock, the pigeon pea would still be able to produce seed at the end of the year which would not be significantly (p<0.05) different from the plant that was not pruned (Table 5). With the exception of the pigeon pea pruned at 30 cm, which produced significant highest amount of litter, the quantity of litter produced by those pruned at 60 cm and 90 cm

ture of the fragile soil of the area.

**6.3. Alley cropping with cover crops**

effectively under this system.

**6.4. Strip cropping**

ing crops.

were similar.

tilizers is required.

#### **6.2. Minimum or reduced tillage**

Minimum tillage is the reduction in the number of times the soil is being tilled as in conven‐ tional tillage method (ploughing/harrow/ridge) before and after the crop is planted. In Gha‐ na, most farmers have adopted the use of weedicide to reduce tillage for land preparation for crop production because of its additional benefits of reducing labour cost. Other benefits of minimum tillage include the reduction in energy costs and it enhances the organic matter content of the soil while conserving the soil.

The vegetation is either slashed or sprayed with weedicides followed by either burning the dead vegetation as done in the forest and transitional zones of Ghana before crops are plant‐ ed. This implies the land is not tilled before planting. However, weeds in this system are controlled by the use of cutlasses in the south while in northern Ghana, this done by hand hoe or the use of bullocks thus reducing the number of times the soil is tilled. The use of hoe as practiced in the north in weed control helps to bury the young weeds that have just emerged after planting which easily decay and return nutrients in to the soil for crop use. The burning of the vegetation before planting the crop by farmers in the south has been dis‐ couraged since the full benefits of mulch which include improved moisture infiltration to re‐ duce soil erosion will not be realized in such a situation (Wagger and Denton, 1992).

It is common to see farmers in northern Ghana planting annual crops such as maize, millet and sorghum on the old ridges constructed in the previous year. In the southern part of Ghana, it is the use of *glyphosate* (a total weed killer) at the recommended rate of 3l/ha which can be increased if noxious weeds such as spear grass (*Imperata cylindrical)* is present. It is advisable for farmers to delay planting of their crops for at least one week after the applica‐ tion of *glyphosate* to allow the breakdown of the chemical and to identify the portions not well treated. The dead weeds are either buried or left on the surface of the soil as done in the south. In both cases however, the number of times the land is physically tilled is reduced since tillage activity before planting the crop is avoided and this helps to maintain the struc‐ ture of the fragile soil of the area.

In some cases, the application of pre-emergent weedicides such as Atrazine for maize pro‐ duction can also help to delay or avoid the use of hand hoe to remove weeds after planting of the crop. Comparing the north and south, not much fertilizer is applied in the south prob‐ ably because the fertility of the soil is always improved after the mulch decomposes in the subsequent seasons. For high yields of crops in the north, application of higher rates of fer‐ tilizers is required.
