**6.4. Strip cropping**

**6.1. Direct seeding**

12 Soil Fertility

crop yields.

**6.2. Minimum or reduced tillage**

content of the soil while conserving the soil.

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

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

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

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‐ ing crops.

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 were similar.


**N fert. rate (kg/ha)**

Source: SARI, 1985

**Acacia Leucaena Parkia Gliricidia Vilellaria**

0 1397 1397 1533 2240 1227 1987 1625

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

40 2250 1960 1937 2623 1887 2860 2253

80 2203 2643 2333 2630 1833 3180 2471

**Mean 1950 1990 1935 2498 1649 2676 2116**

The most common of the materials used as soil fertility enhancing substances however, are the organic and in- organic fertilizers. The recommended rates of in-organic fertilizers for the production of cereals especially maize in Ghana are the basal application of compound fertilizer made up of 15 % each of Nitrogen, Phosphorus and Potassium (NPK) at planting or two weeks after planting of 2 fifty kilograms (50 kg) bags per acre. This is followed by the application of either sulphate of Ammonia or urea at 1 fifty kilogram bag (50kg bag) or twenty-five kilogram bag (25 kg bag) per acre respectively just before the tasseling of maize. However, the acquisition of these materials whether the organic or in-organic fertilizers by

In the first place, most of the small scale farmers are poor and cannot afford the recommend‐ ed rates of the in-organic fertilizers to increase their crop yields. Most often, they just pur‐ chase the quantities that they can afford which are far below the recommended rates for the crops and therefore those quantities are unable to increase their yields. As a result, their

Secondly, even though almost every farm family in northern Ghana possesses few livestock such as cattle, sheep, goats and or poultry, the dung (manure) they produce is highly inade‐ quate to fertilize an area of one acre. Most of these categories of livestock are also on free range thereby making the gathering of their dung very difficult. In addition, some of the farms are very far from their homes so carting these bulky materials to their farmlands pos‐

The above situation where farmers cannot afford recommended rates of in-organic fertiliz‐ ers because they are poor and they also do not have enough animal dung to fertilize their

**Table 6.** Maize grain yield (kg/ha) under agroforestry system at SARI.

farmers have also been faced with a lot of challenges.

crop yields still remain low and that explains why they remain poor.

**7. Application of fertilizers**

ses another challenge.

crops call for the combination of both.

**Check/ control**

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

**Mean**

15

**Table 5.** Effect of pruning on leaf litter production, grain yield of pigeon pea and maize yield after two years of fallow in the northern Savanna zone of Ghana.

It was found that maize yield after two years of pigeon pea fallow was highest in 1998 at 30 cm pruning height which was followed by the pigeon pea not pruned at all in the trial. But maize yields from plots with pigeon pea pruned at 60 and 90 cm heights were similar in val‐ ue but significantly lower than the yield obtained from the plots with pigeon pea pruned at 30 cm. The high maize yields at no pruning and the pruning at 30 cm height were attributed to the higher quantity of litter fall from the pigeon pea.

It was then concluded that biomass obtained from the pruning of pigeon pea up to 60 cm will be able to provide sufficient fodder that may be used to supplement livestock feeding in the dry season (Agyare et. al., 2002). This situation would not be sacrificing much in terms of soil fertility status, pigeon pea grain yield and yield of subsequent maize crop. This option makes pigeon pea a valuable leguminous shrub for short season fallow for the mixed farmer.

#### **6.5. Agroforestry**

Agroforestry involves the integration of trees/shrubs and sometimes animal husbandry in the farming system. It combines annual crops with herbaceous perennials or trees on the same units.

Both exotic and local tree species were screened for Agro-forestry purposes in SARI as from 1985 (Table 6). The results showed that *Gliricidia* and *Leucaena* which are both exotic tree spe‐ cies are better trees for soil fertility restoration than the local tree species like *Parkia.* Both the *Leucaena* and *Gliricidia* produced enough biomass much earlier for incorporation than the rest of the tree species, It was also found that the incorporation of pruned biomass from the tree species was responsible for the increase in soil nitrogen. This therefore suggest that the faster the growth and development of the tree species to produce biomass for incorporation, the better the tree for agro-forestry system.

Enhancing Soil Fertility for Cereal Crop Production Through Biological Practices and the Integration of Organic... http://dx.doi.org/10.5772/53414 15


**Table 6.** Maize grain yield (kg/ha) under agroforestry system at SARI.
