Dry matter (kgha−1) and crude protein (% dry matter) of
In Zimbabwe, most livestock are reared by smallholder farmers who live in marginal areas with low rainfall and hence poor forage production. As a consequence, livestock productivity is low and intermittent droughts result in animal mortalities. Forage crops have been widely promoted to provide feed resources to livestock, particularly during the dry season and in years of low precipitation. However, production of forage crops among the smallholder farmers remains low, especially in areas that receive low rainfall (<600 mm per annum). This chapter reviewed work on the production and promotion of forage crops in Zimbabwe in the past 50 years. The production and adaptation of different forage crops viz. improved grasses, herbaceous, and tree legumes to low and high (>800 mm per annum) rainfall areas is highlighted. Planting of improved grasses and herbaceous legumes in fallows and tree legumes as hedges and on contours hold the best promise in terms of improving the availability of forage crops for livestock feeding. Shortage of moisture remains the greatest constraint to increasing the area planted to forage crops. Therefore, the development of irrigation facilities needs to be encouraged to allow for the growing of forage crops.
- bana grass
- tree legumes
In Zimbabwe, the majority of the people live in rural areas with smallholder cropping and livestock production as the major sources of livelihoods. However, with the ever increasing population, the natural resources are constrained leading to low crop yields and livestock productivity. Livestock are reared on natural rangeland, which in most areas have been degraded leading to a decline in grass production. Thus, to improve livestock production, there is a need to promote forage crop production by smallholder farmers. Forage crops are plants grown for feeding livestock either directly as grazing pastures or as conserved hay and silage. They provide important nutrients (energy, protein, vitamins and minerals) to the livestock, particularly during the dry season when the natural grazing areas will be having poor quality forage.
The introduction of commercial smallholder dairy in Zimbabwe has seen an increase in the establishment of pasture grasses and legumes . Some of the forage grasses grown include giant rhodes (
The aim of this chapter was to provide a review of the work done to date in Zimbabwe to promote forage crop production particularly in the smallholder farming sector. The chapter focused on reinforcing natural grassland with legumes, rehabilitating fallows with legumes, promotion of tree legumes as protein supplements, cropped forage grasses and legumes and forage crop conservation. The future prospects of forage crop production in the smallholder farming sector in Zimbabwe is also highlighted.
2. Reinforcing natural grassland with legumes
To improve animal production under natural rangeland conditions, strategies to increase grass production are required. One such strategy is grassland reinforcement with legumes, which increases both the quality and quantity of grazing. This has been found to improve the performance of individual animals and results in increased carrying capacity of the rangeland . MacLaurin and Grant  reported cattle weight gains of over 60 percent per hectare (10,000 m2) in rangelands reinforced with legumes as compared to the unimproved natural rangelands in Zimbabwe.
Selection of legume species adapted to the conditions in the high rainfall (>800 mm per year) areas of Zimbabwe was undertaken in the early 1960s . Legumes found to be adaptable to these conditions included
For the legumes to successfully establish, it is necessary to disturb the soil surface and to set back grass growth . This can be done by burning-off of top hamper followed by disking the strips where the legumes are to be sown to improve emergence. The hard seeds of pasture legumes are scarified using hot water, dry heat or with concentrated sulphuric acid before planting .
|Dry matter||Crude protein|
A major constraint to grassland reinforcement with legumes has been the poor establishment of most species largely because of the low germination . This has presumably led to the abandonment of reinforcement trials by research stations and farmers. However, it would be plausible to initiate new trials and broaden the legume species to be screened in view of the continued declining rangeland productivity. An alternative to natural grassland reinforcement would be to plant the legumes in fallow abandoned cultivated croplands. Tavirimirwa et al.  estimated that fallows constitute about 50% of the land, which was previously under cultivation in central Zimbabwe. The unavailability of legume species suited to the drier areas (<600 mm rainfall per year) is also a major challenge in grassland reinforcement with legumes. In addition, the nutrient requirements of the legumes in different soil types need to be determined .
Although herbaceous legumes produce high biomass and improve grassland dry matter yield in reinforcement trials, they offer poor foraging opportunities during the dry season because they shed leaves after frost and loose herbage as a result of trampling . Hove et al.  found that herbaceous legumes such as
3. Rehabilitating fallows with improved legumes
In most parts of Zimbabwe, large tracts of land are left to recover naturally following years of continuous cropping. Sowing improved legumes such as lablab or velvet bean (mucuna) has been found to accelerate the restoration to produce these fallows. Velvet beans grown on fallows yielded between 4700 and 11,300 kg/ha . Both lablab and velvet bean crop can be grown, harvested and dried to make hay for feeding livestock or ploughed in as green mature to improve soil fertility. Planting forage legumes to restore fallow land improved maize grain yield by between 8 and 57%, which could be attributed to nitrogen fixation . Therefore, the use of forage legumes in fallow restoration is beneficial in that large amounts of good quality forage is produced in addition to improved soil fertility. Muchadeyi  reported lablab crude protein content of about 12% of dry matter. The restoration of soil fertility is achieved through the fixation of atmospheric nitrogen and/or through an improvement in soil-physical properties . In addition, lablab has been found to be drought tolerant with its deep and extensive root system contributing to soil organic matter content when decomposed, improving aeration and soil structure .
4. Use of tree forage legumes as protein supplements
In Zimbabwe, farmers have traditionally been feeding their livestock using leaves from native trees. However, in the last four decades, exotic (mostly from Central America) leguminous trees have been introduced because of their fast growth rates, acceptability to livestock and tolerance to frequent pruning and drought [18, 19]. In addition, these trees are long lived, require less maintenance and are palatable . For example,
The International Centre for Research in Agroforestry (ICRAF) in Zimbabwe tested and screened a number of leguminous tree forages suitability to provide forage to livestock particularly dairy cattle in the smallholder sector . The biomass yield of five tree legumes in areas receiving high (>800 mm per annum) and low rainfall (<600 mm per annum) when cut once at the end of the rainy season is given in Table 2 .
|Species||High rainfall||Low rainfall|
Leaf yields were higher in areas, which received high rainfall.
Tree legumes can be grown as hedges along the field boundaries or on contours to limit soil erosion or on fallow land and as pure stands or intercropped with other crops . In high rainfall (>800 mm per annum) areas, most farmers intercropped the tree legumes with food (such as beans) and other fodder crops (
Tree legumes are an important feed component in smallholder dairying. For instance, 1 kg of dried
Tree legumes could also play an important role in mitigating the effects of climate change because they are deep rooted, resistant to drought and are able to maintain high nutrient levels during the dry season . In Zimbabwe, currently only a few farmers are exploiting the research findings of higher tree legume performances and the associated improvement in livestock production following their supplementation of basal diets of Napier grass or crop residues. Interestingly, high adoption rates have been reported in areas where tree legumes were introduced to smallholder farmers .
5. Cropped forage grasses
Livestock production can be improved by providing better nutrition through feeding good quality grasses . The provision of good quality grasses maybe achieved through the use of improved grass species, such as Napier grass and its hybrids . Napier or elephant grass (
The nutritive value of forage crops affects their utilisation by livestock, which in turn influences the production of the animals. Turano et al.  reported crude protein values of between 6.4 and 8.3% dry matter and
Star grass (
Forage sorghum (
6. Cropped herbaceous forage legumes
In Zimbabwe, a number of tropical herbaceous legumes have been introduced, screened and the most adapted selected as forage crops. Tropical herbaceous legumes have fast growth rates and perform well in unfertile sandy soils due to their ability to fix nitrogen. They are mainly used as green manure, in intercropping, crop rotation and as fodder for livestock. In addition, forage legumes have higher crude protein content than grasses . For example, Murungweni et al.  reported crude protein content of 17.3 and 20.3% of dry matter for dolichos bean (
Although research and promotion of forage legumes has been going on for more than half a century, smallholder farmers’ adoption rates remain very low . In view of the increasing demands for livestock products, strategies have to be put in place to improve adoption of forage legume production by smallholder farmers to increase animal production. One such strategy would be to identify farmers with irrigation facilities and willing to increase forage production. In addition, provision of information on the performance of different forage legumes under a wide range of environmental conditions can help farmers to make informed decisions. For instance, Murungweni et al.  reported a 15-fold increase in adoption rates of forage legume use by smallholder farmers in the high rainfall (>800 mm per annum) areas of Zimbabwe following on-farm trials. If this success can be replicated on a large scale, livestock production could increase substantially. Mucuna and lablab found to be the most adopted legumes for use in rotation with maize, restoration of fallow lands and for fodder production [34, 51]. The incentive for growing these forage legumes were enhanced soil fertility, which increased maize yield and provision of fodder for livestock. For example, maize yield doubled when the crop was grown a year after a legume . The growing of legume forage crops also enabled smallholder farmers to replace commercial livestock feeds, reducing production costs. In addition to their good forage attributes, mucuna and lablab are also drought tolerant . Furthermore, improved availability of seed could result in more farmers growing forage legumes.
Lablab is a high yielding forage crop with dry matter yields of about 10,900 kg/ha/year. It has a crude protein content of 14–19% of dry matter and low fibre content and high digestibility. Lablab can be fed as fresh foliage, hay or silage, although freshly harvested forage need to be wilted before feeding to avoid a bad flavour in the milk.
Mucuna is a tropical legume, which grows well in soils of low fertility because of its ability to fix nitrogen. It has a crude protein content of 11–23% of dry matter (dried beans contain 20–35% of dry matter crude protein) and has low fibre content.
Cowpeas are drought tolerant, grow well in sandy soils of low fertility and have high crude protein content (20–30% of dry matter). Three types of cowpeas have been developed
7. Forage crop conservation
Forage crops can be conserved as hay or silage for feeding livestock during the dry season when the grass in the natural rangeland would have declined in nutritive quality. In dairy farming, silage is the more preferred method of conserving forage crops. The aim of making silage is to preserve the energy and protein content of the forage for feeding during the dry season. The forage crops are harvested at an early growth stage when their nutrient quality is still high. Silage making is divided into three stages
When selecting material for making silage, the following need to be considered; plant material nutritive value (energy, protein, vitamins and minerals), easy of ensiling and most suited crop for the area (rainfall, soil type, temperature, day length). The amount of silage to be made will depend on the number of animals to be fed, length of feeding period, proportion of silage in total ration and equipment available on the farm.
Since maize is a staple food for most households in Zimbabwe, other grass plants such as bana grass can be used to make silage. To get the best quality silage from bana grass, harvesting should be before it develops internodes (6–8 weeks after onset of resprouting or shoot development). Dry matter content should be between 30 and 40% to get good compaction. Only forage that will be ensiled should be cut on each occasion to minimise wilting loses. Ensiling should be done in as short a time as possible preferably within a day to preserve forage quality. The plant material should be fine and evenly chopped to maintain forage quality. For instance, it can be chopped into 2 cm pieces using a motorised chopper or into 4–5 cm pieces manually using axes. The material should be compacted tightly to remove all the air out of the silo. After compaction, the silo should be sealed tightly to prevent air entrance. All the sides of the silo should be covered with polyethylene and soil put on top of the cover to keep it air tight and avoid soil and water entrance.
Cereal crops such as maize, forage sorghum and bana grass can be ensiled with legumes to improve silage quality. Ensiling tree legumes mixed with maize or Napier grass improves the energy and protein content of the silage . Cereal silages are rich in energy but low in crude protein while the converse is true for legume silages . Ensiling maize with legumes increases the crude protein content of the silage. For instance, crude protein content increased from 7.7% of dry matter for maize silage only to 9.3–15.3% of dry matter with a legume incorporated . Maasdorp and Titterton  ensiled the leaf material of four forage tree legumes with maize, on a fresh mass ratio of 50:50 (w/w) and the crude protein content increased to 14.0, 15.5, 17.2 and 18.7% of dry matter for maize-
|Constituent||Before ensiling||After ensiling|
|Modified acid detergent fibre||28.0||28.5||28.8||31.1||33.7||34.8|
|Neutral detergent fibre||51.6||52.1||52.3||49.9||49.1||47.7|
|Acid detergent fibre||36.3||36.1||36.9||35.0||34.6||35.3|
|Metabolisable Energy/MJ/kg dry matter||11||10||10||10||10||9|
The crude protein content of ABM and LLM silage were above the minimum requirement for growth (11.3% of dry matter) in ruminant animals . Titterton et al.  reported higher crude protein content values of 20.87 and 17.60% of dry matter for ABM and LLM respectively. The metabolisable energy content of the silages was above the minimum acceptable level of 8 MJ/kg dry matter required for maintenance . Ensiling increased the modified acid detergent fibre but reduced the neutral detergent fibre content of the silages.
Although ensiling cereal crops with tree legumes improves the quality of the silage, it has not been widely promoted among the smallholder farmers. For example, Hove et al.  reported a few farmers (7%) as ensiling tree legume leaves mixed with maize in high rainfall (>800 mm per annum) areas of Zimbabwe.
Forage crops can also be harvested during the wet season and preserved as hay for feeding animals during the dry season. To make hay, the forage crops are harvested at 50% flowering stage and air dried for a day or two to reduce moisture content. Legumes such as cowpea, lablab and mucuna can be air dried and rolled into bundles and stored in shades with good ventilation.
8. Future prospects of forage crop production
In Zimbabwe, currently less than 3% of smallholder farmers are growing forage crops . This inevitably means low livestock productivity due to feed shortages, particularly during the dry season. However, farmers with smallholder dairy projects in areas receiving medium rainfall (600–800 mm) grew between 0.1 and 1 ha of fodder crops . Forage and browse legumes grown were