UTILIZATION POTENTIALS OF LABLAB (Lablab purpureus (L.) Sweet) AND THE CONSTRAINTS OF FIELD PESTS AND DISEASES IN NIGERIA

In the last one decade and half, lablab was evaluated for its crop-livestock production potentials in Samaru, Kano and Benin City in both the savanna and humid forest zones of Nigeria. Very early, early and intermediate accessions were identified that may be suitable for dry savanna and late growing season of the humid forest while late, very late and extremely late accessions were identified for moist savanna and humid forest. Vegetable-type, grain-type and dual-purpose lablab were identified. Lablab grain ranged from 600-2400 kg ha with an average protein concentration of 25.3%. Huge litter of leaves and stems was recorded at the end of production period which extended far into the dry season. Short fallow of one year supported maize-cowpea intercrop with component maize having 13.7% grain yields over that of natural fallow. Following a 2-year lablab fallow, subsequent maize yield was 72.7% higher than that from natural fallow. Lablab had an average of 2600 kg ha of biomass and an average of 64.1 kg N ha, meaning that lablab has high potential for green manure and soil improvement. Of six herbaceous legumes, lablab was among those that had the highest soil cover. Fresh biomass of 3200 kg ha was achieved at eight weeks after planting. Various insect pests, fungal diseases and parasitic plant including Ootheca mutabilis (Sahlb), Podagrica uniforma (Jac.), Nematocerus acerbus (Faust), Anoplocnemis curvipes (F.), Helicoverpa armigera (Hbn), aphids, Colletotrichum sp., Curvularia sp. and Cassytha filiformis (Linn.) were found on lablab plants, causing damage to the crop.

Crop and livestock production are major agricultural enterprises in Nigeria, contributing to household welfare and national economy (Kowal and Kassam, 1978;Ndubuisi et al., 1998).However, in the Nigerian savanna, most soils are naturally of low fertility and the amount of organic nitrogen mineralized annually is often well below the requirement for high crop yields.Due to human population and economic pressures, fallow has been shortened or has entirely disappeared (Kowal and Kassam, 1978;Manyong et al., 1997).This has resulted in continuous cropping or land-use intensification which, in turn, are causing serious soil degradation/erosion and fertility problems, decline in natural species diversity and crop yield, weed problems (Kowal and Kassam, 1978;Webster and Wilson, 1980;Ehui and Jabbar in Jagtap and Amissah-Arthur, 1999;Jabbar, 1995;Tian et al., 1995;Anon, 1997a).In the humid forest of Nigeria, land use has also intensified.There are soil fertility problems and crop yields are low together with increased poverty.Farming systems are changing and fertilizer costs and scarcity make N fertilizer input inadequate.With changes in climate, herding is becoming a common farming activity with its attendant social-economic problems.
The introduction and use of forage legumes are considered an essential part of the process of intensification (Thomas and Sumberg, 1995) and can improve the influence of livestock on soil fertility when used as livestock feed (Tarawali et al., 2001).In fact, Anon (1997b) believes that the most promising opportunity for integration of crop and livestock is improved animal feeding through dual purpose fallow-forage systems and use of crop residues.During the dry season, when the naturally available feed resources are of very poor quality, herbaceous legumes can also produce substantial quantities of better and nutritious fodder for livestock (Schaaffhausen, 1963;Makenbe et al., 1996;IITA, 1997).Other reports have shown that the inclusion of herbaceous legumes in farming systems resulted in increased crop yield, reduced weed infestation and prevented soil degradation (Rattray and Ellis, 1953;Vine, 1953;Tian et al., 1995).Herbaceous legumes have also improved soil physical and chemical properties (Vine, 1953;Lal et al., 1978), and can contribute to the control of Striga hermonthica (IITA, 1997).Central to crop and livestock production, therefore, is the inclusion of herbaceous legumes in the farming systems of the savanna and rainforest agroecologies.
In 2000 and beyond, both the International Institute of Tropical Agriculture (IITA) and International Livestock Research Institute (ILRI) showed interest in the evaluation of lablab in the northern Guinea savanna of Nigeria for its potential contribution to crop-livestock production systems (Ewansiha et al., 2007a,b;2008;Ewansiha and Chiezey, 2012).Specific activities involved in the lablab research included evaluation of lablab in Samaru in the Nigerian northern Guinea savanna for morpho-phenological variation, potential for crop and livestock production, maize production and drought tolerance.Other experiments involving lablab have also been conducted.In Kano, in the Nigerian Sudan savanna, Ewansiha and Singh (2006) evaluated lablab together with other grain legumes and cereals for drought tolerance.Ewansiha et al. (2012), evaluated lablab for its effects on soil properties and subsequent maizecowpea intercrop in Samaru.The performance of dual-purpose lablab and cowpea was evaluated under maize in Samaru (Ewansiha et al., 2016a).
In Benin City, in the rainforest agro-ecology, experiment was conducted to evaluate lablab together with other herbaceous legumes for their potential use in green-manuring (Ogedegbe et al., 2016).During the period of evaluation in Samaru and elsewhere, it was observed that lablab suffered from a complex of pests and diseases (Ewansiha et al., 2016b).Despite control using insecticides and fungicides, it was necessary to determine the type of pests associated with lablab.While the results of these various researches have been reported (Ewansiha and Singh, 2006;Ewansiha et al., 2007a,b;Ewansiha et al., 2008;Ewansiha and Chiezey, 2012;Ewansiha et al., 2012;Ewansiha et al., 2016a,b;Ogedegbe et al., 2016), this paper highlights the outcomes of these various researches in terms of production niches for lablab, lablab providing grain and pod for food, lablab as a resource for crop production and for soil protection, and lablab as fodder for livestock production as well as the pests/diseases that affect it.

Production Niches for Lablab
Forty-six lablab accessions were evaluated and classified (Ewansiha et al., 2007b; Table 1).Of these accessions, six maturity groups were identified: very early (av.47 days to 50% flowering), early (av.54 days), intermediate (av.72 days), late (av.98 days), very late (av.123 days) and extremely late (av.144 days).The very early, early and intermediate accessions seem suitable for dry savanna with low rainfall or short growing season and the late growing season of the humid forest.These accessions can be grown either as sole crops or in intercrops with cereals.The late, very late and extremely late accessions appear suitable for moist savanna and humid forest with longer growing seasons.These accessions had faster growth and quick soil cover and can therefore provide protection for soils and suppress weeds as well.Lablab as a Quality Food Crop Of the forty six lablab accessions evaluated, fifteen accessions were suitable for vegetable pods, 11 accessions were suitable for grain-type lablab and three accessions were suitable for food-feed use (Ewansiha et al., 2007b;Table 2).With the very early to intermediate accessions, lablab could provide sufficient grain early in the season when food stores would be getting depleted.Grain yield obtained (600-2400 kg ha -1 ) was comparable with yields obtained with other grain legumes (Ewansiha et al., 2007a; Table 3).The lablab grain had an average protein concentration of 25.3% which was comparable with protein contents reported for the dry seeds of the common grain legumes (Table 3), indicating the potential for lablab to contribute to high quality grain nutrition.It also reveals the potential of lablab to fix and supply N since no N fertilizer was applied.As a grain crop, lablab tolerance to drought ensures that food is available even when rains are erratic and when moisture is limiting.Six accessions were identified to be drought tolerant (Ewansiha and Chiezey, 2012), making it possible to develop drought tolerant varieties through breeding and selection.When various herbaceous legumes and cereals were screened for drought tolerance, the most drought tolerant group comprised of lablab (Ewansiha and Singh, 2006).Lablab is drought tolerant because it has a deep taproot system which can penetrate to more than 2 m below the soil surface thus enabling it to sustain growth on residual soil moisture (NAS, 1979;Kay, 1979;Duke et al., 1981).

Lablab as a Resource for Crop Production
Lablab has a potential for up to an average of 2600 kg ha -1 of biomass and an average of 64.1 kg of nitrogen ha -1 (Ewansiha et al., 2007a;Table 4).This means that lablab has high potential for green manure and soil improvement.Moreso, when the biomass is removed as forage to feed livestock, the soil fertility contribution is balanced with the return of the manure and the contribution of the lablab plant roots.With the huge litter of leaves and stems at the end of the growing season which extends into the dry season, high amount of quality crop residue for conservation agriculture is implicated (Fig. 1).In one trial, performance of maize grown following two years of lablab cultivation and incorporation of its plant residues shows that it can support high yield of maize (Ewansiha et al., 2008;Table 5).Lablab fallow supported similar yields of maize across lablab maturity groups from very early to extremely late.Yields of maize for lablab plots were on the average 72.7% higher than for the natural fallow plots.In another trial, yield of maizecowpea intercrop following one year of lablab fallow and subsequent incorporation of plant residues indicates the ability of lablab to support cereal-legume production systems (Ewansiha et al., 2012;Table 6).Lablab and natural fallows compared well for grain yield and seed weight.Lablab fallow, however, favoured higher fodder yield in maize because it improved the supply of soil organic matter, nitrogen, phosphorus and potassium (Ewansiha et al., 2012;Table 7).Lablab was able to contribute to the observed improvement in soil fertility because it is a nitrogen-fixing crop with remarkable ability to nodulate even without inoculation (NAS, 1979;Duke et al., 1981).

Lablab as Resource for Livestock Production
Sixteen accessions were of good and high quality forage (Ewansiha et al., 2007a; Table 8).These accessions have potential to improve crop and generate residue, which promises to be the dominant feed resource as crop-livestock integration becomes more developed (Smith et al., 1997).Moreover, the various trials recorded huge litter of lablab, lablab biomass and maize stover which provides opportunity for crop and livestock production through sharing of crop residues.Figure 1 show huge litter of lablab leaves and stems at the end of production period which extends far into the dry season.This means that quality fodder can be available for livestock at a time when fodder becomes scarce, natural grasses become less nutritive and animals lose weight.With a dense growth, the lower leaves are shed, which is a potential crop residue for livestock during growing season.Intercrop of lablab and maize gave good grain and fodder yields of lablab relative to that of cowpea (Ewansiha et al. 2016a, Table 9).Several other experiments have shown the importance of lablab.The vines when cut with sorghum (Sorghum bicolor (L.) Moench) straw gave a mixed fodder of high nutritive values (Shivashankar and Kulkarni, 1989).Selvan et al. (1993) found sorghum-lablab intercrop to be superior in grain yield to sorghumsoyabean intercrop.In Zimbabwe, diets based on maize (Zea mays L.) stover and lablab could provide adequate nutrients to maintain goat productivity during the cropping season (Makenbe et al., 1996).

Lablab as a Resource for Soil Protection
Evaluation of the performance of six herbaceous legumes in the humid forest region showed that lablab was among the legumes that had the highest soil cover (Ogedegbe et al., 2016;Table 10).Fresh biomass was highest in Mucuna pruriens followed by lablab.This was achieved in eight weeks implying that both legumes can provide soil protection, biomass for green manure or fodder for livestock early in the growing season.Ewansiha et al. (2008) reported that lablab can be a candidate crop for soil protection, green manure and fodder because it has quick growth combined with high biomass production.

Constraints of Field Pests in Lablab Production
A complex of field pests and diseases were observed on lablab.Insect pests and diseases affected the lablab plants right from the planted seeds through the emerging seedlings and vegetative stage to podding.Young millipedes attacked planted seeds and seedlings.The pests and diseases identified included foliage insects, podsucking insects, pod-eating larvae, aphids, fungus and parasitic weed (Ewansiha et al., 2016b;Table 11).Severe damage to pods was caused by the podeating and pod-sucking insects that caused pod filling to fail after attack (Ewansiha et al., 2016b).The pest complex observed on lablab was however, similar to that associated with cowpea.Therefore, as with cowpea, lablab can be successfully grown with adequate use of pesticides.

CONCLUSION
Lablab, though an underutilized crop, has the potential to serve as a grain, fodder and resource crop in northern and southern Nigeria.Pests can, however, constitute a setback to its production.

Fig. 1 :
Fig. 1: Lablab litter at end of production period and harvest of pods

Table 1 :
Classification of lablab purpureus according to time of 50% flowering

Table 2 :
Lablab accessions good for vegetable pod, grain and food-feed use

Table 3 :
Grain yield and mean crude protein (cp) of some dual-purpose legumes

Table 4 :
Range and mean values of biomass yield and quality of lablab accessions

Table 5 :
Grain yield of maize following 2-year lablab cultivation and incorporation of lablab residues

Table 6 :
Grain and fodder yields (kg ha -1 ) of intercropped maize/cowpea after one-year lablab cultivation and incorporation of lablab residues

Table 8 :
Leaf dry matter yield and quality of lablab

Table 9 :
Grain yield of dual-purpose lablab and cowpea as sole and when grown together with maize

Table 10 :
Soil cover and yield of herbaceous legumes at 8 weeks after planting

Table 11 :
Pests and diseases observed in Lablab purpureus