VII. Intensive production

Leucaena as a forage crop on small farms in Malawi*

R. Savory, J.A. Breen, and C.I.A. Beale

FAO Livestock Project MLW/75/002, Lilongwe

Introduction

Seed production storage and scarification

Establishment

Mineral nutrition

Harvesting

Varietal evaluation

Processing

Utilization

Discussion: the problems

References

Introduction

Leucaena leucocephala (Lam) de Wit is a perennial legume with high potential as stock feed in the tropics and sub-tropics (Dikjman, 1950, Hill, 1971, NAS, 1977). Leucaena has been used for browse purposes (Gantt 1953, Humphreys 1962), and forage cropping (Takahashi and Ripperton, 1949, Ferraris, 1979).

In a pasture introduction and screening programme in Malawi, cv. Peru showed high biological potential at a number of dry land sites but proved unsuitable for the wet "dambo" soils (Savory, 1972). Subsequent establishment and management studies and variety trials were conducted at two contrasting sites, namely Mpemba in the Shire Highlands, and Zunde in the Lower Shire Valley (Tables 1 and 2). At neither site was Leucaena nodulated by the native Rhizobium; at Mpemba the roots were heavily infected by vesicular arbuscular endomycorrhiza (VAE).

Table 1. Site and soil characteristics for Mpemba and Zunde.

Table 2. Climatic data recorded during experimental period.

^a Open pan evaporation c 2300 mm/an.

Leucaena is now produced on small holdings in villages surrounding the experimental sites. The foliage is used as fresh forage or is sun-air dried and either fed as a winter supplement or else sold as a cash crop. This paper describes production, processing and utilisation techniques and discusses the problems that have been encountered on smallholdings.

Seed production storage and scarification

Seed orchards are established either by direct sowing or by transplanting potted seedlings. The plants are spaced at 1.5 m x 1.5 m. At Mpemba, nitrogen and phosphorus are applied annually at 40 and 20 kg/ha respectively. The first pods to ripen are plucked by hand but later in the season the branches are cut back to a 50 cm stubble and windrowed. Yields of 1000-1500 kg clean seed/ha/ are obtained. Seed is stored in Hessian sacks and is not susceptible to attack by normal grain storage pests.

Scarification by the hot water method (Gray, 1962) is effected using a half-200 litre petrol drum over a wood fire. Successive batches of c 10 kg seed are placed in a Hessian sack, immersed in the hot water (80°C) for two minutes, drained and then spread out to dry. The temperature and the immersion period are not critical, and a competent team of men can easily scarify more than one tonne of seed per day.

Establishment

Immediately before sowing, the scarified seed is inoculated with a mixture of Rhizobium strains CB81 and NGR8, using a 10 percent sucrose solution as an adhesive. On occasion, when commercial inocula are unavailable, the seed is inoculated with soil from beneath other Leucaena plants which are known to be nodulating effectively.

Experimental results indicate that the optimum population density is c 200,000 plants/ha at Mpemba and c 100,000 plants/ha at Zunde. To achieve this population at Mpemba, a seed rate of c 18 kg/ha is required. At Zunde, where establishment is difficult due to erratic rainfall and high temperatures, a seed rate of c 25 kg/ha is used, and it may be necessary to supply parts of the field or to resow the whole area.

Most arable crops in Malawi are grown in rows 90 cm apart and this spacing has now been adopted for Leucaena. Although there is less weed competition at a 60 cm row spacing, dry matter yields are not significantly affected. Furthermore, manual operations become more difficult at the narrower spacing.

Leucaena is established either by direct sowing into a well prepared seedbed, or by under sowing to a crop of maize. In the latter method, which is recommended in the Shire Highlands, the Leucaena seed is sown between maize stations on 90 cm ridges, either at the same time as the maize, at the start of the wet season, or else at the first weeding in January. The seed is sown at 2 cm depth along the top of the ridge, using a calibrated container such as a fertilizer cup or bottle top to provide the correct seed rate.

The importance of weed control in the early stages of establishment has been mentioned repeatedly in the literature (Takahashi and Ripperton, 1949; Anslow, 1957; Hill, 1970). The slow initial growth rate of Leucaena makes the seedlings particularly susceptible to weed competition and it is necessary to inter-row cultivate up to four times during the first wet season. In subsequent years weeds become less of a problem, provided an even, high-density crop population has been established.

Leucaena is susceptible to termite attack during the establishment year, especially during the seedling stage. Control is effected by spraying the crown of damaged and adjacent plants with 1% dieldrin.

Goats are very partial to Leucaena foliage, specially during the dry season. Continuous nibbling of small shoots reduces subsequent plant vigour and the situation is aggravated by increased weed competition

Mineral nutrition

Despite the fact that available soil phosphorus levels are low to very low at both sites, foliar phosphorus levels (2.1–2.2 g P/kg DM) lie within the normal range. It is possible that nutrient uptake is enhanced through an association with VAE, as postulated by Possinhgam et al (1977).

Harvesting

The crop is first cut back at the start of the second wet season. By then, the plants are only about one metre high, growth is very uneven and the yield of leaf is usually less than 0.3 t DM/ha. This state of affairs unfortunately leads some farmers to despair of future production and to lose interest in their crop.

In the second and subsequent years, the optimum stage for harvesting is when lower leaves start to drop, i.e. when the tallest branches have grown c 1.5 m above stubble height. If harvesting is deferred beyond this point, yield losses due to leaf drop may be as high as 70 per cent.

The harvest interval is variable, depending on the location and the weather prevailing during the growth period. At the height of the wet season in the Lower Shire Valley, the crop can be harvested at 4-week intervals and dry season temperatures are sufficiently high to allow growth to continue until available soil moisture is exhausted. Production only recommences after the first heavy fall of rain at the start of the following wet season. At Mpemba, on the other hand, cooler temperatures in summer allow only one harvest every 6 to 8 weeks and, as the dry season approaches, growth is limited more by temperature than by moisture stress. As the temperature rises again in September, residual moisture in the soil enables a flush of growth before the rains break. This flush may yield more than 1 t DM leaf/ha.

In normal years 3 or 4 harvests are taken, each yielding 1.5 – 2.5 t DM leaf/ha, i.e. total yields vary between 5 and 10 t DM/ha/an. Production tends to increase over the first 4 years, presumably due to improved root penetration.

At each successive harvest, the branches are cut back to about 2.5 cm above the previous stubble height. It therefore is necessary, after about 3 years, to cut the stems back to a new primary stubble at c 10 cm.

Varietal evaluation

In trials conducted over a three year period at Mpemba and Zunde, the following varieties were studied:

cultivar Cunningham (Cunn)
cultivar Hawaiian Giant K8 (HGK8)
cultivar Peru (Peru)

Differences in germinability and seedling vigour were negligible. Although significant yield differences have previously been reported between Cunn and Peru (Hutton and Beattie 1976) and between KGK8 and Peru (Brewbaker et al, 1972) such differences did not occur under intensive cropping in Malawi (Table 3).

Table 3. Dry matter production of three Leucaena cultivars (3rd year).

	Yield of leaf (t DM/ha/Yr)
	Cunn	HGK8	Peru
Mpemba	6.32a	6.38a	5.44a
Zunde	5.25a	4.93a	5.49a

Figures in each row, joined by the same postscript letter, do not differ significantly at P = 0.05

At Mpemba, the order of flowering was Peru, Cunn, HGK8 and at Zunde, Peru, HGKB, Cunn. Both Cunn and HGK8 tended to produce fewer, longer branches while Peru produced more, shorter branches. Cunn and Peru branches were significantly leafier than those of KGK8 (Table 4).

Table 4. Physical branch composition of three cultivars (Mpemba).

Figures in each row, joined by the same postscript letter, do not differ significantly at P = 0.05

In most respects, there were only minor differences in chemical composition between cultivars; the most important differences being those of the lower mimosine and the higher xanthophyll values of Cunn (Table 5). Overall, Cunn is considered superior to HGK8 and Peru, and is the cultivar currently recommended in Malawi.

Table 5. Chemical and nutritional characteristics of three Leucaena cultivars (January harvest, Mpemba).

	Cunn	HGK8	Peru
Whole leaf
Ash (g/kg DM)	84	69	74
N × 6.25 (g/kg DM)	217	230	234
Crude fibre (g/kg DM)	123	149	136
Ether extract (g/kg DM)	22	28	31
N.F.E.(g/kg DM)	622	590	592
T.D.N. (g/kg DM)	617	609	609
Mimosine (g/kg DM)	23	42	28
D value (DOMD %)	52.6	52.3	54.3
Pinnule
Carotenoids (g/kg DM)
B– carotene	389	310	315
Xanthophylls (total)	873	653	609

Processing

Where fresh Leucaena foliage is fed to stall cattle, bundles of branches are placed in the food rack once a day. There are conflicting opinions as to whether pre-wilting increases or decreases palatability

Where the foliage is to be dried, cut branches are laid on their own stubble in such a way as to provide maximum air circulation and minimum soil contamination. After one or two days drying, the branches are heaped up and threshed by hand-beating. Once the separated leaflets (pinnules) have dried to the stage that they can be easily crushed by hand, they may be stored without fear of mould damage. Dried leaf destined for winter feeding requires no further processing and may be stored in Hessian sacks without being attacked by grain storage pests. Where the dried leaf is to be marketed as an ingredient in poultry rations, it is necessary to sieve off any twigs, flowers, rachises and rachillae. These by-products contain 10-15 per cent crude protein and are fed to cattle.

The grading scheme for dried Leucaena leaf products is presented in Annex 1. for export purposes, the dry pinnules are palletized.

Utilization

The value of Leucaena as a feed for ruminants in the tropics has recently been discussed by Jones (1979).

In Malawi, Leucaena is fed, together with Pennisetum purpureum (Napier grass) and 'madeya' (maize bran) to beef and dairy cattle held in stalls on smallholdings. Although some foliage is fed fresh, farmers are encouraged to conserve the leaf for winter feeding. On a typical smallholding of two hectares, a Leucaena plot of 0.25 ha will produce sufficient dry leaf to feed three dairy cows or fattening steers, at the rate of 3 kg DM/head/day, through the dry season. At this level of intake there have been no clinical symptoms of mimosine-DHP toxicity. Malawi Zebu and Zebu × Fresian steers, fed a ration of Leucaena leaf and maize bran (1:4) and maize Stover gained 1.17 kg/head /day (Thomas and Addy, 1977).

Where Leucaena is produced as a cash crop, dried leaf is sold to the local milling company for incorporation in layers, rations as a source of carotenoid for yolk pigmentation. In a country where neither yellow maize nor Lucerne are grown, Leucaena meal provides an economical alternative to imported synthetic carotenoids.

Inclusion of milled Leucaena leaf in layers, rations at the 5 per cent level provides sufficient xanthophylls to pigment the yolks at intensities of 10 or more on the Roche Scale, with no deleterious effects on egg production or bird health. Egg yolk colour decreases as the age of the meal increases, due to oxidation of the xanthophylls. Oxidation can be reduced to a large extent by pelleting the meal and by adding a small quantity of antioxidant.

Discussion: the problems

We would like to discuss further some of the practical problems that have arisen during our studies in Malawi. While the effect of unfavourable environmental factors can be reduced by research, there is great scope for improved management by the smallholder.

1) Sowing of unscarified seed occurs when a farmer obtains seed from his neighbour. Poor establishment often leads to disillusionment with the crop.

2) Sowing of uninoculated seed can also occur when seed is obtained from neighbours and in some cases there have been nodulation failures following the use of commercial inocula. Rhizobium mortality can be due to desiccation, overheating, freezing, exposure to sunlight or aging of the culture.

3) There have been major establishment problems in the vertisols of the Lower Shire Valley, due either to wet weather causing anaerobic conditions and germination failure of deep-sown seed (c 7 cm), or due to dry weather causing desiccation of shallow-sown seed (c 2 cm). It is essential to have a reserve of seed for supplying poorly established stands.

4) Termite attack at the seedling stage can be a major problem. Daily surveillance of the crop is necessary during the first few weeks and provision must be made for immediate spot spraying with a suitable insecticide such as dieldrin or aldrin.

5) On some smallholdings, weed control during the establishment year is hopelessly inadequate. Understandably, the farmer places higher labour priority on his staple crops than, to him, on an unknown stock feed. The problem is compounded on occasion where the Leucaena is finally weeded, and the thick layer of dry trash is burned accidentally, killing many Leucaena plants. One of the main advantages of under sowing Leucaena to maize is that both crops are weeded simultaneously.

6) The nutritional requirements of Leucaena on different soils have not been clearly defined. The current fertilizer recommendation for latosols of 100-200 kg single super phosphate/ha/Yr is somewhat ad hoc and more research is required in order to obtain economic response curves for the various nutrients.

7) The widespread presence of goats in the villages is the biggest factor limiting the expansion of Leucaena in Malawi. It must be stressed that where free-ranging goats are present, the production of Leucaena should not be attempted unless a suitable wire mesh fence is erected.

8) During harvesting the branches are sometimes cut back as much as 15 cm above the previous cut. The result is that, over a two year period, the stubble height increases unnecessarily and an early cut back to a primary stubble height is required.

9) Considerable yield losses occur on farms due to delayed harvesting. While this may be unavoidable because of inclement weather, in many cases harvesting is delayed because it appears to the farmer, as the crop continues to grow to 2 and 3 m height, that yield is increasing proportionately. He does not appreciate the losses due to leaf drop under the green canopy.

10) Similarly, considerable leaf losses occur during transporting of over-dried branches in the field. This can be avoided by stacking partially wilted branches at the threshing floor or by moving the branches early in the morning, when the higher humidity causes some reimbition of moisture into the leaf.

11) Recently harvested foliage is sometimes damaged by rain and the resulting colour loss renders the leaf unsuitable for sale as poultry food. If the rain damaged foliage can be dried within two or three days, it still retains its palatability and protein value and can be used as cattle food.

References

Anslow, R.C. (1957).'Investigations into the potential productivity of acacia (Leucaena glauca) in Mauritius'. Rev. Agric. Sucr. Ile Maurice 36: 39–49.

Brewbaker, J.L.; Plunkett, D.L.; Gonzales, V. (1972). 'Varietal variation and yield trials of Leucaena leucocephala (koa haole) in Hawaii'. Hawaii Agric. Exp. Stn., Res. Bull. 116. 29 pp.

Dijkman, M.J: (1950). 'Leucaena, a promising soil erosion control plant'. Econ. Bot. 4: 337–349.

Ferraris, R. (1979). 'Productivity of Leucaena leucocephala in the wet tropics of North Queensland'. Trop. Grassl. 13: 20–27.

Gantt, P.A. (1953). 'Utilisation to Leucaena glauca as a feed in the Philippines'. Proceedings 8th Pacific Science Congress (IVB).

Gray, S.G. (1962). 'Hot water seed treatment for Leucaena glauca (L.) Benth'. Aust. J. Agric. Anim. Husb. 2: 178–80.

Hill, G.D. (1970). 'Studies on the growth of Leucaena leucocephala ( i ) Effect of clean weeding and nitrogen fertilizer on early establishment'. Papua New Guinea Agric. J. 22: 29–30.

Hill, G.D. (1971). 'Leucaena leucocephala for pastures in the tropics'. Herb. Abst. 41: 111–119.

Humpreys, L.R. (1962). 'Leucaena glauca'. Queensl. Agric. J. 88: 617–618.

Hutton, M.E.; Beattie, W.M. (1976). 'Yield characteristics in three bred lines of the legume Leucaeana leucocephala'. Trop. Grassl. 10: 187–194.

Jones, R.J. (1979). 'The value of Leucaena leucocephala as a feed for ruminants in the tropics'. Wild. Anim. Rev. 31: 13–23.

NAS (1977). 'Leucaena— promising forage and tree crop for the tropics'. Washington, DC. National Academy of Science.

Possingham, J. V.; Groot Obbink, J.; Jones, R.K. (1971). 'Tropical legumes and vesicular arbuscular mycorrhiza'. J. Aust. Inst. Agric. Sci. 37: 160–161.

Savory, R. (1972). 'Pasture improvement in Malawi: the introduction of legumes into various soil – climate – management ecosystem'. Grassl. Soc. Sth. Aft. Proc. 7: 87–92.

Savory, R.; Thomas, D. (1977). Pasture Handbook for Malawi. (2nd Ed.) FAO/UNDP, Lilongwe, Malawi.

Takahaski, M.; Ripperton J.C. (1949). 'Koa haole (Leucaena glauca) — its establishment, culture and utilization as a forage crop'. Hawaii Agric. Exp. Sta. Res. Bull. 100.

Thomas, D.; Addy, B.L. (1977). 'Tropical pasture legumes and animal production in Malawi'. Wld. Rev. Anim. Prod. 13: 47–52.