Desmodium fodder crop

Written by Maurice Rangoma.

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Desmodium is a trailing or climbing perennial legume with small leaves and deep roots which, in favourable conditions, forms very dense ground cover. Desmodium is popular in cut-and-carry systems.

There are numerous varieties of desmodium but the two most common are the green leafed and the silver leafed ones. Green leaf desmodium is leafer with reddish brown to purplish spots on the upper surface of the leaves and reddish brown stems. Silver leaf desmodium has stems and leaves covered in dense hairs which make them stick to hands and clothing. It has green and white leaves which are light green underneath.

Advantages

High quality, protein rich forage; can be grown between or under other crops - as it fxes nitrogen it increases yields and reduces the need for nitrogen fertilizer.

Disadvantages

Seed is expensive and very small;
Needs rhizobium inoculant;
In very high rainfall areas (more than 1500 mm per year) it suﬀers from pests and diseases;
Does not tolerate drought;
May need irrigation in lower rainfall areas;
Does not tolerate alkaline soils.

Cultivation

Climate	It does well in warm, wet regions at altitudes of 800 m to 2500 m receiving at least 875 mm rainfall per year.
Soils	Adapted to a wide range of soils from sands to clay loams and tolerates slight acidity but not salinity. Acidic soils can be improved by applying manure at the rate of 8 tonnes per hectare prior to sowing or planting.
Site	Desmodium can be grown as a pure stand or as a mixture with Napier grass in cut-and-carry plots. It can also be grown under a maize crop or even as a cover crop under bananas or coﬀee.
Preparation	Desmodium seed is relatively expensive, very small and the seedlings can be swamped by weeds, so it is best sown in a weed-free, well prepared nursery seedbed with fine textured soil. A seedbed 3 m by 3m, raised 15 cm high, will require about 100g of seed. Desmodium needs to grow in close association with a group of very benefcial bacteria called rhizobia. These bacteria live in the roots of desmodium and other legumes and can fx nitrogen from the air, which is then available as a free fertilizer to the desmodium plants. If available, packs of rhizobia inoculant should be obtained. Mix the contents with the desmodium seed and carefully following the instructions on the pack. If not available, mix the seed with a handful of soil from another good desmodium plot.
Sowing	Te best time to plant is at the start of rains. For areas with two rainy seasons, sow seeds during the short rains but plant cuttings during the long rains. Sow the seed immediately after adding the inoculant. The seeds can be sown either by drilling or by broadcasting. For drilling, make shallow furrows about 5cm deep spaced 30cm apart. Cover the seed with 1 cm of soil and press softly. For broadcasting, spread the seed evenly over the seed bed. The nursery bed should be watered carefully and often. Shade may be provided but it should be removed soon after germination. Desmodium can also be established from cutting. Compared to seed, cuttings are bulky but can be obtained at little or no cost from a neighbour and they compete well with weeds during establishment. Get cuttings from an established nursery or from desmodium in the field. Desmodium cuttings should be vines 60cm long with soil still attached to the new roots. Make furrows 30cm apart and 10cm deep and plant the vines 30cm apart. Desmodium can be grown between rows of Napier grass. Plant the Napier grass at a spacing of 1m between plants and, wider than usual, with 2m between rows. Make holes between rows of the newly planted Napier. Plant desmodium cuttings 30 cm apart, as you would sweet potato vines. When grown together with Napier, desmodium adds nitrogen to the soil, benefting the Napier and reducing the amount of nitrogen fertilizer required for topdressing. Once desmodium has fully established, it forms a complete ground cover which smothers the weeds, thus reducing the labour requirement and cost of weeding the Napier plot.
Fertilizer	Apply 500g of phosphate fertilizer, TSP (45% P) or DAP (46% P, 18% N) to the 3m by 3m plot before sowing and mix thoroughly with soil. Alternatively add 15 kg dry farmyard manure to the seedbed before planting. When growing desmodium with Napier grass, add one handful of farmyard manure per hole at planting and mix thoroughly with the soil. Also apply 2 bags TSP or DAP fertilizer per hectare during heavy rains and after every cut apply manure in a furrow and cover with soil.
Weeding	Keep the plot weed-free especially during the early stages of establishment. When well established, desmodium is able to suppress weeds.
Pests	Common pests are aphids and the Amnemus weevil, both of which can be controlled by use of insecticides: be careful to strictly observe use and safety instructions on the pack. If aphids are not controlled, they may transmit a viral disease known as little-leaf. A fungal disease, anthracnose, can aﬀect desmodium especially in poorly drained soil.
Harvesting	Desmodium pure stand: Start harvesting after at least four months. Te best harvesting regime is to cut at 12-week intervals at no less than 10cm above soil level. Desmodium – Napier mixture: First harvest should be at least four months after establishment or when the Napier is about 1 m high and at an interval of 4 to 10 weeks thereafter. Cut the desmodium and Napier together. Leave stumps of 10 to 15 cm above the ground for both crops.
Feeding	Desmodium is a good quality supplementary forage with a high protein content. It should be given in small quantities mixed with basal fodders. Harvest just what is needed and spread it in the sun for a few hours to wilt. Chop and mix thoroughly with other forages, such as maize stover or Napier grass, then feed to the animals. Tree to six kilograms of green desmodium is equivalent to one to two kilograms of the commercial concentrate. Excess desmodium may be cut, dried and baled into hay and used as a protein supplement. It can also be mixed with grass when making hay.