Carpon desmodium

Leguminosae

Desmodium spp. 
Desmodium heterocarpon (L.) DC. var. heterocarpon van Meeuwen 

Synonyms

Hedysarum heterocarpon L.; D. trichocaulon DC.; D. polycarpon (Poir.) DC.; D. capitatum Miq.; D. buergeri Miq.; D. ovalifolium (Prain.) Wall. ex Ridley.

A perennial subshrub, sometimes a shrub or herb, ascending or often creeping with a woody root-stock. Stems and branches up to 1 m long, diffuse and ascending or erect, although prostrate under heavy grazing. Adventitious rooting sometimes occurs from stems lying on the soil surface. Stems range from nearly glabrous to densely covered with white or yellowish hairs. Leaves are generally trifoliate, though unifoliate leaves are common on seedlings and not unusual toward the base of mature stems. 
Leaflets smooth on the upper surface and hairy underneath, often with a light green to almost yellow watermark on the upper surface. Terminal leaflet normally broadly elliptic, ovate or obovate, with tips generally retuse. Inflorescence composed of densely flowered, terminal and axillary racemes; flowers pink. Pods erect or ascending, narrowly oblong, compressed and generally four- to eight-jointed, turning from green to dark brown on maturity. Articles quadrangular to semi-elliptic, straight along the upper suture, somewhat rounded below, separating and then dehiscing. Seeds almost quadrate, cream to orange in colour, 2 x 1.5 mm (Kretschmer et al., 1979; Gillett, Polhill and Verdcourt, 1971).

Native to south-east Asia; especially found in Sri Lanka, India, the Himalayas, Burma, Thailand, Malaysia, Indochina, Taiwan, Ryukyu and Japan, as well as the Pacific islands and Australia.

Carpon grows steadily in spring and rapidly during summer and autumn until flowering begins. From then until the last frost it grows very slowly. Thirty percent of its growth takes place in spring, 65 percent from summer to early autumn and 5 percent during the rest of the year (Kretschmer et al., 1979) .

Requires fairly high rainfall. In Ft Pierce, Florida, United States, carpon grows steadily with 1 250 to 1 500 mm of rain a year.

Has sufficient drought tolerance to withstand the regular severe spring drought in Florida (Kretschmer et al., 1979).

Carpon will not survive extended flooding. Experience in Florida suggests that it can survive up to a week of intermittent shallow flooding (Kretschmer et al., 1979).

Carpon should not be planted in seasonally wet areas, but is adapted to the better-drained mineral soils of southern Florida (Kretschmer et al., 1979) .

Cowpea inoculum is recommended in Florida.

A clean, firm seed bed is desirable. In Florida, a rolling, broadcasting of the seed and rerolling are recommended, especially when a vegetatively established companion grass is being used. Where there is already an adequate grass sod, light disc harrowing or chopping should precede the initial rolling, followed again by broadcasting and rerolling (Kretschmer et al., 1979).

In southern Florida, seed can be planted any time from after the last frost until August, but little or no seed will set the first year unless germination occurs before July. On clean seed beds, the suggested rate is from 3 to 5 kg./ha, but in established grass areas 5 to 10 kg./ha should be used (Kretschmer et al., 1979).

770 000.

One commercial sample in Florida contained 50 percent hard seed, while figures of up to 65 percent have been obtained in experimental harvests (Kretschmer et al., 1976), suggesting hard-seed levels are not particularly high.

In southern Florida, recommendations are about 2.5 tonnes of lime and 90 to 100 kg./ha of P205 and K2O applied as an 0-12-6 or similar fertilizer to virgin flatwood soils, with about 300 kg./ha of 0-10-20 annually thereafter (Kretschmer et al., 1979).

Carpon is well able to compete with companion grasses in Florida, even when early spring nitrogen applications have been made to stimulate grass growth. In one stand, neither nitrogen application nor the subsequent heavy grazing had any adverse effect on carpon stands over a four-year period. Carpon also combines well with white clover (Kretschmer et al., 1979) .

Seedling growth is slow.

Under heavy close defoliation, carpon develops a prostrate growth habit, and a very low protected crown from which the new regrowth occurs. It is not easily killed by grazing.

The foliage contains 1 2 to 20 percent crude protein, depending on growth stage, while grass/legume mixtures average 9 to 10 percent crude protein. Some 130 kg./ha N/year was removed from harvested forage. This was equivalent to 190 to 260 kg./ha N applied to pure pangola and bahia grass pastures. In vitro organic matter digestibility of the legume grass mixture ranged from 45 to 60 percent, depending on the grass and season of the year. Tannin percentages from two cuts were 2.3 and 3.1 percent (Kretschmer et al., 1979).

Initial commercial yields of 100 kg./ha have been obtained.

One cultivar, Florida, was released in 1979 by the Agricultural Research Center, Ft Pierce, Florida. It derives from USDA Plant Introduction No. 217910 from the Forest Research Institute, Dehra Dun, Uttar Pradesh, India, in 1954. It reached Ft Pierce in 1964 via Tifton, Georgia, United States.

Kretschmer et al. (1976), (1979).

Web-worms and other insects can attack the foliage and seed pods in long ungrazed stands during flowering and weed maturation. They are best controlled by grazing until mid-August and only then closing for a short seed-production period. 
At least two species of root knot nematodes (Meloidogyne incognita and M. arenaria) have been found in carpon roots. Old vegetable fields should therefore not be planted. Cv. Florida is particularly susceptible, but two accessions from a collection of eight have apparently proved resistant (Kretschmer et al., 1979). 
No diseases have been observed to date (Kretschmer et al., 1979).

In Florida, flowering begins in early September and seed maturation is complete in November. Mature pods do not shatter readily, but grass/legume mixtures should be mown when 85 to 90 percent of the pods are mature. They then should be allowed to dry for at least one day, and preferably two to three days, before pick-up thrashing. Pick-up thrashing is preferable to direct heading because the vegetative material still has a high moisture content at this stage, and is likely to gum the thrashing bars of the drum if direct headed (Kretschmer et al., 1979).