Legume Cover Crops For Durian Orchard

Farmers choose to grow and manage specific cover crop types based on their own needs and goals. Although cover crops can perform multiple functions in an agroecosystem simultaneously, they are often grown in a durian orchard to prevent soil erosion, to improve or maintain the soil structure and fertility especially soil nitrogen, to suppress other noxious weeds, to prevent rapid loss of water from the soil through evaporation and to keep the soil temperature down during hot weather.

In Malaysia, most of the technology for cover crops establishment is borrowed from the rubber and oil palm industries. Leguminous plants are usually used as they are easy to establish. They are seldom used as green manure but as a living mulch.

The three most common legumes are Pueraria phaseoloides, Calopogonium mucunoides and Centrosema pubescens. The latest addition to this group is Mucuna bracteata which are native to Southern China and eastern India.

Pueraria phaseoloides

 (a) Pueraria phaseoloides is a vigorous, deep-rooted, perennial twining and climbing legume, slightly woody, hairy.  Its main stems are slender, rooting at the nodes upon contact with moist soil.  Secondary branches arise from the nodes to create a dense mass of vegetation 60-75 cm deep if left ungrazed or uncut.  Young shoots are densely covered with brown hairs.  Leaves large, and trifoliate,  tolerant to soil acidity and shade and adapted to humid lowlands and frequent flooding areas. The seed rate is about 3-4.5 kg/ha.

Calopogonium mucunoides

  (b) Calopogonium mucunoides is a vigorous,creeping, twining or trailing, short-lived perennial herb, up to several metres long, forming a tangled mass of foliage 30-50 cm thick, and stems with long rust-coloured hairs.  Leaves trifoliolate. It establishes rapidly from seed to provide early ground cover but intolerant to heavy shade. It is a prolific seeder and tolerant to low soil fertility. The seed rate is 3-4.5 kg/ha.

Centrosema pubescens
 (c) Centrosema pubescens is a perennial, trailing-climbing herb with strong tendency to root at nodes of trailing stems.  Leaves trifoliolate. It is adapted to humid lowlands, fire, and medium to low soil fertility  and can grow in shads. It is a slow grower, not tolerant to wet conditions, and smothers other weeds. The seed rate is 3-4.5 per ha.

Mucuna bracteata
 (d) Mucuna bracteata is a vigorous annual (sometimes biannual), twining herb, with large trifoliate leaves, lateral leaflets conspicuously asymmetrical and terminal leaflet symmetrical, somewhat smaller. it is tolerant to drought and shade. It grows fast and covers the field very quickly and suppresses most weeds. The recommended seed rate is 200g for planting in 420 points/ha.

Mucuna bracteata in oil palm replanting on peaty soil.

The common practice is to use an equal amount of Pueraria phaseoloides, Calopogonium mucunoides and Centrosema pubescens at the rate of 3 - 5 kg/ha. Mucuna bracteata is recommended by RISDA (Malaysia: Rubber Industry Small-holders Development Authority) for oil palm replanting on peaty soil. There is no information of its performance on land planted with fruit trees.

Cover crop seeds or planting materials must be of high quality and free from pathogens to avoid failure through low quality seeds. Usually some seed treatment is required to break the seed dormancy and they are usually seeded just after land clearing and at the on-set of the rainy season. Done properly, the cover crops will grow rapidly and cover the entire area of the farm within two years.