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ROOTS SO DEEP (COGON GRASS AND VETIVER)

Cogon Grass

Imperata cylindrical also known as cogon grass or Kunai grass (Also known as Siru in Nepal) is a rhizomatous grass native to tropical and subtropical Asia, Micronesia, Melanesia, Australia, Africa and Southern Europe. Cogon grass is a perennial, rhizomatous grass that grows from 2 to over 4 feet in height. The leaves are about an inch wide, have a prominent white midrib, and end in a sharp point. Leaf margins are finely toothed and are embedded with silica crystals. The upper surface of the leaf blade is hairy near the base; the undersurface is usually hairless. The flowers are arranged in a silvery, cylindrical, branching structure, or panicle, about 3-11 inches long and 1½ inches wide.


Cogongrass has an extensive rhizome network, the biomass of which accounts for 60% of the total biomass of the plant. They can penetrate up to 1.2 m (3.9 ft) deep, but 0.4 m (1.3 ft) is typical in sandy soil. At Himalchuli Nature Farmstay we were surprised to see the depth to which this plant goes down in search of nutrition. While our workers were preparing the land for retention wall to support the existing plot, we saw the roots go down the soil about 4-5 feet deep. No wonder this perennial plant is known to be a sturdy which can tolerate drought and also monopolize the plot.

The depth of the root helped us reflect on the possibility of using this plant to prevent soil erosion across tight slopes. The land that we obtained was left fallow for about a decade and few patches of this plant were seen. Our plot is a sandy plot with very little organic matter left after years of leeching and absence of added organic matter and manure. In the picture to the right we can see the depth reached by cogon grass in to the soil.


Ecological Threat

Cogon grass can invade and overtake disturbed ecosystems, forming a dense mat of thatch and leaves that makes it nearly impossible for other plants to coexist. Large infestations of cogon grass can alter the normal fire regime of a fire-driven ecosystem by causing more frequent and intense fires that injure or destroy native plants. Cogon grass displaces a large variety of native plant species used by native animals (e.g., insects, mammals, and birds) as forage, host plants and shelter.

On the other hands we have experienced birding activities inside the dense cover. Under the dense cover of this grass, some small birds have been found to be nesting. Hence we don’t fully understand ecological rationale of this plant. Is it a native invasive plant? Does its invasion affect the native ecology? These are few questions to explore further.


Vetiver


(Chrysopogon zizanioides) Vetiver (also known as Khus in Nepal & India) is a perennial plant originating in southern India. The most commonly used genotype “Sunshine” is not invasive because it does not produce fertile seeds. Moreover Vetiver does not have stolons or rhizomes and can only be propagated by division. The roots are fibrous, fast growing and can reach depths of 3-4m after one year in optimal conditions. Vetiver is an aromatic plant used in perfumery and cosmetics. While already popularized among the agriculturist and practitioners, It is also slowly gaining popularity in Nepal as biological control for soil erosion.


Vetiver may be a practical solution for controlling soil erosion on a huge scale in many regions, especially the tropics and subtropics. Vetiver roots grow vertically for at least three metres, not only do they bind the soil, but they are not known to compete with neighbouring crops for water and nutrients although the plant being relatively new in terms of expansion, more study may be needed


Vetiver


Cogon Grass

Non Native to Nepal

Native to Nepal

Very low maintenance

Maintenance Free

Can be used against soil erosion

Can be used against soil erosion

Aromatic Plant, roots can be used

No other usage noted.

Invasiveness not known only if non sterile varieties are used. Noninvasiveness not fully verified.

Invasiveness known

No serious disease. Some pests (like leaf blight) are known to affect the plant.

No serious disease

Can be used as mulching material

Can be used as mulching material

No such usage noted

Used as roofing material in Asia

Root length up to 3 meter.

Root length up to 1.5 meter.

Can be used as fodder

Can be used as fodder

We are in a no hurry to give a verdict over the comparison of these plants as we believe that each plants have their own ecological purposes. We do understand that vetiver has a multipurpose capacity. However, for a farmer it can either serve as an aromatic plant or against soil erosion, not both at a same time because the aromatic part of the plant are its root which when dug out no longer serve against soil erosion. Similarly we also have to reflect on whether or not external monoculture is a good idea to check soil erosion. Also it may be useful to understand that other fodder crops like Super Napier may also be used to check runoffs and soil erosion. There are several other native plants in the forest doing their job and whose capacity and function in the ecosystem are yet to be uncovered. Do you also know such native plants of Nepal who may help to control our landlide and soil erosion? Send us a message (info@himalchuli.org)



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