Soil Conservation in Hilly Areas

After reading this article you will learn about the measures for conserving soil in hilly areas.

Soil erosion is most serious on hills due to steep slopes. Steepness of slopes does not deter any body taking up cultivation on hills. Soil loss from cultivated slopes is quite high particularly during first two to three years of cultivation. It has been estimated that about 6 million ha of land requires intensive conserva­tion measures in Himalayan and sub-Himalayan regions of Uttar Pradesh, Pun­jab and Himachal Pradesh.

The chief reasons of soil loss are cultivation of steep and unprotected slopes, overgrazing and indiscriminate felling of forest trees. However, cultivation on steep slopes is most important which is practiced by about 100 tribes mainly in the hills of Assam, Orissa, Andhra Pradesh, Madhya Pradesh, Chhotanagpur and Santhal Pargana area of Bihar and Madras.

The cultivation in hill areas is shifting cultivation or Jhuming cultivation. Al­though there are local variations in Jhuming cultivation but a typical Jhuming cycle is described below:

The best area, judged by organic matter, is selected in December and January followed by cutting of jungles on it. By the end of March or in early April, the cut material becomes sufficiently dry for burning. Villagers set fire to it, if found ready for firing, after careful examination.

Seeds are sown after the pre-monsoon showers. The crops are mostly grown in mixed cropping, however, occasionally paddy is grown as a pure crop. The particular selected site is cultivated for 2 to 3 years, after which the area is abandoned.

Cultivation in hilly areas is practiced without necessary protective measures rather defective and erosion permitting practices such as irregular terraces, sloping outwards for draining surplus water which aggravate erosion problems.

Soil conservation in hilly areas requires a well-planned and rational land use programme combined with engineering and cultural measures. Steep slopes may essentially be brought under permanent forests and gentle slopes should be terraced and valley bottom should be put under suitable agricultural crops.

To achieve maximum benefit, it is essential to treat various areas on a complete watershed basis for rational use of forestry and agriculture, includ­ing horticulture. Conservation in hilly areas requires a proper land use programme combined with cultural and engineering measures.

A combination of engineering measures such as bench terracing and stone terracing of hill slopes along with afforestation, torrent and slip corrections and silvicultural practices would not only prevent or reduce the erosion on hills but also improve the lots of people in this region.

Afforestation:

Forests play an important role in controlling soil erosion. The forest canopy intercepts the erosive force of rain drops and the forest Utter protects the soil and helps in absorbing more rain water, thus reducing the runoff. Afforesta­tion of economic plants should be done on contour benches to the specific needs of the area.

In dry areas of north-west India, the species such as Acacia modesta, A. catechu and Prosopis juliflora are most successful. For cooler areas of Lahul-spiti valley in Himachal Pradesh and Leh and Kargil in Jammu & Kashmir, Populus alba, P. nigra, P. ciliata and P. candicuas are the most promising ones.

Indiscriminate grazing by cattle, especially sheep and goat including the nomadic herds, are the major causes for soil erosion in hill areas. It is, therefore, necessary that the pastures and grass lands in hilly regions should properly be managed for maximum fodder production and effective erosion control by way of improving their fertility.

The formulation of grazing policy should be based on the following cardinal principles:

(i) Continuous grazing on the same area by large herds is destructive of the better strains of grasses and leads to a deterioration of the grass complex. Wherever it is permitted and is in great demand, efforts should be made to introduce rotational grazing. The benefit of which should be explained and demonstrated to the villagers.

(ii) Cheap forests grazing has a demoralizing effect and leads to the vicious spiral of reckless increase in the number of cattle, inadequate grazing, reduced quality of herds and further increase in the number to offset the fall in quality.

Free and indiscriminate forest grazing is, therefore, a serious disservice to cat­tle breeding. The notation that a farmer’s wealth must be reckoned in terms of the number of cattle he owns regardless of quality, is one of the causes of India’s uneconomic cattle wealth, and must be combated.

(iii) Grazing should not be looked upon primarily as a source of revenue. But simple and obvious way of regulating and controlling grazing, as also im­proving the quality of both grazing and cattle themselves, is to institute a reasonable fee for the privilege of grazing.

(iv) Grazing must not be allowed in regeneration areas and young planta­tions during such periods as the seedlings require considerable time for estab­lishment otherwise they stand in danger of being browsed or trampled upon.

(v) Grazing incidence should be kept at the minimum in protecting the forests.

Torrent and Slip Corrections:

The problem of torrent erosion in both the foot-hills of the northern Himalayan and the north-eastern Himalayan region, has been increasing (Fig. 7.3). The main cause of the problem is the high runoff down the hill slopes with heavy silt load that fills-up the channel beds, thereby reducing their capacity to carry runoff and sediment.

Land slips can be treated by providing proper drainage, using check dams of boulder, masonry and live vegetative and construction of revetment-cum-retaining type walls, etc.

All such measures require engineer­ing skill and are very costly. Soon after stabilisation of slip zones by engineering measures, vigorous efforts should be made to cloth the surface with permanent vegetation comprising suitable quick growing trees.

In the western Himalayas, the conifer bearing zone extends down to 500 m. In eastern Himalayas, conifers do not occur in abundance except above 2700 m. In the Assam hills, the Khasi pine occurs at an altitude of 850 m and above. In central and southern regions, there is natural occurrence of conifers even at the highest altitudes.

Although the hills of the central and southern regions are at present devoid of coniferous forests, the indications are that it is possible to find suitable exotic pines for these climates. Mexico is rich in tropical pines, some of which may adapt themselves to our conditions.

Certain plants are suited to torrent control schemes, particularly the out sprouting types which grow profusely near stream beds, e.g. Salix spp, Vitex negundo, Populus spp., Arundo donax, Ipomea carnea, Jatropha curcas, Pennisetum purpureum (Napier grass).

Bench Terracing:

In Himalayan regions of the Punjab and Himachal Pradesh, cultivation is ex­tended up to 25% slopes. In Orissa and Andhra Pradesh, agriculture is practiced up to 10% slopes. For cultivation, graded bench terracing is recommended.

Graded bench terracing is suited for slopes ranging from 16 to 33%. Bench terracing consists of a series of platforms having suitable vertical drops along contours across the general slopes. These bench terraces may be of the table top type of sloping outwards or inwards with or without grades, according to the rainfall, soil and other characteristics of the region.

Bench terracing is only a supporting practice; it should be supplemented with agronomical practices to get higher yield in sustained manner. Cattle trespass should be prevented either by fencing with barbed wire or live hedge. Lupin (Lupinus luteus) and scented geranium (Pelargonium spp), which are not eaten by cattle, may be planted on terrace slopes.

Cultivation on such slopes without proper soil conservation measures is bound to prove disastrous. The front faces of the terraces should be put under soil binding covers like Eragrostis cunnda, Phalaris tuberosa, Dactylis glomerata, Festuca elatior var arundinacea and Digitaria spp.

The bench terraces executed in Nilgiri district (Tamil Nadu) have an inward gradient of 1 in 40 (2.5%) and a longitudinal gradient of 1 in 120 (0.75%) for safe disposal of excess runoff. Inner drains, sufficient in capacity to carry the runoff from terraces, should be checked regularly during monsoon season. The riser in terraces are given a slope which should be maintained.

This should not be scraped to add a little area for cultivation, for the stability of the struc­ture is thereby affected. The diversion and disposal drains should be properly cleared of all obstructions, fallen earth, silt accumulation, etc. Their full capacity and trapezoidal shape should be strictly maintained to take care of run-off from the terraces. The drains should be protected with grasses such as Paspalum dilatitum.

Stone Terracing of Hill Slopes:

Steep slopes when put under cultivation are subject to severe erosion, with every rain the top soil is washed away at an accelerated rate. In such areas if stones are available in plenty, construction of stone walls across the slope will help in conserving soil.

These stone walls, known as stone terraces, are small embankments constructed with stones across the hill slope and these can be adopted on any slope where stones are available in plenty at the spot. Large areas have been covered with stone terracing in the Muchkund basin (Orissa) and based on the experience the following specifications for stone terraces are recommended.

The cross-section may be 0.5 m² depending upon the depth of foundation. With increasing of slope beyond 10% it is advisable to give a foundation of 30 cm instead of 15 cm. Alignment of stone terraces is to be done with the help of Dumpy level or Abney level. The terraces should be given a longitudinated grade of 0.2 to 0.3 m per 100 m towards the outlet or the storm water drain.

Construction of Stone Terraces:

A shallow trench of 1 m wide and 15 or 30 cm depth, as the case may be, is dug on the lower side of the line. Soil from trench is piled upon the upper side of the pegs to form a narrow ridge so that the percolation of run-off from field through the stone terrace is avoided.

Stones should then be collected and packed directly into the foundation and in the upper structure to form the ter­race. The random rubbles should be interlocked at least 7.5 cm in the joints and the sharp edges should be exposed outside so that proper shape of the bund is obtained.

All the stone terraces should lead to natural outlet available or to an artifi­cially formed waterway. The ridge, formed on the upper stream side of the stone terraces, should be carefully maintained and vegetation may be estab­lished on these ridges.

Control of Shifting Cultivation:

The shifting cultivation is still practiced in Hill areas of Assam, Manipur, Madhya Pradesh, Tripura, Andhra Pradesh, Maharashtra and Kerala. The problem being socio-economic, should preferably be approached to improve the standard of living of the tribes. They should be educated in adoption of improved agricultural practices.

Suitable areas with moderate slopes in hills should be found out and the tribes persuaded to take to permanent agriculture. Some of the suitable areas already cleared under shifting cultivation should be improved with necessary erosion control measures like terracing, contouring, etc., for permanent stabilisation.

Unless the shifting cultivation can be weaned from the practice by a profitable alternative vocation suiting their socio-cultural back ground, the problem of shifting cultivation may not be solved. Though it may not be possible to stop shifting cultivation totally, with above measures it would be possible to control, regulate and contain shifting cultivation and bring it within reasonable limits.

Land Management and Crop Planning:

The mountainous topography of the region demands a well-planned, in­tegrated and rational land use in agriculture, forestry and horticulture. The fundamental principles underlying planned agriculture is that each piece of land is put to uses by which it will produce the most and deteriorate the least. Measured by this yardstick, land management in these hills should conform to the following pattern.

Hill tops and steep slopes should permanently be placed under forest species. Not only will such measures stabilise and improve agriculture on lands down below but they will also have a direct effect in regulating and prolonging the flow of water for irrigation and in preventing damage from unchecked rain water erosion (Fig. 7.5.).

Lower down forestry should give place to Jhuming, i.e., forestry alternating with agriculture. Gentle slopes should be terraced, and these with the valley bottoms should be set apart for agricultural crops in order of their moisture requirements. Horticulture should be developed in suitable localities.

To improve the lot of the average cultivator, he must be assisted to raise not only subsistence crops such as rice, maize and millet but also cash crops. There appears to be no reason as to why pepper (Piper nigrum); cardamom, coffee and cashew-nut (Anacardium occidentale) cannot be introduced under the conditions of north-eastern hills.

Cultivation of fruits such as oranges, pineapple, jackfruits, banana, papaya requires to be stepped up, both in quality and quantity. Crops such as potato, arvi (Colocasia esculenta), tapioca (Manihot esculenta) and ginger offer opportunities which have not yet been fully exploited.

Silvo-Pastoral Practices:

Where Jhuming cannot be abandoned, as indeed it cannot be candised, the species selected for the afforestation of abandoned Jhumed land must fulfill the most exacting conditions. It should be easy to propagate, ready to fell in 8 to 10 years, and should also be able to build up soil fertility during the period.

But what is so baffling a proposition is the fact that after the trees’ crop has been raised, it should be made available to cultivator for being burnt into ashes to provide the necessary manure for his fields and to meet fuel need.

The fuel and fodder plantations of Silvo-pastoral system of grass land development is probably the best system for overcoming the shortage of fuel and fodder in the country today.

A number of fodder trees such as Leucaena latisiliqua, Bauhinia variegata, Albizzia lebbek, A. amara, Grewia oppositifolia, Celtis caucasica, Moringa oleifera, Millettia auriculata, Sesbania sesban, S. gran- diflora, Hardwickia binata are fed to the animal depending upon the region.