MOST deserts of the world are extensive grasslands with scattered shrubs but they sustain relatively a low density of trees. Due to harsh climatic conditions, scanty natural resources and scarcity of drinking water, the deserts are thinly populated by humans. However, a wide variety of wild animals, well adapted to survive in the inhospitable environment, inhabit them due to the fair abundance of fodder, grass and top feed.
Till the beginning of the 20th century, the Thar or the Great Indian Desert was quite similar to other arid zones mostly situated along the tropic of cancer in the northern hemisphere. Soon after India's independence, the desert scenario started changing mainly due to the escalation of human population. Starting with a population base of roughly 3.56 millions in 1901, it registered a sharp rise and increased to 16.1 million in 1991, almost a five-fold increase. In the arid districts of Rajasthan, in comparison, only four to five persons inhabit one sq km in other deserts, whereas the Thar desert houses 84 people per sq km. Moreover, the livestock population has also increased from 10.3 million during the last 30 years resulting increased severe over-grazing, a major pressure on the arid land.
Due to population pressure, the magnitude of rain-fed agriculture has also enhanced, especially, on marginal and sub-marginal lands which are unsuitable for cropping. Even the slopes of sand dunes are cultivated. There has been an increase of about 60 per cent land under the plough. Although the cropping area has increased considerably, the yield of almost all rain-fed ( kharif ) crops has drastically declined per hectare, mainly due to the loss of soil fertility and erratic rainfall.
Kharif crops like millet, sorghum, sesame and moong are usually sown soon after the first shower which may fall by the end of May or during June, although monsoon breaks in western Rajasthan only after the first of July. But in some years, the first showers are received during late May or in June. With this uncertainty in the arrival of the first shower, farmers plough their crop fields late in May and early June to utilise the supposedly early arrival of the rains.
In the modern times, bullock or camel-driven ploughs have been replaced by tractors. These mechanised farmtools till the soil much deeper than ordinary ploughs. May and June are the months when the wind speed in the desert is maximum. The hot, fast-moving winds carry away the ploughed top soil. A number of experiments carried out all over the desert by scientists from the Central Arid Zone Research Institute ( cazri ) in Jodhpur, Rajasthan, have revealed that if natural grass growing in the desert soil is removed, the soil gets air-borne at a much faster rate. The wind can remove soil that is up to 50 cm deep -- a depletion of about 1,065 cubic m.
Estimates have revealed that 0.6 to 5.1 quintal of soil blows over a hectare per day in Rajasthan's desert. As a consequence, space photographs of the earth show the maximum assemblage of suspended dust over the Thar desert. Often, the stratosphere over this desert is called the largest 'dust bowl' of the world. It is, therefore, necessary that the stabilised desert sands -- one of the major causative agents of desertification -- should not be disturbed at all.
Experiments have also indicated that if the desert land is not ploughed and the stabilising vegatation, though dry, is allowed to remain in situ , soil erosion takes place at a very low rate. Ideally, the ploughing of land should be banned in the Thar desert, specially in the extreme arid zone which extends from the west of Barmer, Phalodi and Bikaner. This region receives only 200 mm of rainfall and that too on as irregular basis.
The decision to ban ploughing of land appears to be rather very difficult in a democratic country like ours. But if desertification is to be arrested, this decision must be taken and rigidly implemented. Adoption of this method would require involvement of the state government and environmentalists, and the cooperation of desert dwellers. If ploughing is virtually stopped at a point of time, the source of income for the farmer who depends on subsistence farming is likely to suffer. However, if the yield of millet, which is the major kharif crop of this extreme arid zone, is considered, the land-owner farmer gets a worthwhile and remunerative crop only once during five years due to the periodic failure of the monsoon. His effort to raise a crop fails almost everytime during the remaining four years, but the sand from his crop field that has been loosened by ploughing, is blown away by strong winds, thus leading to unprecedented soil erosion.
If the farmers of the 200-mm rainfall zone are educated to grow grass crops, they will not have to plough the land every year and the monetary benefit from selling the grass will be much more than what is earned from millet ( bajra ). The farmer can graze his animals in the protected grassland. By feeding upon a much superior and nutritive fodder, the production yielded by his livestock will increase manifold.
Highly practical and cost-effective grazing schedules which have been evolved by cazri must be put to use. Traditional millet farming should be stopped as it is a 90-days crop and its water requirement is very high as compared to grasses that are perennial. Most of the grasses complete their life-cycle within 30-40 days. During a good rainfall year, bumper production of grasses can be harvested. This would satiate the fodder requirement for many years to come if the hay is properly stacked.
The 200-mm rainfall region is blessed with excellent fodder-producing grasses. One species is found only in this region and no where else in the world -- the sewan grass ( Lasiurus sindicus ). It is a highly productive and nutritive grass and can be judiciously exploited by the farmers. A little irrigation, if water is available from bore wells or the Indira Gandhi Canal, would keep this grass green all the year round and a number of clippings can be obtained.
Experiments conducted by cazri scientists have clearly indicated that with minimum amount of irrigation from six cuttings taken from June to March, sewan grass yields 19 and 8.7 tonne per hectare green and dry forage respectively. Outside the L sindicus zone, safed dhaman or the Cenchrus ciliaris , a very nutritious and perennial grass, can be also be sown in the farmers' fields. With minimum irrigation again, it too yields 23.7 tonne of green fodder equivalent to 11 tonne per ha of air-dried forage. The production potential of these two grasses is seemingly of a huge magnitude. If over-grazing is not allowed, so much of fodder will be available that there will be a need to establish a 'fodder corporation' of Rajasthan which can manage fodder banks throughout the desert!
These varieties of grass will also be extremely useful during drought years when Rajasthan is compelled to import feed and fodder for its livestock from other states at phenomenal rates. In other words, the production of these grasses in place of millet in the 200-mm rainfall zone can not only be a high profit-generating endeavour, but would also stop deterioration of the overall desert conditions and stabilise the environment. Besides, it would enhance the livestock production which in turn, will also help to raise the quality of life of the desert dwellers.
Ishwar Prakash , former professor of eminence at the Central Arid Zone Research Institute, Jodhpur, is now with the Zoological Survey of India, Jodhpur.