4. Natural resources degradation process: An overview, Contd.

Transcript

Hi Friends in the last previous lectures we learnt about the natural degradation of resources and the factors which are responsible for the degradation process. And in particular we studies about the soil erosion. And in this lecture we will be studying in particular about how the soil erosion is causing further degradation of the natural resources, and the ways to come how to degradation will combat, and how the degradation will be restored, and the other factors which are affecting the degradation process. In the last lecture the soil erosion factors have been described; reduced infiltration capacity and the moisture holding capacity of the soil, impaired soil surface, loss of organic matter, reduced depth of the top soil, siltation of the reservoir leading to reduction in the life of the reservoir and the irrigated area. And decrease in the dry stream flow.

Now let us study what is the soil erosion, what are the types of soil erosion. Soil erosion, the two important factors is as raindrop impact and over-land flow. When the rain is at higher intensity, the soil particles were displaced, and because of the effect of water the soil particles will be over-flowed. The second thing is that excessive tillage without protection. Now we are cultivating the soil with much of the tillage, with much of the implements machineries used, and there will be no protection on the land surface. So whenever the rainfall occurs at higher intensity, the soil will be eroded along with the rainwater.

Then coming to the salinization. The salinization is an important process, wherein the accumulation of salts will be there. The main reasons for the accumulation of salts is that poor drainage. No sufficient drainage will be provided, so as to drain out the salts beyond the root zone. Because of the poor drainage, the salts will accumulate in the topmost layers, and the growth of the crop will be impaired. Coming to the high evaporation. High evaporation is also one of the factors for the salts to accumulate on the surface, because the high evaporation causes the salts to remain on the soil surface. Coming to the depletion of soil nutrients. In that intensive cropping using high yielding varieties. Nowadays we are using the high yielding varieties in almost all the crops. These high yielding varieties are very responsive for the chemical fertilizers. So there will be depletion of soil nutrients.

The second factor is if we take tillage, oxidation of organic matter. The organic matter is the life of the soil. It supports the plant growth amicably. So because of the received tillage, oxidation of organic matter takes place, and it will cause in the impairment of the plant growth. Coming to the different types of soil erosion. Now for the soil to erode, there are some agents which causes the soil to erode. In that the water is considered as the principal agent, which displaces the soil particles. So water erosion, in that the splash erosion. The splash results from the bombardment of the soil by the raindrops. It so happens, whenever the rainfall occurs at an high intensity, the soil particles will be bombarded, and they will be displaced. They will be displaced to what an extent. The raindrops fall at high intensity and behave as little bombs on the bare soil, displacing the soil particles and destroying the soil structure. Splashed particles may rise as high as 0.6 meters above the ground, and 1.5 meters horizontally. This you can imagine, how the soil particles have been displaced, because of the splashing effect of the raindrops.

Now we can see in the figure, in the photo, because of the splash erosion the crust formation will be there. This is the crust formation. This splash erosion results in the formation of the surface crust. What it happens because of this. Infiltration capacity will be reduced, and there will be more amount of surface flow. So in this way splash erosion results in the formation of crust, which impairs the infiltration capacity of the soil and it encourages and surface runoff. Then coming to the sheet erosion. The sheet erosion is nothing but uniform removal of the top soil in thin layer from the field, often from the entire field, more or less uniformly during every rain, which produces runoff.

Now in case of splash erosion only the soil particles are being displaced. But in the sheet erosion, it removes the top soil layer uniformly from the field. Then in the initial stages of the soil erosion, raindrops churn the top soil, and along with runoff the muddy soil moves away from the field. Whenever the soil erosion occurs, the raindrops first churn out the top soil, and then with the runoff the muddy soil also goes out. So this is the picture wherein the sheet erosion occurs like this, and these are all the sheet erosion. The one thing which is about the sheet erosion is, it is least conspicuous. The presence of sheet erosion cannot be identified easily, it is conspicuous. So it can be detected along with the runoff water, the presence of muddy color is the indication of the sheet erosion.

Next coming to the rill erosion. Then in this rill erosion, there will be removal of the soil by the concentrated water running through little streamlets or head cuts. So along with the soil in the streams, the soil will be eroded. Like this in the soil, the eroded we can see that rill erosion is occurring in case of small grooves. Next coming to the gully erosion. It is the last stage of erosion, wherein the tiny grooves develop into wider and deeper channels, which may assume huge size to form gullies. We can see in the picture, these are the gullies, which are being formed and which are in varied depths and in the form of deeper channels. The most spectacular evidences of gully erosion is that they form channels, and make the land unfit for cultivation.

Then coming to the four types of erosion. I have told you what is splash erosion. If the splash erosion is not controlled, it leads to sheet erosion. If the sheet erosion is not controlled, and it will lead to the rill erosion. Finally if the rill erosion is not controlled, it will lead to gully erosion. And the land is not suitable for cultivation.

Next coming to the other factors which are contributing for the degradation of natural resources. It is over exploitation of the ground water. As you know water level has sunk to deeper levels. Tapping of ground water has become costly and also uneconomical. As you are aware nowadays, the ground water has depleted to the lower depths. And we have to extract the water from thousands feet of depth. Even if the water is got from the deeper layers, the existence will not be guaranteed. So in that cases the groundwater has become costly and tapping of this groundwater is being considered as uneconomical.

Coming to the vegetative cover, which is also causing for the purpose of, for the process of degradation. The presence of vegetative cover is not there in most of the cropping fields. It is important in reducing the impact of raindrops on soil, increasing infiltration, and improving soil water holding capacity. Otherwise high intensity rains cause accelerated erosion. In many of the croplands after the harvest of the crop the land is felt, the land is left barren and there is no vegetative cover. What it means, whenever the high intensity rains occurs. There is no cover to obstruct the raindrops. And there is no chance for the water to enter into the soil, because of the lower infiltration capacity. And along with the water the top soil will also moves away. So if there is a vegetative cover, it obstructs the velocity of the rainfall water, and it makes the water enter into the soil.

Some of the factors relating to soil degradation. The first one is, the world is losing 5 to 7 million hectares of arable land every year due to soil degradation. Whatever the resources, they may be degraded. 5 to 7 million hectares of arable land. Arable land means the land which is suitable for cultivation. We are losing on an average 5 to 7 million hectares of land per year due to this land degradation process. Second thing is that, in India about 177 million hectares of land in India are degraded. They may be due to water erosion. They may be due to wind erosion. Totally we have 177 million hectares of land in an area of being degraded. Third one is because of this degradation process, maybe the soil erosion. What is the quantity of soil that is being lost every year. This is a very astonishing figure, wherein the average soil loss in India is estimated to be 16.3 tons per hectare per year. This an amount of soil, it is not only soil. It is a top soil which is very fertile in nutrients. We are losing very important part of the soil, that is the top soil. Then about the depletion of the soil nutrients. For every ton of grains about 105 kg of nutrients are removed from the soil. But the fact is that whatever the amount of nutrients, they have been taken up by the soil, they have not been replenished back into the soil. We are only taking out the nutrients from the soil. We are not adding the same quantity of soil nutrients back to the soil. So this is causing the depletion of soil nutrients.

Then coming to the soil erosion. What is the amount of yield decline due to soil erosion, which is considered as the prime degradation process. The soil erosion is estimated to cause, a yield decline of 0.14 tons per millimeter of soil loss. If we imagine a millimeter of soil has been eroded due to the rain; high intensity of rains, then at the same time we are losing 0.14 tons of yield.

So whatever the strategies for restoration. Is this degradation is allowed to happen. No, not at all. We have to have strategies for the restoration. Let’s see what are the restoration processes.

• Need based soil conservation measures, both in arable and non-arable lands. Suitable soil conservation measures. They may be agronomic measures. They maybe engineering measures. Both of them should be applied both in arable and non-arable lands. They are not only required in arable lands, they are also required in the non-arable lands. The non-arable lands can be put back into the cultivable lands because of this, due to this soil moisture conservation practices.
• The second one thing is afforestation of wastelands and development of grasslands. There are millions of millions of hectares of wastelands are in India, wherein the crops are not being cultivated. It is not possible to grow crops; certain field crops on wasteland. But there is a possibility that some of the forest species can easily be raised in the wastelands. So afforestation in the wastelands, one thing. Then development of the grassland. If we develop the grassland then it will suffice the demand of grazing by the livestock. So that our fields will be covered with a vegetative cover. Then which will arrest the erosion effect.
• Next recharging of undergroundwater through nala bunds, gully checks and percolation tanks. We are drilling the our lands to the most deeper layers. But at the same time, we are not adopting the recharging techniques as we should do. So recharging techniques has to be carried out through nala bunds, gully checks and percolation tanks.
• Then recycling of organic wastes to maintain health. I have already told you, the soil fertility no doubt it has to be enhanced in the drylands, but at the same time there is a limitability, there is limited provision for this, because of the absence of soil moisture in a required quantity. What is the other way? The other way is the recycling of organic wastes. Whatever the organic wastes that are available on the farm field, they have to be ploughed back. They have to be recycled into the croplands, so that the soil health will be maintained.
• The practice of regenerative agriculture. The regenerative agriculture is an approach which can regenerate the top soil, enhance the biodiversity, then improve the farming practices, and also maintain the biodiversity on the croplands.

So these are some of the strategies for the restoration. To conclude, about 15% of the farmland is degraded due to human induced factors. Our task is to increase the present level of food production with the decreased per capita availability of land for agricultural purposes. So over 15% of the land is being degraded. Whatever next strategy, our strategy is to increase the production, productivity in the whatever the available land is there. Then the next one is the only way to provide for the needs of the life system on earth, would be to reverse the process of degradation and improve the productivity. We have to reverse the process of degradation. That means we have to restore back our degraded lands, by suitable strategies like agronomical measures, engineering measures and also soil and water conservation measures. In this way the soil degradation can be avoided and these lands can brought back as cultivable lands, and we can use it for the growth of the crops.

Thank You.