1. Soil and water conservation: An overview

Transcript

Hi friends, in the previous lectures we studied about the selection of cropping systems, and also if the land is not used for the crop production, what are the alternate ways of using the crops. So we have already studied alternate land use systems. Now in case of drylands, it is very pertinent and it is very important to go through the soil and water conservation measures. This soil and conservation measures are the pillars of dryland production. So in this lecture we will study the soil and water conservation measures.

As you all know, soil and water are the most important natural resources on which our survival depends. Then depletion of these resources in tune with meeting the demands of ever increasing population. As you all know soil and water are the important resources, But these resources are not being properly utilized, because in tune with the increased population, then unabated population; these soil and water resources are being depleted. So in this section water is the biggest eroding agent, and wind is the next most significant. So among soil and water; water is the biggest eroding agent in case of drylands. And next wind is the next biggest eroding agent.

What happens in case of drylands? The drylands are far more prone to erosion factors, because the most of the time, these drylands are devoid of vegetative cover, when they are devoid of vegetative cover, the soil erosion is bound to occur at an alarming rate, and all the soil particles will be detached. So in this way the conservation of soil and water is most critical in case of drylands. Coming to the soil erosion. Soil erosion means; it involves two processes.

• One is detachment of the soil particles from the soil surface.
• After the detachment, then the second process is transportation of the detached particles.

So the term soil erosion involves two processes. One is the detachment of the soil particles from the topsoil and the transportation of the detached soil particles by wind or water. So soil erosion is nothing but detachment of the soil particles and then transportation by the other agents like wind or water. So what is the ultimate resistance. What is the ultimate result of the soil erosion? It is surface runoff. Water will be flown away without infiltrating into the soil along with the topsoil particles. That’s what we call as surface runoff.

Then what are the effects of this soil erosion. The soil erosion effects can be grouped into two parts.

• Onsite effect
• Offsite effect

On the onsite effect where the soil erosion has been taken place, there is a decrease in the agricultural production due to the problem of infiltration of moisture into the soil. So this is the onsite effect. So in a way, where the soil erosion occurs, there their will be reduced rainfall infiltration. So because of this agriculture production is decreased. Then what are the offsite effects. Offsite effect means, the effect of soil erosion, where it not taken the site far away from the occurrence of soil erosion. This is because the effect is sedimentation and siltation of the reservoirs. What happens in case of soil erosion? The runoff will be there. Along with the runoff water, the topsoil particles will also be mixed up. And these particles flow away along with the water, and they will be silted up in the water reservoirs. For example lakes, then rivers, then oceans. What happens then, when the siltation occurs? The much of the storage reservoir will be occupied by the siltation. So there will be no much space for the water to store. So storage capacity of these reservoirs depletes or decreases.

Then coming to the forms of water erosion. There are four types of water erosions. As you can see from the figure.

• This is a splash erosion, where the crust formation is there.
• This is the sheet erosion where thin layer of the soil will be eroded
• Then the rill erosion where in the small grooves soil will be eroded
• Then the gully erosion. It will be in the form of thick channels. Bigger channels where the land is considered as unfit for cultivation aspects.

It is in a sequence when the splash erosion is not controlled, it will lead to sheet erosion. When the sheet erosion is not controlled it will lead to rill erosion. And when the rill erosion is not controlled, it leads to gully erosion. Then after the gully erosion if the gullies are not stabilized, it will lead to ravines, and the ravines lead to landslides. This is what happens with respect to soil erosion.

Coming to the soil and water conservation aspects. It mainly involves four aspects.

• Number one is erosion management.
• Then the second one is water conservation

In the erosion management we have preventive measures and control measures. In case of water conservation, we have in-situ management, water table management and runoff management. The other two aspects on which the soil and water conservation aspects are concentrated, or soil fertility management. Then the vegetation management. In case of soil fertility management, it is the organic nutrients, balanced nutrients, nutrient recycling, integrated nutrient management. In case of vegetation management, it is the crops, trees and pastures. So altogether, the soil and water conservation, it encompasses all the factors. It is erosion control measures, then water conservation measures, soil fertility measures, then the vegetation management.

Then what are the principles of soil and water conservation on which they depend. The soil and water conservation practices are grouped into two.

• One is rainwater management. The reduction of splash erosion, detachment and transportation of soil particles.
• Then second one is control of runoff. That is to check sheet, rill and gully erosion.

The principles adopted in soil and water conservation measures mainly has two aspects, that is rainwater management, that is mostly concentrated towards checking the splash erosion, wherein the detachment and transportation of the soil particles will be checked. The second one is runoff management, wherein the other forms of erosion; that is rill erosion, gully erosion will be managed. So these are the principles of soil and water conservation measures.

Then what are the factors on which the soil and water conservation measures are designed. The soil and water conservation measures are being designed on soil, land-slope, rainfall and wind characteristics. In most of the times the soil and the slope counts a lot. Because in the soil characteristics, the type of the soils and when you come to the slope, what is the percentage of slope. On these two aspects most of the soil and moisture conservation practices have been designed. Coming to the classification of soil and water conservation measures that are being adopted in the drylands. There are two types.

• Agronomical measures and
• Engineering measures

These are the two types of methods, soil-water conservation measures, which are being adopted. Coming to the soil and water conservation measures in the arable land management. What do you mean by the arable land? Arable land is the one in which the land can subjected to ploughing, cultivation and for the production of the crops. It is the land which is amenable for the crop production. Whereas non-arable means land which is not confined to arable farming. The land cannot be put to cultivation of the crops, because of the several inherent problems. So what are the soil and what are the conservation measures in case of arable land.

First agronomical measures have been divided into two.

• Wind erosion control measures
• And water erosion control measures.

The wind erosion control measures are,

• Vegetative cover
• Strip cropping
• Stubble mulched tillage
• Then tillage practices
• Then wind breaks and shelter belts.

Wind breaks and shelter belts are being planted are known for this several plant species have been known. And these plant species are being planted on the bunds of the plants, bunds of the fields where they arrest the wind velocity. So as you know the wind is also one of the key carrying factor. So in that way wind breaks and shelter belts are also adopted along with the other practices. If you come to the water erosion control measures. Almost all these agronomical measures and engineering measures have been combined in which

• Contour farming
• Ley farming
• Crop residue management
• Vegetative barriers
• And ridges and furrows are included

So in a way the agronomical measures; controls, consists both wind erosion as well as water erosion measures. Then what are the engineering measures that are being adopted in case of arable land management. In case of arable land management it is

• The contour bunds
• Stone wall terrace
• Gully plugging
• And waterways

Are the engineering measures that are being adopted for soil and water conservation. Then coming to the non-arable land management, what are the soil and water conservation measures that are being adopted in the non-arable land management. They are

• In-situ moisture conservation
• Drainage lines
• Trench and mount fencing
• Barbed wire fencing
• Then vegetative cover

So these are the important non-arable land management in which soil and water conservation measures are being adopted. So to conclude the overview of the soil and water conservation measures. Soil and water conservation measures are best needed for maintaining a balanced ecosystem for sustainable crop production in drylands. Yes these soil and water conservation measures are required for both arable as well as non-arable lands. But the type of practices differ from arable to non-arable. So in both the cases it is required for establishing balanced ecosystem in drylands. The second one is efficient management of rainwater can boost agricultural production from drylands. All these soil and water conservation measures are concentrated or aiming towards management of rainwater. So the efficient management of the rainwater will definitely boost the agricultural production form the drylands.

With this, I am concluding this lecture.

Thank You.