5-Water Management

Transcript

This is the fifth lesson of the third week of our CASI course. In this lesson, we will study irrigation management and its problems. We will look at when to do irrigation management and at what quantity. We will also look at the equipment required for irrigation management and what we can do to increase water efficiency.

First of all, we will talk about water management. As we all know water plays an important role in plant growth and its relating activities. In India only around 40 to 42% of farmland is irrigated while the rest 58 to 60% are rainfed. One of the aims of our prime minister is to double the productivity of our farms and income of farmers by the year 2022. The idea is to grow more food with one drop of water.

When it comes to problems associated with irrigation, we know that farmers don’t have enough information to manage water and as a result, a lot of water is lost due to run off. Also, what type of cropping pattern should we practice plays an important role. If we have limited water supply then after rice, we can grow pulses or oilseeds instead of growing wheat. We can do pulses farming in the rabi season in places we have harvested run off water.

Now we look at the advantages of irrigation. If we have irrigation facilities available in our farms, then we can increase our crop productivity by many times. Also, if we have irrigation water available then we can grow at least three to four crops in a year from our farm. So we can increase our cropping intensity. If we have irrigation resources available, then we can choose to grow those crops that require more water.

Now, how much water we should give to our crops depends on a variety of factors. First we look at our soil structure. Usually, if it is a clay soil then it has more water retention capacity and as such requires less water compared to sandy soil where we have to frequently give irrigation to our farm.

Now, depending on the chemical condition of soil, we can say that high fertile soil requires more water as we can get high yield. Also, the efficiency of fertilizer depends on the availability of water for irrigation.

So basically, fields that are more fertile require a higher amount of water and less fertile fields require comparatively less water.

We also provide water to the field according to the moisture available in the soil. So if the soil is dry then it would require more water for irrigation.

Crop depth also plays a role in the need for water. We select the water requirement according to the kind of root we have like fibrous root or tap root

Water is required by different crops in different quantities. Usually, wheat requires more water than gram and barley. So, we have to provide more irrigation to the wheat crop.

The chemical composition of soil like if the soil is acidic or saline also plays a role in how much water is required for irrigation.

If soil is more saline, then water required for irrigation will be more.

Now we will look at how we can increase the usage efficiency of water. Under conservation agriculture we know that the use efficiency of water is more in a laser leveled farm. So to increase the use efficiency of water we have to first laser level our field.

Another way to increase the use efficiency of water is to use drains that are permanent. Farmers usually have drains in their farms that are made of mud.

We can also use short duration crops in places where water availability is less because in short duration crops, we get higher yield compared to the amount of water we have used.

So these are the various methods by which we can increase the use efficiency of water.

Now next, we look at when we should provide water to our farm. There are various agronomic practices that we can employ to find out if our crop needs water or not.

First, we can look at the condition of our crop to find out if our crop requires water. Usually, if the leaves start curling up then we know that the crop needs water and we immediately provide water to it.

We can also employ the feel method to the soil to know if our crops need water or not. Usually we take a small amount of soil and turn it into a round shape ball and if this soil breaks on even a small drop then we know that the soil needs water.

Now in case of a clayey soil, we again make a round shape ball with this soil and if it cracks on pressing it with a thumb then we understand that the soil needs water.

There are also climatological approaches to know if our crop requires water. We use the pan evaporative method to know what the level of water is in our farm and what our soil requires.

Another approach to know if our farm requires water is to employ the use of indicator plants. Usually sunflower and maize plants require more water. We use these as an indicator plant in other crops farming. If the sunflower start curling we understand that this farm needs water and we provide irrigation water to the farm.

Another approach is to determine the water need during the critical stage of the growth of a plant. Critical stage is that stage when a plant requires more water. In case of wheat the crown root initiation stage is considered the most critical stage. This stage comes within 21 to 25 days and it is very important to irrigate our farm. The other critical stages of wheat are jointing and  milking. In the case of rice, panicle initiation stage and flowering stage are considered critical. For the maize crop, the critical stages are the knee high stage and tasseling or silking.

One more way of finding water requirements is to use soil sand mini kit. We put some amount of sand in one metre square patch of our farm and keep the rest of the farm as it is. Now the water holding capacity of sand is very low so we use this small patch as an indicator and whenever water is low in this patch we irrigate our entire farm.

We also use the method of increasing plant population in the farm. We grow around 1.5 to 2 times more plants in one metre square patch of our farm while the rest of the farm has a normal number of crops planted. Usually where there are more plants, the water deficiency will show quickly and we take that as an indicator to irrigate our entire farm.

We also have an instrument called tensiometer with which we can measure the tension in the soil. It has a ceramic cup which we insert in the soil. This is more common in garden crops. It provides us with a reading that ranges from 0 to 100 kilopascals. In case of sandy soil, if tension metre shows reading between 30 to 40 kilopascals then we irrigate the farm. For clayey or heavy soil, we take 60 to 70 kilopascals as an indication to irrigate our farm. If for any soil, the reading of this metre shows above 70 kilopascals then we take that as dry soil.

There are other instruments as well through which we can know the water requirements of our farm. The first is an infrared thermometer and we use it to measure the canopy temperature and then compare it with the air temperature. As long as the canopy temperature is less than the air temperature, we understand that there is the right level of water in the soil.

We also employ the method of remote sensing to know if our field requires water. It is mainly used in big farms with single crop. Infrared rays reflected by well irrigated crops and crops that are in stressed condition give us an idea about the water requirements.

We can also use different irrigation techniques to improve the use efficiency of water. These days we prefer drip irrigation compared to surface or subsurface irrigation. With drip or sprinkler irrigation we can irrigate more farm area with less amount of water.

Thank you