Variable rate technology saving water for agriculture

The technology in the precision agriculture, used to apply the materials like irrigation, pesticides, fertilizers, weedicides and herbicides etc. in variable rate is known as variable rate technology (VRT).

Variable rate technology is a very healthy and economical tool in precision agriculture for saving inputs. Now, in the current situation of our natural resources especially water, it is very necessary to use the water according to the need and actual situation of the plants/crops present in field and forests etc.

For applying the water according to the need and actual situation of field, the use of VRT is increasing day by day, in order to save the water and minimize its losses.

For water-saving irrigation, variable rate spray technology (VRST) is defined as “a process of collecting, processing and analyzing the data from field and soil with different conditions by using advanced information techniques and equipment’s in order to give the instructions to actuator for variable rate application to control the volume of spray nozzles in real-time.”

Variable rate spray technology (VRST) for spraying of water decides:

1. When to apply
2. How to apply
3. Where to apply
4. How much to apply

Variable rate spraying technology (VRST) for water saving is more effective, cost saving, and water saving and besides these, it reduces the environmental pollution (air as well as water pollution).

Due to these reasons, variable rate spraying technology is widely used in agriculture, especially in crop farming, horticulture, animal husbandry and forestry etc.

Process of variable rate spraying technology (VRST) for water saving

The process of VRT consists of three different phases which are described as below;

1^st phase: It involves identification of the spraying period and obtaining the information of precise-spraying target.

2^nd phase: It involves optimization of decision period, improvement and evaluation of the target information, in order to determine the volume, droplet size and velocity of water for spraying purpose.

3^rd phase: It involves the implementation of variable rate spray according to volume, droplet size and velocity.

For precise spray of water, above three phases are very important but third phase is more important and critical. Greater accuracy in water spraying can only be achieved by more perfection and consistency of variable volume control.

By keeping in view the volume control, droplet size and velocity and perfection, different equipment’s for variable rate spray have been identified and introduced which involve PWM-based intermittent variable rate spray, the direct injection spray, compressed air sprayer with ground speed control and so on.

Application options

VRT should be very economic and viable in different conditions which are given as following;

• When field is unlevelled (terrain), then natural terraces are formed, easily and VRT for spray of water should be used in order to minimize yield losses.
• When rocks, roads and pond are present, VRT for water spray should be adopted to minimize the contamination in the case of pesticides, weedicides and herbicides.
• In water shortage or drought conditions, VRT for water spray should be used in order to apply water only on the specific parts and stages of crop which ultimately, enhances or stables the yield of crop.
• In inter-cropping (especially in mixed cropping), VRT for water spray should be helpful for giving water to both crops on their different requirement times and stages.

Advantages of variable rate spray technology (VRST) for water saving

Variable rate spray technology (VRST) for water saving has many advantages which are given as following:

1. It saves water, which can be used for the other crops grown on the field.
2. It helps the plants to grow effectively, which are sensitive to waterlogging by applying no or minute quantity of water.
3. It reduces the cost of the farmers by minimizing the load on pumping of ground or tubewell water.
4. It minimizes the chances of soil from becoming salt affected by reducing the accumulation of salts on the surface of soil.
5. In the sandy soils, it saves the water by minimizing its leaching in the soil.

Limitations of variable rate spray technology (VRST) for water saving

Besides advantage, it also has some limitations which are given as following:

1. It requires expertise to understand its application processes.
2. Initial cost of installation is very high.
3. Its maintenance is a little bit difficult.

Besides saving irrigation or water in agriculture, variable rate technology (VRT) is very useful, viable and economical for pesticides, nutrients (fertilizers), weedicides, herbicides, seeding and planting in variable rate for saving input resources from losses and contamination of ponds, water channels, present near the cropping areas or fields.

Authors: Tanveer Ahmad*, Ashfaq Ahmad and Muhammad Shaukat

*Agro-Climatology Lab, Department of Agronomy, University of Agriculture, Faisalabad