Agricultural Engineering : Practice Questions and Answers

Artificial sub-irrigation is practiced on a small scale in India for specific high-value crops where precise water control is needed.

Controlled irrigation is another name for perennial irrigation systems where water supply is regulated and available throughout the year.

Drip irrigation is also known as trickle irrigation because it delivers water slowly and directly to the plant roots.

This type of method uses borders to divide the land into strips of width 10 to 20 meters, and 100 to 400 meters in length each. Ridges are provided between borders to prevent overtopping during irrigation, and supply ditches run perpendicular to borders on one side of the field to provide water.

In the sprinkler irrigation method, water is applied to the field through a network of pipes connected to sprinklers. Water comes out as artificial rain and waters the crops in the field.

Good irrigation has uniform water distribution for both light and heavy irrigation. It reduces conveyance and labor losses and facilitates mechanized farming, all of which lead to increased yield.

Irrigation by free flooding is done by dividing the entire land into a number of strips called laterals. Since this method can use contour lines of the field, it is suitable for both flat and steep lands.

In a lift irrigation system, the commanded area of each well is near to it, which gives a higher value of duty when compared to a flow irrigation system.

The lysimeter method is used to determine actual evapotranspiration (AET). It consists of a tight tanker filled with a block of soil installed in a field of growing plants, which is useful for specialized research studies.

Mathematically, FIR = NIR / Na, where Na is application efficiency and NIR is Net Irrigation Requirement. It accounts for water lost due to surface runoff and deep percolation.

Mathematically, Gross Irrigation Requirement (GIR) = FIR / Nc, where FIR is Field Irrigation Requirement and Nc is conveyance efficiency.

Direct irrigation using a weir or barrage is generally preferred in alluvial soil compared to storage irrigation. Alluvial soil is fine-grained, fertile, and provides good drainage, making it highly suitable for agriculture.

A carrier canal is used for both direct irrigation and for feeding water to another canal. Thus, it acts as an irrigation canal as well as a feeder canal.

The Annual Intensity of Irrigation (AII) is the percentage of the Culturable Command Area (CCA) which is irrigated annually. It is obtained by dividing the gross irrigated area by the CCA.

In extensive irrigation, crop production is usually maximized per unit of available water, even though it may not be optimal for the overall land area covered. Therefore, stating that crop production will be minimal is incorrect.

Irrigation water is considered a costly commodity because of the significant infrastructure, maintenance, and energy costs required to store and transport it to agricultural fields.

The installation of lift irrigation systems extracts groundwater, which helps in significantly lowering the water table and preventing water-logging.

Inadequate surface drainage allows rainwater or excess irrigation water to accumulate and constantly percolate into the ground, leading to a rise in the water table and subsequent waterlogging.

Over and intensive irrigation applies more water than the crops require, leading to excessive deep percolation that raises the water table. This is why replacing it with extensive irrigation is often suggested.

When the salt concentration ranges from 0.5 to 2 g/L, the water is moderately saline and should be used with appropriate water management practices to prevent soil salinity issues.