What is 'irrigation efficiency' primarily concerned with?

'Irrigation efficiency' is primarily concerned with the effectiveness of water use for crop production. This concept focuses on how well an irrigation system delivers water to plants and the extent to which that water contributes to the growth and yield of crops. High irrigation efficiency means that a substantial portion of the water applied actually reaches the plants and is utilized for their growth, minimizing waste and maximizing productivity.

This measure takes into account not just the amount of water delivered, but also how much of it is effectively used by the plants, which is critical for sustainable agricultural practices. Efficient water use can lead to higher crop yields with less water, making it essential for resource management, especially in areas facing water scarcity.

The other options, while related to water usage in irrigation, do not capture the essence of irrigation efficiency. The loss of water, the area covered, and the absorption rates are all components that can influence efficiency but do not directly define it. The focus on effectiveness in crop production clearly positions option D as the correct response.