Which of the following is a common water conservation practice?

Planting cover crops is a recognized water conservation practice because it helps to enhance soil health, improve water retention, and reduce erosion. Cover crops, such as clover or vetch, create a protective layer over the soil, preventing it from drying out and decreasing evaporation rates. They also contribute organic matter to the soil when they decompose, which improves its structure and allows it to hold more water. Furthermore, cover crops can help to suppress weeds, which further reduces competition for water among crops. This practice is particularly beneficial in agricultural settings where water conservation is critical for sustainable farming and efficient use of resources.

In contrast, increasing the size of irrigation pipes may lead to more water flowing through the system, potentially leading to excessive water use rather than conservation. Using pesticides is primarily aimed at pest control rather than water management, and while there may be some indirect effects on moisture retention, it is not a primary conservation strategy. Installing a fountain in the field does not contribute to water conservation and can actually waste water by creating unnecessary evaporation. Therefore, planting cover crops stands out as an effective method of conserving water in agricultural practices.