Although the amount of water cotton needs depends on the environment in which it is grown, cotton has been bred to grow and thrive even when water is scarce. In many parts of the world, cotton growers rely solely on natural rainfall to give their crops the water they need. In the U.S., about two-thirds of the cotton crop is produced without any irrigation at all. Most irrigation used for the remaining one-third simply supplements crop needs when rainfall is insufficient.1 Over the last 40 years, the amount of irrigation water used by cotton in the United States has decreased while yields have increased.2
The mineral content of water and soil effects how all crops grow, and even whether they can grow at all. Cotton isn’t just a very water-efficient crop – it is also highly tolerant of the salt content of soil and water. This means it can be grown with water and soil resources that are unsuitable for most other crops.3 Cotton can even make use of drainage or reclaimed water that cannot be used to water other crops, and that would otherwise require environmentally challenging waste disposal.4
The amount and timing of natural rainfall can play a major role in the water management decision making process for cotton growers, but sometimes, plants need more help in order to grow – for example, when weather conditions are adverse (i.e., in a drought). Under some conditions, irrigation also significantly improves the efficiency of other agricultural inputs. In fact, it can as much as double the yield of crop production5, as well as offering safeguards against poor crop performance and insufficient rainfall.
Today, growers can use state-of-the-art technology to map their fields and track exactly where water is needed, ensuring they are not overusing this precious resource. This capability is called precision agriculture, and it has significantly improved the water use efficiency of producing cotton. The technology that supports precision agriculture techniques is constantly improving. There are different types of irrigation systems for cotton production: surface irrigation, sprinkler irrigation and drip irrigation systems. For surface irrigation, siphon tubes are placed in a ditch and water is distributed between the rows of crops. Another method used to irrigate cotton crops is by using a sprinkler system, similar to the way many people water their lawn. The latest irrigation trend is a drip system where tubes are run below the surface of a field, giving water directly to the root zone of the crop. Systems like these, which were first developed in the U.S., help significantly reduce water waste and loss due to evaporation.6
Source: Barnes et al (2020) Forty years of increasing cotton’s water productivity and why the trend will continue.7
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