The study looked at how much water winter wheat plants use compared to how much water evaporates from the soil surface in North China. By measuring these amounts, researchers found that the ratio of water used by the plants to water evaporated from the soil can help determine when the plants need more water. They also found that the amount of leaves on the plants and the moisture in the soil play a big role in how much water the plants need. This information can help farmers know when to water their winter wheat crops.