The roots of plants release substances that can make the soil around them repel water. This affects how much water the soil can hold and how easily it can flow to the roots. Scientists studied lupin plants to see how the soil in the area around their roots behaved when it dried out and got wet again. They found that the soil near the roots held more water when it was drying out but less water when it got wet again. This is because the soil near the roots became slightly water-repellent after drying. This shows that the ability of the soil to hold water changes depending on how wet or dry it has been in the past.