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Plants

Sustainability may also involve crop rotation. Crop rotation and cover crops prevent soil erosion, by protecting topsoil from wind and water. Effective crop rotation can reduce pest pressure on crops, provides weed control, reduces disease build up, and improves the efficiency of soil nutrients and nutrient cycling. This reduces the need for fertilizers and pesticides. Increasing the diversity of crops by introducing new genetic resources can increase yields by 10 to 15 percent compared to when they are grown in monoculture. Perennial crops reduce the need for tillage and thus help mitigate soil erosion, and may sometimes tolerate drought better, increase water quality and help increase soil organic matter. There are research programs attempting to develop perennial substitutes for existing annual crops, such as replacing wheat with the wild grass Thinopyrum intermedium, or possible experimental hybrids of it and wheat. Being able to do all of this without the use of chemicals is one of the main goals of sustainability which is why crop rotation is a very central method of sustainable agriculture.