Rubber mulch provides several advantages over plant material based mulches. Tests have shown that rubber mulch is superior in breaking falls to traditional bark mulches. Soil conditioners, potting mixes, mulches and manufactured soil are examples of possible reuses. Straw from the previous crop mulches the topsoil. Vegetative cover as living mulches protect soil against wind and water erosion. Plastic and organic mulches help to effectively control weeds. Organic farming includes crop rotation, and mulches to control pests and soil fertility. Mulches or ground covers also allow the soils to absorb more water by reducing compaction. Legumes used as living mulches also provide nitrogen fixation, reducing the need for fertilizer. Plastic mulches keep ripening fruits off of the soil. Quality biodegradable mulches are made out of plant starches and sugars or polyester fibers. Living mulches control weeds in two ways. Organic mulches slow the warming of the soil. Favored substrates include hardwood mulches made of oak, eucalyptus, Douglas fir, and alder. In some situations, the allelopathic properties of living mulches can be used to control weeds.