Compaction changes the soil structure by reducing the size of pores and destroying soil aggregates. It increases the bulk density of the soil limiting water infiltration and storage. The ideal soil has 25% water, 25% Air, 45% mineral particles, and 5% organic matter. There are many things that cause compaction. Trucks, equipment, animals, people, and even rain can cause compaction. The result of compacted soils is a reduction in percolation and water holding capabilities resulting in runoff and erosion. The reduced water holding capability makes the soil prone to drought. There is a reduction in gas exchange that can lead to anaerobic conditions resulting in denitrification and acidification of the soil. In sever cases and in areas of standing water gases like carbon dioxide can build to toxic levels for plants. Nutrient cycling is also affected. Altered soil moisture and temperatures negatively affect soil organisms.