water. Decreases the water infiltration rate of soil. (Results in more runoff and erosion as the soil absorbs water more slowly than before) Tilling the soil results in dislodging the cohesiveness of the soil particles, thereby inducing erosion. Chemical runoff. Reduces organic matter in the soil. Reduces microbes, earthworms, ants, etc. Destroys soil aggregates. Compaction of the soil, also known as a tillage pan. Eutrophication (nutrient runoff into a body of water). Archaeology Tilling can damage ancient structures such as long barrows. In the UK, half of the long barrows in Gloucestershire and almost all the burial mounds in Essex have been damaged. According to English Heritage in 2003, ploughing with modern powerful tractors had done as much damage in the last six decades as traditional farming did in the previous six centuries. General comments The type of implement makes the most difference, although other factors can have an effect. Tilling in absolute darkness (night tillage) might reduce the number of weeds that sprout following the tilling operation by half. Light is necessary to break the dormancy of some weed species' seed, so if fewer seeds are exposed to light during the tilling process, fewer will sprout. This may help reduce the amount of herbicides needed for weed control. Greater speeds, when using certain tillage implements (disks and chisel plows), lead to more intensive tillage (i.e., less residue is on the soil surface). Increasing the angle of disks causes residues to be buried more deeply. Increasing their concavity makes them more aggressive. Chisel plows can have spikes or sweeps. Spikes are more aggressive. Percentage residue is used to compare tillage systems because the amount of crop residue affects the soil loss due to erosion. Alternatives Modern agricultural science has greatly reduced the use of tillage. Crops can be grown for several years without any tillage through the use of herbicides to control weeds, crop varieties that tolerate packed soil, and equipment that can plant seeds or fumigate the soil without really digging it up. This practice, called no-till farming, reduces costs and environmental change by reducing soil erosion and diesel fuel usage. Site preparation of forest land Site preparation is any of various treatments applied to a site to ready it for seeding or planting. The purpose is to facilitate the regeneration of that site by the chosen method. Site preparation may be designed to achieve, singly or in any