Tile rainage (in agriculture) is a practice for removing excess water from the subsurface of soil intended for agriculture. Whereas irrigation is the practice of adding additional water when the soil is naturally too dry, drainage brings soil moisture levels down levels for optimal crop growth. While surface water can be drained via pumping and/or open ditches, tile drainage is often the best recourse for subsurface water. Too much subsurface water can be counterproductive to agriculture by preventing root development, and inhibiting the growth of crops. Too much water also can limit access to the land, particularly by farm machinery. In terms of access, most modern agriculture depends on the usage of large machinery -- tractors and implements -- to prepare the seedbed, plant the crop, carry out any cultivation and applications during the growing season, and ultimately, to harvest the crop. Operating most machinery in excessively wet conditions may result in soil degradation because of excessive soil compaction, and inhibit the operation of the machinery (ie, "getting stuck").