Kiril brought up something the other day about water being a fertilizer, I Poo pooed it saying "I don't think so", I was actually looking fro something else but ran across this, it is from an Ag site but still pertains http://attra.ncat.org/publication.html Water Cycle Water is a nutrient, in one sense, since it is one of the raw ingredients used by plants to make carbohydrates. It is also key to nutrient cycling because plant nutrients are soluble and move with water. Downward leaching of plant nutrients occurs with water movement. Soil itself moves in water, taking with it insoluble nutrients such as phosphorus. The area around roots must be moist, since nutrients are taken up dissolved in water. Management determines how effective the water cycle will be in pastures. If rainwater can enter the soil easily, runoff losses are less. Maximum infiltration of rainfall keeps groundwater tables charged up, wells running year round, and drought damage to a minimum. Soil surface conditions that foster high rainwater intake are abundant ground cover (by living plants and surface litter) and good soil aggregation. The best-aggregated soils are those that have been in well-managed perennial grass (sorry about that Kiril). Though aggregation can be maintained under crops, the perennial activity of grass provides both aggregate-forming processes and aggregate-stabilizing humus. A grass sod extends a mass of fine roots throughout the topsoil. The grass sod also provides protection from raindrop impact. A moderate amount of thatch continually provides food for soil microorganisms and earthworms that generate the glue-like substances that bind aggregates into water-stable units. The dead material, as well as the plants themselves, shade the soil, maintaining a cooler temperature and higher humidity at the soil surface. Conditions that reduce water intake and percolation are bare ground, surface crusting, compaction, and soil erosion. These conditions are not usually present in well-managed perennial pastures. Bare ground leads to erosion, crusting, and weeds. Crusting seals the soil surface when the soil aggregates break down. Excessive trampling.especially in wet conditions.and the impact of falling raindrops on bare soil are two common causes of crusting. Therefore, it is important to move water sources, feedbunks, and minerals before bare ground and crusting develop.