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' Colorado State University Master Gardener - Soil Water Holding Capacity and Irrigation Management Pale 1 of 7 <br />CMG Home I Ask a Colorado Master Gardener <br />CMG GarderrNotes I Home Gardening Publications i Related Links <br />AnswerLink I Horticulture Web Search i Home Use Pesticides Database <br />CMG Outreach I CMG Training i Becoming a CMG Volunteer I Benefits of Gardening <br />GardenNotes #261 <br />Soil Water Holding Capacity and. Irrigation Management <br />QWline: Water holding capacity <br />Evapotranspiration, ET <br />Rooting depth <br />Plant's ability to extract water from the soil <br />Irrigation: How much? How often? <br />Other factors influencing irrigation management <br />Fine-tuning <br />Normal irrigation requirement for turf <br />Poor watering practices lead to many common landscape problems including iron chlorosis, low plant vigor, follar <br />diseases, root rots, and water pollution. Gardeners who water by dragging the hose tend to over water by about <br />10% while those who have an automatic sprinkler system tend to over water by an average of 30-440/,,. <br />It is ironic that the automatic sprinkler system, (installed to make life easier and save water) actually uses more <br />water due to poor design, maintenance, and management. The convenience of "set it and forget It" has caused <br />people to pay less attention to the needs of their yards. However, with a little time to team how to precisely <br />manage the irrigation system, we will conserve water, save money and improve the health of a lawn and garden. <br />Several complex factors work together in irrigation management including the following: <br />r The soil's water holding capacity (i.e., the quantity of water held by the soil) <br />• Fvapotranspiratiorr, ET <br />• Rooting depth <br />• The plant's ability to extract water from the soil <br />Yates poldil'ngCapacity <br />Soil texture and structure (actually the pore space created by soil texture and structure) primarily determine a <br />soil's ability to hold water. Water coats the soil particles and organic matter and is held in the small pore spaces <br />by cohesion (the chemical forces by which water molecules stick together). Air fills the large pore spaces. <br />Water readily moves downward by gravitational pull through the large pore spaces. In small pore spaces, water <br />moves slowly in all directions by capillary action. <br />httn://www.ext.colostate.edu/mp/files/szardcxmotes/261-SoilNVater.htmi <br />1/3/2008 <br />64