Laserfiche WebLink
To determine the yield threshold, assuming we are growing a crop that is somewhat sensitive to <br /> water stress and a 40 percent depletion percentage is selected, then our: <br /> ii <br /> "Allowable Depletion" = 0.4 x "Available Water" and <br /> "Yield Threshold" _ "Field Capacity" "Allowable Depletion": <br /> P <br /> Yield Threshold <br /> Jacktone clay 19.63" <br /> Madera sandy loam . 14.56" <br /> Manteca fine sandy loam 13.44" <br /> Stockton clay 21.46" <br /> To avoid yield or harvest quality reductions, the crop should be irrigated before the soil-water <br /> content within the 60 inch root depth falls below the Yield Threshold. <br /> Others factors such as irrigation system capacity, soil infiltration rates, water delivery constraints, <br /> etc. dictate when you irrigate. The depletion from field capacity that is actually used for timing is <br /> called the "management allowable depletion"to ensure optimal crop production. <br /> S . <br /> Application Efficiency <br /> Application efficiency is a measure of irrigation performance. It involves the total amount of water <br /> applied, the uniformity of the distribution, losses (such as runoff, evaporation, and deep <br /> percolation) and the net amount of water needed to meet plant growth requirements and leaching. <br /> Common application efficiencies for various types of irrigation systems, under good-to-excellent <br /> management, are listed in Table 4 (Appendix C). <br /> r How Much To Apply <br /> The gross amount of water to be applied is the net amount required to refill the crop root zone (to <br /> meet plant requirements), divided by the application efficiency.' <br /> Gross application required = Depleted moisture to be replaced /Application efficiency <br /> Liquid manure will be sampled prior'to pumping from the retention pond. Samples will by taken <br /> near the outlet for irrigation water and analyzed for total-nitrogen. <br /> The amount of Nitrogen in the retention pond water to be applied to the fields is determined onsite <br /> with a portable test kit. The total-nitrogen value (in parts per million - ppm) is entered in a series <br /> of templates (see Appendix C for copies) where the gallons per minute needed to achieve a target <br /> application rate of x pounds of Nitrogen per acre is calculated. <br /> See Page 47 for References and Bibliography <br /> C�9 Westem Dairy Design Associates, Inc.2003 <br /> Page 37 <br />