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<br />cycle) for proper water application, In programming the conll'oller, it is helpful if the llTigator is familiar <br />with the advance time that was needed for the water to reach the furrow end under the continuous flow <br />technique, Knowledge of the soil intake rate and length of the field is equally important, <br /> <br />'>~i'~~ <br /> <br />,,) <br />CO <br />.... <br />00 <br /> <br />Surge irrigation can usually be completed in two stages: "advance" and "soak" cycles, The <br />advance cycle, or "out time", advances the water down the furrow for a predetermined distance and then <br />switches to the opposite side as programmed, This process continues until water reaches the end of the <br />field, The number of left and light cycles requll'ed to obtain the proper IWM is dependent on many <br />factors such as field length, soils, slope, furrow or corrugation condition, soil moisture regime and the <br />crop being grown, <br /> <br />When the water has reached the end ofthefuITOW or corrugation, the soak cycle then begins, These <br />cycles are shorter in time so as to avoid excess runoff or tail water. Inigation water applied during this <br />phase needs to meet the growing crop's root zone soil moisture requirements over the complete length <br />and width of the field, However, at any given time during the irrigation, the operator can re-program <br />the surge controller to increase or decrease application time for both the ad vance or soak cycle as needed, <br />This provides the operator with the necessary control so as to prevent deep percolation and/or excessive <br />runoff, while at the same time maximizing irrigation efficiency. <br /> <br />Several theories exist as to why surge inigation really works, The most accepted version is that <br />the water may continue to penetrate the soil even after the application of the irrigation water stops, The <br />on/off application of water created by surge results in impacting capillary flow and compaction of soil <br />particles, causing the soil sUlface to "seal" or slick over, The soil infiltration rate changes from 'intrinsic' <br />to 'basic' more rapidly and the wetted perimeter of the furrows or corrugations change to a smoother <br />sUlface, Hence, there is less penetration dUling each subsequent surge of water, providing more water <br />to be available to move down the fUITOW or corrugation, The penell'ation of water into the soil profile <br />within the root zone can be maximized, creating a condition of uniform depth throughout the field, In <br />addition, the reduction of time dUling both the advance and soak cycles helps prevent excessive runoff <br />as well as reduce deep percolation (water lost below the root zone), This can be amajor cause of potential <br />salt displacement resulting from water running through the salt laden soils, flowing into llibutaries and <br />eventually ending up in the Colorado River, With the use of surge, deep percolation is minimized, <br />Irrigation Water Management is then enhanced, irrigation efficiency maximized and saltload reduction <br />realized, Project results are being continuously published so as to provide infOlmation and education <br />to the public on the potential impacts, <br /> <br />Lower Gunnison Surge Demonstration Project. Page 9 <br />