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<br />1 fertilizers, primarily nitrogen, move with the soil water, and are often <br /> <br />2 lost by deep percolation. Reducing deep percolation by uniform and <br /> <br />3 precise irrigation keeps applied nutrients in contact with roots longer, <br /> <br />. <br />4 increasing the proportion taken up by the crop. But, the chance always <br />~ . <br />5 exists that intense rainfall will leach nutrients beloW the root zone. <br /> <br />6 By applying soluble nutrients frequently in small amounts with the ir- <br /> <br />7 rigation water, little is stored in the soil, which drastically reduces <br /> <br />8 the quantity that can be lost in a single incident. Rawlins and Raats <br /> <br />9 (3) cited an extreme case where ..efficient irrigation could save over <br /> <br />10 300 kg of N per hectare annually compared to current use. Particularly <br /> <br />11 as energy for nitrogen fertilizer production becomes more scarce, this <br /> <br />12 saving alone may play a significant role in determining how water is <br /> <br />13 managed on the farm. <br /> <br />14 Any irrigation scheme certainly must have some disadvantages, and <br /> <br />15 high-frequency irrigation is no exception. The two primary closed- <br /> <br />16 conduit water delivery systems capable of high-frequency irrigation <br /> <br />17 that are now being used commercially are sprinkler and drip. Both can <br /> <br />18 deliver any desired quantity of water directly and uniformly to each <br /> <br />19 plant. But, because pressure is required to distribute water uniformly <br /> <br />with sprinklers, and to force it through filters to prevent clogging of <br /> <br />20, <br /> <br />211 <br /> <br />d~i? emitters, the water saved by increased uniformity of application <br /> <br />Z2 is often at the expense of increased energy required for pumping. And <br /> <br />23 continued supplies of low-cost energy for agriculture are not assured. <br /> <br />24 Continued expansion of food production by expanded use of fossil energy <br /> <br />25 <br /> <br />is risky. He should not be comfortable "ith a food prodlJff,Vllsystem <br />U ~!~JO <br /> <br />that ignores future stability. Any system that depends on fossil fuel <br /> <br />26 <br /> <br />27 energy has a finite life. And although we certainly cannot afford to <br />