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<br />CJ <br />00 <br />':'l") <br />~ <br /> <br />.._1 <br />:_~~ <br /> <br />The amount of deep pe...colation f...om the six co...n sites was excessive <br />ove... the amount ...equi...ed to cont...ol salt movement (Table 6). As <br />stated ea...1 ie... with the updated wate... budget p...og...am, the 1990 <br />estimates of deep pe...colation fo... co...n and othe... annual c...ops should <br />be accu...ate. As stated ea...1 ie..., past estimates of deE'p pe...colation <br />a...e inaccu...ate and maybe highe... because it was assumed that any wate... <br />applied in excess of the soil moistu...e deficit beyond the fi...st foot <br />of the ...oot zone was computed as deep pe...colation unti I full ...ooting <br />depth was ...eached. All data f...om 1985 th...ough 1989 wi II be <br />...ep...ocessed with the updated p...og...am fo... unifo...mity with 1990 data. <br /> <br />I......igation efficiencies at the six co...n sites va...ied f...om 29% to 47%. <br />The ave...age of 38% is quite an imp...ovement compa...ed to othe... annual <br />c...ops such as beans, onions and fal I g...ain and lowe... than alfalfa <br />which had 47% (Table 2). The efficiency at site 15 dr'opped to 34% in <br />1990 f...om 50% in 1989. Howeve..., deep pe...colation was only sl ightly <br />highe... in 1990 than 1989. One ...eason fo... this inc...eased deep <br />pe...colation and lowe... efficiency in 1990 could be attr'ibuted to change <br />in c...op f...om alfalfa to co...n. At this site, 68% of deep pe...colation <br />occu......ed du...ing the fi...st i......igation (Table 7) and the...e was not much <br />deep pe...colation afte... that. Site 30 also switched fr'om alfalfa to <br />co...n in 1990 and as a ...esult the efficiency d...opped from 53 to 45% and <br />deep pe...colation inc...eased f...om 10.6 to 16.9 inches. At site 26, most <br />of the deep pe...colation occu......ed du...ing the fi...st i......igation. The <br />late... i......igations did not meet plant wate... ...equi...ements (Appendix B) <br />acco...ding to M&E computations. Howeve..., seve...al field checks of soi I <br />moistu...e conditions du...ing the i......igation season showed high moistu...e <br />content in the soil. A high wate... table p...obably exists at the site, <br />and the fa...me... feels that he does not need to i......igate as much to meet <br />c...op wate... ...equi...ements. <br /> <br />Data f...om 1985 to 1990 fo... co...n a...e p...ovided in Table 8. <br /> <br />Smal I a...ai": Fou... fields 35 ac...es we...e monito...ed in 1990. A total of <br />25 i......igations we...e applied. <br /> <br />The ave...age deep pe...colation fo... the fou... small g...ain sites was 20.3 <br />inches~(Table 7), about 20% highe... than the ave...age deep pe...colation <br />f 0... a I I 25 sit e s <1 7 . 0 i n c h e s). The 20. 3 i n c h e s de e p p e ... co I at ion i n <br />1990 could be highe... since site 45 and 46 did not have thei... fi...st <br />fall i......igation monito...ed. When compa...ed with su...face i......igated <br />alfalfa sites, deep pe...colation fo... fall g...ain was about the same as <br />alfalfa. <br /> <br />The ave...age deep pe...colation losses fo... smal I g...ain was almost nine <br />times mo...e than the acceptable deep pe...colation ...equi...ed fo... leaching <br />pu...poses (Table 6). Sites 29, 45 and 46 had deep pe...colation lowe... <br /> <br />25 <br />