Laserfiche WebLink
<br />(fj <br />en <br />C"'J <br />~ <br /> <br />:..:.:' <br /> <br />significantly highe... than in p...evious yea...s (Table 11). This may be <br />due to a high wate... table at this site as it has been unde... i......igated <br />ove... the yea...s and the...e has been no deep pe...colation (Refe... to <br />Appendix 8,1990 Individual Site Summa...y Table fo... site 18). <br /> <br />CONCLUSIONS <br /> <br />It is gene...ally bel ieved that some deep pe...colation is ...equi...ed to <br />keep sa I in i ty f ...om ... is i ng into the ...oot zone. I...... i gat i on systems such <br />as mic...osp...ays (site 17) and side...oll sp...inkle...s (sites 33 and 36) a...e <br />easie... to measu...e and cont...ol the pe...centage of deep pe...colation, <br />because they have a ...e I at i ve I y un i fo...m app I i cat ion ...ate. These <br />systems could be used to dete...mine the minimum pe...centage of deep <br />pe...co I at ion ...equ i ...ed in the G...and Va II ey to keep sa, I in i ty be I ow the <br />...oot zone. <br /> <br />Fu......ow i......igation to establ ish a c...op f...om seed wi II undoubtedly <br />...esult in a high pe...centage of deep pe...colation unti I the c...op is <br />establ ished. Soi Is in the monito...ing a...ea have p...ope...ties which cause <br />them to wet ac...oss slowly and p...ope...ties which cause excessive su...face <br />c...usting. Soi I su...faces must be kept moist du...ing establ ishment to <br />keep plants f...om c...usting in. These soi I conditions wi II ...esult in a <br />high pe...centage of deep pe...colation f...om fu......ow i...rigation du...ing <br />estab Ii shment of c...ops. Th i s is ill ust...ated in Tab Ie 7, Pa...t I of <br />this ...epo...t. The g...eatest amount of deep pe...colation fo... annual c...ops <br />occu...s du...ing the fi...st i......igation when seedlings a...e being <br />estab I i shed. As much as 20 inches of deep pe...co I at i on have been <br />measu...ed du...ing the fi...st i......igation (Table 7). This amount of deep <br />pe...colation has a t...emendous leaching effect on the top 30 inches of <br />the soil p...ofile. <br /> <br />Cultu...al p...actices may have as much to do with the annual changes in <br />elect...ical conductivity (ECe) ...eadings as actual ...ise in sal inity <br />levels in the su...face six inches. Fo... example, when fe...ti I ize... is <br />appl ied, it wi II affect the Ece ...eading in the plo,," I aye.... Also, if <br />the sal inity level of the i......igation wate... ...ises, the sal inity level <br />of the so i I wi I I undoubted I y ... i se. <br /> <br />Inc...eases in soi I sal inity levels wi II p...obably occu... when the amount <br />of deep pe...colation is below the acceptable amount ...equi...ed to keep <br />sal inity levels below the ...oot zone (Refe... to Pa...t I fo... mo...e detai Is <br />on acceptable deep pe...colation). <br /> <br />The...e a...e 15 sites that have been monito...ed anywhe...e f...om fou... to <br />seven yea...s. In compa...ing the sal inity values ove... this pe...iod, the <br />on I y conc I us i on that can be made is that sa I in i ty has not changed <br />app...eciably. <br /> <br />A single sampl ing afte... the i......igation season seems to be adequate at <br />this time. Sampl ing done in Novembe... 1984 and Ma...ch 1985 showed <br />little diffe...ence between the two <Table 11>. <br /> <br />36 <br />