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<br />(J <br />'='J <br />('rj <br />. ..-t <br /> <br />-, <br />_"r" <br /> <br />;...-.' <br /> <br />PART 2 <br /> <br />SOIL SALINITY MEASUREMENTS <br /> <br />OBJECTIVES <br /> <br />To monito... long te...m changes in sal inity within the' soi I p...ofi Ie. <br /> <br />ACCOMPLISHMENTS <br /> <br />Du...ing Decembe... 1990, the soi I staff made quantitative salt <br />dete...minations at depths of 6, 18, and 30 inches fo... 19 monito...ing <br />sites (does not include the fou... su...ge sites - 39, 41, 44, and 46). <br />These include the th...ee new monito...ed sites establ ished in 1990. <br />Quantitative salt dete...minations we...e measu...ed at two locations on <br />most sites. <br /> <br />OBSERVATIONS <br /> <br />Sal inity levels a...e ...elatively low in the soi Is at all the monito...ing <br />sites <Tab I e 11>. Fifty to seventy yea...s of i...... i gat i ng these so i Is <br />with up to to fou... ac...e feet of wate... annually have, ...educed sal inity <br />levels to ve...y low values. The p...esent sal inity lelvels in the soi I at <br />those sites have I ittle, if any effect, on c...ops such as alfalfa, <br />ba...ley and wheat g...own in the G...and Valley <Table 12). Some yield <br />...eduction is expected fo... sensitive c...ops I ike beans and o...cha...d. In <br />this a...ea, some deep pe...colation is ...equi...ed to kee1p salinity at a <br />level below the ...oot zone. The amount of deep pe...colation to keep <br />sa Ii n i ty be I ow the ...oot zone is dependent on the so i I type and the <br />I andscape on wh i ch so i Is occu.... <br /> <br />Monito...ing sites 11, 12, and 17 have been monito...ed fo... seven yea...s. <br />Sal inity levels have changed ve...y little du...ing this seven yea... <br />pe...iod. Sal inity levels in these soi Is a...e app...oximately the same in <br />1990 as they we...e in 1984. On site 17, if the data f...om 1984 a...e <br />th...own out, this site may be showing a sl ight incl""€lase in sal inity <br />I eve I. <br /> <br />Monito...ing sites 15, 16, and 21 have been monito...ed fo... six yea...s. <br />Sa Ii n i ty I eve Is on these sites have not changed app...ec i ab I y between <br />1985 th...ough 1990. <br /> <br />Monito...ing sites 26 and 27 have been monito...ed fo... five yea...s. The...e <br />has been I ittle change in sal inity levels on these sites. <br /> <br />Monito...ing sites 29, 30, 31, 32, 33, 36 and 18 have been monito...ed fo... <br />fou... yea...s. Sal inity levels have changed ve...y I it1;je du...ing this fou... <br />yea... pe...iod. Howeve..., the 1990 sal inity levels at site 18 a...e <br /> <br />35 <br />