relatively low concentrations In the drainage from these 

 areas show that nitrogen does not accumulate over long 

 periods in the subsurface waters . The yield of nitrogen 

 from the Gustine-Mendota area in I967 was nearly as great as 

 that applied for the same year. Although there was more 

 yield from this area during 1968, this resulted primarily 

 from an increase in the total discharge, rather than 

 increases in the nitrogen concentrations. The data show 

 that nitrogen concentrations were actually lower for I968 

 than 1967. Although fertilizer data were not collected for 

 1968, it is doubtful that the increase in yield could have 

 been due to increased fertilization of a large number of the 

 tile systems in the area. 



TABLE 15 



APPLIED NITROCEN VS. DISCHARGEID 

 NITROGEN BY MAJOR TILED AREAS 



:Quantity of Nitrogen; Average Discharged Nitro gen 

 Major Tiled : Fertilizer Applied : l§Uj ~~ 



Area :(avg lbs/acre /year) : Yield : Cone. 

 :19^T- 6T: 1962- 6T: 1967 :( lbs/acre ):(mg/l) 



Tq^ 



Yield : Cone. 

 (lbs/aere):(mg/l) 



Byron- Westley 50 6I 72 Uoi/ J.k?-/ 68 9.2 



Westley-Gustine 33 kk 67 l4 7.5 21 10.4 



Gustine-Mendota 88 75 92 85 3J+.6 112 31.8 



Tulare Lake 7!^ 68 43 19 10.5 12 8.7 



1/ Partial year's data (seven months). 



The yield from the Byron-Westley area increased significantly 

 in 1968 over I967 because of a longer sampling period. 



P hosphorous Fertilization . Phosphate fertilizers were found 

 fo be applied less frequently than nitrogen fertilizers in 

 all major tiled areas. Accurate records were not kept on 

 most farms. Application rates were only obtained from one 

 large operation in the Tulare Lake area. Records showed 

 that phosphate fertilizer was applied regularly at the rate 

 of 50 pounds per acre every other year. Phosphate concentra- 

 tions in tile drainage from that area seemed to indicate a 

 relation between application and discharge. Soil investiga- 

 tions (2^) conducted by the Department of Water Resources 

 have shown that an association may exist between shell frag- 

 ments in the soil of the Tulatre Lake soil series and the 

 extraordinary phosphorous content in the tile drainage. 

 Shell fragments removed from the soil profiles contained 



60 



