TABLE 13 



TILE DRAIN DISCHARGE VS. IRRIGATION 

 INTENSITY WITHIN MAJOR TILED AREAS 

 1967 



Average Tile Discharge (ac-f t /ac) 

 Byron- : Westley-: (iustlne-: Tulare 

 Westley ; Gustlne ; Mendota ; Lake 



Irrigation 

 Intensity!/ 



Light (0.0-0.9) 

 Medium (1.0-2.9) 

 Heavy (3-0-3.9) 

 Very Heavy (^.0-8, 

 Flooded 



0) 



2/ 



2.2 



2.2 



.8 



2/ 



2/ 



ITI 



?/ 



.7 



1.1 



1.0 



.4 



.8 



.6 



.6 



1.2 



.5 

 2/ 



1_/ Arbitrary categories based on headgate Irrigation 

 requirements of crops, weighted by acres. 



2/ No tiles within the Irrigation Intensity categories. 



inversely with tile flow. Several tile systems located In 

 the northern area had nutrient concentrations that remained 

 rather constant throughout the study period. However, 

 nitrogen was observed to increase with Increases in tile 

 discharge from several individual tile systems within the 

 study area. 



Denit rl fl cation ■ The variability of nitrogen in drainage 

 from certain tile systems may have been due to denitrlflca- 

 tion which has already been mentioned in regard to crops 

 that were flooded. However, low nitrogen concentrations 

 were found in drainage from tiled areas that were not 

 flooded. Although investigations were not conducted to 

 determine if the seasonal decrease in nitrogen concentra- 

 tions was actually due to denitrlficatlon, findings by other 

 investigators show that under certain conditions denitrlfica- 

 tlon does take place . Ponnamperuma (I6) reports that no 

 more than 3 nigA nitrate had ever been reported in the soil 

 solution of a flooded soil following irrigation and that 

 nitrogen losses sire due chiefly to the reduction of nitrate 

 to the oxides of nitrogen or nitrogen gas. Ponnamperuma 

 concludes that nitrate is not a suitable fertilizer for rice 

 because of denitrlficatlon and leaching losses. Power (17) 

 reports bacterial denitrlficatlon losses may account for a 

 major psirt of fertilizer nitrogen applied in lands with 

 poor drainage. Meek, et al (lo), found significant 

 decreases of nitrogen in saturated fine-textured soils which 

 were fertilized under a laboratory-controlled environment. 



56 



