May 14, 1917 . 
Soil Nitrogen and Nutrition of Citrus Plants 
237 
and in most cases the spots or streaks could be located only with 
difficulty. The lack of characteristic niter spots in the soil following 
the first irrigation is, no doubt, due to the fact that the nitrates which 
had accumulated at the surface during the previous season had been 
leached down to a considerable depth by the winter rains; and, .as the 
new application was plowed down, there was little nitrate in the surface 
soil at the time of the first irrigation. The spring plowing also broke 
up the plowsole formed during the previous season, so that the irrigation 
water was not interrupted in its downward movement, and there was 
consequently a slower lateral movement of the water in the surface 
soil. The evaporation of moisture from the soil is also somewhat slower 
at this time than at the time of the later irrigations. 
Following the second irrigation, niter streaks and spots were abundant 
in soils A, C, G, H, and L; and analyses of scrapings from these spots 
showed them to be very rich in nitrates. The scrapings from soil H at 
this time contained 1.54 per cent of nitrogen as nitrates, and soil A 
1.12 per cent. 
Plots B, M, and R, which have not received any nitrogenous fertilizer; 
plots F and O, which have received manure; plot E, which has received 
only a light application of nitrogen in bone meal; and plot U, which 
has received manure and a cover crop, show a comparatively small 
