232 
Journal of Agricultural Research voi.ix,No. 7 
The samples taken from the grove at Covina were taken between fur¬ 
rows which were run at a distance of 32 inches. The nitrates in the 
upper 3 inches varied from 2.74 mgm. in boring 7 to 13.66 mgm. in boring 
5, showing that there was a lateral movement of nitric nitrogen away 
from the furrows. From 3 to 6 inches the nitrates varied from 0.14 
mgm. in boring 1 to 2.18 mgm. in boring 5. The nitrates found below 
6 inches were comparatively low in all of the samples, and the distribu¬ 
tion does not seem to have been influenced greatly by the irrigation. 
In this grove the feeding roots were fully 6 inches below the surface, and 
a study of the column of averages shows that the bulk of the nitrates in 
the upper 15 inches of soil were located above the feeding roots. 
The soil from Corona had a very high nitrate content, which varied from 
1.09 to 21.88 mgm. in the upper 3 inches. It is observed that the highest 
nitrate content in the surface layers occurred about midway between the 
furrows. The lateral movement of nitrates was also apparent at a depth 
of 6 to 9 inches, but below that depth there seemed to be no movement of 
nitrates away from the furrows. This grove was given rather deep culti¬ 
vation, which kept the feeding roots well below the surface 6 inches. In 
spite of the large accumulation of nitrates in the upper 6 inches the sup¬ 
ply within reach of the roots would seem to have been sufficient for the 
needs of the trees. However, with a supply of nitrogen above the roots 
sufficient for the needs of the tree for a period of at least 18 months, it 
would seem that the loss of nitrogen from leaching or other causes may 
have been considerable. 
The figures for the first three groves in the Tordsburg section, all of 
which were on very light soils, show a strong lateral movement only in 
soil A, in which the nitrates in the upper 3 inches varied from 0.39 to 20.27 
mgm. In soils B and C there appeared to be very little lateral movement 
of nitrates, but there was a large accumulation of nitrates in the surface 6 
inches. 'Because of the very light character of these soils, all the groves 
are cultivated deeply, and the nitrates which accumulate in the upper 6 
inches of soil can be of little use to the tree during the present season. In 
soil C the nitric nitrogen in the upper 3 inches averaged 19.34 mgm., while 
the average nitrate supply within reach of the roots was only 0.27 mgm. 
Such a distribution in these extremely light soils must lead to very heavy 
losses of nitrogen from leaching. In soil D, which is a heavy clay, the high¬ 
est nitrate content was found in boring 4, which was located about midway 
between the furrows. In this soil there were a few feeding roots within 4 
inches of the surface, but even if we consider all the nitrates available 
except those confined in the surface 3 inches, there was approximately 
two-thirds of the nitric nitrogen which was unavailable. 
The distribution of nitrates in soils at Orange, Anaheim, and Whittier 
is shown in Table XXIV. In the grove at Orange the highest nitrate 
content for each section was found in boring 4, which indicates that irri¬ 
gation water caused a somewhat uneven lateral distribution of nitrates. 
