May 14, 1917 
Soil Nitrogen and Nutrition of Citrus Plants 
251 
(8) The furrow system of irrigation frequently causes the formation of 
niter spots. Surface scrapings from these spots in heavily fertilized 
groves may contain as much as i per cent of nitrogen as nitrates. 
(9) The brown color which characterizes the niter spots is probably 
due to a number of factors, but it is believed that the deliquescent char¬ 
acter of the calcium nitrate is important in this regard. 
(10) Where the furrow system of irrigation is employed, the fertilizing 
materials should be plowed down somewhat deeper than the land is 
cultivated. The feeding roots will then have an opportunity to assimilate 
the food as it is rendered available, whereas, if it is formed within the 
cultivated zone, the irrigation will tend to carry it farther away from 
the roots. 
(11) Much nitric nitrogen is lost from Citrus lands by leaching. The 
most effective means of preventing this loss is by growing a winter cover 
crop. 
(12) Basin irrigation or overhead irrigation gives a more satisfactory 
distribution of soil nitrates than the furrow system. 
(13) The basin* system of irrigation seems to give greatest promise 
when combined with a mulching system. However, the rapidity with 
which organic materials rich in nitrogen decay would seem to make it 
inadvisable to maintain a constant mulch with these materials, as the 
nitrates produced will probably be far in excess of the needs of the tree, 
and much loss will result. 
(14) Mottled orange leaves have a higher moisture content than 
healthy leaves of the same age from the same tree. The nitrogen con¬ 
tent of mottled leaves is also generally higher than healthy leaves. 
(15) Extreme mottling is frequently associated with a high nitrate 
content, but the correlation is by no means an invariable one. 
LITERATURE CITED 
(1) Briggs, L. J., Jensen, C. A, and McLane, J. W. 
1916. Mottle-leaf of citrus trees in relation to soil conditions. In Jour. Agr. 
Research, v. 6, no. 19, p. 721-739, 4 fig., pi. H (col.), 96-97. 
(2) Headden, W. P. 
1910. The fixation of nitrogen in some Colorado soils. Colo. Agr. Exp. Sta. 
Bui. 155, 48 p., 8 pi. 
(3) - 
1910. The fixation of nitrogen in some Colorado soils: a further study. Colo. 
Agr. Exp. Sta. Bui. 178, 96 p., 6 pi. 
(4) — 
1913. The fixation of nitrogen in Colorado soils: the distribution of the nitrates 
and their relation to the alkalis. Colo. Agr. Exp. Sta. Bui. 186, 47 p. 
(5) Hii,gard, E. W. 
1906. Soils . . . 593 p.,89 fig. New York, London. 
(6) KeUvERman, K. E., and Wright, R. C. 
1914. Relation of bacterial transformations of soil nitrogen to nutrition of 
citrus plants. In Jour. Agr. Research, v. 2, no. 2, p. 101-113, 7 fig. 
Literature cited, p. 113. 
