_________________________________
| |
Treatment | Composition of leaves | Mg (percent)
________________|__________________________________| Ratio ____________
| | K (percent)
| Ash N P K Ca Mg |
________________|__________________________________|
| % % % % % % |
1. Nitrogen | 6.68 2.52 .129 .945 1.30 .143| .151
2. Phosphorus | 8.56 2.29 .160 .885 1.60 .186| .210
3. Potassium | 9.39 2.31 .150 1.650 1.93 .155| .094
4. Complete | 7.18 2.43 .133 1.175 1.63 .132| .112
5. Nitrogen and | |
potassium | 7.62 2.49 .119 1.480 1.33 .110| .073
6. Check | 7.38 2.32 .188 .890 1.70 .149| .167

Potassium applications produced the greatest effect on leaf composition,
as they increased the concentration of that element in the leaves by
0.285 to 0.760 percentage unit over that in the leaves from the check
trees. In addition, it seems likely that this great increase in the
potassium content of the leaves was accompanied by a decrease in their
magnesium content, since this usually has been found to result. When
the ratios of the percentage of magnesium to the percentage of
potassium in the leaves were calculated, it was found that they were
rather low for the trees that had been fertilized with potassium. The
magnesium-potassium ratio was highest in the leaves from the trees
fertilized with phosphorus only, followed in order by the check and
nitrogen treatments.

Relation of Magnesium Deficiency to Leaf Scorch, Winter Injury, and
Fungus Infection

On August 15, 1950, at the time the leaf samples were taken, each tree
in the experiment was scored as to the degree of leaf scorch present. In
the winter of 1950-51 soil samples were taken from each plot receiving
potassium alone and the lime requirement was determined by the Division
of Soil and Management and Irrigation, of this Bureau. The lime
requirement was found to vary greatly, ranging from 1500 to 6700 pounds
per acre. In early spring of 1951, high-magnesium dolomitic lime was
applied uniformly at the rate of 1500 pounds per acre and in addition
each tree received 5 pounds of Epsom salt.

Each tree in the experiment was scored for degree of wint