Note 112 — Chapter XI · THE ORGANIC CONSTITUENTS OF THE SOIL SOLUTION.
Reading edition
It may not be amiss to point out here that this general law holds for all dynamic phenomena. In chemistry, for instance, the general law is well recognized that the rate of reaction diminishes with increase in the active mass of the reaction products. It can be shown that the principle applies to plant growth. Young plants will withdraw potassium more rapidly than chlorine from solutions of potassium chloride; that is, the solution soon contains free hydrochloric acid. Conversely the plants cause a solution of sodium nitrate to become alkaline. Therefore, if the above principle holds, then the initial addition of small amounts of hydrochloric acid to a solution of potassium chloride should slow up the absorption of potassium by seedling wheat plants, or the addition of sodium hydroxide the absorption of nitrogen from a solution of sodium nitrate. Mr. J. J. Skinner has tested this idea with the following results, growing carefully selected wheat seedlings, for 3 days in solutions of pure potassium chloride, solutions of potassium chloride containing initially enough excess of hydrochloric acid to be of an N/₅,₀₀₀ concentration with respect to the acid, solutions of sodium nitrate, and solutions of sodium nitrate containing initially an excess of sodium hydroxide.
Solutions of KCl containing 80 p.p.m. K₂O.
1 K₂O absorbed 40.0 p.p.m.
2 K₂O absorbed 40.0 p.p.m.
3 K₂O absorbed 36.3 p.p.m.
Solutions of KCl (80 p.p.m. K₂O) and HCl (N/₅,₀₀₀).
4 K₂O absorbed 26.7 p.p.m.
5 K₂O absorbed 29.5 p.p.m.
6 K₂O absorbed 26.7 p.p.m.
Solutions of NaNO₃ containing 80 p.p.m. NH₃.
7 NH₃ absorbed 30.2 p.p.m.
S NH₃ absorbed 30.2 p.p.m.
9 NH₃ absorbed 32.5 p.p.m.
Solutions of NaNO₃ (80 p.p.m. NH₃) and NaOH (N/₅,₀₀₀).
10 NH₃ absorbed 27.8 p.p.m.
11 NH₃ absorbed 34.3 p.p.m.
12 NH₃ absorbed 27.8 p.p.m.