The objectives of the 12-year lysimeter study were to determine (a) annual recoveries of nitrogen as NH3, NO2, and NO3 from ammonium chloride, phosphate, and sulfate applications to a 1-foot stratum of Cumberland silt loam underlain by a 5-foot column of red clay subsoil, and (b) attendant outgo of exchanged Ca, Mg, and K and recoveries of additive CI and SO4.
Quantity of nitrogen input, the soil-subsoil column used in lysimeter triplicates, and the experimental procedure were those described in a 10-year study in which nitrates of Na, Ca, and Mg were applied (2).
Leachings of NH4 were nil to meager; nitrites appeared in the leachings throughout the first 3 years. Largest outgo of engendered NO3 occurred in the second, third, and fourth years, in descending order, and respective totals for the initial 6 years were virtually the same as the totals for the 12 years. The applied NH4 was recovered chiefly as engendered NO3, but substantial fractions were lost through reduction processes and/or fixation. Recoveries of N from chloride, phosphate, and sulfate were 79%, 74.8%, and 86%, respectively.
Chlorine recoveries were 73% in the second year, 93% in the second and third years together, 97% after 4 years, and complete in 12 years.
Sulfate recoveries from the (NH4)2SO4 were only 8.3%. The phosphate caused a significant increase in outgo of SO4 from native supplies, but the chloride did not.
Calcium Outgo: That induced by the chloride was largest in the second year;
That induced by the sulfate occurred chiefly in the second and third years;
That induced by the phosphate was highest in the third year and indicated the early development of dicalcium and dimagnesium phosphates in the upper strata of the soil-subsoil.
The outgo of Ca as chloride was twice the outgo induced by the phosphate and 1.4 that induced by the sulfate.
Magnesium exchange exerted by the three ammonium salts was in the order found for the exchange of calcium, but the mean for Mg exchange was only 52% of the mean for Ca exchange.
Potassium exchange was evidenced by the second year's leachings and by those of the next 3 years; but K-exchange totals were small in relation to the totals for exchanged Ca and Mg. K-exchange was largest from the chloride and least from the phosphate.
The enhancements in outgo of K, Ca, and Mg were induced by the passage of engendered nitrates.
Sodium outgo was uniform in the first 4 years and was not determined thereafter.
It seems certain that heavy applications of nitrogen as ammonium chloride, phosphate, or sulfate to a heavy soil, in fallow, will not be recovered completely in the rainwater leachings that pass through strata of clay subsoil.