Solubility of plant-food elements as modified by fertilizers

The plots receiving composted manure showed nearly twice as much water-soluble potash in the surface foot as any of the other plots. The seasonal averages of this element were not influenced by any other fertilizer treatment. There was a general decrease in the quantity of water-soluble potash from the middle of May till about the middle of July. After that time, the quantity increased to approximately the amount found earlier in the season. Plots receiving nitrate, superphosphate, and composted manure all showed less water-soluble P2O2 then the checks. None of the fertilizer treatments resulted in a marked increase in water-soluble phosphate, though cyanamid, bone meal, and manure plus ammonium sulfate caused a small increase. The variation in water-soluble phosphorus from week to week was less than any other element measured. Taking account of the sulfur added in the various fertilizers, none of the treatments apparently had any marked influence in rendering the sulfates in the soil more soluble in water. There was a decrease in the amount of soluble SO3 from the early part of the season till the latter part of July, corresponding in general to the seasonal decrease in soluble potash. The amounts of water-soluble manganese were very small and disappeared entirely after the middle of June. The plots receiving nitrate, composted manure, waste lime, and manure plus ammonium sulfate, showed the highest manganese content. It is remarked from results of the yields and other data not presented in this paper that the sugar beets grown on plots showing highest amounts of water-soluble manganese and sulfur gave the highest yields and most sugar per acre.