The influence of acid-forming and neutralized fertilizers on the soil reaction and nutrient level in the Irish potato row during the growing season

The fertilizer mixtures applied to potatoes to check the influence of acid and neutral fertilizers on the soil reaction during the growing season markedly lowered the pH of the soil in the row with two sandy soils of eastern Virginia. The acidifying influence varied within the row according to the location of the soil sample with respect to the fertilizer band. There was also a variation in pH with date of sampling. The lowering of the soil pH in the row was a result of the movement of fertilizer salts from the bands. This movement was mostly up and down. The soil in which the tubers formed was much more acid than it was prior to planting and more acid than the soil away from the fertilizer influence. There was undoubtedly some variation in the reaction around different tubers of the same plant, and even a possible difference around the individual tuber with the fertilizer placed in bands. This difference in soil reaction and fertilizer salt concentration within the row means that the roots and tubers of a single potato plant are exposed to a soil with a wide range in reaction and nutrient level. It also means that the nutrient balance or ratio of one element to another is markedly varied around an individual plant. The tubers were confined to the area above and between the fertilizer bands and were thus exposed to less variation in pH and salt concentration than the roots. Limestone added as a fertilizer filler to neutralize the mixture was effective in changing the soil reaction in the fertilizer band and was not effective in neutralizing the acidifying influence of the fertilizer in any of the samples taken 2 inches or more away from the band. Thus with band placement of potato fertilizers on the light sandy soils of the coastal plain of Virginia the acid-forming fertilizers will not lower the pH of the soil around the tubers any more than a neutral fertilizer in one season.