A field experiment was initiated in 2010 to compare the effects of liquid ammonium polyphosphate (APP) and granular diammonium phosphate (DAP) on growth, nutrient content, and yield of Jerusalem artichoke (Helianthus tuberosus L.). Two sites on a coarse-textured Inceptisol with markedly different cropping histories were selected, one with 6 ppm P, the other with >201 ppm P extractable with 0.05 N HCl+0.025N H2SO4.Fertilizers were banded at P rates of 0, 24,48, and 71 kg/Fed. at the low P site, and 0, 10, and 20 kg/Fed. at the high P site. At the low P site tuber yields and tissue P concentrations were lower in case of (APP) than that of (DAP), while tissue concentrations of Ca, Mg, Mn, and Zn were higher in case of (APP). At the high P site, tuber yield and top dry weight were not affected by P source, but tissue Ca and Mg contents were higher and tissue P was lower with (APP). In 2011 and 2012, (DAP) and(APP) were applied at a rate of 24 kg P/Fed. at the low P site. Tissue levels of P again were lower while these of Ca, Mg, Mn, and Zn were higher with (APP) for the two years. Tuber yields were lower with (APP) in 2012.
In 2010, (DAP) and(APP) were applied at the high P site at the same rates used in 2010. Yields were unaffected by P source but tissue P content was lower but tissue Zn content was higher in case of (APP). Extractable P levels in soil samples taken after harvest were higher in 2010 for (APP) treatment .With time, extractable P declined for both sources, and by the following crop season, there were no differences in extractable P between P source. Extractable P again was higher in 2012 where (APP) had been applied. The results showed that availability of P fertilizer for summer planted Jerusalem artichoke was less with(APP) than that of (DAP). Less P was found in tops of Jerusalem artichoke with (APP) regardless of the level of available soil P. Tuber yields, however, were less affected by P source, and the data suggest that most years tuber yields will not be different with these two sources except on soil with very low levels of available P. Application of (APP) also resulted in increased uptake of Ca, Mg, Mn, and Zn by Jerusalem artichoke.