RESIDUAL EFFECTS OF HIGH RATES OF LIMESTONE, P, K AND Mg APPLICATIONS: EVIDENCE OF INDUCED Mn AND Zn DEFICIENCY IN OATS

Abstract

In a field plot study to examine the residual effects of heavy rates of coarse limestone (0, 11, 22 and 44 t/ha) in combination with P (560 kg/ha), K (1120 kg/ha), Mg (560 kg/ha) and PKMg (560 + 1120 + 560 kg/ha) applied five growing seasons previously, dry matter production of oats (grain and straw) decreased with increasing rate of limestone application. The decrease was attributed to lime-induced Mn and Zn deficiency. Both Mn and Zn uptake decreased significantly with increased limestone applications. Plant Mn and Zn concentrations were below critical levels in the heavily limed treatments. Neutral normal ammonium acetate soil extractable Mn was significantly related to oats Mn uptake and yield. This same extractant for Zn was not related to uptake of Zn or yield of oats. After the fifth season of cropping, residual limestone (Ca), P and K effects were evident as increased plant uptake and soil extractable Ca, P and K. Residual Mg was shown only by soil extractable Mg.