The effectiveness of zinc fertilizers as measured by DTPA soil extractable zinc, dry matter production and zinc uptake by subterranean clover in relation to soil properties of a range of Australian soils

Abstract

The effectiveness of zinc fertilizer (Zn) on a wide range of Australian soils was examined using subterranean clover (Trifolium subterranean cv. Nungarin) as a test crop in a glasshouse experiment. The initial effectiveness (IE) of zinc fertilizer as measured by dry matter production (DMP), and zinc content (uptake) of subterranean clover (clover) was found to vary markedly among the soil types. No simple linear retationship between the initial effectiveness measured by either dry matter production or uptake and any one soil property was found. IE values were found to be related to the pH (1 : 5 soil :water) (pHw) and the level of DTPA soil extractable zinc measured in the unfertilized soil (Zno). IE based on Zn uptake by clover tops was also related to the organic carbon (OC) (%) content of the soils. The model for IE measured by DMP in a stepwise linear regression was IEDMP = 2.682 - 0.107 pH,-4.852 Zn, (n = 45; r2 = 0-86). IE based on Zn uptake by clover tops was: IEuptake = 10.842 - 0.882 pH, - 0.310 OC (%) - 1.349 Zn, (n = 54; R2 = 0.85). The IE of zinc fertilizer measured by DTPA soil extraction (IEDTPA-zn) was also found to vary markedly among soil types. The level of zinc extracted by DTPA after the addition of Zn fertilizer was found to be affected by clay (%), organic carbon (%) and calcium carbonate (CaCO3) (%) content of the range of Australian soils. This relationship could be described by: IEDTPA - Zn = 0.178 + 0.0.002 Clay (%) + 0.014 OC (%) + 0.018 CaCO3 (%) (N = 54, r2 = 0.84)