Influence of soil properties on the use of soil and plant zinc to predict zinc response in maize

Abstract

The value of using the diethylenetriaminepentaacetic acid (DTPA) soil zinc and/or the zinc concentration in young maize tops to predict the response, to zinc application, of maize growth on soils from the Liverpool Plains of New South Wales was assessed in a glasshouse experiment. Forty-eight composite soil samples, 23 medium clays (MC) and 25 heavy clays (HC), were collected from the study area and two rates of zinc (0 and 10 �g/g air-dried soil), were applied to each soil in a triplicated randomized block design. Maize was grown for 30 days and the growth response to zinc application was calculated as Bray's percentage yield (%y). Although zinc application generally increased the yield of maize grown on all soils tested (P<0.001), the correlations between %y and soil zinc, plant zinc and soil zinc, and %y and plant zinc of all soils tested, as one group, were not significant. When the soils were treated as two textural groups and the influence of other soil properties on the growth response of maize to zinc application were tested statistically, the %y differed between the MC and HC groups (P<0.05) and between the soils in each group (P<0.001). The multiple regression of %y on soil properties, within each soil group, revealed that, for the MC soils, the phosphorus content, DTPA extractable iron, manganese and zinc, percentage organic carbon and phosphorus sorption capacity were consistently and significantly related to %y and accounted for 93% of variation in %y. For the HC soils, only pH, DTPA-extractable manganese and percentage organic carbon were significantly related to %y and these accounted for 75% of the variation in %y. Zinc concentration in maize tops grown on the untreated soils was 12-40 �g/g. The %y was significantly (P<t0.05) related to zinc concentration in the tops of maize grown on the MC soils (r= 0.63), but not in those grown on the HC soils. These results suggest that, for maize grown in these soils, it is not possible to predict the response to zinc application by considering only zinc levels in soil or in young maize tops.