Mineral composition and responses to fertilizer of wheat grown on a limed and deep-ripped soil in north-eastern Victoria

The nutrient requirements of wheat grown on a soil ameliorated with lime and deep ripping were studied in a field experiment over 5 seasons in northeastern Victoria. Phosphorus (P) fertiliser was required when this soil was limed, although the lime treatment may have increased P uptake (P x lime interaction). The nitrogen (N) concentration in wheat foliage was increased with both lime and deep ripping. It is likely that the availability of N will be the most important factor for sustaining high yields following soil treatment. Molybdenum (Mo) fertiliser (62 g Mo ha-1) increased grain yield in 2 seasons. Molybdenum fertiliser increased grain weight by an average of 4.4% over 3 years, and also the N content of grain in the absence of lime, indicating that a deficiency of available Mo in the soil was affecting the assimilation of N in the wheat. The magnesium (Mg) concentration in the wheat foliage was very low (0.07-0.10%) without soil treatment, but there was no grain yield response when Mg fertiliser (10.5 kg Mg ha-1) was applied in the absence of lime. Lime and ripping both resulted in big increases in manganese (Mn) concentrations in the foliage. Calcium (Ca) and copper (Cu) concentrations were little affected and zinc (Zn) was not affected by lime (Ca, 0.35-0 55%; Cu, 7-20 ¦g g-1; Zn, 50-60 ¦g g-1 at 50 days after emergence), and each nutrient appeared to be adequate for wheat. The concentration of Mn in the foliage was high without lime, but did not approach published figures for critical toxicity concentrations. Liming the soil greatly reduced the manganese concentration.