Abstract
Mn deficiency was identified on an Ustifluvent in a replicated block trial with (NH4)2SO4 treatments equivalent to 0, 22, 44, 66, 88 and 110 kg N/ha. There were very highly significant linear responses not only in terms of weights of cane and sugar, but also in term of leaf and Mn levels. Leaf Mn concentration increased from 23 to 43 p.p.m. A follow-up trial with MnSO4 applications (equivalent to Mn at 8 kg/ha) confirmed the Mn response. Zn deficiency was identified on a Mollic Ustipsamment in an NPK factorial trial. Leaf Zn levels averaged 9·5 p.p.m. The subsequent splitting of plots in this trial to test the effect of Zn at 6 kg/ha resulted in a significant yield response and a significant increase in leaf Zn to 11·0 p.p.m. The Zn treatment also resulted in a significant increase in leaf Mn from 48 to 56 p.p.m.
