Effect of Nitrogen Rates at Different Growth Stages on Corn Yield and Common Smut Disease [<i>Ustilago maydis</i> (D.C.) Corda]

Abstract

Abstract The effect of N fertilizer rates and time of N application on plant growth, N %, N uptake, smut index and yield response of corn were investigated in the field during the summer seasons 1988 and 1989. Increasing N rate from 30 to 60 and/or 90 kg/acre produced greater response on the studied parameters, followed by a limited response at 120 kg N/acre. Opposite results were detected on yield losses, owing to the severity of smut infection. Single application of N at planting was the least productive for DM and grain yields, compared with 2‐split or 3‐split N treatments. On the other hand, splitting N application at planting and 16‐leaf growth stages produced limited smut infection with greater increase in grain yield and lowest DM and N accumulations. The results also showed that 3‐split N treatment acted to accelerate the vigour growth and N uptake to a greater extent, creating more favourable conditions for stimulating smut infection, with an attendant increase on yield losses. Because of the advantage of applying 90 kg N/acre over the N treatments on the measured parameters, with particular reference to yield potential and smut performance, attention was given to splitting N fertilizer at planting and 16‐leaf growth stages.