Effect of soil nutrient status on severity of seedling diseases and root rot of sorghum (Sorghum bicolor)

Abstract

The hybrid NK283 was subjected to a range of nutrient element concentrations to determine their effect on predisposition of sorghum to seedling diseases and root rot. Emergence was not affected by soil nutrient status. Similarly N, P and K did not affect seedling disease severity or secondary root rot. Highly significant correlations with disease were recorded between soil acidity, expressed as pH, exchangable acid (Al+H), acid saturation and total cations. A linear increase in mesocotyl discolouration was recorded with decreasing pH, while secondary root discolouration increased significantly at pH(_KCI)^<4.6. A threshold value of approximately 15% acid saturation was recorded above which seedling diseases and secondary root rot increased significantly. Seedling length and post-emergence damp- ing-off were significantly related to the degree of mesocotyl discolouration. Plant length at 6, 9 and 12 weeks after planting was significantly related to effective root volume (ERV) which was calculated as ERV=(((100-root rot (%))/100)^*root volume(ml)). It was concluded that soil acidity

Keywords:

• Pre-and
• post-emergence
• damping-off
• root rot
• seedling blight