Effect of potassium on rice lodging under high nitrogen nutrition

Lodging of rice in Iraq reduces production by 30-35% and may be related to the agronomic practice of supplying high nitrogen (N) and phosphorus (P) nutrition in the absence of applied potassium (K). An experiment was undertaken in glasshouses at the University of New England to investigate the effect of K fertilisation on rice growth using a standard rice variety similar to that grown in Iraq (Amber13). Two semidwarf varieties known to have different susceptibility to lodging were used for comparison. Amber13 was most susceptible to lodging. Application of K significantly increased tiller number (40-140%), plant height (<30%), shoot (120-140%) and root (80-300%) dry matter production and stem diameter (30-80%) in all varieties, although differences between varieties were observed. Lodging occurred primarily from the base, due to poor root growth in the absence of K. Potassium application successfully overcame lodging incidence in all three varieties. Trials of both K application, and seedling planting depth, should be instigated in lodging susceptible areas of the Iraqi rice production region.