Estimating of Lodging damages in critical growth stages on yield and its component of rice (Oryza sativa).

Lodging of rice plants is caused by the action of some climate factor such as wind and rain and it is may be intensified by the some crop management practices such as N rate and timing and date of transplanting, planting density and water management. It is reported that lodging, prior to harvest, results in appreciable losses in both quantity and quality of rice. It also causes difficulties in harvest operations and consequently results in increased production cost. To diagnosis of lodging inducing climate factors from those induced by crop management practices a field experiment was carried out in Rice Research Institute in Mazandaran, during 2009. A test material has been evaluated in a split plot experiment in Randomized Complete Block Design with 3 replications. Artificial lodging perform Stages (milky, dough and ripening stages) were involved in main plot and different amount of N fertilizer application has been set in sub- plot on main plot experiment layout. A rice cultivar, Tarom, was transplanted and different level of N fertilizer (0, 46, 92 and 138, 184 Kg N/ha as a source of urea) has been applied in sub-plots. P and K Fertilizers applied on basis of soil analysis. Other cultural practices such as water management and crop protection were the same as those of local farmers. Yield and yield component has been evaluated. We also investigated some farmer fields that lodging was happened in the some part of the field and was standing in the other parts. Soil and plant samples were taken from two parts and their N, P and K were analyzed. Plant height, tiller number, panicle length, filled and unfilled grain and 1000grain weight were measured. Analysis of variance showed that there was significant difference between two main plots (artificial lodged in milky stage and unlodged Plots) and average yield of treatment associated with unlodged plot was significantly higher than those of artificial lodged. N fertilizer application rates, significantly differed on grain yield, plant height and tiller number. Results of t-test on data collected from farmer fields showed that there was significant differences between lodged and unlodged parts of fields in view of plant height, leaf color, N, P and K content of plant. The results showed that plant height and its affecting factors including N fertilizer rate and timing have a key role on lodging phenomenon. Key words: climate factors, crop management, lodging, N Fertilizer, Rice, Tall variety.