responses of maize (sc704) yield and yield components to source restriction

understanding the relationship between sink and source in maize is of prime importance in maize growing regions. in this study, a field experiment was carried out during spring and summer 2007 in the experimental field of the college of agriculture, shiraz university, to examine the effects of source restriction (defoliation) on sink size (yield and its components) of  sc704 maize hybrid.  a factorial arrangement in a randomized complete block design with four replications was used. treatments composed of four stages of source restriction including defoliation at half-silking and 3 consecutive 10 day intervals, as well as three defoliation intensities (zero, half and all leaf removal). it was found that delay in source limitation was associated with a lower mean kernel weight achievement. the highest mean kernel weight was attained in defoliation at half- silking (208.14 g), which also resulted in the lowest grain yield reduction, compared to no defoliation treatment. increase in defoliation intensity was associated with a decrease in grain yield; however, delay in defoliation after mid- silking had no significant effect on grain yield. it was concluded that the grain yield of sc704 maize hybrid was more sensitive to source limitation (i.e. defoliation) intensity than defoliation time.