اثر مقادير مختلف كود نيتروژن، روي و آهن بر شاخص هاي فيزيولوژيك ذرت علوفه اي در استان مركزي

Effect of different levels of nitrogen , iron and zinc on physiological indices and forage yield of maize (Zea mays L.) in Markazi province.

In order to investigate the effects of different levels of nitrogen , Iron and Zinc on physiological indices and forage yield maize(Sc 704) a field experiment was conducted as a split plot in a randomized complete block design with 12 treatments and four replications at jihad Agricultural Research center of Markazi province in 2003. The treatments consisted of three levels of 150 , 225 and 300 kg N ha-1 as main plots and microelements at four levels including control , 4 kg ha-1 Fe sulfate , 45 kg ha-1 Zn sulfat, 4 kg ha-1 Fe sulfate + 45 kg ha-1 Zn sulfate as sub plots . physiological indices were affected by N rates . Rasing N levels from 150 to 225 and 300 kg N ha-1 increased leaf area index , crop growth rates and total dry weight at 38 days after planting , that after reprodactive stage were significantly . A maximum LAI of 5.7 was observed during growth season after 1100 growing degree days at level of 300 kg N ha-1 ten day after tasseling the highest TDW equal 1600 g.m-2 was observed 14 days after silking with receving 1150 GDD in 300kgN ha-1 . Among physiological indices, the net assimilation rate was affected less by N application. Net assimilation rate declined during the growth season . the results also show that an application of microelements,particularly Zn , did not significantly increase LAI, CGR and TDW. Maximum LAI , CGR and TDW were obtained with the application of Zn Sulfate and Zn sulfate + Fe sulfate. Among nitrogen levels and microelements , maximum of forage yield equal 84.86 and 79.65 ton ha-1 obteined with the application of 300 kgN ha-1 and 45 kg ha-1 Zn sulfate , respectively. The highest forage yield equal 88.66 ton ha-1 was obtained with application of 300 kgN ha-1 + 45 kg ha-1 Zn sulfate . Considering the importance of LAI, CGR on foroge yield it was concluded that the magor increase in forage yield under high N and Zn sulfate was due to improvement of physiological indices.