Wandao68 was used as material to study the effects of application of nitrogen and potassium in different leaf-age-periods on grain yield and population quality.The results are as follows:(1)The output of applying nitrogen at the third leaf age from top and potassium at forth leaf age from top was tiptop and the differences were significant.(2)Applying nitrogen at third leaf age from top could increase grains per panicle significantly while there was little effect on effective panicles per unit area,setting ...