Effects of Plant Density and Sowing Date on Yield of New Maize Variety Shiyu No.9

The effects of planting density and sowing date on the yield of new maize variety Shiyu No.9 were studied from 2010 to 2011.The results showed that with the increasing of planting density,the yield increased firstly then decreased,it reached the highest under the density of 75 000 plants/hm2 and 82 500 plants/hm2,while it was the lowest under the density of 52 500 plants/hm2.The order of the average yield under different densities was A5A4A3A6A2A1.The average yield under 75 000 plants/hm2 had no significant difference with that under 82 500 plants/hm2,while they were very significantly higher than those under other densities.The yield decreased with the delay of sowing date.The order of the average yield sowed on different dates was B1B2B3B4B5B6.The difference of yield sowed on six dates reached significant level.The planting density and sowing date influenced the yield significantly.The suitable planting density was 75 000-82 500 plants/hm2 in the south centre of Hebei.The suitable sowing date was June 10.It should be sowed earlier under the suitable conditions of crops for rotation.