Effect Of Planting Date And Planting Density On The Population Quality And Grain Yield Of Winter Wheat

In recent years,the average air temperature has been increasing in the north of China, especially the air temperature during late autumn and early winter has increased significantly.This phenomenon led to the change of the ecological conditions for winter wheat to grow and develop before over-winter.Under the situation,winter wheat sown during previously so called "proper sowing period" would lead to pre-winter luxury growing,and yield decrease finally.In order to determine the suitable combination of planting date and planting density under the conditions of warmer climate,a field experiment with a split plot design was conducted to studied the population quality and yield characters of winter wheat at Gaocheng County,the middle area of Hebei Province, during 2006-2007 winter wheat growing season.The main plots were three sowing dates, October 7,13 and 19,and the split plots were four planting densities,180,300,420 and 540 seedlings per m~2.The main results were summarized as follows:1.The effect of planting date on the three yield components of winter wheat was not significant.The effect of planting date on grain yield,however,was significant because of the accumulative effect of planting date on the three yield components.The grain yield decreased with the delay of planting date during the sowing period in the experiment.The effect of planting density on yield and yield components were all significant statistically. Also,the interactions of planting date and planting density on spikes per m~2,grains per spike and grain yield were significant.The comparison among the average yield of four densities of the same planting date showed that,the average yield of wheat sown at October 7 was significantly higher than that sown at October 19,but not significant compared to that sown at October 13.The difference among the grain yields of the three planting densities,300,420 and 540 seedlings per m~2,was not significant,but the grain yields of the three planting densities were all very significantly higher than that of the density 180 seedlings per m~2.2.Planting date and planting density affected more or less the indexes of population quality,such as the dynamics of tillers,dry matter accumulation,LAI and grain-leaf ratio. The effect of planting date on total culms(main stems & tillers)was statistically significant only during early growing stages,but the effect of planting density on total culms was significant during the whole growing period.Spikes per hm~2 decreased with the delay of planting date,and increased with the increaseing of planting density.Dry matter accumulation of wheat in all treatments increasd with growth stage forward.Dry matter accumulation decreased with the delay of sowing date,while the effects of planting density on dry matter accumulation relied on sowing date.Dry matter accumulation of wheat sown at Oct 19 gradually increased with the increase of planting density,but for the treatments sown at October 7 and 13,the dry matter accumulation for the planting density 300 and 420 seedlings per m~2 were higher.The dynamics of LAI in different planting density and different planting date were similar to the trend of dry matter accumulation in addition, when the biggst LAI was similar on the same planting date,the yield of treatment which grain-leaf ratio was high was too high,when the biggst LAI was similar on the different planting date,the yield of treatment which grain-leaf ratio was high was too high.3.The effect of planting date and planting density on Pn was significant.The dynamics of Pn were similar for all treatments,showed bimodal curve.The effect of planting date on Pn showed that,Pn with sowing at October 19 was significantly lower than other density level,Pn of peak with sowing at October 13 were highest,but decreased quickly,From earing to after anthesis 10 days,Pn maintain highest with sowing at October 7.The effect of planting density on Pn showed that,firstly increased then decreased with low planting density.Pn with the planting densities 300 seedlings per m~2 were highest,and The difference among the fourth densities was significant.4.The effect of planting date and planting density on PAR and SPAD was not significant.The PAR at different layers from ground to top of wheat population sown later were higher during all growing stages than those sown earlier.The difference of PAR among treatments with different densities was only significant befor anthesis,when the PAR at various layers in the population all deceased with the increase of planting density. Chlorophyll SPAD showed immobile distribution characteristics,The effect of sowing date and planting density on chlorophyll SPAD was not significant.5.The effect of planting date and planting density on water consumption and water productive efficiency of wheat was significant.The changes of water consumption among different treatments was opposite to those of water productive efficiency,that was to say, the higher water consumption,the lower water productive efficiency.The water consumption was lowest,and water productive efficiency was highest for the treatments sown at Oct 13 among the three sowing dates,and the difference of the two indexes were all significant to those of the treatments sown at Oct 7.The water consumption of wheat with the planting density 420 seedlings per m~2 was lowest,but the water productive efficiency of it was highest among the four planting densities,and the difference of water consumption and water productive efficiency with this planting density was significant to those of other three planting densities. 6.Based on the analysis of population and individual characteristics,and grain yield of all treatments,it was concluded that,October 7 is the best sowing date of winter wheat in the middle of Hebei Province,with the corresponding planting density 300 seedlings per m~2;October 7 to 13 is the suitable sowing period,with the corresponding density 300～420 seedlings per m~2.This conclusion about the suitable sowing period is also consistent to the result based on the accumulative temperature before over-winter of winter wheat in this area.