Effect Of Seeding Date And Planting Density On Grain Yield And Quality In Medium-gluten Wheat Under Warming Winter Climatic Conditions

The global temperature has been continuously increasing in the past decades, especially the air temperature during winter in our country, which has led to the changes of ecological conditions under which winter wheat grows and develops before over-winter stage. Winter wheat sown during previously so called"proper seeding period"would lead to pre-winter excessive growth and cold damage at over-wintering stage and seedling establishment stage, and final declined grain yield and quality. In order to identify the suitable combination of seeding date and planting density, a two-factorial (seeding date×planting density) field experiment was conducted from 2007 to 2009 on the Agricultural Experiment Farm (32°39′E, 119°42′N), Jiangsu Provincial Key Laboratory of Crop Genetics and Physiology, Agricultural College, Yangzhou University, China. The tested wheat cultivar was Yangfumai 4, a locally adapted medium-gluten wheat cultivar widely used in Jiangsu Province. The main results were as follows:1. The grain yield was significantly affected by seeding date and planting density. With the postponement of seeding date and the increase of planting density, the grain yield demonstrated a single peak trend. The effects of seeding date on yield components were significant at the 0.01 probability level. With the seeding date postponed, the number of spikes decreased, the kernel number per spike and 1000-grain weight increased firstly and then decreased. As the increase of planting density, the number of spikes increased, but the kernel numbers per spike and the weight of 1000 kernel decreased. The Path analysis showed that the grain yield for Yangfumai 4 was increased mainly by increasing the number of spike through the optimization of seeding date and planting density.2. Seeding date and planting density produced effects on the indexes of population quality, including the total number of culms and tillers, dry matter accumulation, and leaf area index (LAI). At the same density level, the total number of culms and tillers decreased as the postponed seeding date. When the seeding date was the same, the total number of culms and tillers of the crop population increased with the increased density, but the tillers per plant decreased. Before jointing, LAI increased with the increased density. After jointing, LAI on Oct 31 was bigger than other treatments. In the whole growth period, LAI increased with the increased density. The dry matter accumulation increased with the increased density. Before jointing, the dry matter accumulation of early seeding treatment was more than the late seeding treatments. After jointing stage, the dry matter accumulation of late seeding treatments increased to and even exceeded the early seeding treatments.3. The seeding date and density influenced the physiological parameters of flag leaves after anthesis, hence, on the grain yield. Chlorophyll content, soluble protein content, and the activities of SOD and POD followed a descending order of October 31> November 6> November 12>November 18> October 25 > October 19. There was no observable difference in these physiological parameters between the planting densities of 1.2 million, 1.8 million, and 2.4 million//hm2. But these physiological parameters were significantly higher than those of 3.0 and 3.6 million/hm2 planting densities. 4. Seeding date and planting density produced significant effects on grain quality. Protein content demonstrated a"V-shape"trend as the increase of planting density and the postponement of seeding date. The protein content in all treatments was higher than 13%. Late seeding increased the content of protein. The trends of test weight, hardness, sedimentation volume, and wet-gluten content were similar to that of protein content.5. When the seeding date ranged between October 26 and November 4 and the planting density was 2.4 million/hm2, the grain yield was higher than 6750 kg/hm2. If the seeding was conducted around October 31, the grain yield could be as high as 7500 kg/hm2. When seeding was conducted between October 20 and October 25, the seeding amount should be appropriately decreased. When the planting density was kept at 1.2– 1.8 million/hm2, the yield reached a level higher than 7000 kg/hm2. This combination of planting density and seeding date could be used when pedigree seeds were used. When seeding was conducted between November 6 and November 10, the seeding amount should be appropriately increased. When the planting density was kept at 2.4– 3.0 million/hm2, the yield reached a level higher than 7100 kg/hm2. When seeding was conducted between November 12 and November 20, the seeding amount should be further increased to increase the number of spikes of culms. When the planting density was kept at 3.0– 3.6 million/hm2, the yield reached a level higher than 6000 kg/hm2.