Effects Of Nitrogen And Plant Density On Population Quality And Grain Yield&Quality Of Strip-relay-intercroping Wheat

In order to screen out the optimal nitrogen and planting density of relay intercropping wheat in Sichuan hilly area, Using Chuanmai42, the major wheat cultivar in local production, a two-year field experiment was carried out in Sichuan Province from November2009to May2011under two-factor split-plot design. The main-plot was for N application rate at120kg/hm2and180kg/hm2, and the sub-plot was for plant density in five levels (0.6,1.2,1.8,2.4, and3.0million plants per hectare). The wheat planted in a strip-cropping method, wheat and corn planted in2m strip, planting five row wheat, and leaving the rest for the corn planting. The effects of nitrogen application and planting density on wheat group quality, grain yield and quality were investigated. The main results are as follows:Density has greater impact on change of tillers and stems of wheat, and the advantages of edge line is obvious. The quantities of tillers and effective spikes in edge, second, and central lines were all enhanced with the increase of planting density. but ear rate, per plant tillering ability and ears per plant decreases; Tillering of edge line without significant advantage, but slower tillering extinction after the jointing, and ultimately the effective spike higher than the second and central lines. The edge lines ears reached the saturation in the density of1.8×106plants/hm2, and edge ears increased little with increasing density, while the ear numbers of the second and central lines increased significantly. On the contrary, in high planting density (3.0×106plants/hm2), the ear rate of second edge and central lines decreased. Increased nitrogen application can significantly improve the ear rate, to some extent slow down the change of tillers of edge line.During the whole growth period, LAI dynamics can be divided into three levels of significant difference, such as,0.6X106plants/hm2,1.2and1.8×106plants/hm2,2.4and3×106plants/hm2. Increased density can significantly improve the group LAI and SPAD content of flag leaf, but decrease the leaf area per plant, and advantage of edge line is obvious in middle and low density (0.6-1.8×106plants/hm2); increased nitrogen application can increase leaf area per plant and SPAD content of centre line in high planting density, and effectively improve the quality of individual, but had no significant impact on the LAI of groups. With the density increase, dry matter accumulation of groups increased, while that of the single-stem is reduced. And dry matter of single-stem show obvious advantages of edge line, while accumulation per stem of the second line and central line first stable and then decreased to1.2X106plants/hm2as the critical point. Increasing nitrogen to improve the distribution of the dry matter of ears, and increase dry matter accumulation after flowering (1.8×106plants/hm2reach maximum).The advantage of edge line is more obvious for carbon and nitrogen metabolism after flowering and the trend is more significant with density increase. The greater density after flowering, the worse photosynthesis, the lower soluble sugar content, and the slower rate of accumulation and transportation. Increased nitrogen application can effectively slow down the reduction of nitrogen concentrations after flowering, balance the C/N metabolism, and improve the rate of accumulation and transportation of soluble sugar content, and conducive to production.Density seriously affect wheat lodging properties and show obvious advantages of edge line. With the increased density, outside diameter, wall thickness of culm, internode filling degree, and mechanical strength decreased, but the lodging index rose. Increased nitrogen application would improve stem mechanical strength of central line, lower lodging index and enhance lodging resistance of stem, but overall trend is not significant.With increasing planting density, effective ears significantly increased, while number of grain and1000-grain weight reduced. In terms of difference between the lines, all factors show significant advantage of edge lines, and in result, making the edge lines make the greatest contribution to the whole yiel. For the edge lines and other lines, the main performance of the yield increase show in ear, followed by grain, last for1000-grain weight. In the density of1.8×106plants/hm2, effective ear almost reach to saturation, the yeild components coordinate, the overall yield reach the highest, and yield differences between the two nitrogen rate is not significant.Density has significant effects on grain quality, which showed content of proteins and wet gluten trend to first increase and then decrease with increased density, while the starch content and sedimentation is decrease first then increase. Increased nitrogen application improve the protein content, sedimentation value and wet gluten content to a certain extent, but not starch content. So, improve the level of nitrogen to some extend can obtain excellent quality traits in1.8×106plants/hm2planting density in terms of non-strong gluten wheat. At the same time, the correlation analysis also shows that the quality traits associated with flowers soluble sugar accumulation and translocation.In summary, due to special hilly and dry-land terrain, climate and cultivation style, when the planting density is1.2-1.8X106plants/hm2, intercropping wheat can make full use of light, temperature, moisture, nutrients and other resources to effectively exhibit advantages of the edge line, coordinate quality of group and individual, and enhance the lodging resistance, and ultimately improve the quality of ear, grain, weight coordinately. So, the cultivation style is mode of density allocation for high yield, quality and lodging resistance of intercropping wheat in southwest hilly and dry-land, but the fitting fertilizer should studied further.