Effect Of Nitrogen Fertilizer And Planting Desity On Canopy Structure And Population Characteristic Of Winter Rapeseed With Direct Seeding Treatment

At present, vegetable oil self-sufficiency rate is less than40%in China, and about half edible vegetable oil comes from rapeseed, therefore, improving the production capacity of rapeseed oils can relieve our security problems. As transferring of labor from agriculture to other industries and development of the light simplified cultivation techniques of rapeseed, the area of direct seeding in winter rapeseed increased year by year, the high yield cultivation techniques of direct seeding in winter rapeseed is a main research direction. The study on canopy structure and population characteristics of direct seeding in winter rapeseed is less. In this study, Huayouza62was planted by mechanical seeding on October5th with middle and high nitrogen fertilizer levels (180kg ha-1and270kg ha-1) and five planting densities (15×104plant ha-1,30×104plant ha-1,45×104plant ha-1,60×104plant ha-1and75×104plant ha-1). The differences of yield, canopy structure, population characteristics, plant morphological and physiological index were studied. Through studying these characteristics, the reasonable cultivation measures of direct seeding in winter rapeseed including planting density and nitrogen fertilizer level were provided.The main results in this research showed that:1With the increase of nitrogen, canopy height increased, and with the increase of density canopy height decreased. Height of pod starting of main stem increased firstly and then decreased with the increase of density. Height of pod starting of main stem in the density of45×104plant ha-1was highest at the same nitrogen level.2The number of pods in main stem was highest in different parts, and the number of pods increased firstly and then decreased from top to bottom. In general, the number of pods of middle branch was highest. The number of seeds per pod and1000-seed weight in main stem were highest, and the number of seeds per pod and1000-seed weight in60x104plant ha-1and75×104plant ha-1treatments were less than those of other density treanments. With the increase of density, the ratios of yield in main stem to total yield increased. In the density range of45×104plant ha-1, the low effective branch proportion decreased with the increase of density.3The two treatments with density of45×104plant ha-1and60×104plant ha-1got higher yield ranging from2921.2kg ha-1to3109.8kg ha-1under middle fertilizer level, and the corresponding suitable values of leaf area index (LAI) at beginning flowering stage, pod area index (PAI) at ripening stage, light transmittance of canopy at beginning flowering stage, light transmittance of canopy at seed filling stage, and effective pod number were between3.23to3.47,3.80to3.86,8.2%to10.7%,19.6%to21.2%and55.8×106ha-1to58.3×106ha-1, respectively.4The two treatments with density of30×104plant ha-1and45×104plant ha-1got higher yield ranging from3607.2kg ha-1to3772.4kg ha-1under high fertilizer level, and the corresponding suitable values of leaf area index (LAI) at beginning flowering stage, pod area index (PAI) at ripening stage, light transmittance of bottom at beginning flowering stage, light transmittance of canopy at seed filling stage, and effective pod number were between3.72to3.94,4.32to4.46,6.1%to7.4%,16.4%to18.1%and65.5×106ha-1to68.7x106ha-1, respectively.5By the cultivation measure of reducing nitrogen fertilizer and increasing density, the direct seeding rapeseed, like the traditional transplanting rapeseed, can also obtain high yield exceeding3600kg ha-1with270kg ha-1nitrogen fertilizer and density ranging from30×104plant ha-1and45×104plant ha-1. Reasonable dense planting can effectively reduce the root collar diameter and the height of canopy, and make pod mature periods of different parts relatively concentrate, which would help promote mechanical harvesting in rapeseed production.