Yield Formation And Related Agronomical Control Machanism In Sunflower

Inner Mongolia Autonomous Region has the regional advantages and prospect in growing sunflower, as is of great significance in increasing the farmers'income and in adjusting crop planting structure. Currently, the main constrain on healthy and sustainable development of sunflower industry is cultivation technique, which needs to be systematic and detailed. Systematic study on the dry matter production and yield formation in sunflower under different agricultural measures, therefore, is important in providing theoretical basis and technical support for widely and high-yield production.The study was carried out in 2008-2010. The experiments include studies on population structure, drought-resistance differences in sunflower cultivars, the effect on yield of different densities and planting dates, the regulation on fertilizer requirement and the effect of source-sink relationship on yield. This study summarized optimized and integrated high-yield cultivation techniques for sunflower, and presented the results of evaluations on these techniques. The quantity indexes for a high-yield sunflower cultivation system are as follows:In the study, PEG6000 was applied to 30 oil sunflower cultivars and 25 confectionery sunflower cultivars, to test their drought resistance, indicated by leaf REC,RWC,SOD,POD,CAT and Pro. Membership function and cluster analysis showed these cultivars can be classified into three groups: high drought-resistance (13 oil sunflower cultivars and 15 confection sunflower cultivars), medium drought-resistance (9 oil sunflower cultivars and 8 confection sunflower cultivars) and low drought-resistance (3 oil sunflower cultivars and 2 confection sunflower cultivars). These two methods demonstrated similar classification results: 76.67% in oil sunflowers and 92.00% in confection sunflower.Adopting reasonable high planting density is one of the approaches to enhance crop yield. The reasonable density for confection sunflowers is 43500-45000 per hectare, while that for oil sunflowers is 61500-63000 per hectare.Cloudy and rainy days hinder pollination, resulting in a low seed setting percentage in anthesis stage. Delayed planting makes the sunflower avoid local concentrated rainy period, increasing the seed setting percentage and alleviating the damage caused by Sclerotinia sclerotiorum. The most suitable planting period in Inner Mongolia is during May 20 - May 30.Coordinating the source-sink relationship by enlarging the source and strengthening the sink is the basis for a higher yield. Reductions in source and sink decrease sunflower yield. When the source reduced by half, oil sunflower yield decreased by 37.56%, and confection sunflower decreased by 44.55%; when sink reduced by half, oil sunflower yield decreased by 21.20%, while confection sunflower decreased by 23.43%. In the experiments of cutting sources of different leaf layer, removal of the last 1-5 leaves of confection sunflower or the last 6-10 leaves of oil sunflower resulted in the largest loss in seed yield. Therefore, sunflowers belong to source limited crops.Fertilizer requirements for 100kg seed production are as follow: 5.25 kg N,2.42kg P₂O₅ and 5.01kg K₂O in confection sunflower;5.18kg N,2.23kg P₂O₅ and 4.92 kg K₂O in oil sunflower.Compared with agronomic techniques adopted by local farmers, the new agronomic system developed in this study, which integrates cultivar selection, planting date arrangement, density choice and fertilizer requirement, showed the advantages of optimizing integration technology, including scientificity in dry matter accumulation and distribution, leaf area dynamics, photosynthetic characteristics and root growth characteristics. Population structure and individual development are more coordinated in the integration production mode.This study established a theory of synchronous improvement of population structure and individual function. That is to increase density properly to build a population of high yield, to rationally arranging irrigation and fertilization to enhance individual physiological function. The sunflower population built under the integrated techniques possesses rational yield components, has the potential of a productivity of 4500kg/hm².Yield component index, in the case of oil sunflower, include 45000 effective plates per hectare, 65 setting percentage, 650 full kernels per plate, 100 gram kernels per plate, and over 15 gram in 100-kernel-weight; while in the case of confection sunflower, these index are 60000 effective plates per hectare, 90 setting percentage, 1150 kernels per plate, 75 gram kernels per plate, over 6.5 gram in 100-kernel-weight, respectively.