Influence Mechanisms And The Application Of Water-Salt Coordinated Regulation Technique On Crop Yield And Quality

The shortage of agriculture irrigation resources and the salinization of soil in the Hetao district have been the limiting factors for its sustainable development of agriculture and construction of ecological environment. Recently, increasing the planting proportion of water saving cash crops is becoming one of the important strategies to relieve the contradiction between supply and demand of water resources, as well as increase income of the peasantry. The emphasis was greater on the quality of the cash crops with the growing awareness of food safety. Consequently, a new water saving and quality improving irrigation pattern which is combination of saline water and regulated deficit irrigation may get more and more attention. Therefore, study the response of cash crop’s yield and quality to water and salt stress and establish the irrigation schedules with high water use efficiency is scientifically and practically significant for promoting the sustainable utilization of water resources in the Hetao district.In this research, a pot experiment of oil sunflower was conducted at the Shuguagn Experimental Station of Bayannur in2013-2014. The experiment’s data analysis and function model were combined to systematic study the response of the crop evapotranspiration, crop physiological and ecological characteristics, yield, quality and water use efficiency to regulated deficit irrigation with saline water, and the irrigation schedules of water saving, salt controlling and quality improving was established. The main results are as follows:(1)Under the condition of regulated deficit irrigation with saline water, the season evapotranspiration of oil sunflower was up to448.26mm, water consumption rate at different growth stages ranked as floral initiation stage>anthesis stage>maturity stage. The season evapotranspiration decreased significantly with increasing water salinity irrigated. When in combined water and salinity stress, the influence of salinity stress on crop evapotranspiration was more pronounced than the water deficit except the deficit irrigation with2g/L at floral initiation. The effect of combined water and salinity stress on hundred grain weight, diameter of head and yield per plant is remarkable, and the combined stress at anthesis stage reduced the yield significantly. There was a salinity threshold of coupling effect of water and salt stress on sunflower yield, when the salinity was less than the critical value, the effect was dominated by water stress, on the other hand by salinity stress. The highest WUE was found at the treatment of80%irrigation amount at floral initiation with3.5g/L among the saline water treatments, which was4.35%-53.19%.(2)The plant height and leaf area was more sensitive to salinity stress and aboveground biomass was more sensitive to water stress. Na+was absorbed and accumulated in the root and leaf, while K+ was accumulated in the stem. In water and salinity stress, Na+was accumulated in the root at the floral initiation then transported to leaf at the anthesis and maturity stages, K+was the main osmotic adjustment ion in root and leaf. The net photosynthetic rate diurnal variation curve was transition from bimodal pattern to unimodal pattern under salt stress with reducing the peak significantly. And water stress decreased the net photosynthetic rate when the salinity was less than3.5g/L. At the early growth stage, the effect of water stress on transpiration rate was greater than salinity stress, while the coupling effect of water and salt stress was enhanced at late growth stage leading to the lower peak and advanced appearance of time. Stomatal factor resulting in decline of photosynthetic rate occurred at the floral initiation and anthesis stages with low salinity, but at the maturity or irrigated with high salinity, the main effect was non stomatal factor.(3)Mild water stress increased oil percentage and tocopherol of oil sunflower, but the moderate water stress and salinity stress reduced it, with the effect of restricting. The oleic acid was improved under water and salinity stress with the reduction of linoleic acid. In regard to the stearic acid and palmitic acid, the combined stress could increase the content but without significance. The variation of oil percentage had significant positive correlation with the photosynthetic rate and transpiration rate of different growth periods, and the negative correlation with Na+and Cl" in the root and leaf. However, the oleic acid was only positive related with the K+in the leaf of anthesis and maturity stages.(4)The response of oil sunflower yield to combined water and salinity stress of whole growth stage was nonlinear, transcendental equation model had the smaller error and higher accuracy and sensitivity of simulation. The multi-stage yield-and quality-water-salinity production functions were more precise for prediction. According to the salinity sensitive index and water sensitive index, the yield was sensitive to salinity stress and water stress both at anthesis stages, while oil percentage and oleic acid were sensitive to salinity stress at anthesis and maturity stages respectively, and to water stress at maturity and floral initiation stages. All quality water salinity production functions had higher prediction ability.(S)The fuzzy comprehensive evaluation model and principle component analysis method were used to evaluate the effect of deficit irrigation with saline water, it can be proved that the critical concentration of saline water for oil sunflower was3.5g/L, and the most suitable period of water deficit is the floral initiation stage. When the salinity was3.5g/L, the appropriate irrigation schedules was irrigating with80%of irrigation quota at floral initiation and full irrigation quota at other growth stages.