Effects Of Exogenous Selenium, Water And Fertilizer Joint Regulation On Quality And Yield Of Jujube

The simultaneous occurrence of severe water and soil losses and water shortage is a key problem that affects eco-environment construction and sustainable agricultural development on the Loess Plateau. Jujube trees were widely planted in the past decade for its ecological and economical benefits in the hill-gully areas of Northern Shaanxi Province. Applied with the combination techniques of dwarf, close planting and drip irrigation, jujube trees have been proved to be an effectively and simultaneously solution of the problem. At the same time, Northern Shaanxi province belongs to low-Se regions and is also one of the regions with the serious Keshan disease in China. Selenium （Se）, as an essential micronutrient for animal and human health, can be assimilated efficiently and complemented safely via food-chain. Fruit is one of the main sources of Se for humans. If we can produce Se-enriched jujube so as to meet the needs of human’s health, it will be an important way to improve the jujube’s quality and promote the industrial development of jujube. However, few studies were reported in the mechanism of Se uptake, fruit quality and production technique standard of jujube.Based on the investigation of Se background contents in soil and jujube fruit, three methods including soil addition, trunk injection and foliar application were employed with exogenous Se（Na2SeO3）to produce Se-enriched jujubes. To analyse the Se fertilizer effects and mechanism in jujube trees, the growth and development index of jujube were determined under different soil water and fertilizer managements. Finally, integrating the research results above, Se-enriched jujube production technical specification was proposed. Experiments were conducted in two consecutive years and the main conclusions are as follows:（1） Se background contents in jujube fruit and soil in experimental area were low, which indicating that jujube probably is not a Se-accumulator plant. The mean total Se content at 0⁶0 cm soil depth is 73.37μg kg^-1, so the soil belongs to low-Se soil. Se content in soil profile accumulated mostly at 0²0 cm and showed the distribution characteristic of surface accumulation. Land use effected the content of soil total Se, water solute Se and available Se at 0⁴0 cm depth significantly（P < 0.01）, and showed the trend as article grassland > cropland > jujube orchard （irrigated） > jujube orchard （non-irrigated）. Analysis by stepwise regression, the results showed that soil organic matter content was the most important soil factor affecting soil total Se and water solute Se content, and soil organic matter content, pH and CEC were the most important soil factor affecting soil available Se content.（2） Se accumulation and distribution in jujube trees was obviously affected by different Se-enrich methods and Se fertilizer concentrations. As to one year jujube trees, Se mainly accumulated in root after soil addition method, while in leaf after foliar application method. Se content in all the organs of jujube trees was increased generally with the increase of Se fertilizer concentrations. As to ten year jujube trees, three Se-enriched methods increased fruit Se content significantly which appearing foliar application > trunk injection > soil addition, and fruit Se content was enhanced with increase of Se fertilizer concentrations. Under the same Se fertilizer amount, foliar spray once and twice had no significant difference to enhance fruit Se contents, but foliar spray triple had significant effects. Compared with flowering stage, foliar application at fruit set stage increased fruit Se content 1.3¹.7 times.（3） Se displayed dual effects on growth of jujube trees, which can be promoted at or below optimal concentrations, whereas be stunted at higher concentrations. Under the Se fertilizer concentrations used in the trials, soil addition and trunk injection methods had no significant effects on growth of fruit and new shoots. Foliar application method significantly promoted vertical diameter, horizontal diameter of jujube fruit, new shoots, leaf area and leaf area index at optimal Se fertilizer concentration, however, inverse effects were found at higher concentrations. Moreover, as to foliar application method, the threshold value of Se fertilizer is 300 g ha^-1. Chlorophyll content and photosynthetic characteristics of leaves was significantly increased in three Se-enriched methods, but decreased at higher Se fertilizer concentration in foliar application method.（4） Suitable Se-enriched methods and Se fertilizer concentrations can enhance the quality and yield of jujube. With the Se fertilizer concentrations in the trials increased, soil addition and trunk injection methods enhanced fruit quality of fruit vitamin C content, soluble solid content, soluble protein content and soluble total sugar content and decreased organic acid content. Foliar application method also had similar trend when Se concentration not more than 300 g ha^-1, but had inverse effects when Se concentration more than 300 g ha^-1. Soil addition and trunk injection methods increased jujube yield but had no significant difference.（5） Soil water and fertilizer managements affected significantly jujube fruit Se content, quality and yield. Three treatments including non-moisture conserving technology, straw mulch and drip irrigation and different fertilizer treatments enhanced Se uptake of jujube tree by improving soil water storage, and then increase fruit Se content. The integrated management of drip irrigation and N1P3K3 fertilizer (urea 0.78 t ha^-1, calcium superphosphate 3.75 t ha^-1, Potassium Chloride 0.81 t ha^-1) and treatments had better effects. Applying foliar application with Se fertilizer 300 g ha^-1, jujube yield and fruit Se content were 20.59 t ha^-1 and 46.97μg kg^-1, respectively, which can be recommended for Se-enriched jujube production.These results show that Se-enriched jujube can be produced by the technologies above. Therefore,“planting technical specifications of Se-enriched jujube in the Northern Shaanxi Province”was proposed.