Continuous Cropping On Physiological Characteristics In Buckwheat And Soil Environment Effect

Buckwheat has the characteristics of drought-tolerance, poor-tolerance, strong adaptability, short growth period, high nutritional value, high edible and medicinal value, and it’s important in crop layout in arid regions of northern China. But due to the restrictions of natural conditions, conditional cultivation, and market demand, at present the continuous cropping in buckwheat is very a common phenomenon, cause fertility and quality deterioration, production decline. The continuous cropping restrict the yield and quality of buckwheat to a great extent. Therefore, the study of buckwheat cropping on physiological characteristics and soil environment, study the mechanism of continuous cropping obstacles and internal physiological mechanism of yield formation is important to improve the yield and quality of buckwheat and promote the development of buckwheat in arid region in China.Taken the variety of ‘Xinong 9920’ tartary buckwheat as material and set up four treatment: continuously two years(T1), continuously three years(T2), continuously four years(T3) and rotation(CK). Combined with field experiment and laboratory analysis, research the effect of main physiological characteristics including dry matter, active oxygen metabolism leaves, changes in soil nutrients, soil enzyme activity, soil microbial community, root exudates and grain yield according to rotation and continuous cropping of buckwheat. The main results were as follows:(1) With the advance of the growth period, the dry matter accumulation of different planting patterns shows a increasing tendency, and with the increased of buckwheat continuous years, the dry matter accumulation and grain yield of buckwheat on continuous cropping significantly lower than those on rotation. The grain yield of rotation is 1046.75 kg·hm-2, which is 1.06, 1.13 and 1.20 times compared with continuous 2 years, 3years and 4years. Therefore, the continuous cropping significantly reduced dry matter accumulation and grain yield of buckwheat.(2) Compared with the rotation, the continuous cropping accelerated the functional leaf senescence of buckwheat, with the increased of buckwheat continuous years, after buckwheat’s anthesis, the activity of SOD and the contents of chlorophyll and soluble protein showed downtrend significantly, while the accumulation of MDA and OFR kept elevating significantly, and the buckwheat yield decreased; The POD activity changes a lot, the activity of POD decreased significantly on prometaphase of anthesis and increased significantly in the late growth stage.(3) With the increased of buckwheat continuous years, the contents of N, P, K in rhizosphere soil decreased without fertilization, particularly the content of P and K which decreased more, and the soil nutrient decreased; The p H of soil increased which increased the alkalization of soil. With the increased of buckwheat continuous years, the enzyme activities of alkaline phosphatase and catalase decreased, the activities of urease decreased first and then elevated, while the activities of sucrase decreased on the whole.(4) The total number of soil microorganisms show: Bacteria > actinomycetes > fungi; and between different planting patterns show: continuous > rotation with an interval of one year > rotation; The B/F [(bacteria + actinomyce)/ fungi] of continuous cropping soil microorganisms is higher than rotation with an interval of one year and rotation particularly. There were 26 kinds of chemical materials in buckwheat root exudates by using GC-MS method, there are some allelochemicals whose content are high: dioctyl phthalate, cirmamic acid, 4-hydrozybenzoic acid, 1-glycerol stearate, 2,4-di-tert-butylphenol.Comprehensive showed that, the buckwheat appears certain continuous cropping obstacle caused by continuous cropping, compared with the rotation, the dry matter accumulation decreased, function of activated oxygen metabolism disorders, leaf senescence accelerated aging, soil microbial community activity lose balance, lead to the decreased of buckwheat grain field. Therefore, we should pay attention to the reasonable cultivation models like rotation with legume crops like kidney bean and apply some fertilizers, improve the environment of soil, to slow the continuous cropping obstacle and achieve high yield and quality of crops on buckwheat.