Study on Nitrogen Diagnosis of Cucumber in Greenhouse

Nitrogen is one of the main nutrients for crop growth and yield in Nitrogen is generally difficult to grasp the the nitrogen status change within the field of soil nitrogen nutrient differences and crop growing season, causing nitrogen to be the most difficult crop production one of the accurate quantitation of fertilizer. Crop Nitrogen regulation and the efficiency of nitrogen fertilizer, ultimately depends on accurate diagnosis of the crop nitrogen level. Therefore, the diagnosis of nitrogen nutrition has been the main content of the Crop Nutrition Diagnosis. In this paper, the plot experiments and hydroponic experiments in the facility cultivation conditions, nitrogen rate, SPAD value, nitrate reductase activity and crop vivo nitrate accumulation by analyzing changes in the relationship, using SPAD value and nitrate reductase activity Nitrogen Nutrition Diagnosis of cucumber possibility as a diagnostic indicator and the best diagnostic period and best leaf position, in order to provide a theoretical basis for the rapid diagnosis of the cucumber nitrogen nutrition under the conditions of the facility cultivation. Draw the following conclusions: 1, found by the correlation of cucumber under protected cultivation conditions chlorophyll SPAD value and amount of nitrogen fertilizer, yield, leaf nitrate content, flowering and fruiting period SPAD value and yield and leaf nitrate nitrogen content showed significant correlation can be used to predict the yield of cucumber, more importantly, can predict the nitrate content of the leaves, diagnosis cucumber nitrogen status. SPAD value of the reaction of nitrogen levels the degree of sensitivity of the existence of significant differences in the size of the cucumber leaf SPAD value ranking change significantly with increasing amount of nitrogen. Seedling and flowering stages leaves 3 the result leaves 7 bits of the initial reaction of nitrogen fertilizer is the most sensitive, more accurate diagnosis cucumber nitrogen level, SPAD chlorophyll meter for nitrogen diagnosis Leaf position. 3, 3 leaves, results of the early 13 nitrate reductase activity of leaf position on the reaction of the nitrogen level is the most sensitive, as the best leaf bits of cucumber nutrition diagnosis and the best period of the seedling stage and flowering stage. Two blades during the nitrate reductase activity and SPAD value, nitrate trend consistent with increasing nitrogen levels increased, and the performance of soil available nitrogen to the opposite trend. 4, cucumber leaf nitrate reductase the the active diagnostic threshold in flowering period and the results of the initial 67.45,54.3 ugNO ₂ -g ^{-1 FW · h - 1 , there are some differences in the critical value of the same nitrogen levels at different growth stages of cucumber leaf NRA. 5, the three elements of the entire growth period of plants assimilate content: K gt; N gt; P Cucumber at different growth stages absorb nitrogen, phosphorus and potassium in different proportions, and a higher proportion of phosphorus absorption the lowest proportion of nitrogen and potassium, potassium change in the whole growth period. Shi N250 kg / hm 2 , the highest yield, nitrate content of the leaves and fruits is relatively low, and to determine the optimum nitrogen rate for the test conditions of cucumber.}