Effects Of Different Nitrogen Forms And Ratios On Yield,Quality And Nutrient Uptake Of Mini Chinese Cabbage

Nitrogen is an important nutrient to promote growth and development of plants, as well as nutrient absorption. The effects of different nitrogen forms and ratios on growth, yield, quality, nutrient absorption(N, P and K), dry matter accumulation and available nutrient of soil were tested in the mini Chinese cabbage(Brassic pekinensis). The study was aimed at providing the theoretical foundation for Brassic pekinensis optimum and scientific fertilization grown in plateau area and in summer The results are as follows:1.For the initial growth stage of Brassica pekinensis, no difference in the growth range of plants among the treatments was observed. Between the period of 18 May and 7 June, plants are in their rapid growth stage, during which the plants grew rapidly, and nitrogen significantly increased the growth range of plants and this effect is much better when the ratio of NO3--N/NH4+-N=5:5. Moreover, when plants were fertilized with NO3--N/NH4+-N=5:5,the plant height reached the highest and this treatment was more beneficial for the promotion of leaf head height and leaf head diameter than other treatments. This can lay foundation for increasing the economic yield of Brassica pekinensis and economic income.2. In the circumstances of equal nitrogen fertilization, different nitrogen forms and ratios fertilization had significant effects on the Brassica pekinensis yield. Compared with single nitrogen, combined application of ammonium and nitrate significantly increased the yield, among which NO3--N/NH 4+-N=5:5 treatments produced the best yield and efficiency, followed by NO3--N/NH 4+-N=7:3 treatments.3. Nitrogen forms and ratios had significant effects on the quality of Brassica pekinensis, as nitrogen application significantly increased the content of nitrate. The treatment of solo nitrate lead to the highest nitrate accumulation, the amide nitrogen treatments was second to it.The content of nitrate gradually decreased and ultimately reached the lowest when ammonium nitrogen was together to be supplied to the plants.The soluble protein content reached the highest point when NO3--N/NH 4+-N=3/7. Ammonium nitrogen can help to form the soluble sugar, with soluble sugar content reached its highest point in total ammonium nitrogen treatments. The soluble solid content reached its highest point when NO3--N/NH 4+-N=7/3.4. Different nitrogen forms and ratios have different effects on the absorption of nutrients of Brassica pekinensis in different physiological periods. The nitrogen content showed a stage dependent decreasing order: rosette stage > seedling stage > maturation stage, while the content showed a stage dependent decreasing order:of P and K showed maturation stage> rosette stage> seedling stage. During rosette stage the P content was the highest in single nitrogen treatments, while during maturation stage it reached the highest in combined application treatments. The content of K is the highest within the range of NO3--N/NH 4+-N=7/3 and NO3--N/NH 4+-N=5/5. The result showed that raising nitrogen application increased the nutrients content of Brassica pekinensis, and during the whole growth period, NO3--N/NH 4+-N=5/5 and NO3--N/NH 4+-N=7/3 treatments were beneficial to accumulate more nutrients.5. Nitrogen fertilization of different NO3--N to NH 4+-N ratios had significant effects on dry matter accumulation of Brassica pekinensis, and this effect varied in different periods. Seedling fertilization effectively enhanced the increase of dry matter, with the increase of ammonium nitrogen ratio, dry matter accumulation gradually increased and finally reached its highest point. Rosette stage and maturation stage, combined application of ammonium and nitrate was more beneficial for dry matter accumulation than single nitrogen. In all three growth stages of Brassica pekinensis, the combined application treatments which contains 30%~50% nitrate nitrogen was helpful to increase the growth of dry matter accumulation.6. Nitrogen forms and ratios have significant effects on soil available nutrients. Fertilization obviously increased the content of ammonium nitrogen and nitrate nitrogen in soil, while in terms of the content of soil alkali-hydrolyzable nitrogen, each treatment variously increased except the control treatments(no fertilization). And the content of soil alkali-hydrolyzable nitrogen showed an initial upward then downward trend, reaching its highest point when NO3--N/NH 4+-N=5/5. The content of soil available P maintained stable in every period of Brassica pekinensis when NO3--N/NH 4+-N=5/5. By contrast, the content of soil P in each period among other treatments varied. The content of available K reached the highest in nitrate nitrogen treatments, followed by NO3--N/NH 4+-N=7/3 treatments.