Study On Nitrogen Absorption,Utilization And Distribution By Rubber Tree Seedlings Under Different Combined Level Of Ammonium And Nitrate Fertilizer

Nitrogen plays a key role in the crop yield and quality formation and the effects of different nitrogen forms on plant growth are remarkably different. Rubber trees are perennial trees, the traditional research methods of nitrogen fertilizer on nitrogen absorption, utilization and distribution have a great deal of practical difficulties, and studied on rubber trees using15N tracer are rarely reported. Pot experiment was adopted in this study, and the15N tracer technique was utilized to do researches on the absorption, utilization and distribution of different nitrogen forms by rubber tree seedlings under different combined level of ammonium and nitrate fertilizer, in order to provide the basis for nitrogen optimized management of rubber trees. The results were as follows:(1) Mixed nitrogen sources can significantly accelerated the growth of rubber tree seedlings. Under the combined application of50:50and75:25for ammonium nitrate ratio, the plant height, stem diameter and biomass growth of rubber tree seedlings were better than those under the single application of nitrate or ammonium nitrogen. Besides, the combined application levels of50:50and75:25for ammonium nitrate significantly increased the photosynthetic efficiency of leaves.(2) After nitrogen, under different combined levels of ammonium nitrate fertilizer, variation trends of total nitrogen content of top leaf were broadly in line, both first increased and then decreased.15N content of stable leaf was on an increasing trend, while15N content of top leaf increased at first and then tended to be gentle, and at the late fertilize time,15N content of ammonium nitrogen marked for the top leaf was slightly higher than that of labeled nitrate-nitrogen.(3) The nitrogen rate had a good correlation with the uptake of N by rubber tree seedlings (ammonium nitrogen, R2=0.9687; nitrate nitrogen, R2=0.9711), which was with the nitrogen rate increases; under the combined application levels of ammonium nitrate50:50and75:25, the apparent utilization of N was16.83%and16.69%, respectively, significantly higher than the other. These two types of ammonium nitrate application level promoted the absorption of nitrogen by rubber tree seedlings from the soil.(4) The utilization efficiency of nitrogen under the combined application of50:50and75:25for ammonium nitrate fertilizer was higher than the other,20.47%and18.61%, respectively; the nitrogen fertilizer residued highest rate of about83%under the combined ratio of25:75for ammonium nitrate fertilizer; the loss rate of nitrogen with the combined ratio of50:50and25:75was1.95%and2.18%respectively, which were under the lowest rates. To sum up, the two combined levels of50:50and75:25for ammonium nitrate fertilization under the condition of pot experiment accelerated the growth of rubber tree seedlings and improved its absorption and utilization of nitrogen.