Effects Of Biochar On The Root And Root-zone Soil Nitrate Metabolism Of Apple

Nitrate is not only nitrogen sources of fruit trees, but also the potential environmental pollution factors. Biochar is incompletely burned product of waste biomass materials such as straw. Malus hupehensis (Pamp) Rehd., apple trees in potting, and adult apple trees in field were used as materials in the experiment. Investigate the effects of carbonized straw and carbonized apple branch on nitrate metabolism in root zone soil. The main results are as follows:1. The results showed that the rate of NO formation, the activity of NR and NOS (nitric oxide synthase) in apple root are significantly increased when carbonized straw applied to the soil reached1%-2%(w/w), they significantly dropped while the application reached8%. The application of0.5%carbonized straw significantly increased the activity of NR and the rate of NO formation in soil;but the activity of NR in soil decreased when the application is over1%; the rate of NO formation in soil decreased when the application is over2%. The application of carbonized straw significantly increased the nitrification strength and HyR activity in soil. Soil nitrification strength reached maximum when the application of carbonized straw reached2%, and soil HyR activity increased with the increasing of the application amount of carbonized straw. The application of carbonized straw to soil influences the NO formation in apple root and the soil nitrate metabolism in root-zone significantly. The0.5%-2.0%(w/w) carbonized straw promotes the reduction of nitrate to nitric oxide in roots and soil. The0.5%-4%(w/w) carbonized straws improves the nitrification in root zone soil.2. After the application of carbonized straw in pure soil, the NR activity and NiR activity reduced significantly and showed a decreasing trend with the increasing amount of carbonized straw application.However, the application of carbonized straw increased the nitrification strength, soil organic carbon content and HyR activity in soil significantly and soil organic carbon content and HyR activity increased with the increase of the application amount of carbonized straw and soil nitrification strength reached maximum when the application of carbonized straw reached2%.3.The practical application on adult apple trees showed that carbonized straw+organic fertilizer (YC)can increase the activity of NR、 NiR、 HyR and the strength of nitrification and soil organic carbon content effectively,which is better than that of applying organic fertilizer(Y), carbonized straw(C). 4.The results showed that the leaf net photosynthetic rate, plant height, stem diameter, total dry weight, root activity, root fractal dimension, total root length, root diameter, root surface-area and root volume were all increased significantly after applying carbonized apple branch made by pyrolysis under three different temperature to the soil, and all of them increased with the increasing of carbonization temperature from400℃,600℃,700℃.The root structure of Malus hupehensis seedlings was more complex after treated with carbonized branches. The carbonized can increase the activity of NR、NiR、HyR and the strength of nitrification and soil organic carbon content effectively.5.The effect of2%application of carbonized apple branch to soil is better than that of1%. The application of carbonized apple branch decreased NR activity, NiR activity and the rate of NO formation, however, soil nitrification strength and HyR activity reached maximum when the application reached2%, and all of them increased with the increasing of carbonization temperature from400℃to700℃.