Effects Of Biochar Addition On Nitrogen Uptake And Utilization In Baby Bokchoi

The application of nitrogen fertilizer in China is unreasonable,and the nitrogen utilization efficiency is low,which seriously affect the sustainable development of crop production.A pot experiment was conducted to investigate the effects of biochar derived from rice husk on nitrogen uptake and utilization in baby bokchoi for two consecutive planting seasons in brown soil by using the technique of stable isotope ¹⁵N-traced urea.Biochar was applied at four application rates?0,0.5%,1%and 2%,?/??to the soil.The yield of baby bokchoi,the amount of nitrogen uptake aboveground and underground,the nitrogen content in soil and the loss of N₂O at different growing period were measured,and the nitrogen fate and nitrogen utilization efficiency were calculated.The results are as follows:?1?Biochar addition improved soil pH for two consecutive planting seasons of baby bokchoi.Compared with no biochar addition,soil pH increased 0.1 and 0.3 for 2%biochar application for the 6-leaf stage at the first planting season and the second planting season,respectively.No correlation between biochar application amount and soil pH was found in two consecutive planting seasons.Ammonium and nitrate nitrogen contents decreased with biochar application for the two consecutive planting seasons.Compared with no biochar addition,ammonium nitrogen content decreased 37.8%and 18.1%for 2%biochar application for the 6-leaf stage at the first planting season and the second planting season,respectively,while the values were 12.0%and 37.5%for nitrate nitrogen content.?2?Biochar addition improved the chlorophyll content and yield of baby bokchoi for two consecutive planting seasons.Compared with no biochar application,the SPAD value of chlorophyll increased 7.71 and 7.33,and the yield of baby bokchoi increased 34.5%and 39.9%for the fisrt planting season and the second planting season,respectively.?3?Compared with no biochar addition,soil nitrogen uptaked by baby bokchoi increased 2%for 0.5%biochar application for the first planting season of baby bokchoi,while soil nitrogen uptaked by baby bokchoi increased 0.8%,2.4%and 3.2%for 0.5%,1%and 2%biochar application for the second planting season,respectively.Nitrogen uptaked by leaves and roots increased with the increase of biochar addition for thw two consecutive planting seasons.?4?Compared with no biochar addition,N₂O emissions reduced with the biochar application for the two consecutive planting seasons of baby bokchoi.N₂O emissions decreased 0.30 mg·pot^-1 and 0.10 mg·pot^-1 for 2%biochar application in the first and second planting seasons,respectively.Biochar addition improved the nitrogen utilization efficiency.Compared to no biochar application,nitrogen utilization efficiency increased 16.3%for 2%biochar addition for the first planting season of baby bokchoi.Nitrogen utilization efficiency increased 0.42%,0.72%and 5.3%,respectively,for 0.5%,1%and 2%biochar addition for the two consecutive planting seasons of baby bokchoi.Thus,2%biochar application should be considered a suitable soil amendment for nitrogen utilization.