Study On Millet Growth And The Mechanism Of Nitrogen Transfer And Utilization Under The Coupling Of Biochar And Nitrogen Fertilizer In Northwest China

Millet is a traditional grain crop in our country.Because of its rich dietary fiber,palatability and strong drought tolerance,millet has become a large number of crops in northwest China.Yulin is the largest area and yield of millet in Shaanxi province.Millet needs a lot of fertilizer in the production process to control its jointing and heading,and then get an increase in yield.Bio-carbon,because of its high specific surface and porous nature,can play a role in agricultural production,such as water conservation and fertilizer,combined with fertilizer can effectively promote the absorption of nutrients in crops.In this study,the effects of different amounts of biochar and nitrogen fertilizer on the growth,Spike yield and quality of millet were studied,the dynamic monitoring and correlation evaluation of nutrient uptake by biochar were carried out to provide scientific reference for high quality,high yield and economic production of millet.The main findings are as follows:1.Control the effect of soil C/N ratio on the growth of milletThe effects of biological carbon and nitrogen fertilizer on the growth of millet were significant.The effects of different amounts of biological carbon and nitrogen fertilizer on the agronomic traits of millet were significant,the plant height,stem diameter,chlorophyll content and photosynthetic rate of foxtail millet were improved by the appropriate amount of biochar and nitrogen fertilizer,and the effects of biochar and nitrogen fertilizer on plant height,stem diameter,chlorophyll content and photosynthetic rate of foxtail millet were better than those of low biochar treatment（C1、C2）,（C3、C4）significantly increased plant height,stem diameter,chlorophyll content and photosynthetic rate of foxtail millet to39.46%～67.99%,55.54%,15.02%and 114.62～167.72%,respectively,while compared with low nitrogen treatment（N1、N2）,（N3、N4）significantly increased plant height,stem diameter,chlorophyll content and photosynthetic rate of foxtail millet to 39.46%～67.99%,55.54%,15.02%and 114.62～167.72%,respectively,N3 significantly increased plant height,stem diameter,chlorophyll content and photosynthetic rate of foxtail millet to22.82%～67.79%,44.94%～71.43%,20.74%～35.09%and 95.19%～147.90%,respectively.High application of biochar and nitrogen fertilizer decreased plant height,stem diameter,chlorophyll content and photosynthetic rate,but increased compared with low application of biochar and nitrogen fertilizer.The optimum amount of biochar and nitrogen fertilizer was20 g/m²and 9g/m²when plant height,stem diameter,chlorophyll content and photosynthetic rate reached the maximum.2.Effect of regulating soil C/N ratio on millet yieldThe yield of millet was affected by the application of biological carbon and nitrogen fertilizer.With the increase of the application of biological carbon and nitrogen fertilizer,the yield of millet increased first and then decreased,the yield of millet could be significantly increased by applying appropriate amount of biochar and nitrogen fertilizer.Compared with low biochar treatment（C1）,the yield of millet could be significantly increased by 11.43%under C2 treatment,while under different nitrogen fertilizer treatments,the yield of millet could be significantly increased by 11.43%compared with that under low nitrogen treatment（N1）,the yield of millet could be significantly increased by 28.99%under N3.The yield of millet could not be effectively increased by using too much or too little biochar and nitrogen fertilizer as compared with that of millet with low biochar and nitrogen fertilizer application.Based on the test results and the fitted regression equation,the optimum application rates of biochar and nitrogen fertilizer for millet were 20 g/m²and 9 g/m².3.Regulating the change of soil C/N ratio on soil nutrientThe application of biochar and nitrogen fertilizer can effectively promote the change of soil nutrients,and the nutrient contents of total N,total P and total K in soil increase firstly and then decrease with the application of biochar and nitrogen fertilizer,the contents of total N,total P and total K in soil were significantly increased under 15g/m²treatments,respectively,C2 significantly increased the contents of total N,total p and total K in soil by2.46%～20.11%,4.72%～4.88%and 3.12%～4.43%,respectively,N3 significantly increased the contents of total N,total P and total K by 1.47%～20.71%,3.01%and 2.14%～3.36%,respectively.According to the results of soil nutrient change,the reasonable application of biochar and nitrogen fertilizer did not change significantly compared with the high application treatment.4.Effects of regulating soil C/N ratio on nitrogen transferThe application of biochar and nitrogen fertilizer could effectively promote the transfer of nitrogen in millet,and the N1 treatment had the highest abundance（0.41%）,which was0.03-0.04%higher than other treatment（P<0.05）The C2 treatment was the highest（0.38%）among the biochar treatments,but there was no significant difference compared with other biochar treatments.In the leaves of millet,the ¹⁵N abundance of biochar treatment was the highest in C1（0.38%）,but there was no significant difference among biochar treatments,and the ¹⁵N abundance of N1 was the highest in N1（0.38%）,but there was no significant difference among different nitrogen fertilizer treatments.In the panicle of millet,the ¹⁵N abundance of biochar treatment was the highest in C2（0.38%）,but there was no significant difference among biochar treatments,and the ¹⁵N abundance of N4 was the highest in N4（0.37%）,but there was no significant difference among different nitrogen fertilizer treatments.In general,we found that the abundance of ¹⁵N markers increased with the increase of nitrogen fertilizer application at the same level of biochar application,when the amount of biochar applied increased,the amount of nitrogen fertilizer applied reached the maximum at the N2 and N3 levels.