| Crop production in the arid region of the Loess Plateau has been affected by the shortage of crop water demand and rainfall,and the utilization rate of nitrogen fertilizer is low and the loss is large.Adding biochar is a potential strategy to promote crop production.In order to understand the effects of biochar addition on crop productivity and soil nitrogen turnover under furrow and ridge mulching conditions,three biochar application rates were designed based on furrow and ridge mulching in the semi-arid region of the Loess Plateau（Pengyang,Ningxia）:0.0 t ha-1（RFBN）,4.5 t ha-1（RFBL）and 9.0 t ha-1（RFBH）.The effects of different biochar application rates on farmland water temperature,nitrogen composition,gaseous nitrogen loss,maize productivity and water and nitrogen use efficiency were analyzed.The main results are as follows:The order of annual average soil water content in 0-60 cm soil layer was RFBN>RFBH>RFBL,and that in 60-120 cm,120-200 cm and 0-200 cm soil layers was RFBN>RFBL>RFBH.The trend in 2021 and 2022 was the same,but compared with 2021,the soil water content in 2022 decreased,and the decrease range increased with the increase of biochar application rate.The decrease range of RFBN treatment between two years decreased with the deepening of soil layer,but it was different.The decrease of RFBL and RFBH treatment between two years increased first and then decreased with the deepening of soil layer.Compared with RFBN treatment,the annual average soil water content of RFBL and RFBH treatments in 0-60 cm,60-120 cm,120-200 cm and 0-200 cm soil layers decreased by 5.80%and 4.81%,8.82%and 12.25%,3.85%and 6.55%,6.05%and 7.52%,respectively.The change of 60-120 cm soil layer was the largest,and the difference of soil water storage between biochar and non-biochar was mainly in 60-120 cm soil layer.The trend of soil temperature in10 cm and 20 cm soil layers during the growth period was consistent with that without biochar.The addition of biochar slightly increased the soil temperature in the early stage of spring maize growth,but the annual average soil temperature and effective accumulated temperature of 0-20 cm soil layer were not significantly increased.Compared with RFBN treatment,the two-year average total nitrogen content,soluble organic nitrogen content and microbial biomass nitrogen content in the 0-60 cm soil layer of RFBL and RFBH treatments increased by 5.26%and 7.71%,1.53%and 7.31%,9.44%and22.14%,respectively,and the improvement of RFBH treatment was the most significant（P<0.05）.The average soil nitrate nitrogen content in the 0-20 cm soil layer of RFBL and RFBH treatments increased significantly by 24.04%and 40.25%,respectively,and the average soil ammonium nitrogen content decreased by 49.65%and 26.81%（P<0.05）.The addition of biochar significantly increased the soil nitrate nitrogen storage in the 0-100 cm soil layer at30-120 days after sowing（P<0.05）,and increased with the increase of application rate.The difference was that there was no obvious change trend in the storage of ammonium nitrogen during the growth period.The same is that the soil ammonium nitrogen and nitrate nitrogen residues in the 0-200 cm soil layer during the harvest period are reduced by the addition of biochar,and decreased with the increase of application rate.The nitrous oxide emission flux and ammonia volatilization rate of each treatment will have different degrees of peaks after base fertilizer and topdressing,and the addition of biochar has a peak reduction effect.Compared with RFBN treatment,the cumulative nitrous oxide emission and cumulative ammonia volatilization of RFBL treatment were significantly reduced by 11.83%and 10.32%（P<0.05）,while RFBH treatment was significantly reduced by 18.79%and 19.00%（P<0.05）,respectively.With the increase of biochar application,the loss of gaseous nitrogen decreased.The order of plant height,leaf area index and dry matter accumulation during the growth period of each treatment in 2021 and 2022 was RFBH>RFBL>RFBN.There was no significant difference in plant height between different biochar application rates.The application rate of 9.0 t ha-1（RFBH）significantly increased the leaf area index and dry matter accumulation per plant during the growth period（P<0.05）.Compared with RFBN treatment,the average plant total nitrogen uptake of RFBL and RFBH treatments was significantly increased by 5.68%and 13.09%（P<0.05）,respectively,and the grain nitrogen uptake was significantly increased by 14.16%and 27.31%（P<0.05）.The addition of biochar significantly increased the annual average spring maize yield,water use efficiency,nitrogen use efficiency and nitrogen harvest index（P<0.05）,and increased with the increase of biochar application rate.The annual average of RFBL and RFBH treatments increased by 4.40%and 13.07%,9.70%and 11.14%,7.86%and 14.90%,8.04%and 12.59%,respectively.Considering the yield of spring maize,water and nitrogen use efficiency,soil improvement effect and environmental factors,it is concluded that the application of 9.0 t ha-1 biochar under furrow and ridge mulching can be used as a suitable technical choice. |
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