Effects Of Biochar Combined With Nitrogen Fertilizer Application On The Physicochemical Properties Of Black Soil And Rice Growth And Yield

Rice is one of the main grain crops in China,and its drain planting area accounts for 28%of the country’s grain planting area.As an important rice production base,the black soil region in Northeast China plays a vital role in ensuring national food security.At present,in order to pursue production in the black soil area of Northeast China,it is very common to blindly increase the amount of nitrogen fertilizer used in production.The water consumption is large and the water use efficiency is low,which has caused a serious waste of water and fertilizer resources.Moreover,the excessive application of nitrogen fertilizer did not bring about sustained high yield and high efficiency,but would cause excessive consumption of limited soil moisture in the early stage of rice growth,aggravate the drought stress in the middle and late stages of rice growth,adversely affect grain yield and quality,and reduce the efficiency of nitrogen use in farmland.The search for the ideal carbon and nitrogen input for rice in the black soil region of Northeast China is of paramount importance,for it will help to maintain yield and boost efficiency,while also promoting sustainable growth of water and soil resources in the same area and guaranteeing national food security.An experimental plan for varying biochar and nitrogen fertilizer application,utilizing pot experiments,is as follows:biochar dosage 0%（C1）,2%（C2）,4%（C3）3 levels,nitrogen fertilizer dosage80 kg/hm2（N1）,100kg/hm2（N2）,120 kg/hm2（N3）3 levels,with local conventional fertilization（CK）as the control,resulting in a total of 10 treatments to investigate the impacts of various carbon and nitrogen applications on rice growth.dynamic indicators,physiological indicators,water content The impact of dynamic indicators,water consumption,yield and its constituent factors,water and fertilizer use efficiency,etc.To optimize the optimal carbon and nitrogen input of rice suitable for stable production and increasing efficiency in the black soil region of Northeast China,a comprehensive evaluation of different carbon and nitrogen treatments is necessary to elucidate the biochar effect.This combined application of nitrogen fertilizer with rice cultivation offers a theoretical basis for the cultivation of rice with high quality and high yield in the black soil region of Northeast China.Below are key research findings:（1）The larger the amount of biochar applied,the lower the soil bulk density,and the higher the water content and field water holding capacity.Compared with conventional nitrogen application,the combination of biochar and nitrogen fertilizer can significantly increase the content of soil total nitrogen,ammonium nitrogen,nitrate nitrogen,and microbial biomass nitrogen.Under the same nitrogen fertilizer application conditions,a 4%level of biochar application has the most significant effect on improving the content of soil total nitrogen,ammonium nitrogen,nitrate nitrogen,and microbial biomass nitrogen.The nitrogen fertilizer dosage with the most significant improvement effect under the three biochar dosage conditions is 120 kg/hm².（2）Under the condition of nitrogen fertilizer deficiency,rice leaf area index and effective and efficient leaf area rate will decrease,and the combined application of Biochar cannot compensate for the effect of this deficiency.Under the condition of appropriate nitrogen fertilizer and biochar application,the leaf area index and effective and efficient leaf area rate of rice can be increased,and the photosynthesis of rice plants can be enhanced,promoting the accumulation of dry matter and distribution to various organs in rice.Under the mode of 100 kg/hm² nitrogen fertilizer combined with Biochar,the net photosynthetic rate,transpiration rate,stomatal conductance and intercellular CO₂ concentration of rice at heading and flowering stage were significantly increased,and the photosynthetic efficiency of rice was basically increased with the increase of Biochar dosage.The dry matter accumulation rate of rice was the fastest under the combined application of 100 kg/hm² nitrogen fertilizer and 4%of dry soil weight of Biochar,and the dry matter weight of each organ was in the forefront（3）Under the nitrogen reduction mode（80 kg/hm²）,rice plant height will be significantly reduced,and the compensation effect of Biochar on rice plant height is limited.The water consumption and water consumption intensity of rice could be significantly increased under the mode of nitrogen application rate of more than 100 kg/hm² combined with Biochar.Under the mode of 100 kg/hm² nitrogen fertilizer combined with 4%Biochar of dry soil weight,the water content of rice root can be increased from the end of tillering to the heading and flowering stage,but the water content of rice crown will rapidly decrease in the later stage,accelerating plant senescence.（4）Nitrogen fertilizer combined with Biochar had significant effects on rice yield and nitrogen absorption.The rice yield reached the highest when the nitrogen fertilizer amount was 100 kg/hm² and Biochar with 2%dry soil weight was applied;When 80 kg/hm² of nitrogen fertilizer was applied together with 2%dry soil weight of Biochar,the partial productivity of rice nitrogen fertilizer reached the maximum;However,increasing the amount of nitrogen fertilizer to 80 kg/hm² significantly reduces water use efficiency and nitrogen fertilizer productivity.The TOPSIS model based on entropy weight was used to comprehensively evaluate the effect of different carbon fertilizer control treatments on yield increase and benefit increase.The best carbon nitrogen application scheme for rice in the experimental area was determined as 100 kg/hm² of nitrogen fertilizer and 2%of dry soil weight of Biochar.