Effects Of Biochar And Straw Additions On Soil Properties,Transport Of Nitrogen In Lou Soil

In order to investigate the effect of biochar and straw addition on soil properties,and transport of nitrogen from Lou soil,two field experiments were conducted in Central Shaanxi Plain with biochar single(five biochar addition amounts were set in this study as follows:0,20,40,60 and 80 t?hm^-2)or biochar plus straw application(five treatments were set in thid study as follows:no straw and biochar,0.6 t·hm^-2Straw,30 t?hm^-2biochar plus 0.3t·hm^-2straw,45 t?hm^-2biochar plus 0.3 t·hm^-2straw,60 t?hm^-2biochar plus 0.3 t·hm^-2straw).One was conducted to study the effect of single application of biochar on soil properties for different years?2 and 5 years?,and the other was conducted to study the effect of biochar combined with straw application on soil properties and transport of nitrogen in Lou soil,furthermore,the influence mechanism of biochar combined with straw on the soil properties and nitrogen transport was investigated,and determined the suitable application amount of biochar single and biochar plus straw for Lou soil applying.The main conclusions are as follows:1. Compared with the results of 2 years'application,the effect of biochar on the aggregates of 0–10 cm and 10–20 cm soil layers became less obvious after 5 years'application,and the effect on soil aggregates of 20–30 cm soil layer was significantly enhanced;compared with those of 2 years'application,the aggregate stability and content of aggregates with size of>0.25 mm in the 0–10 cm soil layer increased significantly after 5years'biochar application of 40 t·hm^-2,while that of bulk density decreased significantly;for the 10–20 cm and 20–30 cm soil layers,stability of aggregates and content of aggregates in size of>0.25 mm increased significantly,while the bulk density decreased significantly after 5 years'biochar application of 60–80 t·hm^-2;when the application of biochar was 60t·hm^-2,the increment of soil organic carbon was highest after 5 years.After the biochar was applied for 5 years,its effect on deep soil was more significant;the soil bulk density was significantly reduced,and aggregate stability and the content of aggregates with the size of>0.25 mm increased significantly in 20–30 cm soil layer.Based on comprehensive consideration of improvement effects and economic benefits,the most suitable biochar application amount was 40–60 t·hm^-2;and it could be concluded that the effect of biochar on soil aggregates is gradual and sustainable.2. In the cultivated soil,the soil organic carbon was significantly increased by only straw application and biochar plus straw,among which the combined application effect of biochar with straw is better than that of single straw application.When the combined application was 0.3 t?hm^-2straw plus 60 t?hm^-2biochar,the soil organic carbon content was the highest and the improvement effect of soil organic matter was the best.When straw and biochar were applicated in soil,the bulk density decreased significantly by 4.48%–6.41%.When straw only was applicated in soil,the p H of surface soil decreased by 0.63%–1.03%,but only reduced 0.05–0.08 units from the perspective of numerical.However,the effect of biochar and straw on soil p H wasn't significant.When biochar and straw were applicated in soil,the capability of holding and sluicing of soil was increased,and the soil moisture content significantly increased in 0–40 cm soil layers.The soil moisture of deeper soil didn't show a consistent rule,and was affected by the external water input.Under the condition of sufficient water,the water storage capacity of the deeper soil could be increased.3. The content of total nitrogen was significantly increase in 0–20 cm soil layer when biochar and straw were applicated in soil,and that increased with the increase of the amount of biochar,ahd the increase ranged from 5.77%–23.23%.But the effect on total nitrogen in subsoil was small.Straw single application and biochar combined application had significant the effect of biochar and straw application on content of soil NO₃^--N was significant,but that on content of NH₄⁺-N was little.The content of soil NO₃^--N did not show a consistent rule in different periods.In the early stage,the content of soil NO₃^--N decreased significantly after biochar and straw application,and avoid its leaching and volatilization loss.At the later stage,nutrients were released from biochar and straw to increase the content of NO₃^--N for crop absorption and utilization.In general,the single application of straw and its combination with biochar had a certain effect on the slow release of soil nitrogen.It has obvious adsorption and fixation effect on inorganic nitrogen,which could reduce its leaching,nitrogen loss and improve the utilization rate of fertilizer.When 0.3t·hm^-2straw combined with 45 t?hm^-2or 60 t?hm^-2biochar were applicated in soil,the effect was better than that of the straw single application.In conclusion,the most suitable biochar single application amount was 40–60 t·hm^-2.When biochar and straw were applied in soil,the combined application of 0.3 t?hm^-2straw and 45–60 t?hm^-2biochar was the best.