Effect Of Biochar On Nutrient Use Efficiency And Leaching Losses Under Winter Wheat And Summer Maize Rotation System In Guanzhong Plain,China

A lysimeter experiment was carried out during the year 2016-17 to investigate the effects of biochar application on crop yield,nitrogen and phosphorus use efficiency and their leaching losses under winter wheat and summer maize rotation system in Guanzhong Plain,Shaanxi,China.The experiment was conducted by lysimeters with different depths(_d3=50cm,_d4=80 cm,_d2=120-150 cm and _d1=200cm),and biochar types were wheat straw biochar(BS₁=15t ha^-1,BS₂=30t ha^-1)and tobacco stem biochar(BT₁=15t ha^-1 and BT₂=30t ha^-1).The experiment included seven treatments,i.e.optimization of water and nutrient management(OPT_d2),OPT_d1+BS₁,OPT_d1+BS₂,OPT_d4+BS₁,OPT_d3+BS₂,OPT_d4+BT₁ and OPT_d3+BT₂,respectively.The OPT applied nitrogen at the rate of 150 kg ha^-11 and phosphorus?P₂O₅?at the rate of 120 kg ha^-1during winter wheat,and onlynitrogen at the rate of 180 kg ha^-1 during summer maize crop.The results showed that treatments of OPT_d1+BS₁ and OPT_d3+BT₂ had significantly increased wheat grain yield relative to OPT_d2.However,biochar treatment had no remarkable effect on total biomass of wheat crop.Whereas two kinds of biochar had no effect on maize grain yield,treatments of OPT_d3+BS_2,OPT_d3+BT₂ significantly increased total biomass of maize crop by 19.11and 21.43%,respectively.Biochar treatments had significantly enhanced annual PFP_N?partial factor productivity of nitrogen?relative to OPT_d2.However,the annual PFP_P?partial factor productivity of phosphorus?had significantly reduced in biochar treatments relative to OPT_d1.Annual NHI?nitrogen harvesting index?,annual PHI?phosphorus harvesting index?,annual nitrogen use efficiency and annual phosphorus use efficiency remained unaffected by the application of biochar,relative to OPT_d1.Significantly higher annual DON?dissolve organic nitrogen?,annual NO₃-N?nitrate nitrogen?and annual NH₄-N?ammonium nitrogen?leaching losses occurred in shallow depths of lysimeters(OPT_d4+BS₁ and OPT_d4+BT₁)compared to OPT_d2 treatment.However,no significant annual leaching losses were observed for biochar treatments in deep depths?200cm and 80cm?of lysimeter relative to OPT_d2.Biochar treatment in shallow depths of lysimeters?50cm and 80cm?had significantly higher annual MRP?molybdate reactive phosphorus?,annual PP?particulate phosphorus?and annual DOP?dissolve organic phosphorus?leaching losses relative to OPT_d2.However,biochar treatments in deep depths?200cm?of lysimeters remain unaffected relative to OPT_d2.Overall,our findings suggest that low rate of wheat straw biochar might be a good strategy to improve crop yield and nitrogen use efficiency in studied area.Thus,further investigation is needed to carry out to clarify biochar effectiveness on crop yield and nutrient use efficiency and nutrient losses in normal field condition.