| As an emerging technology,biochar is increasingly attracting the interest of researchers.Application of biochar not only benefits resource utilization of agricultural wastes,but also plays an important role in improving soil fertility,increasing crop yield and remediating the contaminated environment.At present,however,studies mainly focus on the effects of biochar alone,and the interactive effects of biochar with fertilizer have often been ignored,which directly restricts its popuarization and application in agricuture and environment.Hence,field experiments were conducted to investigate soil nutrients,rice yield and biomass,nutrient uptake and use efficiency,dynamics of N in percolation water from paddy fields,and runoff losses of N in paddy fields in response to biochar combined with chemical fertilizer in different ratios and with different slow/controlled-release fertilizer in Tiraoxi River,Taihu Lake region.The main results were as follows:1.To a certain extent,biochar combined with N fertilizer increased soil pH,nutrients uptake,rice yield and biomass,but decreased soil available P and available K,compared to individual biochar.Based on biochar application,combination of 60 kg N·ha-1 did not exert any significant effect on nutrients uptake.Combination of 150 kg N·ha-1 maximized yield increasing potential of N.Combination of 180 kg N·ha-1 caused a significant improvement in rice yield and nutrients uptake by rice.Rice biomass,nutrients uptake and internal nutrients use efficiency significantly reduced,but rice yield showed no significant difference when N supply increased to 240 kg·ha-1.2.The soil organic matter,total N and available P obviously decreased,but available P drastically rose after 2-year consecutive application of biochar.Compared to individual biochar,biochar combined with P fertilizer partly increased soil total N and decreased available K,and significantly increased available P and decreased internal P use efficiency.However,there was no significant difference in internal K use efficiency between individual biochar and biochar combined with P fertilizer.Based on biochar application,combination of 82.5 kg P2O5·ha-1 significantly boosted P and K uptake by rice,rice yield and biomass.Rice yield and biomass were not significantly affected,but a significant decrease in N uptake by rice was observed when P2O5 supply increased to 120 kg ha"1.3.Biochar application caused a significant increase in the soil pH of cold waterlogged paddy fields due to its liming effect,while this application resulted in a significant decrease in soil exchangeable cations,such as exchangeable Ca,Mg,Al and base cations.The interactive effect of N fertilizer,P fertilizer and biochar was significant for soil total N.Moreover,biochar boosted the K uptake into rice,but notably decreased internal K use efficiency.According to the partial Eta squared values,the combined application of N fertilizer and biochar was as effective as pure P fertilization at increasing straw P uptake.The addition of biochar to farmers'fertilization practice treatment significantly increased rice yield,mainly owing to improvements in grains per panicle.Overall,however,notable effects of biochar on rice yieli and biomass production were not detected.4.Organic N prevailed in the N of percolation water from cold waterlogged paddy fields,and inorganic nitrogen was dominated by nitrate.Application rate of N fertilizer,P fertilizer and biochar did not have any significant effect on ratios of different forms of N to total N.Application rate of chemical fertilizer significantly influenced the N concentration of percolation water.The decrease ofN fertilizer from 180 kg·ha-1 to 120 kg·ha-1 significantly decreased nitrate concentration of percolation water by 15.03%.The decrease of P fertilizer from 67.5 kg·ha-1 to 37.5 kg·ha-1 significantly increased total N and nitrate concentration of percolation water by 14.63%and 18.94%,respectively.Therefore,the risk of N losses via leaching in cold waterlogged paddy fields can be notably lowed by controlling application rate of N fertilizer and increasing application rate of P fertilizer.In part,biochar application was beneficial for the decrease in inorganic N concentration of percolation water.5.The pH of surface water decreased by 3.16%-4.48%for biochar combined with controlled-release fertilizer and stabilized fertilizer,and was in the range of 5.64-8.15.The total N concentration of surface water ranged from 19.05 to 25.23 mg·L-1.A significant decrease of 4.75%-6.58%in total N concentration of surface water was observed for biochar combined with controlled-release fertilizer and stabilized fertilizer.The ammonium and nitrate concentration of surface water varied from 0.01-17.26 mg·L-1 and 0.24-3.11 mg·L-1,respectively.Inorganic N was dominated by ammonium in surface water.Compared to individual controlled-release fertilizer,other treatments significantly reduced ammonium concentration of surface water by 35.89%-48.78%and nitrate concentration of surface water by 20.54%-37.01%.Biochar combined with stabilized fertilizer showed a significant reduction in ammonium and nitrate concentration of the surface water,which greatly lowered the risk of inorganic N losses via runoff The runoff loss of total N,ammonium and nitrate were in the range of 16.24-18.09,1.76-2.22 and 0.76-1.38 kg·ha-1,respectively.Compared to individual controlled-release fertilizer,the runoff loss of total N,ammonium and nitrate in other treatments were reduced.Biochar combined with controlled-release fertilizer and stabilized fertilizer showed a significant reduction in runoff losses of N,which greatly lowered the risk of N nonpoint source pollution from paddy fields. |
PDF Full Text Request