不同吸附特性的稻草生物炭对稻田氨挥发和水稻产量的影响

Effects of rice straw biochar with different adsorption characteristics on ammonia volatilization from paddy field and rice yield

秸秆生物炭具有改善土壤生态环境、土壤蓄水保肥和减少温室气体排放等正效应,但其石灰效应会加大稻田氨挥发损失。为充分发挥生物炭吸铵特性,降低其石灰效应的不利影响,对不同热解温度(300、500、700℃)和酸化水平(pH值=5、7、9)稻草生物炭处理下的田面水NH4+-N浓度、氨挥发和水稻产量进行了研究。结果表明:偏酸性(pH值=5)、中性(pH值=7)生物炭处理在基肥期和分蘖肥期均能显著降低田面水NH4+-N峰值浓度(P<0.05),降幅达16.90%~35.60%。全生育期稻田氨挥发损失占施氮量的15.14%~26.05%(2019年)、15.10%~19.00%(2020年)。稻田增施热解温度为700℃、酸化水平为5(pH值=5)的生物炭(C700P5)降氨效果最好,两年氨挥发分别显著降低22.93%、12.61%(P<0.05)。高温热解配合偏酸性、中性生物炭(C700P5、C700P7)增产效果显著,增产率达9.92%~13.50%,结构方程模型表明,其增产原因是生物炭酸化处理降低了稻草生物炭的石灰效应,而热解温度调整提高了生物炭阳离子交换量(Cation Exchange Capacity,CEC),进而降低了田面水NH4+-N浓度和氨挥发损失,最终提高了水稻地上部氮素积累和水稻产量。研究可揭示不同热解温度和酸化水平制备的生物炭在稻田中的应用潜力,并为稻田合理施用生物炭和减少化肥施用量提供理论依据。

Straw biochar has various positive effects on soil ecology and environment improvement,soil water and fertilizer conservation,and reduction of greenhouse gas emission.But the release of carbonate from some calcium carbonate(lime)can increase pH and hence ammonia(NH3)volatilization in paddy fields.In this study,a two-year potted experiment with a completely randomized design was conducted using different biochar for better ammonium absorption while less impact of lime.The japonica rice(Oryza sativa L.cv.Da Li Nuo)and biochar deriving from rice straw were taken as the research objects.Three pyrolysis temperatures(300,500,and 700℃)and three levels of acidification(5,7,and 9)were selected in the experiment.Prior to the test,the surface soil in the rice field was sampled and then air-dried.Biochar and basal fertilizer were applied one day before transplanting.The concentration of ammonium nitrogen in surface water,ammonia volatilization loss from a paddy field,and rice grain yield were measured under different biochar treatments during two rice growing seasons.The results showed that the ammonia volatilization loss ranged from 30.27 to 52.1 kg/hm2(2019),and 30.20 to 38.00 kg/hm2(2020)in the rice fields during rice growing stages,accounting for 15.14%-26.05%of N application rate(2019),and 15.1%-19.0%(2020).High temperature pyrolysis with acid and neutral straw biochar significantly reduced the volatilization loss.Biochar at pyrolysis temperature of 700℃,acidification level 5(C700P5)presented the best performance of ammonia reduction,where the ammonia volatilization was significantly reduced by 22.93%and 12.61%in 2019 and 2020,respectively.The variation trend of NH4+-N concentration in field water was consistent with that of NH4+-N volatilization flux.The peak NH4+-N concentration in surface water decreased by 16.90%-35.60%in the basal and tillering stages with acidic and neutral straw biochar.The acidic and neutral rice straw biochar significantly increased the rice aboveground N accumulation by 9.10%-24.84%at three pyrolysis temperatures.High temperature pyrolysis combined with acid and neutral biochar(C700P5,C700P7)presented a significant yield increase,where the yield increase rate was 9.92%-13.50%.The structural equation showed that there were positive and negative effects of biochar pH value and Cation Exchange Capacity(CEC)on ammonia volatilization,whereas,together with an obvious lime effect.But the obvious adsorption was to inhibit ammonia volatilization.In addition,the ammonia volatilization in the paddy field was significantly correlated with NH4+-N concentration in surface water.The effect of biochar on ammonia volatilization was also described in the regulation on NH4+-N concentration in surface water.The combination of neutral and acid improvement with high temperature pyrolysis biochar(C700P5,C700P7)increased production,because both ammonia volatilization and nitrogen loss reduced significantly,particularly providing for more sufficient nutrients for the growth of rice.This finding can offer the potential application of biochar at different pyrolysis temperatures and acidification levels in rice fields.