生物炭对植烟土壤氮素形态迁移及微生物量氮的影响

为了在植烟土壤中施加生物炭,以及在不同氮素水平下验证生物炭对土壤氮素的淋洗及迁移的影响.采用大田试验,设计5个处理,在磷肥和钾肥施用量相同的基础上,除对照(CK)处理不施生物炭与氮肥外,其余4个处理都添加1 600 kg/hm2的生物炭,施氮量分别为(N0)0、(N1)37.5、(N2)52.5和(N3) 67.5 kg/hm2,对植烟土壤氮素在0～20、20 ～ 40和40 ～ 60 cm土层施加生物炭,研究全氮、碱解氮、硝态氮和铵态氮质量分数的影响及其迁移规律,以及0～20cm土层微生物量氮的变化特征.结果表明:植烟土壤施用生物炭降低了0～ 20 cm以下土壤氮素质量分数,提高了植烟土壤对氮素的固定能力.与CK相比,增施生物炭的N0在0～20 cm以下土层,土壤全氮、碱解氮、硝态氮和铵态氮质量分数降低率最高达到11.21％、49.07％、42.29％和31.35％.而施氮量对植烟土壤全氮、碱解氮和铵态氮的影响,主要集中在0 ～ 20 em土层,且土壤氮素质量分数随施氮量的增加而增加,以N3处理各氮素指标质量分数相对最高,其全氮、碱解氮和铵态氮质量分数最高分别为2.10 g/kg、261.86 mg/kg和49.80 mg/kg.土壤硝态氮质量分数随土层加深而下降,在0 ～ 20 cm土层,以N3处理最高,达264.90 mg/kg;但不同氮水平下,硝态氮质量分数在20 ～ 40 cm土层差异较其他土层更显著.施用氮肥对植烟土壤氮素的影响主要表现在烟草移栽后前30 d.增施生物炭可以提高烟草移栽后60 d时土壤微生物量氮;而施氮量对微生物量氮熵的影响主要表现在烟草移栽30 d之后.施氮量对植烟土壤氮素的影响主要表现在0～20 cm土层,且在烟草生育前期效果显著.生物炭可以明显抑制植烟土壤本身及低量氮肥施用下氮素淋失迁移,但在高量氮肥施用下的抑制作用不明显.在豫中烟区,以生物炭配施氮肥67.5 kg/hm2施肥措施,最利于植烟土壤氮素提高.

Effects of biochar on nitrogen transformation and the microbial biomass nitrogen under different nitrogen application rates

[Background]This paper studies the effect of applied biochar on the nitrogen (N) transformation under different N levels in the tobacco-planting soil,because the C/N ratio in the soil for continuous planting tobacco in Henan province is not balanced,resulting in the tobacco quality reduced.[Methods] The field experiment was carried out with different N levels under the biochar application;it is located in Daguo town of Linying County,Henan province (El13°81′,N33°79′).Five treatments were set as:1) no N no biochar (CK);the other four applied with 1 600 kg/hm2 biochar,with four N levels:2) 0kg/hm2(N0);3) 37.5 kg/hm2(N1);4) 52.5 kg/hm2(N2);5) 67.5 kg/hm2(N3).Based on the five sample points,the total N (TN),available N (AN),nitrate N (NO3--N) and ammonium N (NH4+-N) in three soil layers (i.e.0-20 cm,20-40 cm,and 40-60 cm) as well as the soil microorganism biomass N (SMBN) in 0-20 cm soil layer were measured and analyzed.[Results] The biochar application reduced the N content in the deep layer,which indicated that it elevated N sequestration in top soil layer.Compared with the CK,the decrement of TN,AN,NO3--N,and NH4+-N content was 11.21％,49.07％,42.29％ and 31.35％,respectively under the no treatment.The AN,NO3--N,and NH4+-N content mainly existed in 0-20 cm soil layer,and all of them increased with N application rate.The highest content of TN,AN,NH4+-N occurred under N3 treatment,which was 2.10 g/kg,261.86 g/kg,264.90 mg/kg,and 49.80 mg/kg,respectively.While the NO3--N content reduced with the soil layer increased,and it concentrated in 0-20 cm layer with the highest level as 264.90 mg/kg in N3 treatment.Moreover,the NO3--N content in 20-40 cm soil layer was significantly different from that of other soil layer under different N level.The effect of N application rate on its transformation presented before 30 d after the tobacco transplanted.The biochar application increased the SMBN after tobacco transplanted 60 d,while the effect of the amount of N fertilizer on the microbial biomass nitrogen entropy was mainly reflected after tobacco transplanted 30 d.[Conclusions] The effect of N application rate on soil N content mainly in 0-20 cm soil layer,and it was significantly affected during the early stage of tobacco growth.The biochar restrained the N transformation in soil with lower N application rate,but with little effect under higher N application rate.It is suggested that the biochar combined with 67.5 kg/km2 N application is the optimal practice to improve soil N content in central area of Henan province.