不同温度制备的棉花秸秆生物碳对棉花生长及氮肥利用率(15N)的影响

李 琦， 马 莉， 赵 跃， 王得平， 侯振安

(石河子大学农学院资源与环境科学系，新疆石河子 832003)

不同温度制备的棉花秸秆生物碳对棉花生长及氮肥利用率(15N)的影响

李 琦， 马 莉， 赵 跃， 王得平， 侯振安*

(石河子大学农学院资源与环境科学系，新疆石河子 832003)

【目的】生物碳可提高土壤肥力，增强土壤对养分的保持能力，减少养分损失，提高肥料利用率。研究不同温度热解制备的生物碳对棉花生长和肥料利用率的差异，可以为提高生物碳的有效利用提供依据。【方法】 供试生物碳由棉花秸秆分别在450℃、600℃和750℃高温限氧条件下热解制备而成。本试验为两因素(生物碳、氮)温室盆栽试验， 生物碳处理包括3种不同热解温度生物碳处理(分别以450BC、600BC、750BC表示)和1个空白对照(CK)； 每个生物碳土壤设置3个施氮水平0、 2.1和4.2 g/pot(分别以N0、N1、N2表示)，用15N同位素示踪方法分析不同施氮水平下3种热解温度生物碳对棉花生长、15N回收和淋洗损失的影响。【结果】1)施用3种生物碳处理棉花干物质重总体表现为750BC>600BC、450BC>CK，450BC、600BC和750BC处理分别较对照平均增加了9.2%、12.6%和17.3%；并且棉花总干物质重随施氮量的增加而增加，但生物碳作用随之降低; 2)3种生物碳处理棉花氮素吸收总量总体也表现为750BC > 600BC、450BC > CK。不施氮肥条件下(N0)，600BC和750BC处理棉花氮素吸收总量显著高于CK，但450BC处理与与CK无显著差异；施氮肥条件下(N1、N2)，3种生物碳处理均显著高于CK，450BC、600BC和750BC处理棉花氮素吸收总量平均较CK分别增加29.5%、37.1%和48.8%; 3)15N标记试验结果表明， 450BC、600BC和750BC处理植株15N回收率显著高于对照，分别较CK平均提高27.46%、36.44%和42.87%。而N1和N2水平下3种生物碳处理之间植株15N回收率均没有显著差异; 4)450BC、600BC和750BC处理土壤15N残留率分别较对照平均增加101.4%、147.3%和200.7%。土壤15N残留率在N1水平下随着生物碳热解温度的升高而增加，而在N2水平下750BC处理显著高于450BC和600BC处理，但是后二者之间没有显著差异。土壤15N残留率随着施氮量的增加而降低; 5)施用生物碳可以显著降低土壤15N的淋洗，并且不同施氮水平下(N1、N2)淋洗率都随着生物碳热解温度的升高而降低。【结论】施用生物碳可促进棉花生长，增加棉花氮素吸收，提高氮肥利用率，降低氮素损失，并且生物碳的热解温度越高效果越明显；但是随着氮肥施用量的增加生物碳作用减弱。

生物碳； 制备温度； 棉花； 氮素吸收； 氮肥利用率

农田氮肥的损失途径主要有氨挥发、硝化-反硝化、淋洗和径流，其损失量分别占总施氮量的11%、17%、3%和8%左右[6]。施用有机肥以及秸秆还田等是减少氮肥损失，提高氮肥利用率的主要措施之一。研究表明，秸秆还田可以增加土壤有机质和表层土壤有机氮含量[7]，提高土壤潜在氮素矿化势[8]，减少氮肥损失和提高氮素利用率[9]。近年来，将农田废弃物(如秸秆)制成生物碳还田被认为是土壤增汇减排的一种关键途径[10]。生物碳是生物体在完全或部分缺氧的情况下高温热解的产物，有机碳含量高且稳定性强。生物碳具有丰富的孔隙结构，巨大的表面积和吸附能力。研究表明，生物碳和化学肥料配施可以降低氮素损失，提高氮肥的利用率[11-12]。但是制备原料和温度的不同，使得生物碳对氮素的吸附也有很大差异。Yao等[13]研究了四种原料在3种温度下制备的生物碳对氮素的吸附，发现不同类型生物碳对铵氮的吸附量从1.8%到15.7%不等，并且在相同温度(600℃)下四种不同原料的生物碳对硝氮的吸附量也有非常大的差异。Kameyama等[14]研究发现,700℃以上制成的生物碳才出现对硝态氮的吸附现象。

棉花是新疆的主要经济作物，棉花秸秆资源丰富，在农业生产中通常采用直接还田利用的方式。对于棉花秸秆生物碳对氮肥利用率影响的研究还鲜见报道。本研究以棉花秸秆为原料，在不同热解温度下制备生物碳。采用15N同位素示踪法，研究不同热解温度生物碳和氮肥用量对棉花生长和氮肥利用率的影响，为生物碳的合理利用和提高氮肥利用率提供理论依据。

1 材料与方法

1.1 试验材料

试验于2011年在新疆石河子大学农学院试验站温室进行。供试土壤采自石河子大学农学院试验站农田，采样深度为0—20 cm耕层。土壤类型为灌耕灰漠土，质地为壤土，pH 7.8，有机质12.43 g/kg，全氮0.78 g/kg，碱解氮34.3 mg/kg，速效磷22.51 mg/kg，速效钾239.8 mg/kg。棉花秸秆采自当地棉田，烘干粉碎后用于制备生物碳。分别在450°C、600°C和750°C下厌氧热解6 h后制得3种生物碳(表1)。供试棉花品种为新陆早33号。

表1 供试生物碳的养分含量

1.2 试验设计

试验采用生物碳和施氮量两因素设计，生物碳类型设3个处理：(1)450℃生物碳(450BC)；(2)600℃生物碳(600BC)；(3)750℃生物碳(750BC)；并以空白土壤作对照(CK)。施氮(N)量设3个水平为0、2.1、4.2 g/pot(分别记为N0、N1、N2)。随机区组设计，12个处理，每个处理重复3次，共36个土柱。生物碳的施用量为1%(占干土重)，在装土前与供试土壤混匀后一次性施入。氮肥使用15N同位素标记尿素(15N丰度为10%)，全部作追肥。

1.3 测定指标及方法

试验结束后将棉花植株自基部剪下用去离子水洗净后分成叶、茎、铃壳(含花蕾)三部分。将以上棉花各部分烘干称重,粉碎后测定其全氮和15N丰度。土壤和植物全氮采用开氏定氮法[15]，土壤和植物15N丰度采用稳定性同位素质谱仪进行测定[16]。土壤有机质用重铬酸钾容量法—外加热法，碱解氮采用碱解扩散法测定[15]，速效钾采用1 mol/L NH4Ac浸提—火焰光度法测定[15]，速效磷采用0.5 mol/L NaHCO3浸提—钼锑抗比色法测定[15]。

1.4 数据处理

数据通过SPSS 16.0进行施氮量和生物碳类型的两因素方差分析。不同处理间的多重比较分析采用Duncan法(P<0.05)。

2 结果与分析

2.1 棉花干物质积累

随着施氮量的增加，棉花植株各器官(茎、叶、蕾铃)干物质重均显著增加(表2)。施用生物碳对棉花茎、叶干物质重的影响不显著(P>0.05)，而对蕾铃干物质重的影响在不同氮水平下存在差异。在N0和N1水平下，生物碳处理棉花蕾铃干物质重均显著高于CK，但三种生物碳之间差异不显著；N2水平下，750℃生物碳(750BC)蕾铃干重最高，而600℃生物碳(600BC)和450℃生物碳(450BC)处理与对照(CK)均无明显差异。

施氮量和生物碳处理对棉花植株总干物质重影响显著，但二者交互作用的影响不显著。棉花总干物质重随施氮量显著增加，N1和N2水平下棉花植株总干物质重平均较N0分别高59.8%和73.9%。不同生物碳处理棉花植株总干物质重表现为750BC > 600BC、450BC > CK，施用生物碳处理450BC、600BC和750BC棉花总干物质重平均(三个氮水平下)较CK分别增加9.2%、12.6%和17.3%。

表2 不同处理棉花植株干物质重(g/pot)

注(Note): 同列数据后不同字母表示处理间差异达到5%显著性水平 Different lowercase letters within a column mean significant differences at the 5% level; **表示在1%水平下达到显著，ns表示不显著 Indicate significant differences at the 1% probability levels and ns indicate no difference.

2.2 棉花氮素吸收量

施氮量对棉花氮素吸收的影响与棉花干物质重相似，均表现为棉花植株各器官及氮素吸收总量随施氮量增加显著增加(表3)。不同施氮水平下(N0、N1、N2)，施用生物碳都可以提高棉花茎、叶和蕾铃的氮素吸收量，尤其在蕾铃上效果更加明显。三种生物碳450BC、600BC和750BC处理棉花蕾铃氮素吸收量分别比CK增加了59.8%、64.5%和104.8%。

不同生物碳处理棉花氮素吸收总量为750BC > 600BC、450BC > CK。施氮水平和生物碳处理对棉花氮素吸收总量的交互作用影响表现为：不施氮肥条件下(N0)，450BC处理与CK差异不显著；600BC和750BC处理显著高于CK。施氮肥条件下(N1、N2)，三种生物碳处理均显著高于CK，450BC、600BC和750BC处理棉花氮素吸收总量平均较CK分别增加29.5%、37.1%和48.8%。

2.315N棉花植株回收率

表3 不同处理棉花植株氮素吸收量(g/pot)

注(Note): 同列数据后不同字母表示处理间差异达5%显著性水平 Different lowercase letters within a column mean significant differences at the 5% level；*，**分别表示在5%、 1%水平下达到显著，ns表示不显著 Asterisks indicate significant differences at the 0.05(*) and 0.01(**) probability levels, and ns indicate no difference.

图1 不同处理的棉花植株15N回收率Fig.1 15N recovered by cotton plants in different treatments [注(Note): 柱上不同字母表示处理间在P<0.05水平差异显著 Different letters above the bars indicate a significant difference among treatments at P< 0.05 level.]

2.415N在土壤中的残留率和淋洗率

图2 不同处理氮肥(15N)在土壤中残留率和淋洗率Fig.2 15N fertilizer residual in the soil and leaching loss in the treatments with biochar type and N rate [注(Note): 柱上不同字母表示处理间在P<0.05水平差异显著 Different letters above the bars indicate a significant difference among treatments at P< 0.05 level.]

3 讨论

生物碳是有机体在高温限氧条件下热解得到的产物，不同的制备原料和热解温度使得生物碳的性质有所不同。目前研究认为生物碳中养分元素和金属元素含量主要受制备原料影响[17]，而热解温度主要影响可挥发性物质的含量[18]。本试验中生物碳以棉花秸秆为原料，在三种温度(450、600、750℃)下热解得到。所得生物碳全磷、全钾和有机碳含量随热解温度升高而增加，全氮含量随热解温度升高而降低，这与Rajkovich等[19]的结果一致。

生物碳作为一种土壤改良剂，施入土壤后有利于改善土壤物理化学性质，固持土壤养分，提高养分利用率，改善微生物环境，从而对提高土壤肥力和增加作物产量也有积极的作用[20-21]。本研究结果表明，施用生物碳和氮肥无论是对棉花总干重还是棉花植株的氮素吸收量都有显著影响。施用生物碳可以显著提高棉花总干物质重和氮素吸收总量，分别较对照平均提高了14.3%和44.9%。目前多数研究结果也表明，施用生物碳可以显著提高作物产量[22]；Zwieten等[23]也发现施用生物碳可以显著提高棉花氮素吸收量。本试验还发现生物碳热解温度越高，棉花总干物质重和氮素吸收总量提高越明显。750BC处理下棉花总干物质重和氮素吸收总量分别较对照平均提高17.3%和48.8%。Rajkovich等[19]以四种热解温度(300、400、500、600℃)下制得的生物碳为材料也做了相关研究，结果表明500℃下制得的生物碳促进玉米生长的效果最好，这与本试验结果略有差异，可能与制备生物碳原料有关。本试验中随着施氮量的增加，生物碳对棉花总干物质重和氮素吸收量的增加作用降低，但高氮肥用量(N2)配施生物碳处理棉花的干物质重和氮素吸收量最大。以上结果可能是由于在不施氮肥下，施加生物碳提高了土壤有机碳含量，增强了土壤对养分的吸附能力，增加了土壤肥力，从而促进棉花生长；生物碳与高施氮量(N2)配施(C/N约为30%)比生物碳与低施氮量(N1)配施(C/N约为60%)更接近于作物生长的土壤C/N比25 ∶1，减少了微生物和棉花对氮的竞争，从而提高了产量。刘玉学[24]大田试验研究表明，在不施用尿素下，添加1%的水稻秸秆碳可以提高水稻产量19.9%，在添加尿素下水稻产量提高11.2%，这与本研究结果相符，增加氮肥用量，生物碳增产幅度降低。

4 结论

土壤中施用生物碳可以显著提高棉花的总干物质重和氮素吸收总量，并且生物碳热解温度越高， 效果越明显。生物碳提高了棉花植株的15N回收率和土壤中15N的残留率，但是不同热解温度的生物碳之间没有显著差异。生物碳减少了15N的淋洗率，并且生物碳热解温度越高其作用越明显。随着施氮量增加，生物碳促进棉花生长和提高氮肥利用率的作用降低，并且不同生物碳之间差异减小。因此，生物碳具有促进棉花生长、减少氮素损失和提高氮肥利用率的作用，并且生物碳热解温度越高效果越好；生物碳合理配施氮肥有助于生物碳作用的体现，也有利于促进作物生长和提高氮肥利用率。

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Growth and15N use efficiency in cotton affected by biochar made in different temperatures

LI Qi, MA Li, ZHAO Yue, WANG De-ping, HOU Zhen-an*

(DepartmentofResourcesandEnvironmentalScience,ShiheziUniversity,Shihezi832003,Xinjiang,China)

【Objectives】 Biochar are found having efficacy of retaining ions and reducing nutrient loss when applied into soils. The differences of their beneficial effects of biochar made in different temperatures were studied to provide a base for efficient biochar manufacture and reasonable use in cotton production. And the effect of three N fertilizer rates on cotton growth, N use efficiency and N leaching was studied using15N tracer techniques. 【Methods】 Cotton straw was thermodynamic decomposed to make biochar at 450℃(450BC), 600℃(600BC) and 750℃(750BC), respectively. A two-factor pot experiment was designed using the three kinds of biochar and three levels of nitrogen. The three kinds of biochar recorded as 450BC, 600BC and 750BC, with no biochar addition as control(CK). In each kind of biochar treatment, three levels of15N labeled nitrogen fertilizer: 0(N0), 2.1(N1) and 4.2 g/pot(N2) were added. The biomass and yield of cotton and the N use efficiency were measured. 【Results】 1) The cotton dry weights were generally increased in order of 750BC>600BC、450BC > CK，the increase in cotton dry weights was averaged 9.2% in the 450BC treatments, 12.6% in 600BC treatments and 17.3% in the 750BC treatments. The cotton dry weights increased with the increased rate of N application. 2) The N uptake in cotton was generally increased，and the increase in the 750BC treatments was higher than in 600BC treatments, and also higher than in 450BC treatments regardless of the N application rates. When the N rate was N0, the nitrogen uptakes in the cotton in both the 750BC and the 600BC treatments were significantly higher than in CK，not significantly higher than in 450BC treatment. The input of N increased the N uptake in cotton in all the biochar treatments. The biochar addition averagely increased the N uptake by 29.5% in 450BC treatments, 37.1% in 600BC treatments, and 48.8% in 750BC treatments，respectively. 3) The15N tracer data showed that compared with the CK treatment, plant15N recovery in the 450BC treatment increased by 27.46% and plant15N recovery in the 600BC treatment increased by 36.44%, and plant15N recovery in the 750BC treatment increased by 42.87%. But in two N rates(N1, N2), there were no significant difference among the three biochar treatments. 4) Soil15N recovery in the 450BC treatment increased by 101.4%, and 147.3% in the 600BC treatment, and 200.7% in the 750BC treatment relative to the CK treatment. In case of lower N rates(N1), soil15N recovery increased as the biochar pyrolysis temperature increased. In N2 treatments, the soil15N recovery in the 750BC was significantly higher than in both the 450BC and the 600BC treatments, but the difference between the 600BC treatment and the 450BC treatment was not significant. Soil15N recovery decreased as N application rate increased in all three biochar amended treatments. 5) The15N leaching in the biochar amended treatments was significantly lower than that in the CK treatment. Furthermore,15N leaching decreased as the biochar pyrolysis temperature increased. 【Conclusions】 The beneficial effects of biochar increase as the pyrolysis temperature increased, and decrease as the N application rate increased. Therefore, cotton straws are recommended to be treated at high temperature, and the N input should be reduced for the maximum positive effects of biochar on crop growth and N use efficiency.

biochar; preparation temperature; cotton; nitrogen uptake; nitrogen use efficiency

2014-03-05 接受日期： 2014-09-16 网络出版日期: 2015-02-13

国家自然科学基金(31160415)；新疆生产建设兵团杰出青年创新资金专项(2014CD002)资助。

李琦(1989—)，男，陕西汉中人，硕士研究生，主要从事农业资源高效利用的研究。E-mail：liqi472560420@163.com * 通信作者 E-mail：hzatyl@163.com

S156.2

A

1008-505X(2015)03-0600-08