淋溶条件下生物质炭对红壤中钾和磷含量及其淋出率的影响

朱盼， 应介官， 彭抒昂， 姜存仓*　

(1.华中农业大学资源与环境学院，武汉 430070；2.华中农业大学园艺与林学学院，武汉 430070)



淋溶条件下生物质炭对红壤中钾和磷含量及其淋出率的影响

朱盼1， 应介官1， 彭抒昂2， 姜存仓1*

(1.华中农业大学资源与环境学院，武汉 430070；2.华中农业大学园艺与林学学院，武汉 430070)

采用室内模拟降水的方法，在未施肥红壤和施肥红壤中添加不同用量的生物质炭(0%、1%、2%和3%)，分析在淋溶条件下生物质炭对土壤速效钾、速效磷含量及其淋出量的影响。结果表明：随着生物质炭用量的增加，红壤中速效钾和速效磷含量均显著提高，但淋洗液中总钾量和总磷量并没有显著增加；在未施肥土壤中，0%、1%、2%和3%生物质炭处理的钾淋出率分别为53.6%、14.3%、9.1%和7.5%，磷淋出率分别为88.8%、23.5%、16.3%和7.8%；在施肥土壤中，磷的淋出率随生物质炭用量的增加而减少，由24.1%降至7.2%；而钾淋出率受生物质炭用量的影响相对较小。在淋溶条件下，添加3%生物质炭可使未施肥土壤速效钾降幅由9.8%减少至0.3%，使施肥土壤速效钾降幅由10.8%减少至0.5%，但经生物质炭处理的未施肥和施肥土壤的速效磷含量在淋溶后下降更为明显。上述结果表明，生物质炭不仅能使土壤中速效钾和速效磷含量提高，且生物质炭有较强的养分保持能力，能够减少土壤中钾和磷的淋出率。

生物质炭； 红壤； 淋溶； 钾； 磷

Summary Phosphorus (P) and potassium (K) are the major essential macronutrients required for the biological growth and development of crop. As the mineral resource reserve declined for both P and K, the increasing demand for phosphorus-potassium fertilizer from global food production caused imbalance between supply and demand. As a result, the cost of agricultural production increased, and economic benefits reduced, along with increasing environmental risks. In China, synchronization between rainfall and temperature is common in red soil area, with strong soil leaching, and phosphorus and potassium nutrients are easy to lose, thus excessive application of fertilizer is necessary. Therefore, investigation on improvement of use efficiency and reduction of leaching rate for K and P will have great economic significance on agricultural production, help maintaining good ecological function.

In this study, to investigate the effects of different biochar additions on available potassium and phosphorus and their leaching rates in red soil, a simulated rainfall experiment was conducted in laboratory. Biochar was prepared from peanut shell. Different biochar dosages (0%, 1%, 2% and 3%) were added to fertilization and non-fertilization soils, and the contents and leaching variation of available K and P were further analyzed to measure the influence of biochar on soil K and P availabilities and their leaching loss.

The results showed that the available K and P in red soil were substantially improved with increasing addition of biochar, but the total amount of K and P increased little in the leachate. Among the non-fertilization treatments, the leaching rates of K were 53.6%, 14.3%, 9.1% and 7.5%, and the leaching rates of P were 88.8%, 23.5%, 16.3% and 7.8%, for different biochar additions (0%, 1%, 2% and 3%), respectively. Among the fertilization soil treatments, the leaching rate of P decreased from 24.1% to 7.2% with the biochar addition; while the leaching rate of K was less affected by the biochar addition. Under the simulated leaching condition, the 3% biochar addition could reduce the leaching rate of available K from 9.8% to 0.3% for non-fertilization soil, and from 10.8% to 0.5% for fertilization soil. The influence of biochar on K leaching was associated with the leaching time. In the first ten days, the K leaching induced by biochar application increased in the order of 3% > 2% > 1%>0%, and the order was opposite after the 10th day. However, biochar had no significant effects on the P leaching with different rates, and the available P contents declined for both non-fertilization and fertilization soils under the simulated leaching condition.

It is concluded that biochar addition can increase the contents of available P and K in red soil. Under the simulated leaching condition, biochar also can maintain soil available K in higher level, and it is propitious to decline the leaching rate of K and P in red soil.

磷和钾是作物生长必需的大量元素，其含量高低对作物生长和产量有直接影响。随着这2种矿质资源储量的减少以及全球粮食生产对磷钾肥需求的增加，导致供需矛盾日益加剧，使农业生产成本提高，经济效益降低，并增加了环境风险。我国红壤地区雨热同季，淋溶作用强烈，土壤磷钾等养分易流失，需要大量化肥投入；因此，提高磷钾的利用效率和减少其淋失，对于农业生产有重要的经济意义，并有助于保持良好的生态效应。

由生物残留物在高温、缺氧条件下热解产生的生物质炭，对土壤体积质量(容重)、团粒结构和持水性等物理性质具有较好的改良效果[1-2]，同时，能够提高土壤pH、阳离子交换量和土壤养分含量等[3-4]。生物质炭是一种良好的土壤改良剂，可显著提高土壤肥力和作物产量[5-6]。自20世纪60年代起，研究发现秸秆生物质炭具有强吸附能力，可以有效吸附除草剂非草隆，降低其生物有效性[7]；骨炭对土壤重金属也有良好的吸附效果，能够降低其生物有效性[8]。近年来，生物质炭对土壤养分持留效应的研究也取得了不少成果。CLOUGH等[9]报道称生物质炭保持养分的能力比有机质更强。周志红等[10]研究表明，施用10 t/hm2生物质炭增加了紫色土中氮的淋失，而施用100 t/hm2生物质炭减少了氮的淋失。也有研究表明，生物质炭增加了砂土的氮淋失，减少了粉砂土的氮淋失[11]。NOVAK等[12]发现，添加生物质炭增加了土壤钾的淋失量。此外，生物质炭还可影响土壤中磷的吸附和解吸[13]，以及磷的固定[11]。综上，利用生物质炭改良土壤理化性状以及保肥保水等方面已做了较多的研究，而有关淋溶条件下生物质炭对红壤中有效养分及淋洗液中养分的实际变化影响仍不是十分清楚。为此，本试验通过探讨淋溶条件下生物质炭对红壤速效钾、速效磷及其淋出量的影响，以期为生物质炭改良土壤和改善生态状况提供科学依据。

1　材料与方法

1.1试验材料

试验用红壤取自江西省赣州市，黏性较强(砂粒12%，粉粒60%，黏粒28%)，含速效钾26.6 mg/kg、速效磷0.8 mg/kg、碱解氮20.1 mg/kg、有机质5.4 g/kg，pH 4.55。生物质炭以花生壳为原料制备，热解温度300 ℃，其养分组成为全钾8.5 g/kg、全磷2.6 g/kg、全氮18.8 g/kg、全碳400.9 g/kg，pH 8.49。

1.2试验设计

对试验红壤进行未施肥和施肥处理，并分别设4个生物质炭水平(0%、1%、2%和3%)，共8个处理：未施肥+0%生物质炭(CK：未施肥)，未施肥+1%生物质炭(C1)，未施肥+2%生物质炭(C2)，未施肥+3%生物质炭(C3)；施肥+0%生物质炭(F：施肥)，施肥+1%生物质炭(FC1)，施肥+2%生物质炭(FC2)，施肥+3%生物质炭(FC3)。每处理4次重复。每千克土施用0.14 g KH2PO4，0.51 g KNO3，0.80 g NH4NO3和0.95 g Ca(NO3)2。把过20目筛的生物质炭和土壤混匀，装入底部带孔并铺有双层滤纸的聚氯乙烯杯(r=25 mm)中，摇匀，压实；缓慢注水，土壤水分达到饱和后停止加水；2 d后加入相当于20 mm降水量的蒸馏水，收集淋洗液；此后每2 d加水1次，试验期间共加水9次，累计加水量180 mm，相当于江西省赣州市当地6月份的降水量[14]。

1.3样品采集与测定

将收集的淋洗液离心、冷冻保存。试验结束后，将土样风干至恒量，碾碎后分别过20目和100目筛。样品测定参照鲍士旦的《土壤农化分析》[15]。用火焰光度法测定土壤速效钾和淋洗液中水溶性钾含量；用钼锑抗比色法测定土壤速效磷含量；用过硫酸钾消解-钼蓝比色法测定淋洗液中水溶性磷含量。

qi=ci·Vi/m，

Q=q1+q2+…+qn，

淋出率=Q/Y。式中：qi为1 kg土壤在第i天的淋出量，mg/kg；ci为第i天淋洗液中钾(磷)的质量浓度，μg/mL；Vi为第i天淋洗液体积，mL；m为每个处理的土壤质量，kg；Q为1 kg土壤n天的淋出总量，mg/kg；n为取样时间；Y为1 kg土壤的速效钾(磷)质量分数，mg/kg。

1.4数据分析

采用Excel 2010进行数据整理和t检验(P<0.05)，用SPSS 20.0进行单因素方差分析和相关分析，不同处理间的对比采用邓肯新复极差法。

2　结果与分析

2.1生物质炭对土壤淋洗液中钾和磷的动态影响

生物质炭对淋洗液中钾含量的动态变化有较大影响(图1)。在淋溶的前10 d，淋洗液中的钾含量随着生物质炭用量的增加而增加；与未施肥土壤相比，生物质炭对施肥土壤钾淋洗的影响更为明显，FC3处理的钾淋出量比F处理高2.18～3.92 mg/kg。然而，淋溶10 d后生物质炭处理的淋洗液中钾含量比对照少，且随着淋溶时间的延长，不同生物质炭处理间的差异减少。

CK：未施肥+0%生物质炭；C1：未施肥+1%生物质炭；C2：未施肥+2%生物质炭；C3：未施肥+3%生物质炭；F：施肥+0%生物质炭；FC1：施肥+1%生物质炭；FC2：施肥+2%生物质炭；FC3：施肥+3%生物质炭。CK: Non-fertilization+0% biochar; C1: Non-fertilization+1% biochar; C2: Non-fertilization+2% biochar; C3: Non-fertilization+3% biochar; F: Fertilization+0% biochar; FC1: Fertilization+1% biochar; FC2: Fertilization+2% biochar; FC3: Fertilization+3% biochar.图1　在不同处理下土壤淋洗液中钾含量的变化动态Fig.1　Variation dynamic of potassium contents in soil leacheate under different treatments

由图2可知：在淋溶的前10 d内，添加生物质炭对未施肥和施肥土壤淋洗液的磷含量没有明显影响；磷的淋失峰值均出现在第10天后。说明添加生物质炭延缓了土壤磷的淋出时间。

各处理符号表示的含义详见图1注。Please see footnote of Fig.1 for details of each treatment.图2　在不同处理下土壤淋洗液中磷含量的变化动态Fig.2　Variation dynamic of phosphorus contents in soil leacheate under different treatments

2.2生物质炭对土壤-淋洗液体系中速效钾和速效磷的影响

在淋溶条件下，生物质炭对未施肥土壤和施肥土壤中速效钾的影响有所差异(表1)。在相同的生物质炭施用量条件下，淋溶后施肥土壤比未施肥土壤的速效钾含量下降更为明显。从表1可以看出：添加生物质炭使土壤中速效钾含量大幅度增加；未施肥土壤的速效钾含量在淋溶前后均没有出现明显的下降，随着生物质炭用量的增加其速效钾的下降幅度反而有所减少；施肥土壤淋溶后，F、FC1、FC2和FC3处理的速效钾含量下降了10.8%、19.8%、12.9%和0.5%，即当用量达到一定水平时，生物质炭也可减少淋溶条件下施肥红壤中速效钾的下降幅度；添加生物质炭还有效地降低了未施肥土壤中速效钾的淋出率，CK、C1、C2和C3处理的速效钾淋出率依次为53.6%、14.3%、9.1%和7.5%。

表1　土壤-淋洗液体系中速效钾的变化

各处理符号表示的含义详见图1注。同列数据后的不同小写字母表示在P<0.05水平差异有统计学意义.

Please see footnote of Fig.1 for details of each treatment. The values within a column followed by different lowercase letters show statistically significant differences at the 0.05 probability level.

从表2可以看出：未添加生物质炭处理的未施肥(CK)和施肥(F)土壤淋溶后速效磷含量均有所下降，两者降幅分别为14.3%和5.0%；添加生物质炭后，未施肥和施肥土壤淋溶后的速效磷含量下降加剧，其中，C1、C2和C3处理的速效磷含量分别下降了36.6%、50.3%和45.1%，FC1、FC2和FC3处理的速效磷含量分别下降了15.2%、28.5%和28.8%；然而，添加生物质炭处理明显降低了土壤速效磷的淋出率，当施用3%生物质炭时，C3处理和FC3处理中速效磷的淋出率分别下降至7.8%和7.2%。

表2　土壤-淋洗液体系中速效磷的变化

各处理符号表示的含义详见图1注。同列数据后的不同小写字母表示在P<0.05水平差异有统计学意义.

Please see footnote of Fig.1 for details of each treatment. The values within a column followed by different lowercase letters show statistically significant differences at the 0.05 probability level.

3　讨论

3.1降水对土壤-淋洗液体系中钾的影响

土壤中的钾易因降水而淋失[16]，使得土壤有效钾含量降低，导致土壤缺钾。在本试验中，用生物质炭处理的土壤养分离子浓度较高[17]，在淋溶初期黏粒表面吸附的钾离子占土壤阳离子总量的比例较小[18]，钾离子的淋出总量增加。但是，随着淋溶时间的延长，生物质炭可吸附的钾离子比例增加，所以在淋溶后期土壤钾淋失减少。LEHMANN等[19]发现，施用生物质炭增加了砂土和棕壤中钾的淋洗量，本试验淋溶初期的试验结果与其一致。添加生物质炭显著提高了土壤交换性钾含量[20]，可能是生物质炭增加土壤钾淋失的主要原因[21]。本试验结果表明，添加生物质炭虽会导致土壤淋洗液中总钾量稍有增加，但生物质炭对土壤速效钾含量的提升幅度更加明显，因此，研究生物质炭对土壤钾淋溶的影响以钾的淋出率作为标准更有意义。本试验表明，添加生物质炭对于降低土壤中钾的淋出率、提高肥料利用率具有一定的作用。此外，未施肥和施肥土壤添加生物质炭后速效钾含量在淋溶条件下降幅均减少，使土壤能够保持较高的速效钾含量。DELUCA等[22]认为，生物质炭可以通过改变土壤pH、阳离子交换量和有机质等含量来影响土壤中钾的形态。在本试验中生物质炭对未施肥和施肥土壤钾形态的作用效果有所不同，可能与2种土壤的速效钾含量不同有关。

3.2降水对土壤-淋洗液体系中磷的影响

在本试验中添加生物质炭大幅度提高了土壤速效磷含量，但淋洗液中总磷量并没有相应增加。说明添加生物质炭具有减少红壤磷淋失的效果。李际会等[23]发现，添加2.5%改性生物质炭后，土壤有效磷淋出量减少了45%。RAAVE等[21]研究认为，磷淋失减少的主要原因是施用生物质炭后增加了土壤的持水量。

施入生物质炭可大幅度提高红壤的速效磷含量，但经过一段时间淋溶后红壤的速效磷含量会出现明显下降，这与酸性红壤对磷的固定机制有关。在酸性红壤中，磷主要通过铁铝氧化物、矿质胶体表面被吸附，以及与铁铝化物反应生成难溶性的磷酸盐，从而使土壤磷从可溶态向难溶态转变[24]。洪顺山等[25]认为，在强酸条件下磷肥可能主要以无定形磷酸铝被固定下来，且通过试验证实了活性铝对酸性红壤固磷的贡献率可达40%以上。已有研究表明，生物质炭能够有效地提高红壤pH，减少其活性铝含量[26]。因此，添加生物质炭的初期会大幅度减少红壤对磷的固定，显著增加土壤有效态磷；但随着淋溶时间的延长，在酸性红壤中最初被吸附、固定的磷盐具有向磷铝石及粉红磷铁矿转化的趋势，且它们的溶解度极低[25]，使土壤有效态磷又出现下降。本试验添加生物质炭后，红壤速效磷的下降量明显大于淋洗液中的总磷量.说明生物质炭能够增加土壤对磷的吸附或固定能力。这与UZOMA等[27]的研究结果类似。但也有报道表明，生物质炭对磷的固定作用极小[28]。总之，生物质炭对土壤磷形态的影响较为复杂，可能与土壤类型和性质有关。

4　结论

施入生物质炭后，红壤的速效钾和速效磷含量大幅度提高，且添加生物质炭可减少淋溶条件下未施肥和施肥红壤中速效钾的下降幅度，使红壤能够保持较高的速效钾含量。添加生物质炭后，土壤速效磷含量虽有大幅度提高，但淋洗液中磷的总量并没有相应增加。说明添加生物质炭可显著减少红壤中磷的淋出率。

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Effects of biochar on the contents of potassium and phosphorus, and their leaching rates in red soil under simulated leaching condition.JournalofZhejiangUniversity(Agric. &LifeSci.), 2016,42(4):478-484

ZHU Pan1, YING Jieguan1, PENG Shu’ang2, JIANG Cuncang1*

(1.CollegeofResourcesandEnvironment,HuazhongAgriculturalUniversity,Wuhan430070,China; 2.CollegeofHorticultureandForestrySciences,HuazhongAgriculturalUniversity,Wuhan430070,China)

biochar; red soil; leaching; potassium; phosphorus

公益性行业(农业)科研专项(201303095)；国家现代柑橘产业技术体系岗位资助项目.

Corresponding author)：姜存仓(http://orcid.org/0000-0003-4742-003X),E-mail:jcc2000@mail.hzau.edu.cn

联系方式：朱盼(http://orcid.org/0000-0001-8609-3102)，E-mail:zhupanss@foxmail.com

2015-12-15；接受日期(Accepted)：2016-05-30；网络出版日期(Published online)：2016-07-18

S-3; S 156

A

URL:http://www.cnki.net/kcms/detail/33.1247.S.20160718.2026.008.html