酸性土壤施用石灰是一项良好的管理措施

LIMING ACID SOILS-A GOOD MANAGEMENT PRACTICE

 

Jose Espinosa

磷钾研究所拉丁美洲项目部主任

Director, Potash and Phosphate Institute, Latin American Office, P.O. Box 17-17-980, Quito, Ecuador, South America

 

1. 引言 Introduction

农用石灰，不管是粉细的白云石质石灰岩，还是方解石质石灰岩，直接施到酸性土壤是提高作物产量和降低肥料成本的一条廉价途径。这一土壤改良剂已在全世界广泛应用。保持恰当的土壤pH值对于保持良好的土壤肥力和制定良好的养分管理方案是必需的。一些导致土壤酸化的因素包括母质、降雨、天然植被、作物种植和施用氮肥等。

Agricultural lime, either finely ground dolomitic or calcitic limestone, applied directly to acid soils is an inexpensive way to increase crop yields and reduce fertilizer input costs. This soil amendment is widely used around the world. Maintaining an adequate soil pH is indispensable in a sound soil fertility and nutrient management program. Several factors contribute to soil acidity including parent material, precipitation, native vegetation, crops grown and nitrogen (N) fertilization.

 

由基性岩母质发育的土壤通常比那些由酸性岩发育的土壤具有更高的pH值。在高降雨条件下形成的土壤比在干旱条件下形成的土壤酸性强。土壤有机质不停地被微生物分解成有机酸和CO2，从而加重土壤酸化。森林植被下发育的土壤比草地植被下发育的土壤酸性强，针叶林土壤比落叶林土壤酸性强。随着作物收获部分盐基养分的移走，土壤酸度增强。氮肥施用由于在硝化过程中产生多余的H+，因而加速了土壤的酸化。硝化作用是在微生物的作用下把铵态氮转化为硝态氮的一种自然过程，这里的氮无论来源于无机肥料、有机肥料和粪肥，还是来源于豆科固定的氮，均发生这一过程，使土壤变酸。

Soils developed from parent materials of basic rocks generally have higher pHs than those formed from acid rocks. Soils formed under high rainfall conditions are more acidic than those formed under dry conditions. Soil organic matter is continually being decomposed by microorganisms into organic acids and carbon dioxide (CO2)  which add to soil acidity. Soils formed under forest vegetation tend to be more acid than those developed under grasslands, and conifers create more acidity than deciduous forest. Soils become more acid due to base (plant nutrient) removal in harvested parts of the crop. Nitrogen fertilization speeds up the rate at which acidity develops in soil due to excess H+ produced in the nitrification process. Nitrification, a natural process mediated by microorganisms, changes ammonium forms of N to nitrate forms. Nitrogen coming either from inorganic fertilizers, organic matter, manure and legume N fixation undergo this process contributing to soil acidity.

 

土壤酸性是以土壤pH即H+活度的对数来度量的。土壤酸性随着交换复合体固持的和土壤溶液中的H+数量的增加而增加。大多数丰产土壤pH变化范围为4.0~9.0。土壤中铝表现酸性元素的行为，事实上在大多数pH低于5.5的土壤上铝是H+的主要来源。铝水解形成氢氧化铝单体和多聚体，这些过程也产生H+，造成土壤酸化。单体铝的水解以下列方程表示：

Soil pH measures soil acidity as the logarithm of the activity of the hydrogen ion (H+). Soil acidity increases according to the increment in H+ held in the exchange complex and present in the soil solution. Most productive soils range from 4.0 to 9.0 in pH. Aluminum (Al) in the soil also acts as an acidic element and in fact is the principal source of H+ in most soils with pH below 5.5. Aluminum hydrolysis (reacts with water) to form monomeric and polymeric hydroxyaluminum complexes. These reactions also produce H+ adding to soil acidity. Hydrolysis of the monomeric forms are shown in the following equations:

   Al3+ + H2O —→ Al(OH) + H+

   Al(OH) + H2O —→ Al(OH)2 + H+

   Al(OH)2 + H2O —→ Al(OH)3+ + H+

 

这些反应释放H+，H+反过来了使Al3+数量增加，利于反应的再次发生。有研究显示，土壤溶液中即使低量Al3+对多数作物也是有毒的。因而Al3+是这些酸性土壤上的主要限制因子。

These reactions release H+ which in turn increases the amount of Al3+ ready to react again. It has been demonstrated that even low amounts of Al3+ in soil solution are toxic to most crops. The Al3+ concentration is the main limiting factor in these acid soils.

 

石灰通过把一些H+转化为水来提高pH降低酸度。pH高于5.5，Al3+形成Al(OH)3沉淀，毒性影响以及H+的主要来源也被消除。一旦需要，施石灰就成为保证高产稳产的一项管理措施。

Lime reduces acidity (increases pH) by converting some of the H+ into water. Above pH 5.5 Al3+ precipitates as Al(OH)3 and the toxic action the main source of H+- is eliminated. When needed, liming is a management practice that allows higher and sustainable yields.

 

2. 施石灰是一项良好的管理措施Liming as A Good Management Practice

施石灰是向土壤中掺入含钙或含钙镁的物质来降低酸性和提高pH的一项措施。

Liming is a management practice that incorporates in the soil calcium or calcium + magnesium materials that are capable of reducing acidity and increase soil pH.

 

2.1 石灰物质  Liming materials

有多种物质能在土壤中反应提高pH。其中最重要的有氧化钙、氢氧化钙、方解石和白云石。

There are several material that can react in the soil increasing pH. The most important include calcium oxide, calcium hydroxide, calcite and dolomite.

 

氧化钙（CaO）—-即生石灰，是一种腐蚀性白色粉末，施用时难度较大。工业上生产氧化钙是通过在熔炉中焚烧方解石质石灰石得到的，其纯度取决于原材料的纯度。当施入土壤时，它几乎立即反应，因此在追求立即见效时它是理想的石灰物质。但施用时应与土壤充分混合，否则很快结块、失效。

Calcium oxide (CaO)- Also known as burned lime or quicklime, is a caustic white powder, disagreeable to handle. It is manufactured by roasting calcitic limestone in an oven or furnace. Its purity depends upon raw material purity When added to soil, it reacts almost immediately, so it is ideal when rapid results are required. It should be mixed completely with the soil, because it rapidly cakes and can become ineffective.

 

氢氧化钙［Ca(OH)2］—-通常称作水合石灰或建筑石灰，是一种具腐蚀性的白色粉末物质，运输和施用时难度较大。加入土壤后与酸性物质迅速发生中和反应。由氧化钙水合制得。

Calcium hydroxide [Ca(OH)2]- Frequently referred to as hydrated lime or builders' lime, is a caustic, white, powdery substance, difficult and unpleasant to handle. Acid neutralization occurs rapidly when it is added to the soil. It is prepared by hydrating CaO.

 

方解石(CaCO3)和白云石［CaMg(CO3)2］—-这两种物质是农业上最常用的石灰物质。白云石的优点是可向土壤中加入镁，这一点在一些土壤很重要。二者的质量依赖于其含有粘土或有机质等杂质的多少。

Calcite (CaCO3) and dolomite ［CaMg(CO3)2］- These two materials are the most commonly used lime sources in agriculture. Dolomite has the benefit of adding magnesium (Mg) which in some soils is important. Quality of these materials depends on impurities such as the clay or organic matter they contain.

 

其它几种物质也可用来施用石灰，如蠔壳灰、泥灰、钢渣磷肥（碱性炉渣）、草木灰和工业水泥的副产品等。

Several other materials can be used for liming purposes, such as, baked or burned oyster shells, marl, basic slag, wood ashes, and cement industry by-products.

 

2.2 石灰质量  Lime quality

石灰性物质应检验其中和值和细度。所有石灰性物质的中和值都是以其与纯CaCO3的中和值比较来确定的。把纯CaCO3的中和值设为100，其它物质的中和值就可确定。这个值称为相对中和值或CaCO3当量。一些石灰性物质的相对中和值列于表1。

Liming material should be checked for neutralizing value and degree of fineness. Neutralizing value of all liming materials is determined by comparing them to the neutralizing value of pure calcium carbonate (CaCO3). Setting the neutralizing value of pure CaCO3 at 100, a value for other materials can be assigned. This value is called the Relative Neutralizing Value or Calcium Carbonate Equivalent. The relative neutralizing values of some liming materials are shown (Table 1).

 

表1 一些石灰性物质的相对中和值

Table 1 Relative neutralizing values of some liming materials

石灰性物质 Liming material

相对中和值 Relative Neutralizing Value(%)

纯CaCO3 Pure calcium carbonate

100

白云石 Dolomite

95—108

方解石 Calcite

85—100

生石灰 Burned lime

150—175

熟石灰 Hydrated lime

120—135

牡蛎壳灰 Baked oyster shells

80—90

木灰 Wood ashes

40—80

 

当一定量的石灰与土壤混合时，它的反应速率和反应程度就受到颗粒大小的影响。粗粒石灰反应慢且不完全，细粒石灰反应更快更完全。

When a given quantity of lime is mixed with soil, its reaction rate and degree of reactivity are affected by particle size. Coarse lime particles react more slowly and less fully. Fine lime particles react more rapidly and much more completely.

 

石灰成本随粉碎细度增加而增加。因而最终目标是通过最少量的粉碎却含有足够的细质物质以达到快速的pH变化。因而，农用石灰物质同时含有粗粒和细粒。从实践的角度来看，一种良好的石灰物质应该是完全通过60目筛。

Cost of lime increases with the fineness of grind. The goal is to have a material that requires a minimum of grinding and yet containing enough fine material to cause a rapid pH change. As a result, agricultural liming materials contain both coarse and fine materials. From the practical point of view, a good liming material should have particles that pass completely through a 60 mesh sieve.

 

2.3 土壤中的石灰反应  Lime reactions in the soil

土壤中石灰反应的机理是中和土壤溶液中的H+。石灰与H2O反应生产OH -。因此，只有在土壤水分充足的条件下施石灰才有效。基本的石灰反应可用CaCO3在土壤中发生的反应来说明。其反应过程是：

Reaction mechanisms of liming materials in soil neutralize H+ in the soil solution. Lime reacts with water to produce OH- ions. For this reason, liming is effective only when adequate soil moisture is present. Basic lime reactions can be illustrated with the reactions that CaCO3 undergoes in the soil. They areas follows:

    CaCO3 —→ Ca2+ + CO32-

    CO32- + H2O —→ HCO3- + OH –

    HCO3- + H2O —→ H2CO3 + OH –

    H2CO3 —→ CO2↑+ H2O

         H+ (土壤溶液)+ OH –—→ H2O

 

因而，上述反应的速率，也即CaCO3的解离速率，与土壤溶液中和H+ 时OH -的消耗速率和H2O形成速率有关。只要土壤溶液中有H+存在，CaCO3就会不停地反应，从而提高pH。

Rate of the above reactions, therefore, the dissociation of CaCO3, is related to the rate OH- are removed from the soil solution through H+ neutralization and H2O formation. As long as H+ is present in the soil solution CaCO3 will continue reacting, increasing pH.

 

值得一提的是，上述反应的终产物为CO2，它散逸到在空气中。这就解释了为什么石灰施用的效果只局限于石灰颗粒所在的地方。换句话说，表施石灰一定要均匀，然后与土壤充分混合。因此，石灰的均匀混合对于控制酸度是非常必要的。

It is interesting to note that the final product of the above reactions is CO2 which dissipates to the atmosphere. This is the reason why the effect of liming is restricted to the site where lime particles are located In other words, it is necessary to make a uniform surface application of lime which then needs to be completely mixed with the soil. Good incorporation of lime is essential for effective control of acidity.

 

在一些种植制度下，如多年生草皮或种植园作物，混施石灰只能在种植前才有可能。一旦作物长出以后，石灰就只能表施了。表施石灰反应较慢，不象石灰与土壤混合一样反应完全。然而现已证明，在免耕系统中，表施石灰是有效的，主要是由于在土壤剖面中发生的物理和化学变化使得0~10cm的表层土壤保持较高的根系活性。

In some cropping systems, such as perennial sods or plantation crops, mixing is only possible before seeding. Once the crop is established, lime must be topdressed. Surface applied lime reacts more slowly and not as completely, as lime mixed with the soil. However, it has been proven that in no-till systems surface lime application is effective mainly due to the physical and chemical changes in the soil profile that concentrate root activity in the 0-10 cm superficial layer.

 

3. 石灰需要量Lime Requirement

虽然土壤pH是土壤酸度很好的指标，但并不能确定出石灰需要量。石灰需要量是指在某一种植系统中把pH调至一定范围所需的农用石灰数量。测定pH时，只能测定土壤水中的活性酸度，被土壤粘粒和有机质吸持的潜在酸度也必需考虑。

Although soil pH is an excellent indicator of soil acidity, it does not determine lime requirement. Lime requirement is the amount of agricultural lime needed to establish the desired pH range for the cropping system being used. When pH is measured, only active acidity in the soil water is determined. Potential acidity, that is held by soil clay and organic matter, must also be considered.

 

石灰需要量不仅与土壤pH有关，而且与阳离子交换量(CEC)有关，而CEC又与主要粘粒的数量、类型和土壤有机质的含量有关。这些因素决定土壤缓冲性的强弱，即抵御pH变化的能力，其缓冲容量随粘粒和有机质数量的增加而增加。砂土含粘粒和有机质少，缓冲性弱，需要很少的石灰就能改变pH。

Lime requirement is not only related to soil pH, but also to cation exchange capacity (CEC) which in turn is related to total amount and type of clay predominant and soil organic matter content. These factors determine how strongly soils are buffered or how strongly they resist a change in pH. Buffering capacity increases with amount of clay and organic matter. Sandy soils, with small amounts of clay and organic matter, are weakly buffered and require less lime to change pH.

 

3.1 温带土壤的石灰需要量  Lime requirement for temperate soils

有证据表明，施用石灰时必须考虑该土壤的主要粘土矿物。我们常在温带地区发现的2:1型粘土矿物（蒙脱石、蛭石、伊利石）为主的土壤，也出现在热带和亚热带地区。这些土壤不同于世界范围内广泛分布的典型的热带红壤(以铁铝氧化物和高岭石为优势粘土矿物的老成土和氧化土)，也不同于由火山灰（以水铝萤石、伊利缟石和腐殖质-Al复合体为优势粘土矿物的火山灰土）发育的土壤。这些重要的差别决定了评价石灰需要量的方法。

It has been demonstrated that successful liming has to take into account the dominant soil clay minerals in the soil to be limed. Soils dominated by 2:1 clays(montmorillonite, vermiculite, illite), more frequently found in temperate zones, but also present in tropical and subtropical areas; behave different from the typical tropical red soils (Ultisols and Oxisols dominated by Fe and Al oxides and kaolinite) and from the soils developed from volcanic ash (Andisols dominated by allophane, imogolite, and humus-Al complexes) that are widely spread over the world. These important differences determine the approach to evaluate lime requirements.

 

以2:1型粘土矿物为主的土壤（软土、变性土），由于脱盐基（K、Ca、Mg等离子减少）作用导致土壤酸性，由此引起粘土矿物的解体和Al的释放并占据盐基损失后的交换位点。这些土壤通过施用石灰很容易把pH调至6.5~7.0，以挖掘最大的生产潜力。在这个过程中，CEC（永久电荷土壤）的变化极小。表2的数据显示了在阿根廷的软土上施用白云质石灰石对土壤pH和大豆、玉米产量的影响。

In soils dominated by 2:1 clays (Mollisols, Vertisols), the reduction in base saturation (loss of K, Ca, Mg) leads to acidity. This increment in acidity in turn leads to the breakdown of clay material and release of Al which occupies exchange sites left by the lost bases. These soils can be easily limed to reach a pH range of 6.5 to 7.0 to obtain the highest productivity. During this process there is very little change in CEC (soils of permanent charge). Data (Table 2) illustrates the effect of dolomitic lime on soil pH, and soybean and corn yields in a Mollisol from Argentina.

 

表2 在阿根廷的软土上白云石对土壤pH和大豆、玉米产量的影响

Table 2 Effect of dolomite application on soil pH, and soybean and corn yield in a Mollisol from Argentina

白云石 (公斤/公顷)

Dolomite (kg/ha)

pH

籽粒产量(公斤/公顷)

Grain yield (kg/ha)

大豆 Soybans

玉米 Corn

0

5.7

2622

8397

2000

6.5

3368

9942

4000

6.8

3365

10249

 

通常确定2:1型土壤的石灰需要量是依据缓冲溶液与土-水悬浮液的pH变化。最常用的就是SMP方法，该法用来测定美国温带地区酸性土壤的石灰需要量。土壤-水-缓冲溶液三者的悬浮液的平衡pH值，与用CaCO3培养法使同一土壤样品达到一定的pH所需的石灰量是相关的。应用这种方法就能推算出使土壤pH达到一特定值所需的石灰量。该方法使我们能够对永久电荷酸性土壤石灰需要量进行快速测定。表3是一个应用SMP缓冲液校正法进行石灰推荐的例子。

Common methods of determining lime need in soils dominated by 2:1 clays are based on pH change of a buffered solution compared to pH of a soil-water suspension. The most popular of these methods is the SMP (Shoemaker, McLean and Pratt) method developed to determine lime needs in acid soils of the temperate zones of the USA. The equilibrium pH value of a suspension made of soil water buffer solution is correlated with the amount of lime needed to increase soil pH to a certain value, using a CaCO3 incubation procedure, in the same soil sample In this way, recommendations can be developed to indicate the amount of lime required to bring soil pH to a particular value. This method allows a rapid determination of lime requirement in acid soils of permanent charge. An example of liming recommendations based on calibration of a SMP buffer solution is presented (Table 3).

 

表3 应用SMP缓冲溶液方法确定的石灰量

Table 3 Liming rates determined using SMP buffer solutions

SMP指数* SMP Index*

目标pH  Desired pH after liming

5.5

6.0

6.5

石灰施入量(吨/公顷) Lime rate (t/ha)

4.4

15.0

21.0

29.0

4.6

10.9

15.1

20.0

4.8

8.5

11.9

15.7

5.0

6.9

9.7

12.9

5.2

5.5

8.0

10.6

5.4

4.4

6.5

8.7

5.6

3.3

5.1

7.0

5.8

2.3

3.9

5.5

6.0

1.4

2.8

4.1

6.2

0.6

1.7

2.7

6.4

0.0

0.0

1.5

*土-水-缓冲液的pH。pH of the suspension soil-water-buffer solution

 

3.2 热带土壤的石灰需要量  Lime requirement for tropical soils

确定热带红壤石灰需要量的方法是不同的。在这些土壤中，pH低到5.0时粘土矿物的Al和Fe是稳定的，此时Al被包埋在粘土颗粒中，对植物不构成威胁，直到pH降低到使氧化物和高岭石溶解，把Al3+ 释放到土壤溶液中，有时会达到毒害水平（pH<5.3）。当这一情况发生时就要把土壤pH提高到5.5以上，这就能使Al3+ 沉淀下来，同时大幅度增加土壤可变电荷CEC（如表4、表5）。在这一pH下作物生长和产量最佳的。

However, determination of lime requirement of tropical red soils is different In these soils, Al and Fe present in mineral clays are stable at pH values as low as 5.0. In this case Al is buried in the clay particle and is not a threat to plant growth until pH reaches values where the oxides and kaolinite dissolve bringingAl3+, sometimes in toxic quantities, into the soil solution (pH < 5.3). When this arises it is advisable to raise soil pH to values of about 5.5. This allows Al3+ precipitation and appreciable increment in CEC (soils of variable charge) as presented (Tables 4 and 5). At this pH, crop growth and yields are excellent.

 

表4 巴拿马红色老成土施用石灰的效果

Table 4 Effect of lime application to a red Ultisol from Panama

处理 Treatment

pH

Ca

Mg

K

A1

有效CEC Effective CEC

旱稻产量(kg/hm2) Upland rice yield (kg/ha)

cmol(+)/kg

 不施石灰 No lime

4.9

1.79

1.2

0.11

2.15

5.18

2751

施石灰(4吨/公顷) Lime(4t/ha)

5.8

7.90

6.7

0.14

0.09

14.85

4271

 

表5 巴西氧化土施用石灰对土壤pH和作物产量的影响

Table 5 Liming effects on soil pH and the yield of various crops in Oxisols from Brazil

玉米  Corn

小麦  Wheat

大豆   Soybeans

CaCO3 (t/hm2) (t/ha)

土壤 pH  Soil pH

产量(kg/hm2) Yield (kg/ha)

CaCO3 (t/hm2) (t/ha)

土壤pH  Soil pH

产量(kg/hm2)  Yield (kg/ha)

CaCO3 (t/hm2) (t/ha)

土壤pH  Soil pH

产量(kg/hm2) Yiele (kg/ha)

0

3.9

1150

0

4.7

1320

0

4.6

1943

2

4.5

4090

3.5

5.0

2364

3.5

4.9

2514

4

4.7

4420

7.0

5.2

3031

　

　

　

6

5.3

5340

　

　

　

　

　

　

 

在热带土壤上应用缓冲溶液方法确定石灰需要量很不适用。用该方法推荐的石灰量过大，使pH升到6.0~7.0，而实际上相对少量的石灰就能使pH升高足以沉淀Al3+，因此，石灰推荐应依据表层土壤交换态Al的数量来确定。按照这一概念，大部分热带土壤的石灰需要应根据下述方程来确定：

CaCO3当量（吨/公顷）= 因子×厘摩尔Al/公斤土壤

In tropical soils, determination of lime requirements using buffered solutions does not work adequately. Using this approach large amounts of lime are recommended to force soil pH to values in the 6.0-7.0 range while only moderate amount of lime is needed to raise soil pH enough to precipitate Al3+. In this case it has been suggested that lime recommendations be based on the amount of exchangeable. Al in the top soil Following this concept, lime requirement for most tropical soils can be predicted applying the following equation :

CaCO3 equivalent (t/ha)=Factor×cmol Al/kg soil

 

因子值因作物特性和土壤类型不同，其变化范围是1.5~3.0。这可通过在某一特定地点工作的农学家或农民来精细地调整。

The factor used can vary from 1.5 to 3.0 depending on the crop characteristics and the soil type. This factor can be fine tuned by the agronomist or farmer working at a specific site.

 

该方法的主要目标是中和全部Al3+，但有一类耐铝作物在土壤交换复合体处于中度铝饱和时能够生长良好并获取令人满意的产量。既然不需要沉淀所有的Al3+，施用较少量的石灰就能把铝饱和度降到所需的水平。多数情况下，施用石灰是为了克服在低CEC的风化土上生长的作物缺乏Ca和Mg。咖啡、香蕉、油棕和许多热带牧草和豆科植物都属于高度耐铝植物。通过作物育种已经培育出水稻、高粱和玉米等一些作物的高度耐铝品种。

The primary goal of this approach is to neutralize all Al3+ but, there are Al tolerant crops that can grow and yield satisfactorily at moderate aluminum saturation of the exchange complex. Since not all Al3+ needs to be precipitated, a lower amount of lime can be used to reduce Al saturation to the desired level. Inmost of these cases, applied lime is used to overcome Ca and Mg deficiencies which can limit plant growth in weathered soils of low CEC. Coffee, banana, oil palm, and a number of tropical grasses and legumes are among the crops that tolerate high Al saturation. Plant breeding has developed cultivars of certain crops like rice, sorghum, and corn that are also tolerant to high Al saturation.

 

另外一种计算石灰需要量的方法与铝的饱和度有关，是以土壤的盐基饱和度为依据的。尽管盐基饱和度不影响生长在2∶1型矿物上作物的产量，但其在低CEC和低Ca、Mg含量的高度风化土壤（老成土和氧化土）上却非常重要。上面提到的白云石，其不仅用来较正这些土壤的酸性，而且可以补充土壤的钙和镁。有研究证明，风化土壤较高的盐基饱和度可在一定程度上改善土壤肥力和提高作物产量。

Another common method used to calculate lime requirements, related to Al saturation, is based on soil base saturation. Though it has been determined that base saturation does not influence yield in soils dominated by 2:1 clays, this parameter is very important in highly weathered soil (Ultisols and Oxisols) of low CEC and low Ca and Mg content. As indicated above, dolomitic lime is used not only as an amendment in these types of soils, but also as a source of Ca and Mg. Research has demonstrated that, within certain limits, higher base saturation in weathered soils improves fertility and increases crop yields.

 

一种考虑施石灰后获得目标土壤盐基饱和度来确定石灰需要量的方法逐步完善起来。巴西的经验表明，咖啡在盐基饱和度为60％时产量最佳，换句话说，即咖啡在土壤为铝饱和度为40%时生长良好。根据这一标准，石灰需要量可根据下式计算：

A method for determining lime requirement was developed taking into account a targeted soil base saturation attained by lime application. Brazilian experience indicates, for example, that the best coffee yields are obtained at 60 percent saturation. In other words, coffee can grow satisfactorily in a soil having up to 40 percent Al saturation. According to these criteria, lime requirements can be calculated using the following equation:

 

CaCO3(吨/公顷)=(BS2-BS1)×CEC/100

式中 BS1＝起始盐基饱和度

 BS2＝目标盐基饱和度

CaCO3 (t/ha)=((BS2BS1)×CEC/100)

Where BS1= Initial base saturation

  BS2= Required base saturation

 

3.3 火山灰土壤的石灰需要量  Lime requirement for soils derived from volcanic ash

火山灰土壤的石灰需要量的计算方法有些不同，主要是高的缓冲容量使得石灰需要量难以计算，而且其缓冲容量的强度随着海拔、降雨和温度等影响火山灰风化的因素变化而变化。因此，评价这些土壤的石灰需要量并不是遵循一个简单的原则。应用交换态铝为标准有时会对石灰需要量估计偏低（表6）。

Liming approach for soils derived from volcanic ash (Andisols) is somewhat different. The high buffering capacity (resistance to pH change) complicates lime requirement evaluation. Intensity of the buffering capacity varies from one place to another according to altitude, rainfall and temperature the factors controlling volcanic ash weathering. For this reason, there is not a simple rule to evaluate lime requirement in these soils. Use of the exchangeable Al criterion sometimes underestimates lime needs as illustrated (Table 6).

 

表6 厄瓜多尔高原的火山灰土壤施用石灰对土壤化学性质和作物产量的影响

Table 6 Effect of lime application on soil chemical properties and crop yield in an Andisol of the highlands of Ecuador

CaCO3 (吨/公顷) (t/ha)

pH

Al

K

Ca

Mg

CEC*

作物产量  Crop yield

蚕豆 Faba beans

大麦 Barley

燕麦 Oats

 cmol(+)kg

(吨/公顷)(t/ha)

0

5.0

2.1

0.30

2.54

0.36

5.30

13.9

2.2

3.6

1.5

5.1

1.5

0.29

2.58

0.36

4.73

12.8

3.0

4.4

3.0

5.2

1.6

0.29

3.30

0.39

5.58

17.1

2.9

4.3

4.5

5.2

1.5

0.30

4.67

0.29

6.76

18.9

3.7

4.4

6.0

5.3

0.6

0.28

4.69

0.40

5.97

19.2

3.9

4.7

9.0

5.4

0.4

0.27

4.70

0.41

5.78

21.5

3.9

5.2

12.0

5.4

0.2

0.30

5.59

0.40

6.49

21.6

4.1

4.8

15.0

5.8

0.1

0.29

8.60

0.42

9.41

21.0

4.3

4.7

*以中性盐计算的阳离子交换量  *CEC evaluated with an indifferent salt

 

火山灰风化形成的水铝萤石、伊利缟石和腐殖质-Al复合体粘土颗粒表面非常活跃。当施用石灰时，其与粘土颗粒产生电荷（CEC增加）的表面反应，使pH升高和沉淀Al难以进行。沉淀Al所需的石灰需要量应随火山灰形成的时间及其风化的程度而变化。因此，为了准确计算某一地点的石灰需要量，应布置一些简单的田间试验。

Clay particles resulting from volcanic ash weathering (allophane, imogolite and humus-Al complexes) have a very reactive surface. When lime is applied to these soils it reacts with clay surfaces creating charge (increment in CEC) failing to increase pH and to precipitate Al. The amount of lime needed to precipitate aluminum varies with the age and weathering of the volcanic ash. For this reason, it is necessary to conduct simple field trials which can indicate precisely the amount of lime needed in an specific site.

 

在热带土壤，不管应用何种方法计算石灰需要量，均要注意石灰施用量不能过大，通常把土壤调至中性就会出现这种情况。热带土壤仅需中和铝，这只需把pH调至5.5~6.0即可。过量施石灰会导致土壤结构退化，B、Zn、Mn的有效性下降，产量降低。

Regardless of the method used to determine lime requirement in tropical soils, it is advisable to avoid excessive lime applications. Usually this happens when such soils are limed to neutrality. Tropical soils should only be limed to neutralize Al, which generally brings soil pH to values in the 5.5 to 6.0 range. Over liming leads to soil structure deterioration, reduced boron (B), zinc (Zn) and manganese (Mn) availability, and lower yields.

 

4. 结论Conclusions

土壤酸性在多方面影响作物生长，最终对产量影响也很大。合理施用石灰能控制由低pH带来的有害作用，也能降低铝锰毒害，这可能是酸性土壤施用石灰主要的积极作用。其它作用还有改变土壤的物理条件、刺激土壤的微生物活性和共生固氮作用，提高其他营养元素的有效性，增加可变电荷土壤的CEC含量。酸性土壤中，一项精细设计的石灰施用计划对于作物的高产稳产是非常重要的。

DM-15 -土壤酸度水分计
DM-15
土壤酸度水分计 		DM-1-土壤酸碱度计
DM-1
土壤酸碱度计

Soil acidity affects plant growth in many ways, in consequence, crop yields are also affected significantly. Properly applied lime controls the detrimental effects of low pH. A good liming program reduces Al and Mn toxicity. This is perhaps the main favorable effect of liming acid soils. Other benefits include an improved soil physical condition, stimulation of soil microbial activity and symbiotic N fixation, increment of availability of other nutrients, and increase in CEC in soils of variable charge. In acid soils, a well designed liming program is fundamental to high sustainable crop yields.

 

参考文献  Bibliography

Brad, N 1976 Naturaleza y propiedades de los suelos Editorial Hispano Amica Mico Espinosa, J.1987.Efecto del encalado en las propiedades quimicasde suelos ecuatorianos

Memorias del Primer Congreso Nacional de Ciencias de la Comunidad Cientifica Ecuatoriana Quito, Ecuador

Espinosa, J.1996.Liming tropical soils a management challenge Better Crops 80:28~31

Fox, R. L.1980.Soil with variable charge:  Agronomic and fertility aspects In, C. Theng (ed).Soils with variable  charge  Palmerston North, New Zealand Society of Soil Science

Fernandes de Sequeira, et al, 1987.Recomendacoes de adubacao e calagem para os estados do Rio Grande do sul e Santa Catarina Centro Nacional de Pesquisade Trigo Passo Fundo, Brasil

Gambaudo, S, y.H.Fontanetto.1995.Correcion de la acidez edafica en el centro de Santa Fe, Argentina INTA, EEA Rafaela Santa Fe, Argentina Documento de trabajo

Guillman, G. P.1979.A proposed method for the measurement of exchange properties on highly weathered soils Aust. J. Soil Res.17:129~139

Guillman, G.P, and.R.L.Fox.1980.Increases in the cation exchange capacity of variable charge soils following superphosphate applications Soil Sci Soc Am.J.44:934~938

Guillman, G.P, and G.Uehara.1980.Charge characteristics of soils with variable and permanent charge minerals: 2.Experimental Soil Sci Soc Am.J.44:252~255

Kamprath, E.1990.Crop response to lime in soils of the  tropics In F. Adams (ed) Soil acidity and liming Agronomy Series No.12.American Society of Agronomy

Malavolta, E.1992.Reaccion del suelo y el café Memorias del seminario "Fe rtilizacion y Nutricion del Café"ANACAFE INPOFOS Guatemala

Malavolta, E, A.Lopes, y., L. Guilherme.1991.Fertilizantes, correctivosy productividad Memorias de simposio "El Suelo y la Productividad" Itaguai, Rio de Janeiro

Name, B.1992.Dinamica de fosforo en un Ultisol de Panamá Reporte del ciclo 1991~1992 Instituto de Investigacion Agropecuarias de Panamá Divisa, Panamá

Osaki, F.1991 Calagem e adubacaoCampinas, SP:Instituto Brasileiro deEnsino Agricola

Parfitt, R. L.1980.Chemical properties of variable charge soils In: C.Theng (ed) Soils with variable charge Palmerston North, New Zealand Society of Soil Science

Parfitt, R. L , and T. Henmi 1980 Structure of some allophanes from New Zealand Clays Clay Min.28:285~294

Potash and Phosphate Institute.1996.International Soil Fertility Manual Atlant, Georgia

Raij, B.Von.1991.Fertilidade do solo e adubacao Editora agronomica Ceres Ltda Sao Paulo, Brasil

Schoemaker, H.E, E.O.Mclean, and P.F.Pratt.1961.Buffer methods for determining lime requirements of soils with appreciable amounts of exchangeable aluminum Soil Sci Soc Amer Proc.25:247~277

Uehara, G, and G.Gillman.1981.The mineralogy, chemistry and physics oftropical soils with variable charge clays Westview Press, Boulder, Colorado

Uehara, G, and J.Keng.1975.Management implications of soil mineralogy in Latin America In: E. Bornemizsa and A.Alvarado (eds) Soil Management in Tropical America N.C.State Univ, Raleigh