Four steps to a decision on buying lime, that is all a farmer should know about lime preparations


Ladies and gentlemen,

Several years of research and implementation conducted by our company resulted in developing the formula of the POLCALC OF THE 3RD GENERATION calcium fertilizer. At that time we cooperated with a large group of farmers from several regions of Poland. In the course of these contacts plantation owners formulated a number of questions concerning our product and a process of soil liming itself. Below, we present, in a clear and user-friendly form, most often raised doubts. We hope that we will make it easier to decide on which lime should be chosen for the field to obtain expected results. We want out texts to be most understandable. As it is the conscious use of lime preparations what is a necessary element to obtain excellent crop and, at the same time, is the key to your satisfaction. Therefore, we encourage you to read.

dr hab. Seweryn Rzepecki, Professor of the University of Lodz

POLCALC SP. z o.o.



1. FARMER: What are the benefits from soil liming?

Expert`s answer: The effect of liming is a number of positive changes in soil properties. Let us organise them:

– the main and most important aim is to decrease soil acidification or so-called soil pH. Each farmer should know how to measure the soil pH and what doses to use for a particular plant. It is nowadays the essential knowledge and one should not rely only on information from fertiliser producers because it is usually too vague. Some plants are very sensitive to liming and the knowledge how to prepare the soil for a particular crop may result in the production increase even by 20-60%.

– proper soil structure is another very important advantage of liming. The most important parameters include:  improvement of soil cloddishness, its better aeration, increase in soil porosity and balance of microbiologic systems as well as activeness of living organisms, better water circulation and exchange of organic substance, improvement of mineral components accessibility. All these processes have a beneficial influence on soil welfare and stop processes of its biodegradation.

– liming neutralizes acids of chemical origin causing stopping their penetration into agricultural products. Most chemicals in contact with calcium are neutralized. It is easy to imagine how it is important for the quality of agricultural products, especially these recipients of which require high-performance products.

2. FARMER: How to know that the soil needs liming?

Expert`s answer: Even 20-30 years ago scientists recommended so-called bioindicators of soil acidity occurring in fields. These indicators are some kinds of wild plants that prefer soils with high level of acidity. The newest research revealed huge inaccuracy of such a method. Only determining the acidity with laboratory methods can be reliable. The obtained result allows for fairly precise determination of the range and time of optimal field liming or sowing. PH range for most crops in Poland should oscillate around from 5.5 to 6.5. As far as sensitive plants are concerned,  pH should be from 6.0 to 7.0. What is especially worth recommending is implementation of a systematic and intelligent system of liming for individual fields and crops. It requires systematic control of soil acidification (pH) and flexible determining the doses of calcium preparation.  Detailed tables of dosage are always included in information materials of the producer. The effects of such measures  will be obtaining and maintaining plants welfare – and hence the increase in crop and farmer`s satisfaction. Another problem is acidification which is so strong that causes even soil contamination, and in such cases a need of liming is best visible during sprouting and vegetation of the plants. Yellow sites, irregular growth, pathologies, and excessive diseases may be of local character, and then what is necessary is top-dressing that saves the crop.

3. FARMER: How to test the soil pH and where to look for information about the proper pH for a specific crop?

Expert`s answer: Testing the soil pH is not a complicated activity. However, not everyone has the knowledge and time to carry out such kind of tests by themselves. As to the equipment for pH testing you should be careful, such devices can be found on the market but their reliability is very doubtful (the cheaper the worse, devices without calibration possibilities stop working properly after several measurements). Experiments conducted with the use of such equipment showed their complete inconsistency with the actual soil pH.  A better solution is commissioning tests of this kind to a specialist laboratory – e.g. in the nearest local chemical-agricultural station.

4. FARMER: What are the types of lime used in agriculture?

Expert`s answer: In agriculture three main types of lime are used, which essentially differ in composition and chemical properties; they are:

Calcium oxide (other terms: quicklime or building lime) with chemical formula CaO is artificially obtained as a result of thermal processing of limestone. It is lime which is too much reactive. In this case, there is a real threat of soil over-fertilization because a reaction with water results in emergence of calcium hydroxide with the formula Ca(OH)2 which is strongly corrosive substance. This type of lime should only be applied in case of heavy soils in appropriate weather conditions (on moist humus) and the soil should be strongly mixed. Products of this type are troublesome in application and very dusty.

Calcium carbonate (other terms: chalk, fodder chalk, limestone dust or lacustrine chalk) with the chemical formula CaCO3 obtained as a result of crushing and grinding limestone or as mineral in open pit mines. Calcium carbonate is found in nature in the form of limestone. The main problem in this case is different degree of chemical composition purity. Not all calcium carbonate gives good results as fertilizer! The best carbonate fertilisers are these which are finest ground and do not contain contamination or water. It is easy to imagine that buying a product which contains only 70% of pure component, and the rest is contamination such as clay and water, is the same as buying 100 bags, from among which 70 contain lime and 30 water and clay. This type of lime has the biggest number of variants. An important factor determining the effectiveness is crumbling of the product. A crumbled product can be even 200 times less effective than a ground one.

Dolomitic lime – (mining lime, magnesium lime, finely crushed lime) is the worst and least reactive kind of lime used in agriculture. Its effectiveness in deacidification is often almost zero. Unfortunately, farmers are frequently cheated and pay big sums of money for such products lured by high magnesium content. Whereas the truth is that  magnesium accessibility is strongly limited by crystalline structure of carbonate (similar to marble) and too high fraction of grains. It is just dolomite coming from strongly weathered deposits and finely ground (or roasted) can be deacidifying and supplies the soil with magnesium.

5. FARMER: How often should soil be limed?

Expert`s answer: Hitherto soil liming was recommended every few years. Measures of this type do not however prevent the soil degradation. The problem is also discretionary, often even incidental dosage of lime. Nowadays more conscious farmers are aware of a fact that systematic use of lime preparations brings better effects. Huge, often shock doses of lime introduced to soil bring fast but quickly  disappearing changes in soil condition improvement. This type of uncontrolled fertilising fields with lime is accompanied by usually quick return to unfavourable degree of arable layer acidification.

6. FARMER: When should the soil be limed?

Expert`s answer: The liming method depends on the crop. The best time to spread lime falls to a period between the harvest and late autumn, or even winter. Post-harvest period is characteristic of generally good water content what directly results in acceleration of lime dissolution in soil. An important element is also the time of lime activation which is longer in that period because it lasts from the moment of crop collecting to sowing or planting. As it can be noticed, this long time allows to collect soil samples, unhurried selection of appropriate fertilizer what finally results in correctness of the whole procedure. What can be specially recommended is granulated fertilisers. They do not need to be mixed with soil, and can also be applied in winter time and early in spring on a shallow snow cover (recommended under winter crops, rape, long-term plantations, permanent grasslands). Granulated fertiliser is also the best form of lime for top-dressing – saving the crop. Then the sowing time can fall to the growth phase of plant.

7. FARMER: How much lime should be spread per hectare?

Expert`s answer: Lime dosage is influenced by a number of environmental and agricultural factors. Therefore it cannot be univocally stated, without additional testing, what amount of lime will be sufficient to achieve satisfying results. An important factor is, for instance, pH of soil and the kind of applied lime fertiliser. Calcium oxide, calcium carbonate or chalk lime have different applications for different soils and differentiated time of reaction. What is not without influence is the method of liming. Many farmers think that soil liming with big doses of fertiliser every few years is sufficient. It is obviously not true. The latest scientific research show that the best results can be achieved through systematic, annual liming – with the use of lower doses. Maintaining such a strategy of agronomic activities, in case of most types of soil and plant types doses from 200 to 500 kg per 1 ha will be sufficient. The doses increase in the case of acidified heavy soils, then liming needs can be estimated at about 500 – 1000 kg per 1 ha yearly. Attention: in the case of calcium oxide no rapid, high doses in deacidification should be used because there is a risk of soil over-liming or over-drying!

8. FARMER: Why do some producers recommend spreading even 10-15 tons of calcium oxide, while others recommend 1-2 tons per hectare?

Expert`s answer: It all depends on liming system and the soil pH. Applying granulated lime fertilisers is often an element of a year-round system of plant nourishing as in the case of nourishing with nitrogen or NPK fertilisers. This results in using lower doses. Lime products therefore are used to apply the necessary dose of calcium – and on this occasion an effect of maintaining the appropriate soil pH is obtained. In the case of powdery carbonate fertilisers a dose to deacidify the soil is often applied for 4-5 years. Therefore, the dose is adequately higher. The dosage is also dependent on chemical composition of the product. One rule is obligatory: the better fertilizer the lower doses. As far as calcium oxide is concerned, differences in applied doses also result from CaO content. It may oscillate between 40 and 80%.



9. FARMER: Can liming harm the plants?

Expert`s answer: In the case of calcium oxide there is a risk of soil over-liming because too big amount of calcium hydroxide, which will emerge as a result of contact with water contained in the soil, may destroy the crop. Whereas, over-liming with calcium carbonate is in fact impossible due to the constant pH level of the fertiliser itself. It is also a product of natural origin, and its absorption is “controlled” by plants themselves – gathering adequate amount of the product from the soil. A good example is soils from areas with shallowly occurring limestone. Calcium carbonate can constitute even 20-30% of the matter, i.e. in soil from 1 hectare of the field area lime makes up about 1000-1500 tons! At the same time, only c. 1% of calcium present in the soil actively takes part in soil processes connected with plants nutrition.

10. FARMER: Can lime be mixed with water and used as for instance trees or shrubs spraying?

Expert`s answer: As far as the lime use effectiveness for spraying is concerned, common opinions are varied and often contradict. This mainly results from confusing two kinds of lime that is artificially obtained calcium oxide (quicklime) and natural lime, i.e. calcium carbonate. Using calcium oxide as spraying can have very serious and unfavourable for plants consequences. A choice of inappropriate doses can even cause burning of vegetables or trees. Whereas, calcium carbonate is absorbed by leaves to a limited extent. When there is a need of intervention liming in the phase of growth what is more effective is spreading granulate in order to enable its faster reaction in the soil.

11. FARMER: How is top-dressing lime used and what are the advantages?

Expert`s answer: Top-dressing of lime fertilisers is only possible with the use of calcium carbonate. In the case of calcium oxide (quicklime) top-dressing will affect plants and destroy the crop. What is especially recommended to nourish plants in the phase of their growth is granulated carbonate fertiliser. It is easily absorbed from the top soil level. It should be surely added that not all plants react to top-dressing liming in the same way. It mostly depends on the degree of sensitivity to liming. The higher degree of sensitivity the more efficient is the intervention. For details producers of granulates should be asked. Another kind of top-dressing liming is liming that saves the crop, which is used for plants in the growth phase when places with uneven growth occur, yellow sites, plants with inhibited growth, excessive diseases and pathologies – in such circumstances this is the only method to improve the situation and change the soil conditions.

12. FARMER: What lime is best for spreading?

Expert`s answer: Nowadays among farmers a belief about effectiveness of liming with powdered fertiliser still lingers. More conscious users of calcium fertilisers however notice considerable limitations of such products. They are connected with problems with regular spreading and, resulting from them, wastes of product. To overcome these limitations lime granulating was started – it enables elimination of the mentioned wastes. An important factor is also the method of dosage, in the case of large doses it is necessary to mix the soil, and the granulate after spreading on the surface soaks through root systems and soil colloid, hence wastes are smaller and smaller dose can cause pH change from the top layer towards the bottom of humus layer.

13. FARMER: Can lime be mixed with manure, nitrogen or phosphate fertilisers?

Expert`s answer: There is a lot of discrepant opinions on this problem. In fact, there are some quite simple rules which should be taken into consideration during soil liming.

– calcium oxide is not suitable for mixing (in any form) with most fertilisers. Exceptions are: Polifoska and ground phosphate rock. Let us emphasise again: other fertilisers cannot be mixed with calcium oxide, under any circumstances!

-calcium carbonate is not suitable for mixing with manure, ammonium nitrogen, ammonium phosphate (granulated), ammonium sulfate (powdered) and Super Fosfat (powdered). What is more, an interval (4-8 weeks) between lime spreading and introduction of the above mentioned products into the soil is recommended. At the same time, calcium carbonate (especially in granulated form) can be mixed with: urea, Polisfoska, Super Fosfat (granulated), ground phosphate rock, potassium chlorides, potassium sulphate and calcium oxide.

14. FARMER: What lime should be used for heavy and fertile soils?

Expert`s answer: For heavy, fertile soils calcium oxide, calcium carbonate or oxide-carbonate – as required can be used. In case of fast soil deacidification calcium oxide would be best. But its application should be minimised because in the long term it has a negative influence on chemical and physical properties of the soil. It is better in the long term, and safer to use slow release carbonate fertilisers.

15. FARMER: How long does lime decompose?

Expert`s answer: The rate of lime absorption by soil environment to a large degree depends on its physicochemical properties and environmental conditions (irrigation, aeration, and soil temperature). For example, calcium oxide fertilisers (quicklime – building lime) react rapidly and cause soil over-drying. In the case of carbonate fertilisers the most important factor is their crumbling. The finer powdery fractions are, the faster is effect of soil infiltration and the fertiliser is more effective.



16. FARMER: What do types of lime mean, e.g. type 04, type 06a, etc.?

Expert`s answer: Terminology of lime fertiliser types is regulated by the Act of 26 July 2000 on fertilisers and fertilisation; Journal of Laws no 89, item 991 (Dz.U.Nr 89, poz.991). In the Act the types of lime fertilisers are clearly described and classified. The basis of assessment was physical condition and chemical composition of lime and methods of its obtaining. From the point of view of the farmer type 04 is the most profitable. A class of fertilisers which do not contain magnesium includes together 13 kinds of lime, of which five types come from limestone processing, four are by-products, and four other are considered minerals. And beware of types containing magnesium because they are usually dolomites.

The most effective granulated lime is lime of type 04 which contains over 50% of CaO and over 90% of CaCO3. Until now in Poland there was no producer of fertilisers of this type, only fertilisers imported from Germany and France have been sold, price of which may reach even over PLN 2000 per ton. Nowadays the only producer of fertiliser of this class is POLCALC in Lubień Kujawski which sells fertiliser under a trade mark POLCALC OF THE 3RD GENERATION. The price of this fertiliser is about PLN 450 per ton.

17. FARMER: What does CaO converting mean and why is lime determined like this?

Expert`s answer: Converting is required by the Act which orders producers to inform about the fertiliser composition expressed in the amount of oxide, in spite of a fact that chemical composition of calcium carbonate does not contain oxide (CaO) but calcium carbonate (CaCO3). Such a solution was introduced in order to easily evaluate the amount of fertiliser needed to deacidify the soil after pH testing and to easily estimate fertiliser value of lime.

18. FARMER: How to test whether the producer does not inform about overstated composition? Who should conduct an analysis?

Expert`s answer: Each producer is obliged, on customer`s demand, to present an attestation of quality for the calcium fertiliser. Documents of this type are issued to producers by Local Chemical-Agricultural Stations or the Institute of Soil Science and Plant Cultivation in Puławy. The information should be placed on packages of sold products. In case of any doubts product testing should be assigned to the nearest Local Chemical-Agricultural Station.

19. FARMER:What are dolomitic limes and what do they differ in?

Expert`s answer: Dolomitic fertilisers are produced by crushing of sedimentary rocks, so-called dolomites. Microscopic structure of this material mostly consists of calcium carbonate and not large amount of magnesium. Therefore, they are mostly calcium-magnesium fertilisers. Unfortunately, natural physical-chemical properties of these rocks cause that it is the least effective fertiliser. It is very poorly absorbed, and advantages of its application are  very questionable.

20. FARMER: What is lacustrine chalk lime and how does it differ from others?

Expert`s answer: Lacustrine chalk calcium carbonate, determined as type 06a is fertiliser of very fine structure, especially when it is a dried and granulated product. However, low CaCO3 content in relation to fertilisers derived from limestone processing of type 04 makes it considerably less efficient.

21. FARMER: What about waste lime?

Expert`s answer: There are also waste limes, so-called post-cellulose and others, however their agricultural usability is doubtful and the use of such fertilisers can surely negatively impact on the soil and products health. It is lime of the highest degree of contamination what means that the proper calcium makes up only about 30-50%. The rest is contamination of difficult to estimate usefulness. Such lime should be obligatorily chemically tested because there is a high risk of field area contamination with toxic heavy metals. However, even such caution may be too little. Chemical-agricultural stations only determine the content of two major heavy elements: cadmium and lead. Other toxic substances are not identified in such testing! The price of such “lime” ranges from PLN 1 to PLN 15 per ton.

22. FARMER: How to distinguish good calcium carbonate?

Expert`s answer: The simplest way is to test the degree of lime crumbling. A simple test may be carried out. After  putting two spoonfuls of lime to a glass of water we should obtain a kind of “milk” in suspension. Products of poor quality leave sand or other admixtures at the bottom of the glass. What should also be noted is producer`s attestation issued by a Local Chemical-Agricultural Station or the Institute of Soil Science and Plant Cultivation in Puławy. Good calcium carbonate should contain over 90% of pure CaCO3 what converted to oxide matter gives about 50-55% of CaO. It should not contain water or other additional substances. In the case of lime with magnesium we mainly deal with dolomite that is a product of very poor reactivity. Remember – when buying always demand attestation and confirmation if the form of the fertiliser parameters testing issued by recognised centres such as the Institute of Soil Science and Plant Cultivation in Puławy or Chemical-Agricultural Stations. Otherwise, you are exposed to fraud at your own request. If the seller or producer does not have such documents, the purchase may be highly risky.

23. FARMER: What is lime reactivity?

Expert`s answer: Lime reactivity is a factor indicating the quality of fertiliser. In other words, the more reactivity, the better. Reactivity directly tells us about what percentage of fertiliser will be absorbed by plants and soil. On the market there are numerous products of low or very low reactivity, the use of which brings nothing to the soil and is economically unprofitable. It is better to buy highly reactive products and be sure that they will work than buy poor quality non-reactive products such as encapsulated stone or mine crumble.

24. FARMER: What is the composition of granulated lime, what is an active ingredient? What is its reactivity?

Expert`s answer: Granulated lime is usually calcium carbonate because it is impossible to granulate calcium oxide (quicklime – building lime). The chemical formula of such lime is CaCO3 what is often improperly understood by recipients because producers convert calcium carbonate to calcium oxide CaO and wrongly give the composition as CaO, e.g. 50%. In that case, 50% of fertiliser is composed of pure calcium oxide (CaO) in general elemental mass. It must be remembered that this is only, imposed by the legislator, obligatory form of product`s composition presentation. However, in fact, good carbonate lime should contain over 90% of calcium carbonate CaCO3.

25. FARMER: What are the advantages of granulated lime?

Expert`s answer: The main advantage of granulated fertilisers is their effectiveness, uniformity, and economy. The cost of the treatment is the lowest of all types of lime and is averagely about PLN 225 per hectare. Granulate ensures a high comfort of work and high accuracy of liming process. What is especially worth recommending is highly reactive, granulated lime preparations stored in big-bags. They make transporting and use of fertiliser easier.

26. FARMER: How can we distinguish between genuine granulate and fake?

Expert`s answer: Many farmers, searching for false savings can be deceived and they buy so-called “pseudo-granulate”. It is ordinary, finely ground stone. It is usually obtained from dolomite, and has no usable values. At the best, producers sell finely ground limestone. Its useful value is limited. Low reactivity of such a “product” causes its negligible impact on soil environment.

Distinguishing lime granulate from fakes is very easy. It is just enough to put a product sample (2-3 spoonfuls) to a glass of cold water. If we almost immediately obtain “milky” suspension, we deal with a genuine product. But if after a while tiny stones are found – we deal with a fraud attempt.


27. FARMER: Is it worth buying lime with magnesium?

Expert`s answer: On the grounds of research conducted by the Institute of Soil Science and Plant Cultivation in Puławy, it may be stated that lack of magnesium often result from lack of the proper soil pH, and their effective supplementing depends on the soil specificity. In other words, first the soil should be deacidified to increase the availability of magnesium forms that are included in it, and then  magnesium content testing on the proper pH should be conducted. It follows that in case of increased soil acidification what is more effective is application of fertilisers without magnesium. Although a number of producers present on our market show that  their fertilisers contain highly reactive magnesium, the truth is different. In Poland there is no a producer of integrated (calcium-magnesium) granulated fertiliser  which would be based on carbonate type of the highest reactivity parameters. Many farmers use compound fertilisers or kieserite (magnesium sulphate) in which the required amount of magnesium in contained, and in such a case magnesium application with lime is pointless and farmers bear the costs without additional advantages.

28. FARMER: When is it best to buy fertiliser?

Expert`s answer: Lime itself, when its storage conditions allow, may be bought throughout the year. In periods when atmospheric conditions are unfavourable it is important not to waste it by freezing (for granulated wet lime) or moisturising. As far as good quality granulated lime is concerned, it can be bought after the season, i.e. in January-February, and in June-July. Many producers use encouraging discount prices at that time.

29. FARMER: How to get subsidies for lime?

Expert`s answer: Throughout the country only in certain voivodships there is a possibility of trying to get such a subsidy. What is noteworthy is a fact that subsidies within voivodships may be changed from one year to another, and the system of applying changes almost every year. Therefore, it is best to contact the nearest Local Chemical-Agricultural Station or Agriculture Chamber in the area to ask for complete information.

30. FARMER: In which packaging it is worth to buy lime?

Expert`s answer: The choice of package is dependent on consumer`s needs, that is a purpose of lime and storage capabilities. For big farms a convenient package is a big-bag type containing from 500 to 1200 kg. They are equipped with foil liner protecting from moistness. Buying such protected, dry fertiliser allows to gather some savings. It is easy to imagine that in the case of lime preparation with a humidity of 30% per 100 purchased bags as many as 30 contain only water! After adding the cost of transport, the initial, low price of such a product becomes definitely less competitive. In this connection, we recommend buying completely dry fertilizers – without water admixture.

31. FARMER: Why is granulated lime more expensive than other forms of lime fertilisers?

Expert`s answer: The price of lime is influenced by a lot of factors. The most important is the quality of an intermediate product (raw material) from which the granulate is obtained. A price-setting factor is also a long and technologically advanced production process of granulate. It begins with obtaining “raw” stone in open pit mines. The following stages are rock crushing, purifying the intermediate product from inconvenient admixtures, grinding in ball mills, drying and granulation. Moreover, costs of transport, storage and market service, and scientific research ensuring the high quality of product are added.

32. FARMER: How is granulated lime stored?

Expert`s answer: Granulated lime, like other granulated fertilisers, should be stored in a dry place, preventing from its moisture or freezing. Granulated carbonate lime under the influence of water will not change its chemical composition, whereas it may weaken the structure of granules.