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Soil Acidity Management and Liming Practices

de José A. Quaggio.

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Double productivity and enrich your land.

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Brazilian territory is composed of about 70% acid soil. In 40% of these soils, its crop productivity
are reduced to half and even then, the amount of limestone is still lower than the optimum,
compared to other commodities.


If soil pH is not optimum, nutrients availability to the plants become harmed. It happens because of the hydrogen concentration that block plants uptake. An acid soil, typically, has low levels of
calcium and magnesium – essential nutrients to plants live – and high levels of aluminum, what is toxic.

Liming, the pliers of a production.

Limestone is an industrialized product originated from carbonated rocks, crushed and screened below 2 mm size, that aim to amend soil acidity when applied to them.
By raising soil pH, the amendment neutralizes the negative effects of the toxics aluminum and manganese and raise basis saturation, guaranteeing the levels of calcium and magnesium that plant
needs and increases the availability of nutrient and micronutrient elements. Liming also helps on the development of the plant root system, powering the effects of compost and
increasing water uptake. Calcium and magnesium are indispensable to plant nutrition. In a short period of time, without a regular replacement of these losses, soil loses its productivity. Liming done
with technique is an imperative practice that improves soil physico-chemical and biological properties, aerating it and collaborating with the microorganisms activities.

Soil analysis.

The soil sampling must be done with technique and addressed to a laboratory to be analyzed. This
corresponds to the first step of rational evaluation of limestone and compost quantity to be applied; it is a critical stage and must be done carefully. Poor interpretation appears when this is not well done. It´s important to alert about the correct sample extraction, once a failure on it can modify the chemical analysis results.
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Dolomitic limestone.
The food of our food.


The nutritional effect of dolomitic limestone is very significant, beside its capacity to amend the soil acidity.
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In order to prepare a sampling plan, it is necessary to split the property in homogenous areas that do not exceed 20 hectares. Through the chemical sample analysis conclusion, done exclusively by an qgronomist engineer, it´s defined the required quantity of limestone to be used. The required limestone quantity to amend soil acidity and raise basis saturation is determined by the soil analyze; vary, basically, from 6 to 7 tons/hectares for the first application and from 1 to 3 tons/hectares for the next applications, depending on the soil and crop types.

Factors to be considered:

• Soil analysis (chemical and texture);
• Foliar analysis;
• Indications of lack of calcium and magnesium and toxicity by aluminum and manganese;
• Factors that affect nutrients availability;
• Area description dairy (limestone and fertilizers quantities, productions, preparation practices, period of crop and others).


Factors that contribute to soil acidification and depletion:

• High productivity;
• Calcium and magnesium quarry by the plants;
• Rainfall (the rain water leaches nutrients);
• Fertilizers (nitrogen fertilizers react with soil elements and acid them);
• Organic matter decay (decayed compounds react with calcium and magnesium, reaching acidity);
• Surface layers removal by erosion;
• Irrigation.

............................................................................................ BackespalhandoThe nutritive importance of Dolomitic Limestone.


Limestone must be chosen by its calcium and magnesium levels and chemical purity (PN). If these macronutrient levels in soil are not above the minimum necessities, the other nutrients added by the
fertilizers – note that they are 15 times more expensive! – do not allow to achieve better levels of productivity, even using seeds that have a good feedback to compost.
Additionally, plants can become weaker with lack of calcium, showing symptoms like atrophy of root system, disastrous on drought. Magnesium, by the other side, is an activator of many enzymes related to carbohydrate and nucleic acids synthesis.
In case of its lacks, there will have big loss on photosynthesis process.For this reason, liming is always recommended based on the usage of dolomitic lime, that is perfect to agriculture. Dolomitic lime amend soil acidity and meets the demand of macronutrients like calcium and magnesium. The levels of these macronutrients must remain steady, once the proportion of them is not important in respect to plants growth and productivity, as shown on scientific studies. Dolomitic lime is easier found due to market supply and it is lower-cost.

THE PRNT.

The Total Neutralizing Power Ratio (PRNT – Poder Relativo de Neutralização Total) is an index that measures the proportion of limestone that will react until 90 days, considering that the soil have enough moisture to promote the reaction.
A limestone that is severely crushed below 2 mm will react with soil at the same way of a finely crushed limestone. Limestone with bigger particle size should be preferred, mainly in areas under
direct plantation system, pasture and permanent crops. A finely limestone will react in a short term compared to a bigger limestone, but is does not mean that bigger ones won´t react. On the contrary, its residual effect is higher compared to finely limestone. Although, it is essential to give preference to products with higher chemical quality (PN equal to 100%).

PRNT is represented by the following equation:

PRNT = PN X RE(%)
                   100

PN means the neutralizing power of the amendment, which indicates the chemical purity of the rock, free from impurities, in neutralizing basis.
RE is the reactivity rate of the amendment and represents the ground grade of limestone particles


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Residual effect.

It is the limestone quantity that will react after 90 days. The residual effect is represented by the subtraction between limestone's PN and PRNT. The liming effects may linger for several months, depending on limestone´s particle size and its PN and on the crop.


Agricultural lime classification.

Regarding MgO (magnesium oxide) concentration:

• High calcium limestone – less than 5% MgO
• Dolomitic limestone – above 5% MgO


Dosage calculation methods.
The two most useful methods appropriated to Brazilian soil conditions that verify limestone requirements are: saturation by basis (V%), typically recommended (from 60 to 80% of cases), and
the calculation of calcium and magnesium replacement needed to soil and plant nutrition.

Application Timing.
The optimum situation is to apply limestone from two to three month before the first fertilization in case of permanent or annual crops. But, even if the producer does not dispose of this time the
limestone must be applied. In the case of pasture, limestone must be applied after reduction or plants cutting down.
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Research indicate that it´s necessary about 800 kg of dolomitic lime per hectare in order to replace calcium and magnesium levels that are extracted annually by the main crops.
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An excellent investment.

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Just few agricultural investments are so profitable such as dolomitic lime. Researches show that limestone application in highly acidic or harmed soils allow to double the productivity of plants. In a short term, liming of acid soils might bring economic returns reaching over ten times the initial investment.
Additionally, it is the cheaper source of calcium and magnesium.

Purity warranty.

Limestone is an industrialized product made of pure rocks. It means that it does not contain any kind of impurities and harmful chemical elements to soil and plants, neither show unfruitful effects to soil
(this is what happens when the amendment is done by chalk). Some amendments offered in market come from by-products and industrial wastes that can contain heavy metals and sodium that poison and salty the soil. These kind of "amendments" are traditionally from metallurgical, chemical and cellulose industries.

A product that comes noble from the nature.

We estimate that for more than 14 thousand years limestone has been used by humans. Even in the Bible, limestone is referenced on ink and plaster manufacturing Even before Christian Era, Greeks and Romans already applied a mixture of friable limestone with clay in their cropping areas in order to improve the productivity Limestone makes part of the composition of hundreds of things that we use and consume daily, like toothpaste, soaps, cosmetics, medicines and foodstuffs.
Limestone is also essential in building construction, glass manufacturing, asphalt, paper, sugar and metal production; we can talk about a lot of other important applications, especially in chemical industry.

In order to have an appropriated usage of limestone according to the necessities of your crop,
consult an agronomist engineer expert on the modern concepts of acidity amendments and its
applications.

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