The Importance of Soil Analysis – Soil Liming
According to Assmann and Soares (2016), soil should be considered a single living organism, being the interface for the transfer of nutrients between agricultural crops. Soil analysis is an important tool that allows us to know the soil's capacity to supply nutrients to plants, even before planting. According to Cardoso et al. (2009), it is the simplest, most economical and efficient way to diagnose soil fertility, constituting an essential basis for recommending adequate amounts of correctives and fertilizers to increase crop productivity and, as a consequence, crop production and profitability.
Other aspects that favor the use of soil analysis as a basis for planting are its low cost and speed in obtaining results, adequate planning of purchasing and use of inputs, avoidance of nutritional imbalances and the ability to minimize damage caused to the environment, especially in terms of water contamination due to excess fertilizers. Therefore, with the analysis in hand, it is possible to determine the correct amounts of fertilizers and limestone to be added to the soil.
Soil sampling procedures
Soil sampling is considered the most critical step in the entire soil analysis process, since a small portion of land will represent a few hectares, and there is no way to correct possible errors made during sampling (FURTINI NETO et al., 2001). Cardoso et al. (2009) state that, for the results of soil analysis to truly represent the sampled land reliably and serve as a basis for recommending appropriate liming and fertilization, the area must be sampled correctly. Care with sampling must be given special attention, therefore, it is essential that the person in charge of collecting samples in the field has full knowledge of the procedures necessary for appropriate and representative sampling (CARDOSO et al., 2009).
According to the Agronomic Institute of Campinas (IAC), the property should be divided into homogeneous plots, never with areas larger than 20 hectares, to be analyzed separately. In order to calculate the average area correctly, the ideal is to walk through the plot in a zigzag pattern, collecting 20 samples per plot. Avoid points close to termites, anthills, houses, roads, corrals, animal manure, fertilizer deposits, limestone or soil stains. It is also important to emphasize that all materials used in the collection must be clean and, above all, free of any limestone or fertilizer residue.
What is the purpose of soil liming?
Soil reaction is the first factor that must be taken into account when planning to grow crops, because if it is not favorable, corrective measures must be taken before planting and preparing the soil (fertilization) (SOARES et al.). Most Brazilian soils are considered acidic. When not corrected, especially in sandy soils, acidity can become a virtually irreversible problem. This acidity is basically due to the presence of two components: H ions+ and Al+3, and is caused by the intense washing and leaching of soil nutrients, by the removal of cationic nutrients by the crop without proper replacement, and also by the use of acidic fertilizers. When acidity is high, the most advisable measure for its correction is liming.
Soil liming is the recommended technique to reduce this acidity, where limestone (CaCO) is applied.3) – a rock with low solubility, with the objective of correcting the soil pH, increasing the calcium and magnesium levels, neutralizing aluminum and preparing the environment for the roots to grow in a way that provides the best development of crops. In addition to the benefits mentioned, Santiago and Rossetto also highlight the increase in the availability of phosphorus, since it reduces the fixation sites of this element in the soil; reduction of the toxicity of aluminum and manganese through the formation of hydroxides, which are not absorbed; increased mineralization of organic matter and, consequently, greater availability of nutrients. Liming also favors nodulation and consequent biological fixation of nitrogen. In the physical properties of the soil, liming increases aggregation, since calcium is a flocculating cation and, therefore, reduces compaction. Therefore, liming is essential to improve the physical, chemical and biological properties of the soil, representing one of the most cost-effective investments for rural producers.
Criteria for soil liming recommendation
According to Lopes et al. (1991), among the various methods for recommending liming, three are mainly used in Brazil, in addition to some local variations. These methods are: 1. Aluminum neutralization; 2. SMP buffer solution; and 3. Base saturation, which will be briefly described below.
- Neutralization of aluminum:
It is characterized by being one of the simplest methods of recommending liming, since exchangeable aluminum is one of the main factors related to soil acidity. It is worth noting that this technique is considered inefficient in clayey soils with a lot of organic matter, in addition to the fact that the limestone dose calculated by this method is insufficient to raise the soil pH significantly, generally only to pH 5.7, or a little less.
- SMP buffer solution:
According to Lopes et al. (1991), this method consists of shaking a quantity of soil with a volume of SMP buffer solution, and is widely used in the states of Santa Catarina and Rio Grande do Sul. The Fertilization and Liming Manual for the States of Rio Grande do Sul and Santa Catarina states that the amount of corrective to be applied depends on the pH in the water that should be achieved (reference value). This amount increases with the potential acidity of the soil expressed by the SMP index. The potential acidity of the soil decreases as the SMP index increases. Furthermore, the Manual suggests that, in poorly buffered soils, the SMP index may underestimate the need for limestone. In these cases, this can be calculated by the organic matter and exchangeable aluminum contents of the soil, depending on the pH to be achieved.
- Base saturation:
The amount of limestone to be used can also be indicated by the saturation of the cation exchange capacity (CEC)pH 7,0) by bases. It is generally used in the states of Paraná and São Paulo, and is based on the relationship between pH and base saturation, where, in the calculation, parameters related to the soil, the corrective and the specific crop are considered, which makes it a more flexible method with a greater theoretical basis.
Soil is considered the foundation of terrestrial life on the planet as well as a non-renewable natural resource, and understanding how it works is essential. Therefore, proper management and preservation of soil through sustainable activities become essential tasks, since it is limited, and unbridled exploitation can cause many future problems. For this reason, liming, which aims to eliminate all possible harmful effects of soil acidity, helps to enhance the effect of ILSA fertilizers.
Bibliographic references
ASSMANN, TS; SOARES, AB Migrating from crop fertilization to system fertilization through Crop-Livestock Integration. Informativo Integrar, Triunfo, n.15, 2016.
CARDOSO, EL; FERNANDES, AHBM; FERNANDES, FA Soil analysis: purpose and sampling procedures. Technical Communication, Embrapa, Corumbá, n. 79, 2009. 5p.
Embrapa Temperate Climate – Soil Analysis: Procedures for collecting samples. Soil Fertility Laboratory, Pelotas.
FURTINI NETO, AE; VALE, FR; RESENDE, AV; GUILHERME, LRG; GUEDES, GAA Soil fertility. UFLA, 2001. 252 p. (Course completion work)
Agronomic Institute of Campinas (IAC): How to take a soil sample. Available at: http://www.iac.sp.gov.br/produtoseservicos/analisedosolo/retiraramostrasolo.php
LOPES, AS; SILVA, MC; GUILHERME, LRG Technical Bulletin: Soil acidity and liming. National Association for Fertilizer Diffusion, São Paulo, n. 1, 1991. 22 p.
Fertilization and liming manual for the states of Rio Grande do Sul and Santa Catarina. Brazilian Society of Soil Science. Soil Chemistry and Fertility Commission. – 10th ed. – Porto Alegre, 2004. 400 p.
SANTIAGO, AD; ROSSETTO, R. Liming: Tree of Knowledge – Sugarcane. Ageitec, Embrapa. Available at: https://www.agencia.cnptia.embrapa.br/gestor/cana-de-acucar/arvore/CONTAG01_34_711200516717.html
SOARES, AHV; SILVA, CA; ZAMBALDE, AL An Expert System for Calculating Liming Needs and Recommending Correctives. UFLA, Lavras.
Authors
- Agricultural Eng. Msc. Aline Tramontini dos Santos
- Agricultural Eng. Msc. Carolina Custodio Pinto
- Agricultural Eng. Msc. Thiago Stella de Freitas
