Agricultural Soil Analysis: Practical Guide
We know that many farmers are concerned about good fertilization. To achieve this, analyzing agricultural soils at the beginning of the campaign is very important. For this reason, in this article, we will talk about soil analysis: how to do it, how often, what parameters to analyze and how to interpret the results.
Agricultural soil analysis
The analyzes of the agricultural soil help us to know our soil and to know what nutrients it has for the crop. A soil test can be very extensive and include many parameters. Sometimes it may seem to us that we need to know everything, but each analysis has a cost. For this reason, it is important to be clear about what parameters to analyze and how often to analyze them.
“To achieve a good analysis, it is essential to take the samples well. It is not the same to analyze the surface of the soil than the soil at a depth of 60 or 90 cm”
Nor is the soil of a flat area the same as the soil of a sloping field. For this reason, it is also very important to do a good planning before taking the samples.
We are going to break down all the basic points to take into account when doing soil analysis.
Sampling of plots
For the result to be reliable and representative of a plot, the samples must be well collected.
It is important not to mix areas with texture differences as this causes variations in other soil parameters. It is also important not to mix soil from plots that are managed differently. In other words, do not mix a plot that is frequently fertilized with slurry with another that is fertilized with mineral fertilizer or one that is tilled with one that is directly sown.
Within the same plot or group of plots with a more or less homogeneous soil there is also a certain variability. This is why it is important to collect samples from more than one point in the plot or group of plots. Depending on the shape and size of your field you will see the best way to collect the samples.
At a minimum you should obtain sub-samples from 3 different points per plot. In large plots you can take one per hectare, approximately. These points must be well distributed in the plot and contain the center, the margins, sloped areas, etc.
The soil taken at all points you have to mix thoroughly. Then, from this mixture, you have to take the final sample of approximately half a kilo. The rest of the soil can be discarded.
Sampling depth is also important. In general, it is interesting to pick between 0 and 40 cm, which is where the plant develops its roots. In very deep soils that are easy for roots to penetrate, it is good to take samples up to 60 or 70 cm.
What soil parameters should I test and how often?
There are different types of parameters to consider.
Invariable soil parameters: This means that once is enough.
Soil texture
Texture indicates the proportion of different sized particles in the soil. In a familiar way we talk about coarse soils, fine soils, soils with a lot of clay, etc.
As a farmer, you surely know the type of texture you have in each plot of your farm. Even so, performing a texture analysis can give you extra information and help technicians to better advise you on issues such as soil management and soil fertility analysis.
At a technical-scientific level, textures are divided into four large groups according to the proportion of clay, silt and sand in the soil. The categories are:
· loamy soils
· sandy soils
· slimy soils
· open soils (no predominant fraction)
There may also be soils between the two categories, for example, open-loamy soils.
Soil pH: stability is the key
pH is a chemical parameter that indicates whether a substance is acidic or basic. The scale of results goes from 0 to 14. Being the soils of pH 7 neutral, those of more than 7 basic and those of less than 7 acids. The closer the value is to 0, the more acidic the soil is, and the closer it is to 14, the more basic.
pH affects nutrient availability and crop growth. Soils with very extreme pH are not fertile as there are no nutrients available to plants.
Little variable parameters: once every five years
1. Organic matter: the key to a fertile soil
Organic matter is key to having a fertile and productive soil. Soil organic matter are those soil compounds that are organic. Roughly, you can tell if a soil has a lot of organic matter by looking at its color: dark soils tend to have more organic matter.
Organic matter affects many soil properties and increases biological activity. It helps make soil nutrients available to the plant, keeps soil pH stable and reduces the risk of erosion.
There are different actions that can be carried out to increase or decrease the organic matter of a soil. For this reason, it is interesting to carry out an analysis of agricultural soils on a regular basis. Every 5 or 10 years, for example. These analyzes of organic matter are especially interesting if some action is taken to increase it, such as the application of manure or direct sowing.
2. Electrical conductivity: knowing the salinity of your soils
As you know, crops do not grow properly in saline soils. In fact, in very saline areas of the Ebro Valley, frequent localized irrigation is necessary to wash the salts from the root zone of fruit trees.
Soils can become salinized due to water with many dissolved salts and lack of good drainage. This especially occurs in irrigated areas in arid areas. For this reason, it is important to calculate a washing fraction in irrigation.
In rainfed areas, a single conductivity measurement may suffice. In irrigation, it is a parameter that can vary. For this reason, it is interesting to carry out periodic analyzes every 5-6 years.
3. Phosphorus: the key to growth
As you know, phosphorus is one of the macronutrients that crops require to grow properly. Depending on the humidity, the temperature of the soil and the type of roots of the crop, it will be able to intercept more or less phosphorus from the soil.
For this reason, the interpretations of the analysis of phosphorus in soils are complex. Depending on the areas and crops there are different interpretation tables.
Phosphorus is not very mobile in the soil, so carrying out an analysis every 5 years is enough to know what level you have in your soil.
4. Potassium: a quality production
Potassium is another of the macronutrients necessary for the correct development of the crop. Potassium is modified by various agricultural techniques such as mineral and/or organic fertilization, soil management, removing vegetable residues that are rich in potassium, etc. Even so, it is a little mobile element on the ground.
For this reason, carrying out potassium control analyzes every 5 years is enough to know if you have the correct levels in your soils and to be able to plan fertilization.
Potassium is of great importance in the quality of the final product. At this point, not only are deficiencies important, but also excesses of potassium. That the tree has enough potassium increases the level of sugars in the fruit, but an excess of this is related to rottenness in the fruit. In cereals, it increases lignification and produces better quality straw.
Highly variable parameters
In this type of parameters, the more analysis the better.
5. Nitrogen: maximizing yield
Nitrogen is the main macronutrient. As a farmer, you are surely very concerned to ensure that your crops do not suffer from nitrogen deficiency.
Nitrogen is found in the soil in many different forms. Some are accessible to crops while others are not:
Nitric nitrogen is the fraction of nitrogen directly assimilable by plants.
Ammoniacal nitrogen is also assimilable by plants as long as it is previously converted to nitric.
These two nitrogen fractions are what are analyzed in a soil nitrogen test.
In general, the ammoniacal part is very small, so analyzing the nitric nitrogen is usually sufficient. With this you can already plan the fertilization.
The nitrogen content in the soil is highly variable both in space and in time. Rainfall, soil management, fertilization and residue management, among others, directly affect the nitrous nitrogen content of the soil. As a result, winter exit levels after a rainy winter can be radically different from the previous fall’s levels.
For this reason, it is recommended to do at least one soil test per year. This analysis can be done before sowing or at the end of winter:
If it is done before sowing, it is possible to calculate the nitrogen available at the end of winter, knowing parameters such as: crop needs, applied fertilization, temperature and rainfall, etc.
If it is analyzed at the end of winter, it is ensured that the necessary nutrients are provided to the cover, even though the background fertilization has been carried out “blindly”.
Conclusion
As you can see, analyzing agricultural soils gives you a lot of information about your plots. This information can help you on a daily basis in many ways. It is important to link the results of the analyzes with operations such as tillage, fertilization, etc. And, based on the results and where you want to go, prepare future actions.
Source: Villar, J.M. Villar, P. Guide to Soil Fertility and Plant Nutrition on Integrated Production.
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The Digitalization Process of Agriculture
In recent years, technology has allowed digitization in all work areas. The primary sector is no stranger to technological changes and has also been immersed in digitization.
The digitization of agriculture was born in order to save and improve the handling, management, parameterization and quality of life in general for farmers. In this post we are going to see how digitization in agriculture can help us and benefit us in the agricultural management of our farms.
What are the objectives of the digitization of agriculture?
The digitization of agriculture aims to put paper aside and record all data electronically in the field notebook. Within the agricultural sector, this process arises with several clear objectives based on pre-existing needs.
Reduce physical documents
The agricultural sector stands out for its heavy burden of bureaucracy and paper documents that in many cases make order and management difficult. Unlike an office, in the field papers can get wet, dirty or lost very easily, in addition to storing a large number of folders.
With the digitization of agriculture, we want to avoid all these papers and documents and work digitally with the same mobile phone. Today, the vast majority of people in the agricultural sector carry a state-of-the-art mobile phone with an Internet connection in their pocket. This allows the digitization of agriculture to be very easy and attractive for all farmers.
Use of Data
The digitization of data in agriculture is a very important first step to meet other challenges that facilitate the organization and daily management of agricultural and livestock farms.
The key to being able to easily and safely manage a farm is to use data to make our work easier. The digitization of agriculture can allow us to quickly know the yield per hectare of a crop plot by plot, the exact amounts of herbicide that we must apply, or the sowing dose per hectare depending on the plot we are working on, etc.
All this implies the use of data that we have previously digitized and allows us to improve efficiency and consequently increase the profits of our agricultural company.
Business development
The digitization of data and its subsequent use to manage our farm allows us to take a much broader view and go further at the business level. The agricultural digital transformation implies modernization and therefore the capacity for business development and new business models that are increasingly economically and environmentally sustainable.
The digitalization of agriculture today
As we have been saying, there are multiple advantages of digital transformations in agriculture. There are currently many examples of practices that are already being developed to promote the digitization and modernization of the sector.
Precision farming
Precision agriculture was born as a result of the digitalization of agriculture. It intends to use data and images obtained from satellites to analyze different agricultural parameters, the behavior and development of crops, soil fertility, etc.
All this allows the farmer to be able to fertilize or pay with the exact amount that is needed at any given time, irrigate area by area of the farm with the water resources that the plants need, or automate fertigation processes in greenhouses or orchards.
There are agricultural management programs that start from the beginning: collect data and then be able to use it and exponentially improve the management of your farm.
A mobile application allows field workers to record the different tasks that are being carried out on the same farm. This allows you to enter all the plots of the farm or agricultural company to later be able to parameterize the data.
With a mobile phone you can write down very easily and from anywhere what sowing dose you are using, what treatment you are doing and what plots you have worked.
This easy and comfortable task then allows us to automatically extract a whole series of historical data, calendars, dates, cost control, and even automatically download the official notebooks that have to be presented before an agricultural inspection.
Currently there are also programs for agricultural companies, with an application and program focused on the management of a large agricultural company, as well as the management of workers.
The digitization of agriculture, an issue of the present
We have seen that agricultural digitization is already part of the present in the agricultural sector and no one doubts that it is here to stay. The advantages of digitization are multiple: saving time, phytosanitary products, losing paper and, above all, reducing costs and increasing profits. If you are interested in digitization and you are one of those who believes that you cannot be left behind.
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The Organic Processes of the Soil
Soils are characterized by being poor in nutrients or presenting deficiencies in some of them, so the maintenance of high levels of organic matter contributes through biological cycles, to constitute a biodeposit of nutrients, as well as to contribute to the capacity of cation exchange.
The productivity of a sustainable agricultural system is closely linked to the magnitude and efficiency of the use of nutrients, and the reduction of their losses, which can be reduced, but not eliminated, since processes such as volatilization, fixation and immobilization of nutrients, to name a few, cannot be totally eliminated.
The use of plant residues as such or incorporated into the soil can help reduce erosion losses by keeping it covered, while increasing the rate of incorporation of organic matter.
The production of compost from crop residues, household waste, manure and other locally available organic residues is another important strategy for the recycling of nutrients. Compost is the final product of the decomposition of organic matter by soil microorganisms and constitutes an organic fertilizer that fulfills a double function: it contributes to improving its structure and provides nutrients; its organic acids make the nutrients in the soil more available to the plant.
Similarly, the use of the earthworm for the transformation of organic waste into humus and its incorporation into the soil as organic fertilizer is a practice that allows the life of the soil to be intensified due to the abundant microbial flora it contains. The earthworm humus is a biological stimulator of soil fertility due to the balanced contribution of vitamins, enzymes, auxins, macro and micro elements, fulvic and humic acids that with its application is achieved.
Macros and micro elements can be radically assimilated, while enzymes, vitamins and auxins exert their function in the rhizosphere and at the same time stimulate the development of concurrent microorganisms in that area.
Mineralization is the decomposition of humus, coming from both composting and vermiculture processes and natural transformation phenomena in soils, in addition to giving rise to the formation of products or substances assimilated by plants (ammonium, nitrates and mineral substances). As a process, it is a biological oxidation in the presence of calcium (Ca) and phosphorus (P) that occurs slowly. It is carried out by highly specialized organisms and takes place under suitable conditions of humidity, pH, temperature and the presence of oxygen.
Fulvic acids appear as an initial result of the biological oxidation of organic matter and, in the presence of calcium, phosphorus, potassium and nitrogen, they are in turn biotransformed into humic acids that are subsequently degraded to become the aforementioned nutritional substances. An excess of calcium, a product of liming in the soils, which is associated with pH values higher than 8 units, causes the retransformation of this chemical species to fulvic acids again and stops the mineralization process. This situation draws attention to the need to take into account the characteristics of the soils before applying organic matter to them.
The increase in the biological fixation of atmospheric nitrogen by the use of bacteria-based biopreparations (Rhizobium, Bradyrihzobium, Azotobacter, Azospirillum, etc.) that allow supplying part of the nitrogen that plants need, as well as the use of other microorganisms capable of solubilizing fixed or non-assimilable phosphorus from soils are effective alternatives to maximize the use of nutrients by plants.
There are many commercial versions of these products and their use is already a common practice in modern agriculture. Their choice depends on the edaphoclimatic conditions in which they must exert their effect and the management possibilities available to the producer.
The application of organic matter to the soil must not only respond to the need to guarantee the improvement and / or conservation of this natural resource: it must also take into account the nutritional consumption of the plant species to be cultivated, so that it is equally valid by the net contribution of elements that is obtained.
Thus, the nutritional richness of the different organic sources used in agriculture must be taken into account. In this regard, cachaça, worm humus and manures of various origins are among the most widely consumed and recognized materials.
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Soil Fertility
Three nutrients are recognized from the quantitative point of view as main: nitrogen (N), phosphorus (P) and potassium (K), followed by sulfur (S), calcium (Ca) and magnesium (Mg) as secondary elements and another group of which plants need only small amounts and are known as trace elements; iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), boron (B) and molybdenum (Mo).
For the metabolic functioning of the plant to be adequate and its optimal development, it is necessary that the nutritive substances are in balance and interact harmoniously, while in excess or deficit weak plants are originated, susceptible to attack by pests and diseases, low food quality and short-lived crops.
Each nutrient cannot be evaluated in isolation but in its relationship with the others, being of fundamental importance the knowledge of the functions of each of these in relation to plant metabolism.
Nitrogen. – It is essential for vegetative growth and essential in the protein formation process. Its deficiency causes low yields, weak tillering in cereals, premature maturity, light green or yellowish leaves, among others. An excess of this element translates into less resistance against pests and diseases, capsizing of plants, dark bluish-green leaves and delayed maturation.
Phosphorus. – It plays a fundamental role in cell division and is an elemental part in high valence protein compounds, influences the formation of roots and seeds, being a main regulator of all the life cycles of plants. Its deficiency is manifested by a delay in flowering and a low production of fruits and seeds. Too much can cause elements such as zinc to stick to the ground.
Potassium. – It actively intervenes in the process of cell division, regulating the availability of sugars, as well as in the absorption processes of calcium, nitrogen and sodium. Its deficiency is manifested in the form of necrosis in the margins and tips of the oldest leaves, low yield and little stability of the plant, poor quality and high loss of the harvested product. In excess of fixation the fixation of magnesium and calcium.
Calcium. – It is a fundamental part of certain compounds and very important in the regulation of pH, strengthens the roots and cell walls and regulates the absorption of nutrients.
Magnesium. – Constituent of chlorophyll, it has a predominant role in the activity of enzymes related to carbohydrate metabolism. Its deficiency is manifested in the plant by the presence of lower chlorotic leaves, reducing the harvest and the size of the fruits; an excess of this element causes calcium deficiencies.
Sulfur. – Indispensable for the protein formation process, especially in legumes, its deficiency symptoms in general are not very visible.
Iron. – It constitutes an important catalyst for photosynthesis and oxidation participating in the processes of formation of carbohydrates and chlorophyll, its deficiency causes chlorosis between the veins, mainly in the youngest leaves, reduces growth speed and limits fruiting; in excess it causes necrosis spots on the leaves.
Copper. – It is a catalyst for plant metabolism, as well as a component of fundamental enzymes such as polyphenol oxidase. When there is a lack of this element, the leaves appear dark green and roll up, while its excess is harmful, especially if there is a presence of more than 10 ppm of this element in the soil since it is toxic to the microbial life of the soil. and the roots of the plants themselves, inducing iron deficiency.
Zinc. – Important factor in the production of auxins, an essential component of enzymes and coenzymes and its deficiency produces chlorosis, shortening of the internodes and decreased seed production, and its excess brings with it an iron deficiency.
Manganese. – It is an activator of many essential enzymes, its lack produces chlorotic leaves with necrotic and malformed lesions.
Boron. – It has the property of forming complexes with sugars, playing an important role in their transport, its lack causes death of the apical meristems, the plants have a bush-like appearance with many branches, flowering often
does not exist and when there are fruits, these are usually badly formed. Excess causes chlorosis and burns. The range between sufficiency and toxicity is very narrow.
Molybdenum. – It is essential for nitrogen fixation from Rhizobium. In a state of deficiency, a chlorosis that varies from a greenish-yellow to pale orange color develops, and may present necrosis; flowering can be suppressed and legumes often show symptoms of nitrogen deficiency.
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