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Is it possible to measure indoor temperature with a telephone?
The mobile phones we buy today have temperature and humidity control sensors . Normally, the device, through software, makes use of them to control the overheating of the same.
What you don't know is that we can give it a totally different use. In a simple way such as installing an application, you can measure the ambient temperature with your mobile.
At the end of the post, I leave you a series of free applications, which will use the internal thermometer of your smartphone , to show you the interior temperature of your house . In addition, they will use the Internet to detect the outer degrees and that you can make a comparison.
As you have probably wondered how it is possible that your phone is able to detect the temperature that is right now in your room, I am going to explain the three ways that are currently used:
Internal humidity and temperature sensors: Since almost the manufacture of the first smartphones, companies have introduced these sensors to monitor the proper functioning of the device. They are generally used to detect the entry of water and / or the heating of some of the components, such as the processor.
Battery temperature control: It is the least reliable of them, since it is a battery's own sensor . When there is an increase in the degrees in the battery, it can be due to: an increase in the ambient temperature, an increase in the active processes in the phone or even the load itself.
Internet: It is the fastest method , and therefore not very precise. It is based on an estimate of the outside temperature and using algorithmic calculations to remove the inside.
As I think it is logical, and I hope you have reached the same conclusion, we are going to download applications that make use of the internal sensors dedicated to them. Let's go to point 1.
Apps to measure indoor humidity and temperature
Here are two of the most downloaded applications from the Google Play Store. However, here is a link with more thermometer applications .
Thermometer - Intelillgent System : Uses the built-in sensors to detect the ambient temperature and the Internet to detect the outside. In a very simple interface, you will be able to see the real difference between your room and the outside.
Thermometer - Mobital : I like this one more, since it is more complete than the previous one. It allows you to carry out calibrations, and also play with changes in ºC and ºF and give you information about the weather.
As you can see, it is possible to measure the ambient temperature with your mobile. With a few simple applications, get very precise data thanks to the sensors incorporated in your smartphone.
What is the best room temperature?
To live in a comfortable home it is necessary to maintain an optimal room temperature. We explain how to get it. There is a lot of talk about what is the best room temperature to live. And we think that it is necessary to know it so as not to abuse energy and not to put, for example, the heating higher than we really need. At Healthy Housing we want to clarify this issue in the simplest way.
Best room temperature
The most comfortable temperature for humans in a resting state is between 18º and 20ºC. If you are working, the figure drops to the interval between 15º and 18ºC, depending on the type of movement and the intensity with which it is performed.
To get an idea, we can compare man to a stove whose fuel is food. Specifically, a 70kg man is equivalent to a stove that generates 105 Kilocalories every hour, an amount that is enough to boil 25 liters of water. This is the reason why when we are many in a room the temperature rises. Each person who enters is like putting one more stove.
The best way to heat a room is to install moderate heat sources in the coldest areas. Be careful with the temperature of the heat source, if it is higher than 70ºC, dry mouth and mucous membranes occur. Also raising the temperature too much is not energy efficient. For this reason steam heaters and iron stoves are not particularly suitable inside homes.
Ways to improve the room temperature
A concept associated with the best ambient temperature is that of air humidity. A pleasant environment should have a relative humidity of 50-60% and between 40% and 70% is considered acceptable. An environment that is too humid favors the development of harmful germs and fungi.
Of course each person contributes with their breathing to increase humidity. Let us bear in mind that man inspires oxygen with the air and releases carbon dioxide and water vapor in an amount that varies according to weight, age, diet or activity. Since carbon dioxide is toxic, proper ventilation is necessary .
Plants can be a way of balancing the humidity of the environment in humid environments, and they also help us improve the quality of the air in our home, since they absorb the CO2 that we expel and release oxygen. In this way we achieve cleaner and purer air inside the house.
On the other hand, today there are systems capable of controlling the temperature, and sometimes even the humidity of the environment, while optimizing the energy consumed. Some of the most popular examples are underfloor heating or blue heat.
Avoid heat losses
Finally, to maintain a stable and correct temperature, we must not only choose the heat sources correctly but also make sure that this heat is kept inside the house. The changes in temperature from one room to another that usually occur in poorly insulated environments are one of the main causes of cooling and expose the body to alterations that prevent us from maintaining a comfortable temperature.
To avoid these heat losses, it is essential that both walls and exterior enclosures such as doors and windows are adequately insulated . In this sense, windows are usually the weakest point in the house, poorly installed or poor quality windows can cause large heat losses, which means a significant increase in the expense necessary to heat the house. We leave you with a recommendation: when in doubt, if we are looking for good insulation, it is always better to choose windows that are not sliding, if possible made of PVC and with double glazing, in this way you ensure a correct insulation that you will notice on the bill of heating at the end of the month.
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Visually and biologically effective lighting for indoor plants
The integration of plants in workspaces and rooms requires a special lighting approach What are the challenges involved in making appropriate lighting for ornamental plants indoors? Dr. Karolina Zielinska, with the collaboration of Julia Hartmann and Carla Sigillo, raises in her work LED Light Sources and Their Complex Set-Up for Visually and Biologically Effective Illumination for Ornamental Indoor , the essential points around the subject through a practical case based on the analysis of the existing bibliography, and of photographic evaluations of plants under different sources of LED light, in which properties such as correlated color temperature (TCC), color rendering index (CRI) are measured , color spectral distribution (DEC), maximum wavelength of light (λP), among others.
Karolina M. Zielinska Dabkowska is a RIBA accredited architect and award-winning lighting designer. She is an assistant professor at the Faculty of Architecture, Gdansk Technical University in Poland; and co-founder of GUT LightLab, where she leads a research team focused on various aspects of light and lighting in the construction of environments. Karolina actively participates in the work of international organizations, such as the International Association of Lighting Designers (IALD), Illuminating Engineering Society (IES), and the International Dark-Sky Association(IDA), where it offers a guide towards a better practice of night lighting in public spaces and natural environments. Likewise, he has participated in numerous international conferences and has collaborated in national and international publications.
As a background to this analysis, Karolina Zielinska explains the integration of plants in work spaces and bedrooms, a practice that has been increasing in recent decades -called biophilia-, and has led to a growing interest on the part of researchers and professionals in different areas of architecture, with which multiple interpretations arise today about its meaning, as well as its applications in the generation of green and healthier environments for the user.
In accordance with this trend, argues the Polish academic, a philosophy of green architecture must involve an approach that can minimize negative environmental impacts - this through the correct application of sustainable energy sources, materials, and materials. construction processes of these spaces.
In this sense, there are numerous certification programs and standards that have been established to measure and verify that certain criteria for responsible construction and design are met; but there is still a lag in terms of the regulation of requirements for natural or artificial lighting for indoor plants -the latter are even non-existent-, a situation that contrasts with the interest that has been given to the practice of lighting in cases of commercial cultivation of plants for consumption (fruits and vegetables).
Resolving this deficiency and providing lighting that is appropriate for indoor plants requires taking into account factors such as the impact of wavelengths in the light spectrum on processes such as photosynthesis, photomorphogenesis and photoperiod, the study states. As is known, both natural light and artificial light affect the life cycle of plants; but, while the need for UV light from plants is an accepted fact, its use indoors is not frequent due to the negative effects it can cause in man, such as premature aging, burns, among others.
Despite the widespread use of specific lighting in horticulture - with the purpose of stimulating plant growth times - recent studies have confirmed that wavelengths in the green light range (497-570 nm) can penetrate more deeply in the leaves, and consequently favor the photosynthesis process.
Therefore, an optimal visual perception of decorative indoor plants should simulate natural lighting conditions; But, also considering that the effect of the lighting quality seems to be different for each species (especially during the growth phases), in the case of decorative indoor plants, if they grew only under artificial lighting conditions, they would be compromised. their appearance and biological functions, so it would be necessary to consider the evolutionary arrangement of certain plants and replicate as far as possible the appropriate characteristics within the spectrum of solar radiation through LED technology.
So artificial light or natural light for indoor ornamental plants?
As Dr. Zielinska maintains in her work, natural lighting is the most favorable for plant growth, as it is a source that provides both energy and the ideal spectral range; Unfortunately, illuminating an interior space with this type of light turns out to be a challenge due to several factors, since to the extent that plants complement an interior space, it is also necessary to balance lighting and the use of space to optimize the positive impact of light on plants and users.
The light distribution, direction, and vertical and horizontal lighting levels have a significant influence on the way architecture is perceived by humans, so the introduction of sustainable green architecture designs can become especially beneficial in design solutions.
In addition to this, most LED devices illuminate without generating heat and this results in a benefit for both plants and humans, but both respond differently to intensity, or light energy.
Based on these notions, the researcher seeks to emphasize the imperative of finding a formula that establishes the appropriate levels for both species, but also to understand that units such as lux or lumens cannot be used in the first place to measure intensity. of lighting systems for plants, because the values vary and depend on the spectrum of the luminaire, because in interior spaces, to stimulate the natural processes of a plant, the flux density of photosynthetic photons must be measured, which it is normally between 30 and 100 times higher than that required by humans, and it is also necessary to implement light sources that emit the correct wavelength.
On the other hand, for humans, factors such as visibility, visual performance and comfort must be considered, which are categorized based on visual function and use of space. These levels are determined from the perception of the brightness of visible white light, to increase the growth of plants in indoor environments it is necessary to first evaluate the intensity of light using appropriate metrics and meters, and only then to alternate it according to specific needs.
Despite the technical challenges, LED lighting is established as the preferred solution for lighting interiors, since when combined with an appropriate control system it offers enough flexibility to regulate the spectral composition, as well as to select an emission in the peaks of wave range more suitable for the correct development of ornamental plants.
As the academic concludes in her article LED Light Sources and Their Complex Set-Up for Visually and Biologically Effective Illumination for Ornamental Indoor, published on the academic portal Sustainability. It is then that, from this type of research work, the need for professional practice and a guide in the implementation and development of lighting sources for indoor plants can be based, and in this way contribute to the search for improvements. in the area of green architecture and biophilic design.
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What is the best artificial light for plants?
We know that for good plant health and growth, light is necessary, especially sunlight. But we can have a series of alternatives to sunlight for indoor cultivation that allows us considerable energy savings, such as LED lighting for plant growth.
Depending on three fundamental factors, we will see what type of artificial light is good for plant growth. These factors are as follows:
Light color
Hours of light
Amount of light we supply to plants
Light color
Here we will see the sum of colors that make up the light that reaches the plant. Within electromagnetic radiation, visible light is the part of electromagnetic radiation that we can see. The color of light depends on its wavelength (or frequency) , normally measured in nanometers ( nm , one millionth of a meter). Specifically, visible light or the visible spectrum (what the human eye can perceive) is composed of radiation ranging from 380 nm (blue) to about 740 nm (red). They are very approximate data since it depends on the perception of each person. Beyond the blue we have the ultraviolet (with a shorter wavelength) and on the other side we have the infrared (with longer wavelength).
If we divide this spectrum of colors into fragments of interest to plants, we have a blue one , a green one (a color that plants do not absorb and for that reason we see them as green), a red one, which includes the called far red.
Light emissions (for example from the sun) are composed of photons (which have some of the properties of a wave and some of a particle) of different wavelengths (colors). For example, sunlight is a combination of certain wavelengths, giving white light . In addition, the sun gives other wavelengths that we do not see, such as infrared (heat) or ultraviolet, which are outside the visible spectrum.
Color Blue (between 400 and 500 nm):
the blue color is responsible for vegetative growth (which occurs after germinating and until flowering). When we give a plant only blue light, it grows shorter and has a darker color.
Red / Far Red (600-700 nm):
Plants interpret these colors as the ratio of one to another. This relationship influences the elongation of the stem , especially in direct light crops. Plants reflect far red much more than red. A consequence of this is that when there are many plants together, the amount of far red increases (the red / far red ratio decreases) and this causes the plants to lengthen their stems (for example, to capture the light better since there is competition) .
Blue and red:
This combination favors flowering.
Choosing good lighting (artificial or solar) is important to have the best results.
Number of hours of light or Photoperiod
The photoperiod is the number of hours of continuous light that a plant receives in a 24-hour period. In the case of being in the field, the photoperiod will last the same as the hours of sunlight , as is logical. In addition, it must be taken into account that the photoperiod varies depending on the season and as we have seen before it can affect the flowering of some plants.
Short-day plants are those that bloom especially when the day is shorter than a certain amount. And on the contrary, those with long days are those that flower only or more easily when the day is longer than certain hours. We could say that this number of hours is around 12 , although it varies by species. Finally we have neutral plants in terms of day, whose flowering does not depend on the photoperiod. Apart from flowering, it can affect branching, growth, and other aspects of the plant.
Amount of light
By quantity we mean the number of photons that a surface receives and photosynthesis can take place. We can refer to the amount at a certain moment (light intensity) or all the light it receives during a day.
What kind of light do I need?
The first thing to consider would be the type of plant you have, if you have some sunlight or no sunlight. They are the different situations that we can find. In each of them the differences will be the power of light that we need.
We have seen that plants need blue light and red light, depending on how much blue and red light we will favor the growth of the plant as well as its flowering. The redder the more flowering.
With LED lighting we can get "pure" colors from a light source since we can give blue light and red light that the plant needs without providing anything more than what is necessary for growth and flowering. This will save on energy costs, for example, to illuminate with green if the plant does not absorb it.
In this diagram we can see the light distribution of a led luminaire for plant growth, ideal for indoor cultivation
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What type of lighting to use in indoor growing
We review the different lighting systems for indoor crops, their advantages and disadvantages, so that each grower chooses what best suits their needs.
Cannabis needs sunlight and the passing of the seasons. This way you know when to stop growing and start flowering, as the days get longer and the daylight hours increase. However, for so many plants around the world, the sun may well not exist. It is as unknown to them as the sea could be to a monk high in the Himalayas (we assume that this monk never went on vacation). It is about the millions of indoor crops that supplant the sun by lamps of different types that give plants the energy they need, and determine their cycles. There are several types of lighting systems, each with its own characteristics and suitable for different types of crops.
In order to make a good choice, you first need to know what is the appropriate light spectrum for cannabis. To reflect what happens in nature, marijuana plants basically need blue light during growth and red light during flowering. The green spectrum does not affect them, so if it is necessary to use a light in the crop without altering the cycle, a lamp of this color is suitable.
Another very important factor is heat. The different types of lamps emit more or less temperature, which must be taken into account. Although the more watts, the more production, this has a limit. More is not always better, especially in tight spaces or naturally hot climates. The most commonly used powers are 400W and 600W with their ballasts.
Lighting systems for indoor growing
Each lighting system has its pros and cons, and even its functions. Different types can be combined, or choose an integrated system. Let's see the different options:
Fluorescent tubes and CFL
In the early stages of the plant, it needs less light output. For this reason, fluorescent tubes or CFL (Compact fluorescent light) energy-saving lamps are ideal for germinating seeds or rooting cuttings thanks to their blue light spectrum and low consumption. They are inexpensive and easy to use. CFLs also come with a built-in ballast. In terms of power, fluorescents range from 18 to 55W per tube, and CFLs are 100, 125, 200 and 250W. Due to this low wattage, a good number of bulbs are required for efficient lighting. There are CFL bulbs in the red spectrum, which can be used for flowering, but may not be the best option.
HID bulbs: sodium (HPS) and metal halide (HM) lamps.
Both sodium (HPS) and metal halide (HM) lamps are types of HID (High Intensity Discharge) bulb. In general, these are two types of complementary lighting, since HM are more appropriate for growth (due to their blue spectrum), and HPS for flowering (because they are rich in red). Both usually use the same ballast, but for this it must be taken into account that both are of the same watts. The most common is that 250W, 400W and 600W are achieved.
HPSs are known for their great performance, but they generate a lot of heat, so it may be necessary to install a ventilation system. In addition, they can result in high energy costs (with its consequent electricity bill). All HIDs degrade over time. HMs do it faster than HPS, but both require replacement after a few crops. There are also mixed versions, which are HPS lamps with dual spectrum, that is, for growth and flowering, such as the Dual Spectrum from Lumatek or the Son-T Pia Green Power from Phillips.
Led lamps
LED bulbs are rapidly gaining ground, partly thanks to their low power consumption and the fact that they produce little heat. Although the initial investment is much higher, they allow great energy savings over time, in addition to having a longer duration. You can get panels of different power and different spectrum, to configure them according to the phases of the plant. There are even LEDs that include infrared and UVB spectra, which helps in the generation of trichomes. However, it is recommended to use these spectra with caution due to potential health risks. Another thing to keep in mind is that the fact that they don't generate as much heat can be good for summer crops, but it can be a problem during winter,
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Soil Analysis: Diagnosis, Quality and Assertiveness
The Beginnings of Soil Analysis
Since 50 BC in Ancient Rome the first attempts were made to analyze the soil; this diagnosis consisted of taste, acidity and salinity tests. It came to be thought that the total content of nutrients in the soils was what we wanted to know, so that later it was learned that this content did not correlate with its availability.
The Evolution of soil analysis
There are three periods that define the development of soil analysis in modern times. 1) 1845 to 1906. The foundations of modern soil analysis were laid, procedures to evaluate soil fertility were evaluated and developed, there was already a first distinction between less soluble and more soluble nutrients and extractants such as carbonated water began to be evaluated, Hydrochloric acid, acetic acid and nitric acid (HNO 3) . 2) 1907 to 1924.This period was very centered between the chemical composition of the soil and the production of the crop, an abundant data base was generated that served as a foundation to improve the analytical methods and to interpret the results of the soil analyzes. It was during this period that soil fertility monitoring was promoted to avoid soil depletion . 3) 1925 to 1950. During this period two currents developed: One, in which researchers promoted the use of multi-elemental extracting solutionsand another, in which the use of extracting solutions for specific nutrients was promoted. Chapman and Kelly (1930) developed the 1M ammonium acetate extractor solution for exchange bases (Ca, Mg, Na and K), an extractor solution that is still used with excellent results today. Morgan (1941) developed the universal extraction solution that bears his name, using acetic acid and sodium acetate at pH 4.8. At the same time, Bray and Kurtz (1945) developed various procedures to evaluate available phosphorus using Ammonium fluoride + hydrochloric acid, which are still used today for the determination known as Bray P1 and P2, in the second case, with a higher HCl concentration.
Mehlich (1953) developed the multi-elemental extractant using sulfuric acid and hydrochloric acid, known as the double acid method or North Carolina method. For their part, Olsen et al . (1954) developed the extractant based on sodium bicarbonate at pH 8.5, which gained popularity for alkaline soils and is a very popular method today in America and part of Europe, for neutral and alkaline soils. Other methods were showing its ineffectiveness, such as carbonated water, which even today there are laboratories that use it, and the Mehlich method 2 which also did not show sufficient effectiveness and has been discarded in practically all laboratories.
Trends in soil analysis
The search for universal extraction solutions continues to be an issue that worries many laboratories, since together with the appearance of plasma emission spectrophotometers (ICP) it is possible to analyze hundreds of samples in a single day (Mallarino and Sawyer, 1999). This makes the analysis very economical, however recent history has told us that the quality of the diagnosis is sacrificed too much, since precision is lost when trying with a single extractant to evaluate the availability of the 12 elements: nitrates (NO 3), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), sulfur (S), iron (Fe), zinc (Zn), manganese (Mn), copper (Cu ), boron (B) and in the case of acid soils: aluminum (Al) and hydrogen (H). Some references that support the low efficiency of multielemental methods such as Mehlich 3, are cited below: To interpret the phosphorus analysis it is necessary to know the soil analysis method before any fertilization recommendation is derived. This consideration is imperative as many methods have been developed to test the availability of phosphorus to crops. Thus, some laboratories are interested in using tests that do not use traditionally recommended extractions for P. This is where the question of whether the Mehlich 3 method is efficient or not lies. To discuss it, it is first necessary to remember that the result of a laboratory analysis is the culmination of the entire method of soil analysis, including extraction and the analytical measurement method. Mehlich 3 is a multi-element extractant and nutrients are measured in ICP. The United States Central Regional Committee for Soil Testing and Plant Analysis (NCR 13) and Iowa State University (ISU) do not recommend the determination of phosphorus with the ICP method, extracted with Mehlich 3, as variations in P concentrations measured with ICP compared to the standard colorimetric method measure up to 40% more P, and making corrections in this regard is not an effective strategy. Furthermore, they do not recommend the use of Mehlich 3 to determine Calcium (Ca), Magnesium (Mg) and Cation Exchange Capacity (CEC) in calcareous soils and micronutrients in any type of soil, due to the lack of correlation. Micronutrient interpretations, particularly zinc, are based on DTPA tests and for lime requirements in the method known as SMP, developed by Shoemaker, McLean and Pratt in 1961. For each geographic region the ISU recommends only using authorized and calibrated methods in those soils, this means the recognition of both the laboratory extraction and chemical analysis method (Mallarino and Sawyer, 1999) . For his part, Pittmanet al , 2004, testing 6400 soil samples at Oklahoma State University, found clear differences between analyzing Mehlich 3 with ICP and Mehlich 3 with the colorimetric method. Despite this, many laboratories use the Mehlich 3-ICP for phosphorus analysis, without considering that this practice could lead to the misapplication of nutrients and contribute to crop losses or negative environmental effects. Kleinman et al ., 2015, suggest that obtaining correction factors or equations is not a trivial matter, since the relationships are potentially influenced by the type of soil, and factors such as soil pH and organic matter. In Ohio soils the recommendations for phosphoric fertilization in crops are based on the Bray-Kurtz P1-colorimetric method. Comese et al ., 2007 working on rotations of corn, wheat and soybeans with increasing doses of phosphate fertilizers found that the Bray & Kurtz I method is the one that best adapts to the diagnostic practices and regional recommendations for the use of phosphate fertilizers. They concluded that Mehlich 3 overestimates the value from 15 ppm of P in the soil. Bray & Kurtz I is the method that best detected the variation of the added phosphorus doses. Performing potassium calibrations with Mehlich 3 in corn and soybeans for Iowa soils, Barbagelata et al ., 2002 detected the need to adjust K levels to interpret and make fertilization recommendations, concluding that the research should be focused on providing information to establishing different interpretations of K for different soils.
Soil analysis in Mexico
Due to the low cost of the Mehlich 3 method, foreign laboratories operating in Mexico have been encouraged to promote its use in the country. However, the country's soil specialists have not approved this procedure because it is not correlated or calibrated in Mexico and because they do not have evidence that it works correctly for the majority of Mexican soils. Its use allows to lower the cost of the analyzes but reduces the efficiency in the diagnosis with respect to the methods approved by the Official Mexican Standard (NOM-021-RECNAT-2000). Even in the United States, many more laboratories use up to 6 extractions to diagnose soil fertility than those that use the Mehlich 3 method (Sikora and Moore, 2014), for the same reasons we discuss here. On the other hand, the scientific community of Mexican soil scientists is inclined not to recommend it as a method for diagnosing soil fertility, since the lack of correlation and calibration at the regional level of a given method reduces its value for its use as a diagnostic tool. of soil fertility. This is vital to maintain credibility in soil testing with users. It is vital that Mexican laboratories adhere to the analysis methodologies established by the Official Mexican Standard.
Correlation and calibration concepts
In order for a soil analysis procedure to be authorized for its use, it must comply with the following development: 1) The evaluation of various extraction solutions and analysis methods; 2) Correlating the crop yield or the amount of the nutrient extracted by it, with the amount of nutrient extracted by each of the extractor solutions; and 3) Calibration of the analytical procedure, which consists of estimating the concentration of the extracted element at which a performance response is no longer observed, that is, estimating the critical level, above which the response to the nutrient in question is unlikely. With adequate precision, the correlation defines the analytical method that best reflects the content of the nutrient available in the soil in relation to the growth of the crop and predicts with greater precision the response of the crop to said nutrient. The degree of correlation can vary with the soil class. On the other hand, calibration is the process by which the levels considered critical are established. The most commonly used procedure to define critical levels is the one proposed by Cate and Nelson (1971), whose diagram is presented in Figure 2. Later, with other more detailed statistical regression studies, a series of interpretive values is proposed, ranging from very low or
poor, even very high or excessive. Without these values, the soil analyzes cannot be interpreted. The characteristics of these levels are presented in Figure 3, which Fertilab supports with its own research. A method that is not calibrated or correlated in the field, gives unreliable results and there are reports that even in the United States, there are many regions where the Mehlich 3 method has not been correlated or calibrated and in the best of cases only correlations with conventional methods, to estimate a conversion factor and to establish sufficiency levels for interpretation purposes.
Diagnostic methods authorized in Mexico
In October 2000, the Official Gazette of the Federation published the Official Mexican Standard 021-RECNAT-2000, which establishes the specifications for fertility, salinity and soil classification, studies, sampling and analysis with application throughout the territory. national. The purpose of this standard is that analysis service providers are duly regulated, in order to provide users with a quality service and high reliability in analytical information, preventing each laboratory from using the method that best suits them for reasons Low cost. Below is a summary of the methodologies authorized by NOM 021 for use in Mexico.
N-Nitric (N-NO 3 ). It is the N of the soil that is available for immediate use by the crop. It is extracted by means of a KCl extractor solution, followed by steam distillation. It can also be estimated using the cadmium reduction column method.
Phosphorus (P). It is determined using the Olsen Methods (neutral or calcareous soils) and Bray 1 (acidic or neutral soils). Critical levels range from 10-15 ppm for the Olsen method and 25-30 ppm for the Bray 1 method.
Potassium (K), Calcium (Ca), Magnesium (Mg) and Sodium (Na). These cations are extracted with 1N ammonium acetate at pH 7 and quantified by Atomic Absorption or by ICP. In calcareous soils it is recommended to extract with 1 N ammonium acetate at a pH of 8.5, to avoid overestimations of Calcium and Magnesium.
Iron (Fe), Manganese (Mn), Zinc (Zn) Copper (Cu). They are extracted with DTPA and quantified by Atomic Absorption or by ICP. The critical level considered for Fe and Mn is of the order of 5 ppm, for Zinc 1 ppm and for copper it ranges from 0.5 to 1 ppm.
Boron (B). It is extracted by means of a hot and diluted CaCl 2 solutionand it is quantified by ICP or Azomethine H. Its critical level is of the order of 0.8 to 1 ppm and the excessive level is greater than 4 ppm.
Sulfur (S). The method is semi-quantitative. The S is extracted with KCl and the determination is carried out in a turbidimetric way. The critical level is 5-10 ppm.
As mentioned at the beginning, the use of specific extracting solutions is the most accurate and precise way for the determination of nutrients in the soil. A laboratory adhering to the NOM and with rigorous quality control allows users to give assertive diagnoses.
Quality control in laboratories
Quality control and the use of appropriate methodologies allow laboratories to maintain certainty in the analyzes they offer. The soil analysis provided by a reliable laboratory is a robust guide to recommend fertilization rates, as it is the basis for ensuring a successful fertilization program. From this idea derives the importance of an assertive and quality diagnosis, since it will depend on it that correct decisions are made regarding plant nutrition. The establishment and monitoring of a rigorous quality control is the only way that defines "reliability" in laboratories. The purpose of the regulation is to supervise the performance of the laboratories, where Internal and External Quality Control are a very important part of the process. The intercomparison allows to measure and standardize processes with international laboratories as part of external quality control. Additionally, an internal quality control is carried out, through the use of certified standards, which allow to ensure the certainty in the analysis. These known concentration standards for each of the elements analyzed and the use of blanks are run in each batch of 10 samples and allow us to ensure the certainty of the analysis in the samples we receive from our clients. The data are statistically analyzed and allow the generation of ranges and work intervals, as well as the validation criteria of the determination. This process is called Statistical Process Control (CEP), which has also been used in the automotive industry for many years.
How to choose the services of a Laboratory?
Below are 11 criteria that serve as a guide for the correct choice of a laboratory. 1) Check how many and which determinations the laboratory makes, 2) What delivery times it offers the user, 3) Check if it is certified in ISO-9001-2008, 4) If it has international accreditations, 5) If it has intercalibrations with different laboratories in the world, 6) If it uses its own analysis methodologies for Mexico and that marks the NOM, 7) If it conducts research on its methods, 8) If it uses certified standards, 9) If it uses standard samples for every 10 analyzes, 10 ) If you have a friendly report and 11) If you give an interpretation and a recommendation of fertilization at no cost to the client. High crop yields are the result of multiple factors that begin with a good diagnosis of soil fertility. It is important to use an adequate sampling system, a good analysis procedure, authorized by the official Mexican standard, and a good analytical quality control in the laboratory. The next step is to carry out a good interpretation of the results of the analyzes and later generate an adequate recommendation for fertilization, based on a specific yield goal.
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QUICK SOIL TEST AIMS TO DETERMINE THE NEED FOR NITROGEN
Healthy soil contributes to healthy crops. Farmers know this, so they do what they can to ensure their soil is in good shape. They send samples of their soil for laboratory testing to find out if they are low on important nutrients. If it is, you can take steps to improve the health of your soil. These could include adding fertilizers or growing cover crops that feed the soil.
One of the essential nutrients for vigorous crop production is nitrogen. However, most routine tests performed in commercial soil testing laboratories do not measure available nitrogen in the soil. Nitrogen tests do exist, but for a variety of reasons they cannot be done quickly and cost-effectively. As a result, farmers can stop guessing about the health of their soil. They can apply more or less nitrogen fertilizer than is actually needed.
There are a couple of reasons why this is not good practice. One is the cost. Nitrogen fertilizer is one of the most expensive inputs in the soil, so farmers can spend money they don't need to spend. Another reason is the environment. When more nitrogen is added than plants can use, it can run out of the ground and cause problems for bodies of water downstream.
The lack of a quick and cost-effective test for soil nitrogen is clearly a problem. Soil scientists at Ohio State University and Cornell University believe they have found a solution. They have shown that a test originally developed to extract a particular protein in soil is actually a good test for a variety of proteins. Proteins are by far the largest group of organic nitrogen available in the soil. A good rapid soil protein test could also be used as a test for available nitrogen.
The process measures a protein known as glomalin. Glomalin is generally believed to be produced by a common soil microorganism that has a beneficial relationship with plant roots. The tongue-twisting name for this organism is arbuscular mycorrhizal fungi.
An earlier study suggested that the glomalin extraction method could extract proteins from other sources. Steve Culman and his research colleagues decided to test that idea. They added a variety of protein sources to the soil samples. They used corn husks, beans and common weeds (vegetable sources), chicken and beef (animal sources), and white mushrooms and oyster mushrooms (mushrooms).
They applied the so-called glomalin protocol to these soil samples and found that proteins from all sources were extracted through this method. In fact, the procedure was not limited to extracting proteins produced by mycorrhizal fungi.
The researchers therefore recommend the adoption of new terms such as soil protein, rather than glomalin, to more precisely describe the proteins extracted through this method.
This soil protein extraction procedure is a quick and cost-effective method that commercial soil testing laboratories could easily adopt. However, some specific protein types may not be recoverable with this method. More research on that point would be helpful.
"We don't have many quick ways to determine how much nitrogen a soil can provide and store during a growing season," Culman said. “This test is one way that could help us quickly measure a significant nitrogen pool in the soil. More work is needed to understand soil protein, but we believe it has the potential to be used with other rapid measurements to assess soil health in a farmer's field. '
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Soil analysis methods
It is very difficult to know what elements are present in the soil, so a generalized procedure for analyzing the elements present cannot be recommended due to the great diversity of the elements to be determined.
Soil analysis methods
The difficulties involved in determining the different elements in organic and inorganic samples are not fundamentally associated with the reliability of instrumental techniques, but with the choice of methods for sample preparation, which constitutes one of the most critical processes. of the analysis. In choosing the analytical technique, its sensitivity, precision and accuracy must be taken into account.
Both the most abundant elements and the trace elements are found in different compartments of the soil, the main forms in which the elements are found in the soil are as follows:
Forming part of the crystalline network of the primary minerals, inherited from the starting material and secondary, formed as a consequence of the alteration processes.
Adsorbed to oxides and hydroxides of iron, aluminum and manganese.
Complexed or included in the structure of macromolecules.
Retained by animal and plant waste.
Forming part of the exchange complex and, therefore, associated with clays and humic compounds of the colloidal system.
In soluble phase, forming part of the soil solution.
To obtain the total concentration of an element, it is necessary to extract all the forms of the element to be determined, including those that are part of the crystal lattice of primary and secondary minerals (silicates, clays, carbonates, etc.).
Usually, the reagents most used in the analysis of elements in soils have been a mixture of hydrofluoric and perchloric acid (HF + HClO 4 ) or aqua regia (HNO 3 + HCl). In some types of soils, the values of total elements released by these two agents may present wide differences, so that when this occurs the aqua regia provides lower values. This makes it difficult to compare total element values obtained by different extraction methods.
The total analysis of the elements present in the soil can be carried out using two different methods, a semi-quantitative method, X-ray fluorescence (X-ray fluorescence), as well as with a quantitative method, Argon Plasma Induced Emission Spectroscopy (ICP -MS).
SEMI-QUANTITATIVE METHOD
X-ray fluorescence (XRF) The X-ray fluorescence (X-ray) technique is based on the principle that if an atom is bombarded with high-energy photons, some of its electrons are expelled. As other electrons fill in the vacant levels of energy occupied by the ejected electrons, they emit a quantum of radiation characteristic of that particular type of atom, hence each element has its own series of emission characteristics or X-ray fluorescence lines. .
X-ray fluorescence can be used to perform the analysis of the elements from the soil samples. Using this analytical technique, metals such as Cu, Mn and Zn, Ti and Zr can be determined at a normal concentration in the soil. Other heavy metals and metalloids (As, Cr, Ni and Pb) can also be determined, but in the case of Cd, Hg and Sn a previous pre-concentration of the sample is required.
Some applications of the FRX are, the following:
Rapid qualitative determination of elements present in an unknown material with virtually no sample preparation and semi-quantitative determination using simple correction factors.
Detection of all elements of the periodic table below B from the detection limit of a few ppm to 100%.
Quantitative determination of all the elements in a sample (excluding elements with an atomic number below 5).
Surface composition (1 µm) compared to volume (> 10 µm) using emission lines with different depth of penetration in certain samples (ceramics).
The FRX offers an impressive number of benefits. Generally, the method is non-destructive and can therefore be used without damaging the sample. Another advantage would be the precision and speed of the procedure. However, it also has some drawbacks; for example, it is not as sensitive a method as other optical methods. In the most favorable case, concentrations of a few ppm can be measured; furthermore, XRF methods are not considered suitable for light elements so that the difficulties in detection and in measurement progressively increase below atomic number 23 (Vanadium). Another disadvantage of this procedure is the high cost of the instruments. Despite this, X-ray analysis techniques are the most widely used in soil analysis.
QUANTITATIVE METHOD
Mass Spectrometry-Plasma (ICP-MS) Many analytical methods require the sample to be in solution. This can be an inconvenience when working with soil samples, because the organic and inorganic components of the same require different treatment for their dissolution. The easiest method is the dissolution of the sample after previous heating, since all the organic matter is destroyed. Sequential treatment of soil samples with HF and HNO 3 is often effective even though inorganic residues must be treated again with HF and HNO 3 until completely dissolved.
The extraction method used, following the official procedure for soil analysis used by the United States Environmental Protection Agency (USEPA - “United States Environmental Protection Agency”), was the EPA-SW-846-3051 method. Through it, the oxidation of organic matter occurs using nitric acid and subjecting the sample to conditions of high temperature and pressure. In this way, it is not possible to solubilize the silicate fraction of the sample, so the real amount of the elements present in the soil cannot be quantified, although it dissolves those not bound to silicates. However, most of the heavy metals present as pollutants in soils belong to the latter type; thus,
Microwave digestion techniques at 8,000 ° C are among the newest methods for dissolving soil samples. Its main advantages lie in the fact that: it is more difficult to contaminate the sample, it produces a more complete dissolution of the sample and a lower loss of volatile elements. Its main disadvantage is the large amount of time required for the digestion process to complete.
ICP-mass determination is achieved by subjecting the flow of a gas at atmospheric pressure to the action of a magnetic field induced by a high-frequency current. The gas used, called plasmogen gas, is usually argon, although for certain applications it can be used in combination with a low proportion of some other gas. Due to the high plasma temperatures, matrix interferences are minimized. Argon is used for being an easily found material in a high degree of purity and for developing a chemically inert environment.
In addition, argon (Ar) itself together with a flow of water are responsible for cooling the system. ICP is a good source of ions, in which the gas or aerosol from the introduced sample is volatilized, automated and ionized at a very high temperature. Since the ion source (ICP) works at atmospheric pressure and the mass analyzer and detector work in a high vacuum regime, an interface has been developed that allows the transfer of ions to the mass spectrometer in charge of analyzing them.
In this interface, an ion jet is formed that is finally directed to the analyzer system, which can be of two types:
the magnetic sector and the quadrupole ones, the latter being the most widespread due to their greater simplicity, scanning speed and lower cost.
Quadrupole analyzers act as a filter, so that only those ions that meet a certain charge / mass ratio pass through them and reach the detector.
The sample introduction system is pneumatic nebulization, where the liquid sample interacts with a gas stream in a nebulizer, generating an aerosol that passes through a spray chamber where large drops are eliminated and small ones are led to the plasma.
