Soil investigation, soil analysis


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Fertilizer: Much does not help much

With nutrient deficiency, plants grow poorly and are more susceptible to pests and pathogens. What few know: Excessive nutrients cause similar symptoms. These excessive fertilizers weaken both the plant tissue and the soil. Because some of the unused nutrients, such as nitrogen, are washed out of the ground and washed into lower layers of soil, where they pollute the groundwater. On the other hand, phosphate accumulates in the soil when too much fertilizer is added and even inhibits plant growth above a certain concentration. But not only the environment and nature suffer from excessive fertilizer, and the purse is unnecessarily emptied. In the soil laboratory, the experts get to the bottom of the problem using the soil samples sent in. After the soil analysis, they provide reliable information on the type of soil and the pH and also give concrete fertilizer recommendations.

Cross section through the garden floor

The garden soil has a lot to do: it should give our plants a foothold and provide them with enough nutrients for good growth and rich yields. A soil analysis shows what is below the surface

Necessary nutrients

Soil analysis measures the levels of some key nutrients in the soil necessary for plant growth and development. Magnesium (Mg), phosphorus (P) and potassium (K) are the main nutrients that each plant needs in larger quantities. Their green protégés, however, are also dependent on a number of trace elements, which are absorbed in smaller quantities. These trace elements include iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), sodium (Na), boron (B), molybdenum (Mo) and sulfur (S). They are usually already supplied via a fertilizer with compost in sufficient quantity.
In addition to the more elaborate analysis of the trace elements, the concentration of the nutrient nitrogen is usually not recorded in the standard analysis. This is because the nutrient in the soil is very mobile and the content fluctuates sharply over the course of the year. The nutrient, which is usually present as nitrate, is easily washed out by the rain. For a reliable test result, the soil would have to be frozen immediately after sampling and delivered in this condition in the soil laboratory. This is too time-consuming for amateur gardeners, but is done in professional horticulture and agriculture.

Determine pH with test strips

The pH of the garden pond can be easily determined with a test strip. Comparable test sets are also available for the garden floor

Analyze the pH

The pH regulates the nutrient uptake of the plants. Most of its value must be between 6 and 7, in order to make the nutrients optimally available for the plants. The soil type, ie the amount of sand, silt and clay as well as the humus content, has an influence on the pH value. So it is usually a bit lower in sandy soils than in loamy and can be here with a calcium fertilizer also affect more. You can determine the pH value yourself with inexpensive test sets at the garden retailer and thus calculate at least the lime requirement of your soil. If you have your soil examined for the first time, you will also learn the pH and the exact soil that is present in your garden.

The correct depth for sampling

Always remove the soil sample from the entire root zone of the respective plant type. For example, if you want to sow a new lawn, you should take the soil samples down to a depth of no more than 10 centimeters because the grass roots hardly penetrate further into the ground. In the vegetable garden and in the perennial border, on the other hand, some soil must be removed over the entire area from 0 to 30 centimeters deep. Deep-rooted fruit trees, but also asparagus plants even penetrate into the subsoil. Sampling up to a depth of 60 centimeters is recommended here.

The right depth for taking a soil sample

The right depth is crucial when taking a soil sample - after all, only the nutrient supplies are important, which are also accessible to the respective plants

The removal of soil samples

The starting material for the soil analysis is the so-called soil sample, ie 250 to 500 grams of your garden soil. It is important that you send a so-called mixed sample, which comes from a uniformly used garden area, for example from the vegetable garden or the lawn. Evenly spread over the entire area of ​​the garden area take multiple samples and collect them in a bucket. The more samples you take, the more reliable the result. Finally, thoroughly mix all the amount of soil removed from the vegetable patch or lawn and then fill 500 grams into a foil pouch. You should first label this with your name, the current date and the garden area from which the mixed sample originates.
For a consistently good soil quality, the soil should be examined at intervals of three to five years. If the nutrient contents fluctuate only slightly during this time, you can allow yourself more time with the next examination. Best practice a soil analysis in early spring, before the start of the season, or in the autumn after harvest.

Step by step: Take soil samples

Take soil sample in the vegetable garden

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Take soil sample

Soil investigation, soil analysis: soil

The soil for an investigation should come from a uniformly used garden area, such as here from the vegetable garden. Basically, the smaller the area and the more subsamples are taken, the more meaningful the result. A good guideline is 20 evenly distributed sampling points per 100 square meters of vegetable garden. Place the soil profile in the appropriate places within the area down to a depth of 20 to 30 centimeters with the spade

Soil investigation, soil analysis: soil

With the hand scoop you scrape at each hole from bottom to top along the side wall some soil and fill it into a bucket

Soil investigation, soil analysis: garden

Then thoroughly mix the collected soil samples from your vegetable garden with the bucket in the bucket

Soil investigation, soil analysis: analysis

Using a waterproof marker, label a foil pouch with your name, the name of the area from which the samples originated (for example, vegetable garden, lawn or rosary), and the current date. For your safety, you can also make a note of your address on it

Soil investigation, soil analysis: soil

From the mixed sample from the bucket, add a heaped hand scoop (at least 250 grams, better 500 grams) into the foil bag and send it to the soil laboratory in the parcel post. Triennial research makes sense in vegetable gardens and other areas that are used intensively. If the nutrient contents have hardly changed within this time, you can also spend more time. By the way: The cause of many turf problems can also be tracked down with a soil examination. Because of the shallow root system, however, soil samples are taken only at a depth of no more than 15 centimeters

Take soil sample in the vegetable garden

Take soil sample

Mix soil sample

Label shipping bag for soil sample

Shipping soil sample

Soil samples are taken with the auger

In professional horticulture, soil samples are often taken down to a depth of 90 centimeters using a special soil sampler - for example in orchards, viticulture and other permanent crops to determine the nutrient requirements of the plants. The purchase of this stock is worthwhile because of the high purchase price usually only for professionals.
If you want to take the soil analysis samples, for example an orchard, with a drill, use a plastic hammer to drive it 90 centimeters deep into the ground. Then he is pulled back from the ground with a slight turn. Make sure that the core remains intact. The bottom 30 centimeters of the drill core are separated by means of a pointed object, such as a screwdriver, and filled into a bag labeled "60-90 centimeters". The inscription indicates the depth of the floor from which the sample was taken. The next 30 centimeters of the core are filled in another bag labeled "30-60 centimeters". The rest of the core can be found in the third bag "0-30 centimeters". Please pay attention to the correct labeling. It is crucial for a perfect result of the soil laboratory.

Step by step: The soil analysis in the laboratory

Process soil sample for analysis

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Analysis of a soil sample in the laboratory

Soil investigation, soil analysis: soil

The soil sample is first dried and ground. Then a defined amount is weighed with a precision balance and filled into a plastic bottle

Soil investigation, soil analysis: garden

A solvent is added to dissolve the nutrient salts from the soil particles. This process is accelerated with a machine that shakes the mixture for several hours

Soil investigation, soil analysis: soil

With a filter, you now separate the nutrient solution from the solid soil components

Soil investigation, soil analysis: garden

In the atomic absorption spectrometer, part of the solution is burned. Based on the intensity of the flame coloration, the connected computer calculates the potassium and magnesium content

Soil investigation, soil analysis: analysis

Photometry determines the phosphate content. An added substance forms a dye with the phosphate in the soil solution. Based on the color intensity, a computer calculates the phosphate concentration in the soil solution

Soil investigation, soil analysis: analysis

The pH is determined by an electronic pH meter using an unfiltered sample infused with calcium chloride solution

Soil investigation, soil analysis: investigation

The soil type is determined using the finger method: The laboratory staff rub a small amount with water between their fingers. The felt soil components show, for example, whether it is a sandy, clay or clay soil

Process soil sample for analysis

Soak soil sample with solvent

Filter the soil sample

Analysis of a soil sample in the atomic absorption spectrometer

Determination of phosphate content of soil sample

pH determination soil sample

Determination of soil type with finger test

The aim of the soil analysis is to provide a fertilizer recommendation for the respective soil, taking into account the nutrient contents, the pH and the soil type. Important in such a recommendation is also the nutrient requirement of the plants, which are cultivated on the soil. If the pH of the soil is too strong in the acidic area, a corresponding Kalkgabe is proposed. The soil sample shows the current supply levels of the individual nutrients in the soil. Based on these values, a fertilizer recommendation can be given for each nutrient tested.
The standard examination program shown above is usually limited to the nutrients phosphate, potassium and magnesium, which is perfectly sufficient for hobby gardeners. Depending on the laboratory, the costs for the soil analysis of a mixed sample are usually between 20 and 30 euros. Incidentally, the experience of the laboratories shows that, for example, the nutrient phosphate and also potassium are abundant in many garden soils, in some even too abundant. If you consistently follow the recommendations of the soil laboratory, your garden also controls optimal nutrient balance or is kept at the optimum level - ideal conditions for sustainable gardening success.

Video: Take soil samples and have them analyzed

In our practice video, editor Dieke van Dieken shows you how to collect and process the soil samples and how a soil analysis works in the laboratory.

Video Board: Understanding Soil Test Results Part 1: CEC, Organic Matter, Soil pH, & Buffer Index.

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