Soil texture

The collective term soil testing refers to the combination of various methods and procedures for the determination of soil parameters such as nutrient and humus content, soil organisms, properties of water and air balance, the pressure sensitivity and physical composition (grain size distribution). The examination starts in general with the removal of a soil sample.

• 2.1 fertilizer requirements
• 2.2 Other areas of application

Removal of the sample

A representative sampling is a prerequisite for a meaningful soil analysis. For the analysis of nutrients in agriculture sampling instructions by the Association of German Agricultural Investigation and Research Institutes ( VDLUFA be published). One distinguishes the sampling for basic nutrient analyzes and for analyzes on plant-available nitrogen.

The soil sample is taken in the context of sampling for soil investigation of a single area. It is customary to form a composite sample of approximately 0.2 kg to 0.5 kg soil, which is obtained from about 20 individual samples.

Sampling for basic nutrient analysis

Are on farmland aside a minimum of 15 punctures on machining depth (see plowing ) is required to grassland at least 20 punctures to 10 cm depth. For hops, fruit and viticulture at least 15 punctures up to 30 cm depth should be made. For some questions ( grapes wilt, stem necrosis ) on the producer also an investigation of the subsoil ( 30-60 cm depth) is useful. The individual samples should be taken evenly distributed over the surface in the main root zone. The sampling device is to use a simple boring rod with footrest. The individual cores are well mixed and homogenized in a bucket. Of these, a sub-sample of about 200 grams is placed in a plastic bag and sent to a laboratory floor.

From the same soil sample was drawn for the basic nutrient analysis, and the humus content can be determined. The humus content allows for a conclusion to the organic matter in the soil. The laboratory analytical measurement of humus content is prescribed as part of cross-compliance under certain condition.

Sampling for analyzes on plant-available nitrogen ( Nmin )

Since the mineral nitrogen is very mobile in the soil samples are taken up to 90 cm soil depth for this. Is suitable for this Pürckhauer with a mallet. A much more convenient is the automatic removal with an electric impact hammer. Soil samples which are to be analyzed for mineral nitrogen must be placed immediately after collection in a research laboratory or frozen. Otherwise, there is an increase in the nitrate content and the analysis result is no longer meaningful.

The soil samples are thoroughly mixed after collection and prepared for transportation. If the state of mineralization of the nutrients are determined, it is necessary to refrigerate the sample for transport. In the laboratory, further evaluation. For this, the samples are dried at 105 ° C. For soil analysis of the fine soil is sieved ( mesh size 2 mm). The plant-available nutrient content of the fine earth is obtained with various extraction reagents from the sample and determined by means of various analytical instruments.

Analyzes

Fertilizer requirements

A number to be examined parameter is set to the fertilizer needs assessment in the fertilizer ordinance. It prescribes the minimum annual determination of soil nitrogen. This can be done either through a laboratory analysis of the Nmin value in the spring or through the acquisition of test results comparable areas. Each farm can decide whether he wants to perform an accurate laboratory analysis to its own shock, or whether he wants to take the values ​​from the appearing in the agricultural weeklies during the fertilization period in spring benchmarks. For phosphate, however, an analysis is mandatory. This needs to be kept agricultural land from a size of 1 hectare - with few exceptions - are performed at least every 6 years. The determination of phosphate is part of the extensive ground floor study. The plant nutrients are phosphate, potassium, and magnesium, as well as pH are determined. The aim of the investigations is to enable a demand- fertilization and thus to reduce nutrient inputs into surface water into the groundwater and other ecosystems. The entry of washed-off from agricultural land nutrients, especially phosphate may result in stagnant and slow flowing waters to their eutrophication and should therefore be avoided. A beyond the plants need nitrogen fertilization leads to nitrate leaching into groundwater.

Before a nutrient analysis can be performed on the soil samples, an extensive sample preparation is required. The samples need to be dried and then finely ground using a floor grinder. After a precisely defined quantity of the soil sample is weighed and mixed with an extraction solution.

Atomic absorption spectrophotometer for measurement of nutrients such as potassium and magnesium

Ciliates colonize the ground in great abundance of species

Testate amoebae are found mainly in spruce forest soils

Other areas of application

• In the context of contaminated sites soil samples were taken in order to prove the existence of hazardous substances.
• Soil samples are also taken in order to avoid the spread of soil-borne pathogens, such as potato cancer. This is determined several years after disease onset by field trials in the extracted soil the pooled sample, whether a ban for the area concerned is still justified.