The content of this article ‘Fruitage: what can I prune right now?’ has been prepared by The University of Minnesota Extension and has been reviewed and republished by FreshFruitPortal.com.
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There are 14 essential plant nutrients derived from the soil that are considered essential for the growth of all plants.
These are divided into six macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S), and eight micronutrients: iron (Fe), manganese ( Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), chlorine (Cl) and nickel (Ni).
If any of these nutrients are deficient in the vines, it can negatively affect the yield and quality of the grape. When the soil cannot provide enough of each nutrient for adequate growth, you need to apply additional fertilizer.
There are two main tools for determining the fertilizer needs of a vineyard: tissue analysis and soil analysis. The need to provide fertilizer is also based on a number of factors including vine vigor and visual symptoms on the leaves.
Grapes in cold climates often need fertilizer to provide the optimum levels and balance of nutrients for plant growth. But fertilizers cannot compensate for poor insect and disease control, or correct problems like severe winter damage.
Vine tissue analysis
Tissue testing (sometimes referred to as tissue analysis or leaf analysis) refers to a set of laboratory tests that measure the concentration of several key nutrients in the leaf tissue of a vine.
Tissue tests are based on these facts:
- Optimal concentration ranges exist for each nutrient in plant tissue.
- Maximum yield and fruit quality occurs when nutrients are within these ranges.
If the level of a nutrient falls outside its optimal range, corrective action should be taken, such as applying fertilizer or raising or lowering soil pH with lime or sulfur. , respectively.
Analysis of the vineyard soil
Soil tests measure soil pH, percent organic matter (OM%), and the concentration of key nutrients such as phosphorus, potassium, magnesium, boron, and micronutrients.
Perform a soil test within the year before planting a new vineyard. This allows time to amend the soil and apply fertilizer before planting the vineyard. It is easier to incorporate fertilizer before planting.
Once the vineyard is planted it becomes more difficult to change the soil pH and the levels of many nutrients as it will not be possible to incorporate fertilizer more than a few inches deep without damaging the roots of the vine.
Soil tests are also recommended every three to five years for established vineyards, to supplement interpretations of tissue tests.
When to use tissue tests vs. soil tests
Both tissue testing and soil testing have important purposes in grape production. Soil tests show the levels of nutrients, pH and organic matter in the soil. Tissue tests show the actual nutritional status of the vines; in other words, the amount of each essential nutrient taken up by plants.
Tissue tests should be done at least once a year to check the nutritional status of the vines. This can take place at flowering, veraison or both.
On the other hand, soil tests should be used before planting to determine organic matter and pH levels, lime requirements, as well as the soil’s phosphorus, potassium, magnesium and micronutrient requirements. They should also be carried out at any time after the application of major soil amendments, in order to measure their effect on the chemical properties of the soil. In established vineyards, soil tests are primarily used as a supplement to tissue analysis information and should be performed every three to five years.
The leaf tissue of the vine is collected by the operator of the vineyard and sent to a laboratory for nutrient analysis. The lab then creates a report that the vineyard operator can use to determine fertilizer needs.