Winegrowers Supplies  -  Soil analysis and nutrient requirements for vines

Please note that I am still in the process of writing this webpage.

How to take soil samples:-

Samples should be taken at two depths, 0 to 30 cms and 30 to 60 cms, they must be analysed separately.

It is recommended to repeat the soil analysis every 6 years at the most; 3 to 4 years with soils at risk of leaching or very heavy soils.

Soil pH:-

The ideal pH is 6.5 which is slightly acidic; neutral being 7.0

It's easy to make an acid soil less acidic, simply by adding limestone or preferably magnesium limestone.

It's very difficult to make an alkaline soil less alkaline, but fortunately vines (grafted on a suitable rootstock) can grow well in limestone/chalk soils, even up to pH 8.4

The most important nutrients for vines:-

the ideal levels of these nutrients are different from general farming soil 'indexes'.

P = Phosphate; in plant available form P2O5. Above 280 mgms per 1000 grams of soil is more than sufficient, above 200 mgs is suffcient, above 150 mgms is adequate.

K = Potassium; K2O. Above 340 mgms per 1000 grams of soil is sufficient, above 150 mgms is adequate.

Mg = Magnesium: Mg. Above 250 mgms per 1000 grams of soil is sufficient, above 130 mgms is adequate.

B = Boron. Above 1 mgm per 1000 grams of soil is sufficient, above 0.3 mgms is adequate.

N = Nitrogen; humus content is important, 2.5 to 3.5% is normal in German vineyards.

Ca = Calcium; chalk, limestone.

On light soils, potassium, magnesium and boron are inevitably leached out. On light soils, any necessary K or Mg fertiliser should be applied annually.
on heavy soils, potassium can be attached to clay minerals.

The classification of the content classes is shown in Table 1. If the nutrient content of content class C is present in the soil, an annual maintenance fertilization with the amount given in Table 2 is usually sufficient.

These nutrient levels include a surcharge for possibly unfavourable nutrient utilization rates of the fertilizers due to weather or soil conditions.

Phosphate removal by cropping vines is only about 10 kilos per hectare per year on average. This means that a maximum of 30 kilos per hectare with organic fertilizers may be applied as a third-year application.

The Nmin method vs the EUF method for determining the plant-available nitrogen:-

With the Nmin method, the existing nitrate nitrogen (mineral N) is determined before the N fertilization in the soil layers 0-30 and 30-60 cm.
The nitrogen fertilization is based on a target value (70 kilos N / hectare for a grape yield of 100 kilos/are), from which the measured nitrate nitrogen of the soil is subtracted.
A surcharge or discount can be added to the fertilization level determined in this way:
Surcharge (up to +30 kilos N / hectare, temporarily, max. 5 years) for new sowing of whole-area permanent greening or for existing greening with a low proportion of legumes, if there is stunted growth due to acute N deficiency or very low humus content.
Reduction (up to -50 kg N / ha) in the case of very strong vine growth, very high humus content or ploughing of a long-term permanent greening as well as with reduced yield expectations e.g. due to frost damage (see also 3.1).

With the EUF method (electro-ultrafiltration), organic, easily mineralisable nitrogen compounds (Norg) are extracted from soil samples from 0-60 cm in addition to nitrate nitrogen.

Foliar feeding is very useful when there is a lack of some nutrients in the soil (e.g. magnesium deficiency or iron deficiency causing chlorosis).

Good effects can be expected when spraying early in the morning (with dew on the leaves), when the sky is overcast or in the evening.
When combining with a spray of fungicides, the relevant instructions for use must be observed.
Foliar feeding must be avoided during flowering and during the final spray before harvest, as well as in strong sunlight.