Potato – a food product and renewable raw material
Regardless of the direction of utilization, yield, and the specific quality required determine the economic viability. Excellent cultivation management with regard to fertilization is essential, because it is the key factor in determining success.
- Quality requirements in potato cultivation determine the fertilizer strategy.
- Potassium ensures reliable yields and top potato quality.
- Do not risk magnesium deficiency; assimilation performance and root growth are at risk.
- Micronutrients strengthen potato plants.
Quality requirements in potato cultivation determine the fertilizer strategy
The potato's range of usage has steadily expanded in recent years. In addition to its traditional use as a foodstuff, its importance in the "non-food" sector is increasing all the time. Starch extracted from the potato, for example, is used in the paper industry, as a building material, as an adhesive, in biotechnology, as a cleaning agent, in cosmetics, and pharmaceutical products.
The profitability of potato cultivation is determined by yield and quality. The basis for this is, on the one hand, the natural environment and, on the other hand, a correct choice of variety depending on the direction of utilization as well as controlled crop management. In addition to maintenance measures, fertilization is of great importance, as the potato has a high nutrient requirement (nutrient consumer). Fertilization adapted to yield performance has a positive influence on a large number of quality characteristics. It also improves the resistance of the plants and the storability of the tubers.
The most important nutrients for potatoes
Potassium – for reliable yield and highest potato quality
Potassium is absorbed most by the plants in terms of quantity and is a major factor in determining yield and quality. A potato crop withdraws about 60kg of K2O from the soil for every 10 tonnes of tuber yield.
Potassium has a positive influence on:
- Leaf health
- Efficiency of nitrogen fertilization
- Water balance of the plants
- Tuber yield and vitamin C content
- Yield security
Different quality requirements in potato cultivation
The quality requirements in potato cultivation depend on the respective utilization direction (table potatoes, processed potatoes, starch potatoes or seed potatoes). A medium-high starch content is required for refined products (French fries and potato chips), for example, and a high starch content for starch production.
For table potatoes, cooking characteristics are more important than the level of starch content. Potatoes, for example, should not disintegrate during cooking and should not show any discoloration.
The right choice of variety and targeted fertilization are essential to meet the respective quality requirements.
The nutrient potassium in particular influences a large number of quality characteristics that have a positive effect on the proportion of marketable product:
- Potassium reduces the tendency to discoloration in the tuber such as black spotting, cooking darkening, and raw mash discoloration.
- Potassium increases the citric acid as well as vitamin C content and influences the starch content of potato tubers.
- Potassium reduces the content of reducing sugars (important for industrial processing).
- Adapted potassium fertilization improves harvest tolerance as well as storability. This leads to a reduction in shock sensitivity as a result of good tuber maturity.
Sulfur – for protein formation and nitrogen efficiency
Sulfur activates important enzymes in energy and fatty acid metabolism. It is essential for the synthesis of sulfur-containing amino acids, influences overall protein synthesis and thus has a positive effect on yield.
An optimal sulfur supply leads to efficient nitrogen utilization. This is because in the case of sulfur deficiency, the nitrogen taken up cannot be converted into proteins and a signal is sent to the roots to take up less nitrogen. Therefore, the plant's need for sulfur must be met for optimal nitrogen utilization.
Furthermore, sulfur enables the potato plant to maintain its physiological processes optimally even under drought stress and to avoid or at least minimize yield losses. Sulfur is a component of the metabolic product glutathione, which, as an antioxidant, renders oxygen radicals formed during drought stress harmless and therefore prevents necrosis of the leaves.
Magnesium, manganese and boron – the icing on the cake through foliar fertilization
Potatoes are often grown on light, magnesium-poor soils. Fertilization must be used here to ensure the supply of magnesium.
Magnesium is essential for the assimilation performance of the plants and influences the formation of proteins and carbohydrates as well as their storage in the tubers.
Magnesium, but also manganese, promotes the concentration of value-determining ingredients such as citric acid and vitamin C. Furthermore, they increase the potato tuber's resistance to discoloration during further processing of processed products.
Boron is important for cell formation, stabilization of cell walls, and for the formation of energy-rich ingredients such as sugar and starch.
The positive effect of magnesium but also of the micronutrients manganese and boron on the reduction of black spot in potatoes could be proven by fertilization trials with epsoTOP and epsoMICROTOP.
Fertilizer recommendations for potatoes
The aim of fertilization is to maintain soil fertility for long-term exploitation of the natural yield potential. For this purpose, an optimum nutrient content must be maintained in the soil (in Germany, soil content class "C"), i.e. nutrients removed with the harvested crop must be replaced by fertilization. In addition to nutrient removal, there are surcharges for soil-specific losses (for example, through leaching) and to compensate for earlier deficits.
The total nutrient removal of a crop is calculated by removing the main crop (e.g. grain, tuber, beet) and the crop residues (e.g. straw, haulm, leaves). If the crop residues remain on the land, only the nutrient removal must be replaced by the main crop product.
Recommendation for soil fertilization
Nutrients requiring fertilization should be applied in sulfate form, as potato is one of the chloride-sensitive crops. The best time for potassium fertilization is just before planting.
Fertilization in potato crops must be tailored to yield expectations and, most importantly, to the direction of utilization.
The following fertilization recommendations are calculated on the nutrient removal of the main crop on the basis of optimum soil nutrient contents (in Germany soil content class "C"). Surcharges for soil-specific losses due to leaching, fixation, or erosion are not taken into account.
For a tuber yield of 45 tonnes, the following fertilizer application is used for nutrient removal at optimum nutrient soil content class per hectare measured by total removal and removal by major core products:
Total removal (incl. harvest residues)
300kg/ha K2O, 25kg/ha MgO and 12kg/ha S
Removal through main crop
270kg/ha K2O, 18kg/ha MgO and 11kg/ha S
Recommendation for foliar fertilization
Foliar fertilization effectively supplies the plant with the micronutrients boron, manganese, zinc, or copper.
It also supplements soil fertilization with rapidly available macronutrients such as magnesium or sulfur. In phases of strong growth, fertilization via the leaf covers peaks in demand and reliably ensures an optimum supply of nutrients even in dry conditions or when sulfur mineralization is too slow.
This ensures the best yields and qualities. If deficiency symptoms have already occurred, foliar fertilization provides an effective and quickest possible remedy.
20-25kg/ha epsoTOP in a 5% solution (5kg per 100l) for magnesium or sulfur deficiencies. 20-25kg/ha epsoMICROTOP in a 5% solution (5kg per 100l) for high periods of high demand as well as control of latent deficiency of magnesium, sulfur, boron, and manganese.