Potatoes show the best yield on loosened and well aerated soil. This is one of the few crops that is capable of producing a good harvest at the same place for a long time, provided that organic and mineral fertilizers are sufficiently applied.
The optimum land density for sprouting potato tubers on medium loamy soils is 1-1.2 g / cm³, on sandy loam 1.3-1.4 g / cm³. With an increase in the density of the soil of medium loamy soil up to 1.4 g / cm³, the yield of tubers is reduced by 30-40%. Not only the total weight of the crop depends on the density of the soil, but also the quality of the tubers - their shape, size, and ability to store.
Potatoes tolerate high concentrations of soil solution and soil acidification quite well. The optimum pH value in the range of 5.0-6.5 units. The root system of potatoes is underdeveloped, 90% of its total mass is in the arable layer. In middle and late ripening varieties, roots penetrate deeper into the soil than in early ripening ones.
For the formation of 1 ton of tubers and the concomitant amount of tops, potatoes takes from the soil:
Early varieties are characterized by a high intake of potassium, in the later ones all the figures for nutrient intake are lower. An important feature is the short period of the fastest absorption of nutrients is approximately 30 days. The main part of the root system is at a depth of no more than 60 cm and 4 times shorter than that of wheat. Suction capacity is small, so the potatoes always respond well to timely feeding.
The content of dry matter in tubers is 13-37%, starch: 8-29%. The quality of the crop is influenced by many factors.
Nitrogen fertilizers contribute to the growth of green mass, which is responsible for the processes of photosynthesis. Their introduction lengthens the growing season and maturity of tubers. During a drought, the process of photosynthesis and starch accumulation is inhibited due to the lack of moisture, so nitrogen fertilizers can have a negative effect.
A good source of nitrogen for potatoes is ammonium sulfate, which simultaneously reduces the incidence of scab.
The period of the most active absorption of minerals from the soil covers the phase of budding, flowering and the formation of tubers. At the initial stage of growth, the presence of nitrogen is more important in order to form a photosynthetic mass, on the stage of beginning of the formation of tubers — phosphorus and potassium. An excess of nitrogen at the stage of tuber formation leads to the continued growth of green mass, slows the growth of tubers and the accumulation of starch in them.
At the same time, a strong lack of nitrogen can lead to premature death of the tops, which will reduce the yield.
Dose of applied nitrogen fertilizer (kg/ha), depending on the purpose of growing potatoes:
When selecting tubers for chips, a solids content of 24% is needed, a lot of starch (more than 16%) and a minimum of reducing sugars. The latter, during frying, enter into a chemical reaction with amino acids, which spoils the taste and color of the chips.
Phosphorus is important for proper growth of roots and tubers. Therefore, we can expect an increase in yield from 10 to 71% when using this type of fertilizer. In addition, the starch content and the quality of the peel of tubers are increased, which is important for their storage and transportation. Since this element is important for the formation of roots and tubers, the farmer should provide the plant with a sufficient amount of this mineral before the stage of the formation of tubers.
With a sufficient amount of phosphorus, the content of nitrates in tubers is reduced, the damage to them is well healed. Phosphorus accelerates ripening, reduces the percentage of blight infestation, increases resistance to viral diseases of potatoes, black leg, ring rot, and rhizoctonia.
Signs of phosphorus deficiency in potatoes:
Although potatoes are not chlorophobic, the presence of chlorine in potash fertilizers impairs yield. This is especially noticeable on poor soils, with a low content of mobile compounds of phosphorus and potassium. Chlorine increases the water content of tubers, which slows down their maturation, and also violates the accumulation of starch. Therefore, chlorine-containing potash fertilizers are better to be applied for autumn tillage, so that the chlorine ions before spring have time to move into the soil layers, which are below the layer of the main mass of potato roots.
Potassium is responsible for managing carbohydrate metabolism. With its sufficient amount, the processes of creation, transfer and accumulation of carbohydrates (starch) flow well. Affects the osmolar pressure in plant cells and the water regime of the plant. With a sufficient amount of potassium, potatoes tolerate drought better and spend less liquid to form the same amount of dry residue. The content of mobile potassium compounds should be at least 60 mg/kg in the soil.
Signs of potassium deficiency in potatoes:
In addition to those described above, for the normal development of potatoes, elements such as boron, manganese, molybdenum, copper, iron, zinc, cobalt, etc. are needed. In most cases, their average content in the soil can provide only an average yield.
When combining fertilizers, it should be remembered that an excess of nitrogen can help disguise the signs of viral damage, promotes the transfer of viruses from tops to tubers. While a sufficient amount of phosphorus contributes to earlier maturation and increases resistance to viral infection.
Sulfur is an important element - its introduction in a dose of 50 kg/ha in the form of ammonium sulphate, potassium or magnesium usually covers the need of potatoes.
A sufficient amount of calcium in the soil reduces the incidence of the skin, increases the overall resistance to diseases such as rhizoctoniosis, brown and necrotic spotting.
When using only concentrated mineral fertilizers, the ratio of magnesium, calcium and sulfur should be the same as in the ash of the tops.
On sour sandy and sandy sod-podzolic soils, potatoes may experience magnesium deficiency. With an expected yield of 30-40 t/ha, about 70 kg/ha of MgO should be applied.
Potassium and magnesium have an antagonistic effect, therefore, with excessive use of potassium fertilizers, we can expect a lack of magnesium in potatoes. When the plant lacks magnesium, the movement of assimilates in tubers is disturbed and the starch content decreases.
If there are symptoms of acute magnesium deficiency, you can use a 5% solution of magnesium sulfate along with the first spraying against late blight.
When liming soil, it should be borne in mind that the maximum effect is manifested by 2-3 years. In tubers, starch content is reduced and scab damage is more common. If this happens, then you need to increase the dose of potassium, boron (0.7 kg/ha) and copper. It makes sense to increase the dose of potassium by 15%. Thus, it is desirable to conduct liming either right before planting potatoes, or a few years before.
Good results can usually be seen if organic and mineral fertilizers are combined. If both types of fertilizers were applied in spring, then in summer the effect of conventional mineral fertilizers ceases, just at the time when organic ones begin to decompose and feed plants. A possible application scheme can look like this: 1.5 kg of nitrogen is added to each ton of manure. It makes no sense to add more than 80 tons of manure per hectare. The best dose is 40 t/ha on sod-podzolic soils and 20 t/ha on black soil.
On sandy soils good results show siderats with the obligatory addition of phosphorus and potassium.
At the same time, it is desirable to apply the indicated doses of phosphorus and potash fertilizers in the fall, for the main treatment, and nitrogen doses - in the spring for cultivation or the formation of ridges.
To save mineral fertilizers can be applied by the belt method. But to divide the total dose, which is usually made before planting in two parts, to make additional feeding, it is possible only in regions with a sufficient amount of moisture. Nitrogen can be made in the form of urea in the foliar way by adding magnesium sulfate to the solution.
With its deficiency a rapid darkening of the tubers, their cracking is noted. Boron can be applied simultaneously with other fertilizers at a dose of 3 kg/ha.
Lack of manganese can be suspected if the leaves of the tops turn yellow and gray stripes appear on them. The recommended dose of 7 kg/ha or treatment of tubers before planting in a dose of 20 liters per ton of planting material.
It is noted that early varieties of potatoes are better grown on soils of light grain size, which are heated faster by the sun. For varieties yielding a crop later suitable soils of heavy particle size distribution. Early varieties use mineral fertilizers less efficiently than later ones, which is associated with a shorter growing season. It is also important to remember that when watering, the need for fertilizers increases, as water contributes to the movement of minerals below the growth zone of potato roots.