The Influence Of Potash Fertilizers And Micronutrients On The Quality Of Potatoes

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

Read the previous part. ← Influence of nitrogen and phosphorus fertilizers on the quality of potatoes

The role of potash fertilizers

Potassium has a positive effect on the yield and quality of potatoes. It is necessary for the formation of tubers and the better movement of starch from the leaves to the growing tubers. Potato tops contain more potassium than tubers. This potassium gives the plant frost resistance.

Usually the aboveground part (stem and leaf) dies during autumn frosts of -1 … -30C. In many potato growing regions, after the first frost, the weather is warm for quite a long time. Therefore, preventing the complete or partial death of potato tops from the first frosts by applying potash fertilizers is of great importance in increasing yields and improving the quality of tubers. When potash fertilizer was added to the nitrogen-phosphorus background, the death of the tops was only 12%. The frost resistance of potato tops increases with increasing doses of potash fertilizer.

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With a lack of potassium in the soil, potato leaves acquire a dark green color, curl, dry out and fall off prematurely. One of the characteristic signs of potassium starvation of plants is the appearance of bronze spots on the leaves, which is often observed in potatoes grown on sandy and especially on peat and floodplain lands poor in mobile potassium. The liming of such soils further enhances the potassium starvation of plants, since the calcium of the lime fertilizer is an antagonist of potassium and reduces its supply to the plant. Therefore, the use of potash fertilizers to prevent signs of potato leaf bronzing is critical.

Potassium has a positive effect on the relative resistance of potatoes to a number of diseases, among which ring rot is one of the most common. With massive damage to plants, it sharply reduces yields and the quality of tubers. Ring rot bacteria develop more intensively in a glucose-rich environment. Potassium, in contrast to nitrogen and phosphorus, limits the rate at which glucose accumulates in the leaves, stems and tubers of potatoes. Therefore, fertilizing the soil with this element increases the resistance of tubers against ring rot.

Potash fertilizers also prevent the incidence of potato fungal disease - macrosporium, which is expressed in the appearance of dry brownish spots on the leaves. With a strong development of the disease, spots cover all leaf lobes, as a result of which the leaves dry out prematurely, which leads to a decrease in yield and a deterioration in the quality of tubers.

Potassium also helps in the fight against late blight of potatoes, this is especially effective when copper, boric, molybdenum and cobalt fertilizers are applied together with potatoes.

The effect of potash fertilizers on the starchiness of tubers depends on the doses and forms of fertilizers used. Chlorine-containing potash fertilizers reduce the starchiness of tubers. A decrease in the starch content of tubers was noted with the introduction of 40% potassium salt both against the background of NP and together with 3 kg / m2 of manure. The starch content of tubers with the introduction of increasing doses of chlorine-containing potassium fertilizers (up to 12 g of K2O per 1 m2) decreased both on a manure and on a manure-free background approximately equally (from 12.9% to 11.9%).

On peaty soils, poorly supplied with mobile phosphorus and well supplied with exchangeable potassium, these fertilizers did not impair the taste of potatoes. They somewhat reduced the content of vitamin C, but did not reduce the starchiness of the tubers. Even high doses of potassium fertilizers (12-14 g / m2) on soils well supplied with exchangeable potassium did not reduce the starch content of tubers, but contributed to a significant increase in yield.

The effectiveness of potash fertilizers depends on the ratio of the applied fertilizers. With an optimally selected ratio of nitrogen to phosphorus and potassium, the starchiness of the tubers increases.

On soddy-podzolic sandy loam soils with an average content of mobile phosphorus and exchangeable potassium, potassium chloride reduced the digestibility and powderiness of potatoes and worsened its taste in comparison with chenite and potassium sulfate. Tubers fertilized with potassium sulfate, chenite and cement dust had the best taste. The content of vitamin C in potato tubers fertilized with potassium chloride was 18.4 mg%, and in potassium sulfate - 20.9 mg%. Potassium chloride also turned out to be the least profitable fertilizer compared to potassium sulfate and potash. So, against a nitrogen-phosphorus background, the starch content in potato tubers was 16.7%, with the introduction of potassium sulfate - 17.9%, with the introduction of potash - 17.9%, and when using potassium chloride - only 16.5%. The best results were obtained with the introduction of potassium magnesium: the starch content in the tubers increased to 16,5% and the collection of starch - up to 256 g / m2.

Thus, low-percentage chlorine-containing forms of potash fertilizers (kainit, sylvinite, carnalite, etc.) usually deteriorate the quality of potatoes, reducing the starch content in them and impairing the taste of tubers. Concentrated forms of chlorine-containing potassium fertilizers (potassium chloride and 40% potassium salt) insignificantly affect the starch content in tubers, and chlorine-free fertilizers (chenit, potash, potassium magnesium, potassium sulfate) significantly increase the quality of the crop. Chlorine-containing forms of potassium fertilizers reduce the starchiness of tubers due to the fact that chlorine increases the water content in tubers, enhances growth processes and retards the development and maturation of plants.

The best results in increasing the starchiness of tubers are obtained with the introduction of magnesium-containing potassium fertilizers, especially when growing potatoes on acidic sandy soils.

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Influence of various trace elements on potato quality

So, to summarize: organic and mineral fertilizers, when applied in optimal doses and the correct ratio of nutrients, increase the nutritional value of potatoes and do not negatively affect the starch content and taste of tubers.

Trace elements: boron, manganese, molybdenum, copper and others, in combination with high agricultural technology, increase the yield and improve the quality of potatoes. The positive role of macronutrients in improving the quality of the crop is due to the fact that they are important in metabolism, change the rate of redox reactions in the cell, and have a noticeable effect on respiration and photosynthesis.

The ability of boron to increase the activity of invertase (an enzyme that breaks down sucrose into glucose and fructose) in potato leaves leads to an accelerated accumulation of carbohydrates in the tubers. Potatoes cannot develop normally without boron, they are susceptible to a strong disease in the form of a mosaic with leaf rolling. Foliar dressing with boron increases the content of soluble sugars in leaves and starch in tubers.

With a lack of manganese, potato leaves turn yellow. Manganese contributes to a more economical consumption of nutrients, plays an important role in plant respiration and photosynthesis, which leads to a more intensive accumulation of starch in tubers.

Copper has a strong influence on the growth and development of potatoes. Foliar feeding with copper reduces the incidence of potato rhizoctonia and late blight. It increases the content of chlorophyll in leaves, starch, vitamins and minerals.

Cobalt, zinc and manganese increased the yield of tubers and increased the starch content from 17.2% to 18.5%, manganese increased the amount of starch to 17.8%.

Boron and molybdenum in the form of a solution of boric acid (0.05%) and ammonium molybdenum (0.01%), which moistened seed tubers on the eve of planting at the rate of 3 liters per 10 kg, as well as foliar dressings with a solution of boric acid 0.01 % and ammonium molybdate 0.01% (7 ml per m2), the yield and starch content increased by 20%. Presowing treatment of seeds with boron increased the starch content from 14 to 15.7%. The use of boron in the form of foliar feeding made it possible to obtain tubers, which contained 19.2% starch. Molybdenum had a similar effect on the starch content.

The greatest influence on the yield and quality of potato tubers was exerted by soaking the seeds in a 0.1% solution of cobalt sulfate.

Thus, micronutrient fertilizers increase the yield of potatoes, increase the content of dry matter, starch, ascorbic acid and protein in tubers.

The effect of doses and ratios of mineral fertilizers on the yield and quality of potatoes is stronger than the use of nitrogen, phosphorus or potassium fertilizers alone. The predominance of phosphorus or potassium in the early phases of plant development accelerates metabolic processes and leads to their faster aging, the yield of tubers is somewhat reduced, less dry matter is accumulated, but the plants contain much more starch.

In the case of a predominance of nitrogen in the early phases, the development of plants is inhibited, their maturation is delayed. They develop a powerful vegetative mass, due to which the outflow of nutrients into the tubers is insufficient, which also leads to a decrease in yield, nitrogenous compounds accumulate in the tubers and their starchiness decreases. Therefore, by changing the ratio of the basic nutrients introduced into the soil, one can influence the intensity and direction of metabolism in potato plants during the growing season and achieve high yields of good quality tubers.

On soddy-podzolic medium loamy soils, moderately supplied with available phosphorus and potassium, the most favorable ratio of nutrients in obtaining a high yield of good quality is N: P: K = 1: 1: 1 or 1: 1.5: 1. Potato yield with such amounts of applied fertilizers is 2.38 kg / m2, and the starch content in tubers is 17.3%. The application of these amounts of mineral fertilizers against a background of 3 kg / m2 of manure also contributes to the production of high quality tubers.

The best results in terms of yield and quality of early varieties were achieved with the predominance of nitrogen in the applied fertilizers over phosphorus and potassium. When applying mineral fertilizers for early ripening varieties of potatoes, nitrogen fertilizers should prevail over phosphorus ones, and for later varieties it is necessary to give more phosphorus fertilizers than nitrogen ones. In this case, the most favorable conditions are created for obtaining the maximum yield of tubers with good quality products.

For early potatoes, it is recommended to apply increased doses of nitrogen fertilizers (1: 0.8: 1), for mid-late varieties - increased doses of phosphorus-potassium (1: 1.3: 1.7), for seed potatoes, the doses of phosphorus-potassium fertilizers are even higher (1: 1.4: 2.0).

Causes of darkening of potato pulp

A serious factor that reduces the organoleptic quality of potatoes is the darkening of their flesh. At present, domestic and foreign scientists have established some of the causes of this phenomenon. According to German researchers, the darkening of the flesh of potatoes is associated with the oxidation of the amino acid tyrosine to melanin, which has a blue-black color, as well as with the oxidation of iron and the formation of its complex compounds with chlorogenic acid. These iron compounds take on a bluish green color. Mineral and organic fertilizers several times reduce the content of free tyrosine in tubers and increase the amount of absorbed potassium, which reduces the degree of darkening of tubers or completely eliminates this phenomenon. It is recommended to apply increased doses of potash fertilizers under potatoes, which can reach 30-40 g per 1 m2,and the potassium content in tubers is not less than 2.0-2.5% of the dry matter weight.

On clay soils with a potassium content of 2.54% in tubers, a slight darkening of the pulp was observed, and with 2.0% potassium, 50% of tubers darkened. On loamy soils, potato tubers did not darken even when they contained 2.0% potassium. A unilateral increase in the doses of nitrogen fertilizers promotes darkening of the potato pulp. However, the use of these fertilizers against the background of potash or organic fertilizers containing a lot of potassium reduces sharply darkening of tubers.

In most cases, the use of mineral fertilizers, especially in doses calculated according to the removal of nutrients by the crop, reduced the tyrosine content by more than four times and significantly increased the amount of potassium in tubers. Such tubers did not darken at all.

Some darkening of the pulp of potato tubers grown on peaty soils was found. Application of potash fertilizers on these soils also reduces tuber browning. Thus; To obtain tubers that are not subject to browning, potatoes should be grown in soils that contain sufficient potassium. The lack of this element in soils must be compensated for by the introduction of potash fertilizers.

The influence of fertilizers on the palatability of potatoes

The opinions of scientists about the effect of fertilizers on the taste of boiled potatoes are somewhat contradictory. Canadian researchers are of the opinion that increasing doses of fertilizers impair the taste of boiled potatoes. German scientists say that fertilizers do not reduce this figure. Only a one-sided increase in nitrogen doses up to 24-30 g per 1 square meter slightly worsens the taste. Evaluation of the taste of potatoes in Sweden showed that the use of fertilizers slightly worsens the taste of potatoes, but it is recognized that all products in terms of taste meet the requirements of the Swedish standard.

Russian scientists believe that the sugar and free amino acids in the tubers negatively affect the taste of boiled potatoes. As their sum increases, the taste and smell of potatoes deteriorate. An unpleasant smell and taste are caused by the formation of a number of low-boiling volatile compounds from sugars and free amino acids during cooking - methanyl thiol, acrolein, hydrogen sulfide, etc. However, this happens only when unbalanced doses of fertilizers are applied.

It is sometimes believed that nitrogen fertilizers, along with an increase in the protein content in the tubers, cause a deterioration in the culinary quality of potatoes, in particular, after cooking it becomes more sticky and less mealy, its aroma deteriorates, and boiled tubers darken quickly. However, such fears are often in vain. The deterioration of the culinary quality of potatoes can be only when relatively high doses of nitrogen are introduced, more than 40 g per m2.

The timing and methods of using mineral fertilizers also significantly affect the yield and quality of potatoes. Fertilizers applied during potato planting enhance the effect of the main fertilizer. Superphosphate at a dose of 5-7 g / m2 and urea 5-6 g / m2, introduced when planting potatoes, accelerate the rate of germination of tubers due to the initial increase in starch hydrolysis in uterine tubers, increase the number of germinated eyes in tubers, which leads to an increase in yield and starchiness … In addition, nitrogen fertilizers increase the chlorophyll content in leaves by 1.5-2 times.

As a result of the discussion of the problem, we come to the conclusion that the combination of the main fertilizer (manure 5-6 kg / m2, urea 15-20 gm2, double superphosphate 30-40 g / m2, potassium magnesium 40-50 g / m2, boric acid 1 g / m2, copper sulfate 1 g / m2, ammonium molybdate 0.5 g / m2, cobalt sulfate 0.5 g / m2 in the spring for digging the soil), local application (superphosphate and urea, 5-7 g / m2 each when planting in the nest) with top dressing (10-15 g / m2 of ammonium nitrate and potassium sulfate before the first hilling) allows potato plants to develop a more powerful root system, increase the yield and improve the quality and nutritional value of tubers.

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