The Role Of Potassium In Maintaining Soil Fertility. How To Balance It

2023 Author: Sebastian Paterson | [email protected]. Last modified: 2023-11-26 20:34

On the example of the land holdings of the farms of the Central Black Earth Region

Providing plants with the necessary nutrients is an integral part of the cultivation of all agricultural crops. Nitrogen, phosphorus and potassium are absorbed by plants more intensively than other elements. That is why they are called macronutrients. All of them are extremely important for plants, which is proved by the most important law of agrochemistry - the law of minimum or Liebig's law. It states that the determining element of the yield and its quality is the element that is at the minimum, no matter how much the plant requires. Thus, if the plants do not receive any nutrient, then the yield and its quality will decrease precisely due to its lack, even if there are plenty of other nutrients in the soil. If you look at the statistics of the introduction of macronutrients, for example, in the Lipetsk region,then it can be concluded that the optimization of potash nutrition is paid much less attention compared to other elements (see Fig. 1).

Figure: 1. The introduction of nitrogen, phosphorus and potassium in the Lipetsk region (according to the data of the Lipetsk State Central Asia-General Center)

Often, such an attitude arises from the conviction of farmers that the soils of the Central Black Earth Region contain a sufficient amount of potassium, and

there is no need to make it additionally. Indeed, the cartogram of mobile potassium in soils indicates that its content in the arable lands of the Kursk, Lipetsk, and Tambov regions is increased and ranges from 81 to 120 mg / kg of soil (Chekmarev, 2014). And most of the territory of the Belgorod and Voronezh regions is provided with a high content of exchangeable potassium from 121 to 180 mg / kg of soil (see Fig. 2).

Figure: 2. Cartogram of the content of mobile potassium in soils of arable land in the Central Black Earth Region according to Chirikov

Methods of Kirsanov, Chirikov, Machigin, Maslova, Brovkina and Protasov are used to determine exchangeable potassium (see Table 1).

Table 1. Interpretation of soil analysis results

Provision of plants
	Mobile K *, mg K 2 O / kg soil
	according to Chirikov	according to Kirsanov	according to Maslova	according to Machigin
	Chernozems	Sod-podzolic soils		Gray soils, carbonate chernozems
1) Very low	0 - 20	0 - 40	0 - 50	<100
2) Low	21 - 40	41 - 80	51 - 100	101 - 200
3) Medium	41 - 80	81 - 120	101 - 150	201 - 300
4) Increased	81 - 120	121 - 170	151 - 200	301 - 400
5) High	121 - 180	171 - 250	201 - 300	401 - 600
6) Very high	> 180	> 250	> 300	> 600

However, it is known that potassium is found in soils in accessible and inaccessible forms. Mobile potassium is an available form and is represented in soils by the sum of exchangeable and water-soluble potassium. Water-soluble potassium is the salts contained in the soil solution (nitrates, phosphates, sulfates, chlorides, carbonates). For plants such potassium is available, but its content is very small 1-7 mg K ₂ O per kg of soil, or 3-21 kg per hectare.

Exchangeable or absorbed potassium is represented by cations in the AUC. This is the main power source. Its from 0.5 to 3% of the total potassium of the soil. However, plants use only 5.7-37.5% of its stock, depending on the type of soil, particle size distribution, biological characteristics of crops, and other conditions (Wildflush, 2001). Thus, at best, plants can absorb only 30.4-67.5 mg / kg of potassium soil from the soils of farms in the Central Chernozem region.

In addition, a significant removal of potassium and other elements with the crop occurs annually (see Table 2).

Table 2. Approximate removal of the main nutrients with the harvest of agricultural crops (Smirnov, 1984)

Culture	Harvest of main products (centners per hectare)	Carried out with the harvest, kg per hectare
		N	P 2 O 5	K 2 O
Cereals	30-35	90-110	30-40	60-90
Legumes	25-30	100-150	35-45	50-80
Potatoes	200-250	120-200	40-60	180-300
Sugar beet	400-500	180-250	55-80	250-400
Corn (green mass)	500-700	150-180	50-60	180-250
Cabbage	500-700	160-230	65-90	220-320
Cotton	30-40	160-220	50-70	180-240

The table below shows how the annual depletion of the soil by nutrients occurs when the main crops are grown with their average yield. With an increase in productivity, the loss of nitrogen, phosphorus, potassium increases proportionally. Thus, the initial soil fertility can be maintained by applying mineral fertilizers in doses: N 90-250, P 30-90 and K 50-400 kg / ha, depending on the crops grown.

However, there is often an opinion among agricultural producers that soil fertility is fully restored due to natural processes of mobilization of nutrients, the transition of inaccessible forms of nutrients to available ones, humus mineralization, etc.

Indeed, the transition of sparingly soluble compounds to an assimilable form constantly occurs in the soil under the influence of biological, physicochemical and chemical processes.

First of all, due to the mineralization of the humus of the soil, nitrogen, phosphorus and sulfur pass into the mineral form assimilable for plants. Every year, 0.6-0.7 tons of humus are mineralized in the arable layer of sod-podzolic soils, and 1 ton per hectare in chernozems, with the formation of 30-35 kg / ha and 50 kg / ha of mineral nitrogen available to plants, respectively. With an average nitrogen content in humus of about 5%, for every unit of nitrogen available to plants, twenty times the amount of humus should be mineralized. Humic, fulvic acids and carbon dioxide, contained in humus, have a dissolving effect on hardly soluble mineral compounds of phosphorus, calcium, potassium, magnesium. As a result, these elements also pass into a form accessible to plants, but in much smaller quantities.

The most intensive humus decomposes in clean vapors, where up to 100-120 kg of nitrogen per hectare can accumulate in the soil. Intensive mineralization and deficiency of nutrients of arable land over the years causes depletion of humus. Over the past hundred years, the chernozems of the Voronezh and Tambov regions have lost up to 30% of humus. A similar picture is observed in the chernozems of the Volgograd region and other regions. Its losses are also significant on other types of soils. Thus, the lack of agrotechnical methods for applying mineral fertilizers leads to the depletion of the natural fertility of the soil and to a decrease in the yield of crops grown due to nutritional deficiencies.

Among other things, the reverse processes of binding and immobilization of soil nutrients into their forms inaccessible to plants occur in the soil every year. BelNIIPA studies have established that from 1 hectare of soddy-podzolic soils of different granulometric composition, from 8 to 15 kg of potassium can be washed out, on peat soils - up to 10 kg. From erosion, depending on the degree of soil erosion, is lost from 5 to 20 kg of potassium per 1 hectare.

A small amount of potassium enters the soil with atmospheric precipitation (up to 7 kg per hectare). However, neither this potassium, nor supplied with organic fertilizers, can compensate for its removal with the harvest and losses from the soil. Therefore, to increase soil fertility, to obtain high yields of crops, especially demanding on this nutrient, mineral potash fertilizers play an important role.

The given factual data on the intake and alienation of potassium compounds available for plant nutrition with the crop confirm the need to increase the doses of potassium fertilizers applied when growing major crops in the Central Black Earth Region.

The need for some regions of the Central Chernozem region in potash fertilizers is presented in Table 3.

Table 3. Demands for potash fertilizers in the Tambov, Lipetsk and Oryol regions (based on the materials of the Unified Interdepartmental Information and Statistical System 2015)

Culture	Sown area, thousand hectares by regions			Potassium dose for the CCR zone, kg / ha	Potassium needed, tonnes by region
	Lipetsk	Orlovskaya	Tambov		Lipetsk	Orlovskaya	Tambov
POTASSIUM CROPS, responding well to the introduction of the element
Sugar beet	107.6	53	98.5	90-120	9684-12912	4770-6360	8865-11820
Sunflower	171.3	33.4	387.7	60	10278	2004	23262
Potatoes	49.1	30.9	40	60	2946	1854	2400
Soy	35.2	57.4	44.1	30-40	1056-1408	1722-2296	1323-1764
WINTER GRAINS, including:
Wheat	283.2	449	414	60	16992	26940	24840
Rye	2.7	2.7	3.9	30-60	81-162	81-162	117-234
SPRING GRAINS, including:
Wheat	104.1	41.9	134.5	thirty	3123	1257	4035
Barley	279.2	190.9	345.8	thirty	8376	5727	10374
Corn for grain	99	68.5	120.1	60	5940	4110	7206
Fodder crops	89.5	109	65.1	60	5370	6540	3906
TOTAL				30-120	63846-67507	55005-57250	86328-89841

E. N. Sirotkin,

candidate of agricultural sciences;

E. Yu. Ektova, teacher, OGBPOU "Ryazhsky Technological College"