Efficiency of Fertilizers

Soil conditions

Maximum increases in yields of all crops from organic and mineral fertilizers, both when applied separately and together, are achieved on the poorest soils. When moving to more fertile and cultivated soils, climatic and other conditions increasingly manifest as limiting factors for plant growth and development, so the efficiency of fertilizers most often decreases. Such a decrease is observed when moving from sod-strongly podzolic to medium- and weakly podzolic, then from light- to dark-gray forest, then from podzolized and leached to ordinary and southern chernozems, then from dark- to light-chestnut soils. On light sod-podzolic soils, organic fertilizers are more effective; on heavy and medium loamy soils, mineral fertilizers are more effective.

Within one type and subtype, the effectiveness of fertilizers is determined by soil texture. In general, a pattern is observed: the poorer the soil of lighter texture, the greater the relative yield increases from fertilizers. Although absolute increases in t/ha on more fertile soils are often higher than on less fertile ones. For podzolic loamy soils, the following average supply of crops with individual elements is typical: nitrogen — 38% of maximum productivity, phosphorus — 76% of maximum productivity, potassium — 82% of maximum productivity.

According to particle-size composition, on light soils of all types, the effectiveness of nitrogen, potassium and micronutrient fertilizers increases; on heavy soils, the effectiveness of phosphorus fertilizers increases. In the first case, this is due to easier leaching of elements; in the second, to greater binding of phosphorus into poorly available compounds. If heavy soils are represented by minerals capable of fixing potassium and ammonium, then potassium and nitrogen fertilizers are also effective on them.

The effectiveness of fertilizers on soils with acidic or alkaline reaction depends on the crops cultivated. Chemical amelioration should always precede fertilizer application. The effectiveness of all types of fertilizers and for all crops increases when acidic and alkaline soils are neutralized, reaching a maximum at the reaction optimal for the cultivated crops.

The effectiveness of each type of fertilizer decreases with increasing supply of plant-available forms of the corresponding elements in the soil and often disappears at high or very high (5th-6th class) supply. Similar patterns of effectiveness of all types of mineral fertilizers are characteristic of all crops on any soils, but manifest with unequal intensity.

Fertilizers and ameliorants simultaneously change agrochemical indicators and other soil properties. For example, according to long-term stationary experiment (since 1912) of the Department of Agriculture of the Moscow Agricultural Academy named after K. A. Timiryazev on sod-podzolic medium loamy soil, in the treatment without fertilizers the average potato yield for 1955-1972 was 6.7 t/ha; in 1973, with application of N₁₀₀P₁₅₀K₁₂₀ — 16.0 t/ha, while the soil had pH 3.83; humus content 1.45%, mobile phosphorus and exchangeable potassium (according to Kirsanov) respectively 19 mg/kg and 41 mg/kg. In the treatment with systematic fertilizer application, the average potato yield for 1955-1972 was 15.4 t/ha; in 1973, at the same dose — 24.7 t/ha; soil pH 3.92, humus content 1.61%, mobile phosphorus and potassium respectively 100 mg/kg and 133 mg/kg. In the treatment with systematic application of mineral fertilizers, manure and periodic liming, the average potato yield for 1955-1972 was 19.1 t/ha; in 1973, at the same fertilizer dose — 32.1 t/ha; the soil was the most fertile — pH 5.67, humus content 2.07%, mobile phosphorus and potassium respectively 128 mg/kg and 207 mg/kg. Similar results were obtained with potato and other crops in other long-term experiments in different countries.

Mobile forms of nutrients accumulated through fertilizers and ameliorants are distributed over time throughout the entire root-inhabited layer and prove most necessary under unfavorable conditions, when the application of fresh fertilizer doses, even in high doses, with inevitable localization may be less effective.

Systematic agrochemical soil surveys conducted since 1965 in all farms, including household and dacha plots, revealed heterogeneity of agrochemical indicators within not only soil types, subtypes and varieties, but also within a single field and part of a field. This circumstance indicated the need to take into account existing differences when classifying soils by these indicators and when determining and correcting fertilizer doses.

According to relative indicators (classes, groups) of soils, the recommended fertilizer doses for crops are corrected; in the absence of recommendations, correction coefficients are introduced. Correction coefficients to doses should ensure obtaining planned crop yields of good quality while simultaneously regulating soil supply with nutrients. At average supply for a specific crop, for example, for cereals, grain legumes and grasses — class 3, for row crops — class 4, for vegetables — class 5, the correction coefficient to the dose is 1. When cultivating crops on soil poorer than the average class, the correction coefficient is increased (more than 1); on soil more fertile than the average class, it is less than 1. When changing by one class, the fertilizer dose on average for all crops should change by 20-30%, that is, for soil poorer than average by one class the correction coefficient should be 1.2-1.3, by two classes — 1.4-1.6, etc.; for soil richer than average by one class — 0.8-0.7, by two classes — 0.6-0.4, etc.

According to absolute indicators, the content of available forms of nutrients in the soil based on field experiment results determines the part assimilated by the crop. This part is called the soil nutrient utilization coefficient (SNUC), determined by the formula:

where

B₀

— economic removal in the treatment without fertilizers, kg/ha;

S

— reserves of mobile forms of the element, kg/ha;

100

— conversion to percent.

Nutrient utilization coefficients change significantly under the influence of fertilizers, and they are determined for all crops only in treatments without fertilizers.

Generalization by L. M. Derzhavin (1992) of experimental data of CISAA showed that even at the same initial supply, the SNUC of phosphorus and potassium varies greatly: for winter wheat 63% and 55%, winter rye 78% and 89%, spring wheat 52% and 56%, spring barley 55% and 95%, potato 63% and 85%, sugar beet 71% and 41%, fiber flax 64% and 86%.

When moving from low to high soil supply with mobile elements, the SNUC of phosphorus and potassium decreased even more significantly: for winter wheat by 4.6-5.7 and 2.7-3.4 times, winter rye by 3.7-4.5 and 3.9 times, spring wheat by 1.7-3.2 and 2.7-2.8 times, barley by 3.9-5.1 and 1.8-2.6 times, potato by 3.8-4.4 and 2.9 times, sugar beet by 4.9-6.4 and 2.3-2.6 times, fiber flax by 6.0 and 2.0-2.3 times.

The effect of once-applied ameliorants, organic, phosphorus and, to a decreasing extent, potassium and nitrogen fertilizers, depending on dose, type and soil-climatic conditions, manifests over 4-5 years, sometimes at high doses — more than 10 years. On average over 55 years on heavy loamy soil under cereals, mineral fertilizers were more effective; under clover, manure was more effective; under potato, they were equivalent. In terms of productivity of rotations, an advantage of mineral fertilizers is noted in experiment 1 (with clean fallow) and in experiment 2 (with clover fallow). The combination of half doses of manure and mineral fertilizers in a rotation with clean fallow (experiment 1) increases crop yield of the rotation compared with manure, bringing it closer to the treatment with mineral fertilizers.

Climatic conditions

The SNUC of elements changes under the influence of weather conditions. According to data generalized by the Department of Agrochemistry of the Moscow Agricultural Academy from various sources, the coefficients of utilization by crops of mobile phosphorus depending on weather and agronomic conditions differ by 10-15 times, and of potassium by 10 times. Therefore, for correcting and determining fertilizer doses based on the results of soil supply with mobile forms of nutrients, it is better to use not absolute but relative indicators, that is, classes and correction coefficients, since the above variability of absolute indicators leads not to an increase but to a decrease in fertilizer efficiency.

The higher the level of light nutrition at normal moisture supply, the more carbohydrates are synthesized and the more nitrogen plants are able to assimilate. Light affects plant nutrition not only through photosynthesis but also through transpiration. With increasing air humidity, plant resistance to increased concentration of nutrient solutions increases.

Soil temperature affects the rate of transformation of nutrients and their uptake by plants. At a temperature of 8-10 °C, the entry, movement and incorporation into metabolism of nitrogen and phosphorus decrease, and at 5-6 °C the consumption of nutrients by roots sharply decreases. At 10-25 °C, mobilization and uptake by plants of nutrients from soil and fertilizers increase.

The optimal daytime temperature (23-25 °C) corresponds to 14-16 °C of average daily temperatures. In the Non-Chernozem zone, according to A. P. Fedoseev, a mean monthly summer temperature above 18.1 °C reduces fertilizer efficiency; in the Chernozem zone, an increase in air temperature for May-July by 1 °C above the long-term norm reduces the increase in grain yields from fertilizers at doses of 120-180 kg/ha a.i. on average by 0.02 t/ha.

An increase in air humidity deficit by 1 hPa in May reduces fertilizer efficiency on average by 40 kg/ha, in July — by 4 kg/ha.

A decrease in annual precipitation norm from north to south by 100 mm in the European part of Russia reduces the efficiency of average fertilizer doses on average by 0.11 t/ha for all grain crops and by 0.19 t/ha for winter crops. A decrease in soil moisture reserves by 10 mm during the growing season of grain crops reduces yield increases from fertilizers on average by 10-20 kg/ha. If at a ratio of precipitation to evaporation equal to 1, fertilizer efficiency is taken as 100%, then each increase in aridity by 10% reduces the fertilizer effect by 15%.

With an increase in moisture to 90% MWC on soils with bulk density 1.2-1.3 g/cm³ and to 80% on soils 1.5-1.6 g/cm³, fertilizer efficiency increases. Further moistening of soils to 100-120% MWC on the former soils gradually, and on the latter sharply, reduces efficiency.

Excess moisture in soils of the Non-Chernozem zone and in irrigated areas causes subsurface and surface water runoff, which leads to leaching of nutrients. Calcium, sulfur, magnesium, nitrogen, carbon, sodium, and potassium are leached from fertilizers and soils. Phosphorus is leached least. Maximum leaching occurs during spring floods and after harvest in autumn.

On loamy and sandy loam soils of the Non-Chernozem zone, with fertilizer saturation (N₆₀P₆₀K₆₀), atmospheric precipitation leaches up to 50 kg/ha (on loamy) and 70-120 kg/ha (on sandy loam) of calcium, 3-7 kg/ha and 10-15 kg/ha of magnesium, 14 kg/ha and 25 kg/ha of sulfur, 7 kg/ha and 10-12 kg/ha of potassium, 1-6 kg/ha and 14-18 kg/ha of nitrogen, respectively, on loamy and sandy loam soils.

The efficiency of average doses of mineral fertilizers (120-180 kg/ha a.i.) depending on moisture conditions in summer months can change by almost 2 times.

The effectiveness of fertilizers on loamy soils in years with insufficient or excessive summer precipitation decreases, and with insufficient moisture it decreases more significantly. On light soils with excessive precipitation under wheat and spring crops, effectiveness remains high, while under rye it decreases.

According to data from a long-term experiment of the Department of Agriculture of MAA, in years with a dry June, with precipitation less than 50 mm and temperature above 18 °C; normally moist June (50-90 mm and 16-18 °C); and wet June (more than 90 mm, temperature less than 16 °C), at rotation saturation with fertilizers (N₅₀P₇₅K₆₀), the payment of 100 kg a.i. of fertilizers was: winter rye grain — 0.35 t/ha; 0.44 t/ha and 0.75 t/ha; oat grain 0.17 t/ha, 0.27 t/ha and 0.46 t/ha; potato tubers 4.3 t/ha, 6.3 t/ha and 7.6 t/ha; clover hay 1.4 t/ha, 1.6 t/ha and 2.9 t/ha; flax straw 0.16 t/ha, 0.72 t/ha and 0.92 t/ha.

The effectiveness of mineral fertilizers in years with a dry June decreased on average by 36% (especially strongly under flax), and with a wet June increased by 52% (especially under clover) compared with a normally moist June. When the same doses of mineral fertilizers were combined with manure (10 t/ha), the negative effect of insufficient moisture in June was mitigated; the effectiveness of mineral fertilizers decreased on average by 27%.

On average in the Non-Chernozem zone, the increase in grain yields from mineral fertilizers is 0.6 t/ha with fluctuations due to weather conditions of ±40%; in the Central Chernozem zone — respectively 0.52 t/ha and ±44%.

Scientifically justified use of fertilizers weakens the negative influence of unfavorable weather conditions (low temperatures, frosts) on crop productivity.

According to data from 40 experiments generalized by A. P. Fedoseev, against a background of phosphorus-potassium fertilizers, the number of winter rye and wheat plants killed during overwintering decreased from 42% (without fertilizers) to 27%; when phosphorus-potassium fertilizers were combined with optimal doses of nitrogen fertilizers before sowing, winter crop death decreased to 18%.

The relationship between fertilizer efficiency and meteorological factors is characterized by correlation coefficients.

Correlation coefficients developed by A. P. Fedoseev (Institute of Experimental Meteorology) and regression equations for assessing fertilizer efficiency from meteorological factors show that weather-climatic conditions explain 25-60% of fluctuations in fertilizer efficiency in the Non-Chernozem zone and 35-70% in the Central Chernozem zone.

When determining optimal and maximum fertilizer doses, it is necessary to focus on long-term average meteorological data of specific territories and annually correct them taking into account the forecast for the coming year. With increasing saturation of crops with fertilizers and growth of crop productivity, the fluctuation of yield depending on meteorological conditions of a specific year in absolute values (t/ha) increases, while in relative values (% of average) it decreases.

Moisture supply

In zones of insufficient moisture and arid climate, fertilizers are of low effectiveness and are applied in small amounts — up to 20-30 kg/ha a.i.. Under these conditions, phosphorus fertilizers applied at sowing in doses of 10-20 kg/ha a.i. are more effective. Only under irrigation does effectiveness increase substantially, primarily of nitrogen, then phosphorus and organic fertilizers.

Under conditions of insufficient moisture and arid climate, splitting the total dose into basal fertilizer and top dressings is most often agronomically and economically impractical.

The use of fertilizers and ameliorants in arid conditions provides up to 20-30%, under insufficient moisture — up to 30-50%, and under sufficient moisture — up to 50-70% of the total productivity of all cultivated crops.

Methods of fertilizer application

The task of fertilizer application methods is to provide optimal conditions for plant nutrition during the growing season. When choosing application methods, it is necessary to take into account the crop's need for nutrients by growth phases and the possibility of placing them in the zone of greatest contact with the root system.

The choice of fertilizer application methods is influenced by the properties of fertilizers, their mobility, features of interaction with the soil absorbing complex, the presence of impurities in the fertilizer and the attitude of crops to them. The placement of fertilizers in the arable layer depends on the application method and method of incorporation.

When incorporated with a harrow, 75-98% of applied fertilizers are located in the upper soil layer at a depth of up to 3 cm. This method may be effective in areas of sufficient moisture or under irrigation on light soils, as well as for surface top dressing of solid-sown crops, for example, winter wheat, with soluble and mobile nitrogen fertilizers. In steppe regions with insufficient and unstable moisture, this method of incorporation is of little effectiveness.

When fertilizers are incorporated with a plow with a skimmer, most of the fertilizers are placed in the lower soil layers, where they act well and are used by plants when the root system is sufficiently developed. However, at the beginning of the growing season the crop may experience a lack of nutrients. Therefore, in this case there is a need for additional fertilizer application to provide plant nutrition in the first phases of growth.

For soluble fertilizers absorbed by the soil, effective application methods are local and local-band. The basal fertilizer for crops with row sowing can be applied by the local-band method using special attachments to plows and flat-cutting cultivators. With local application, nutrients are less fixed by the soil and more available to plants, increasing their utilization coefficient.

With broadcast application of fertilizers over the field surface, incorporation by various tillage implements is unsatisfactory and does not correspond to the needs of crops. Even when treated with the same implement, the distribution of broadcast-applied fertilizers through the soil profile depends on their physical properties.

The greatest effect under all crops is achieved with local application of fertilizers to a specified depth, which is usually not less than 8-10 cm for heavy soils and 12-15 cm for light soils in texture. According to data generalized by ARRIFASS over more than 20 years, yields of all crops from localization of equal fertilizer doses increase on average by 0.5-1.0 t/ha of grain units compared with broadcast application, and more significantly under intensive crop varieties. With localization, fertilizer nutrients are used more fully by plants, their losses are reduced, and fertilizer doses can be reduced by 30-50% compared with broadcast application, thereby increasing the fertilized area and efficiency by 2 times.

The effectiveness of fertilizers increases with the depth of incorporation and with decreasing moisture supply of crops. At the same moisture supply, it depends on the mobility of fertilizer types and forms. The depth of incorporation is important for organic and phosphorus fertilizers, less so for potassium, nitrogen and micronutrient fertilizers.

With sufficient atmospheric precipitation, the effectiveness of organic, phosphorus and potassium fertilizers, primarily on sod-podzolic soils, increases with increasing depth of incorporation within the cultivated arable layer. With deeper tillage of such soils, effectiveness decreases, since they are diluted by a large volume of soil poor in nutrients with unsatisfactory agrochemical and physical properties.

The effectiveness of fertilizers depends on the time of primary tillage, especially for nitrogen fertilizers. For example, with late autumn tillage, mineralization of root and stubble residues due to the short period is minimal, therefore against such a background the effectiveness of nitrogen fertilizers increases.

The effectiveness of fertilizers is influenced by the timing and methods of sowing (planting), the quality of seed (planting) material, the seeding rate and plant density, that is, the plant feeding area. The transition from high-class seeds of elite varieties to less quality ones reduces fertilizer efficiency. High-quality and timely performance of work before sowing, at sowing, during the growing season and harvesting increases fertilizer efficiency.

Mutual influence of plant protection products and fertilizers

Fertilizers in optimal doses and ratios reduce the activity of snow mold in winter crop sowings and at the same time increase the competitive ability of solid-sown crops, especially winter crops, in relation to weeds. Fertilizers do not replace plant protection by biological, chemical and agronomic means.

Weed infestation of crops reduces the yield of cultivated crops due to competition of weeds for nutrition conditions. Weeds, due to different and greater nutrient requirements than cultivated plants, change the populations of predominant species when crops are fertilized. Therefore, the predominance of a particular type and form of fertilizer allows predicting the predominant weed species and correcting the system of measures to control them.

Before pre-sowing tillage, joint application of fertilizers and soil-acting herbicides is possible. Herbicide treatment is also combined with top dressing of winter cereals and perennial grasses with nitrogen fertilizers, as well as with foliar top dressing with nitrogen and micronutrient fertilizers in combination with fungicides, insecticides and plant growth regulators. In a series of field experiments with maize on sod-podzolic and gray forest soils, generalized at the Department of Agrochemistry of MAA, weeds reduced fertilizer efficiency in crops by 5 times; herbicides increased fertilizer efficiency by more than 4 times compared with weedy crops, but were less effective than manual weeding of crops.

Optimization of fertilizer doses and ratios for a specific crop increases competitive ability against weeds, against applied herbicides and other unfavorable environmental factors. A healthy plant not damaged by pests or other environmental factors responds better to improved nutrition conditions. Thus, according to data from Rothamsted Experimental Station, the grain yield of spring wheat damaged by nematodes and fungal diseases with N₇₅ was 1.45 t/ha, and when soil was treated with formalin it increased to 3.75 t/ha. Application of N₂₂₂ without formalin provided a yield of 2.93 t/ha, and in combination with it — 4.49 t/ha.

Crop rotation

The effectiveness of fertilizers depends on the type and yield of predecessors of the fertilized crops, on the composition and scheme of crop alternation, that is, on crop rotation. Increasing fertilizer efficiency under crops in rotations is also due to improvement of the phytosanitary state of crops.

Mineral fertilizers are applied in optimal doses primarily for industrial crops, potatoes, grain crops, cultivated meadows and pastures. Increasing doses of mineral fertilizers is primarily advisable on soils with regulated water regime, limed or not requiring liming, as well as on soils cleared of stones, shrubs, and weeds.

According to data from an 86-year experiment of the Department of Agriculture of MAA, generalized by A. A. Alferov for 1978-1998, on average yields of crops under different fertilization in rotation and in continuous sowings on sod-podzolic light loamy soil, the average yield of winter rye under continuous cultivation and in rotation was: without fertilizers 1.29 and 2.51 t/ha; with mineral fertilizers 2.33 and 2.97 t/ha; with combination of mineral fertilizers with manure against lime background 2.68 and 3.25 t/ha. Thus, the fertilizing value of crop rotation decreases with the use of mineral fertilizers, but the phytosanitary role still ensures higher fertilizer efficiency.

The average yield of potato tubers was respectively: without fertilizers 8.3 and 9.2 t/ha; with mineral fertilizers — 19.1 and 19.1 t/ha; with combination of mineral fertilizers and manure against lime background — 16.7 and 23.3 t/ha. This crop can be cultivated continuously, but the phytosanitary role of rotation manifested in the combination of lime, manure and mineral fertilizers with maximum yield.

The average yield of barley was respectively: without fertilizers — 0.39 and 0.31 t/ha; with mineral fertilizers against lime background — 2.59 and 2.83 t/ha; with combination of mineral fertilizers, manure and lime — 2.79 and 3.25 t/ha. The phytosanitary role of rotation in this example manifests in increasing the efficiency of increasing fertilizer saturation only against lime background.

The average yield of clover hay was respectively: without fertilizers 1.95 and 3.60 t/ha; with phosphorus-potassium fertilizers against lime background — 5.55 and 6.66 t/ha; with combination of mineral fertilizers, manure and lime — 5.85 and 5.99 t/ha. This example shows the fertilizing and phytosanitary role of rotation and the real possibilities of clover to meet nitrogen needs.

As crop agronomy improves under the influence of fertilizers, yields increase both in rotations and in continuous sowings; both on poor and cultivated soils. Different crops respond differently to fertilizers, cultivation in rotations, and combinations of these factors. According to generalized data from experiments of the Department of Agriculture of MAA, the contribution of rotation, fertilizers and their combination in the Non-Chernozem zone to the total yield increase is respectively:

• winter wheat 57%, 32% and 11%;
• oats 56%, 36% and 8%;
• potato 22%, 55% and 23%;
• beet 10%, 69% and 21%;
• maize 6%, 81% and 13%.

In grain crops, more than 55% of the yield increase is due to rotations and only 32-36% to fertilizers; in row crops, 55-81% is due to fertilizers and only 6-22% to rotations. This means that row crops should be placed in farm-adjacent rotations; repeated sowings and cultivation in diversion fields are permissible.

Under conditions of insufficient moisture, clean fallows in rotations improve moisture supply, enhance mineralization of organic matter and facilitate weed control. Therefore, under crops following clean fallow, the effectiveness of phosphorus-potassium and organic fertilizers increases, while that of nitrogen fertilizers decreases. After occupied fallows, the effectiveness of all fertilizers is usually higher than after clean fallows.

After the sod and turnover of sod of perennial grasses, the effectiveness of organic and nitrogen fertilizers decreases, while that of phosphorus-potassium fertilizers increases.

Application rates

The effectiveness of fertilizers depends on the amount (total dose) and quality (ratio of types, form, methods and timing of application). The dependence persists as long as the deficiency of a nutrient remains a limiting factor for plant growth and development. With increasing total dose and increasing soil fertility, effectiveness decreases. Maximum yields of vegetable, forage and other crops are achieved with a combination of optimal doses of organic and mineral fertilizers; on acidic and alkaline soils also with ameliorants.

Long-term studies in Stavropol Krai with winter wheat, generalized by A. I. Podkolzin (1998) over 30 years, confirm a decrease in fertilizer efficiency with increasing doses and fertility of chernozems and chestnut soils.

Influence of fertilizer ratio

The correct ratio of nutrients is important; its violation complicates the use of elements by the plant. The optimal ratio of nutrients affects their entry into the plant, the direction of synthesis of organic compounds, growth and formation of yield and product quality. Even J. Liebig noted that fertilizers act most favorably if through them a correct ratio of nutrients is established in the soil. D. N. Pryanishnikov also pointed this out, writing that the effect of phosphate fertilizers depends on the supply of plants with other elements, primarily nitrogen.

Due to an increase in doses and improvement of ratios (N:P₂O₅:K₂O), the average annual yield of grain crops in some farms of Moscow Oblast increased from 1.1 to 4.6 t/ha. Only due to improvement of fertilizer ratios corresponding to crop needs and soil fertility, at 188 and 182 kg/ha a.i., yield increased by 0.6 t/ha, or by 48%.

Together with organic fertilizers, mineral fertilizers, primarily nitrogen, are applied to reduce nitrogen consumption from soil humus.

Methods for assessing fertilizer efficiency

The effectiveness of fertilizer types, doses and combinations is assessed by the amount of increases, total crop yield and rotation productivity, by the payback of 1 kg a.i. of fertilizers by yield increases and rotation productivity. However, when total doses are equal but types and ratios differ, and when equal increases or total yields of individual crops and rotation productivity are obtained, as well as to determine the contribution of individual fertilizer types to productivity, it is necessary to determine the use of fertilizer nutrients by crops. These assessments are calculated by different methods.

Balance method

In reality, to obtain equal yields of any crop on poor soil, more fertilizers are required than on cultivated soil, since in the former part of the fertilizers is absorbed by the soil rather than by the crop or is lost. Infinite exploitation of cultivated soils at low fertilizer doses leads to depletion and loss of fertility. To prevent this, fertilizer application is controlled using balance coefficients of nutrient utilization.

The balance method is based on determining the balance coefficient of fertilizer utilization (K_bal):

$$K_{bal} = \frac{B_f}{D_f} \cdot 100,$$

where

B_f

— economic removal of the element by the crop in the fertilized treatment, in kg/ha;

D_f

— fertilizer dose in kg/ha in this treatment.

Balance coefficients are determined in experiments and production sowings. They give an idea of the degree of assimilation by crops of nutrients from fertilizers and soil and of possible changes in soil supply with these elements.

Table. Application and consumption of N, P₂O₅, K₂O in rotation (clean fallow — winter crops — potato — oats) of DAOS on heavy loamy sod-podzolic soil (average over 56 years for 4 fields; data of Klystovsky, 1992).

Treatment	Applied, kg/ha	Economic removal, kg/ha	Difference utilization coefficient, %*	Balance utilization coefficient, %*	Return coefficient*	Annual balance, kg/ha	Balance intensity, %
Nitrogen (N)
No fertilizers	—	1526	—	—	—	-27	—
Manure	2576	2415	34.5	93.3	1.06	+3	106
NPKCa	2576	2989	56.7	116	0.86	-7	86
Phosphorus (P2O5)
No fertilizers	—	533	—	—	—	-10	—
Manure	1204	980	37.2	81.5	1.23	+4	123
NPKCa	1204	1043	42.5	86.5	1.16	+3	116
Potassium (K2O)
No fertilizers	—	1582	—	—	—	-29	—
Manure	2198	3157	71.6	143	0.70	-17	70
NPKCa	2198	3318	78.9	151	0.66	-20	66

Balance coefficients are higher than difference coefficients, and also higher on fertile soils than on poor ones, that is, they do not have the disadvantages of difference and isotopic coefficients.

Balance results are also expressed in relative indicators:

• return coefficient — the ratio of fertilizer dose to economic removal;
• balance intensity — the ratio of dose to economic removal, that is, the return coefficient multiplied by 100.

The balance is expressed in absolute indicators (kg/ha) as the difference between the dose and economic removal of the element. The balance is positive if the dose exceeds removal, or negative if the dose is less than removal. When dose and removal are equal, the balance is called zero, or deficit-free, balanced.

The balance coefficient, return coefficient and balance intensity are respectively equal: at zero balance — 100, 1 and 100; at positive balance — less than 100, more than 1 and more than 100; at negative balance — more than 100, less than 1 and less than 100.

All relative indicators are equivalent only at zero balance; in other cases, the advantage remains with the balance coefficient, since in its calculations the basis is not the fertilizer dose but the economic removal, which characterizes yield and product quality. Balance coefficients of fertilizer utilization can be determined for different years from the moment of application until the end of fertilizer action, whereas return coefficients and balance intensity — only at the end of fertilizer action, that is, for most fertilizers — 4-5 years after application or per rotation, which is important for periodically applied fertilizers.

The use of balance coefficients allows determining optimal doses and ratios of fertilizers for individual crops and in rotations while simultaneously monitoring and correcting soil supply with nutrients. At the same time, the need for calculating element balances in fields, rotations, and farms disappears.

For the Non-Chernozem zone, the following balance coefficients of utilization of mineral and organic fertilizers are recommended for soils of different degrees of cultivation.

Table. Balance coefficients of utilization of mineral fertilizer elements (%) on soils of different fertility in the Non-Chernozem zone.

Soil fertility (class)	N*			P2O5					K2O
	1st year	2nd-4th year	Total	1st year	2nd year	3rd year	4th year	Total	1st year	2nd year	3rd year	4th year	Total
1	70-75	5-10	75-85	30-40	30-25	5-10	—	65-75	60-70	10-15	10-5	—	80-90
2	70-75	5-10	75-85	35-45	30-25	5-10	—	70-80	65-75	10-15	10-5	—	85-95
3	75-80	5-10	80-90	35-45	30-25	10-15	—	75-85	70-75	10-20	10-5	—	90-100
4	75-80	10-15	85-95	40-50	30-25	10-15	5	85-95	70-75	25-15	5-10	0-10	100-110
5	85-90	10-15	95-105	45-55	35-25	10-15	5-10	95-105	75-80	30-20	10-15	5-10	120-130
6	90-95	10-15	100-110	50-60	40-30	20-15	10-5	110-120	35-25	15-20	10-15	10-15	140-150

Note.

^* The aftereffect of nitrogen fertilizers is small, therefore they are accounted for in the total for the 2nd-4th year.

If mineral fertilizers are applied for all crops of a rotation, the balance coefficients of mineral fertilizer utilization when determining optimal doses need not be taken into account by year, but the total for all years can be used.

For organic fertilizers, coefficients are selected taking into account the year of action, since these fertilizers are, as a rule, applied not for all crops of a rotation.

Table. Balance coefficients of utilization of organic fertilizer elements (%) on soils of different fertility in the Non-Chernozem zone.

Soil fertility (class)	1st year	2nd year	3rd year	4th year	Total
Nitrogen (N)
1	30-40	25-15	5-15	—	60-70
2	30-40	30-20	10-20	—	70-80
3	35-45	30-20	10-20	5	80-90
4	35-45	30-20	10-20	5-10	90-100
5	35-45	40-30	15-25	10-15	100-115
6	35-45	40-30	20-30	15-20	110-125
Phosphorus (P2O5)
1	35-45	30-25	5-10	—	70-80
2	35-45	35-25	5-15	—	75-85
3	40-50	35-25	5-15	—	80 — 90
4	40-50	35-25	10-15	5-10	90-100
5	45-55	35-25	10-15	10-15	100-110
6	50-60	40-30	15-20	10-15	115-125
Potassium (K2O)
1	60-70	10-15	10-5	—	80-90
2	65-75	10-15	10-5	—	85-95
3	70-75	10-20	10-5	—	90-110
4	70-75	25-15	10-15	5-10	105-115
5	75-80	30-20	10-15	5-15	120-130
6	80-85	35-25	15-20	10-20	140-150

References

1. Yagodin B. A., Zhukov Yu. P., Kobzarenko V. I. (2002). Agrochemistry. Ed. B. A. Yagodin. Moscow: Kolos.
2. Mineev V. G., Sychev V. G., Gamzikov G. P. et al. (2017). Agrochemistry. Textbook. Ed. Mineev V. G. Moscow: Publishing House of VNIIA named after D. N. Pryanishnikov.