Methods and Timing of Fertilizer Application
Critical and Maximum Period
In nutrient uptake, critical and maximum periods are distinguished.
Critical period — a period of plant vegetation during which a deficiency of any element has the most negative effect on growth, and subsequent optimization of nutrition does not fully correct this effect.
Maximum period — a period in plant nutrition during which the average daily consumption of nutrients is maximal. Most often, the maximum falls on the period of greatest dry matter accumulation.
Methods of Fertilizer Application
Methods of fertilizer application:
- basic (before-sowing);
- pre-sowing;
- at-sowing (row), or at-planting;
- post-sowing (top dressing).
According to the method of fertilizer incorporation, the following are distinguished:
- broadcast;
- localized — in rows, nests, or holes;
- locally banded.
Basic (Before-Sowing) Fertilizer
Basic, or before-sowing, fertilizer is intended to meet the plant requirement for nutrients after emergence until the end of vegetation. These fertilizers are used by plants when their root system has developed well.
Depending on natural and economic conditions, basic fertilizer is applied annually for each crop; sometimes, for example, for spring cereals with undersowing of perennial grasses, the total dose of phosphorus, sometimes together with potassium, is applied immediately under the cover crop, for it and the grasses cultivated for one or two years. This technique is called periodic, or reserve, application. This technique includes phosphorization of soils, application of organic fertilizers, or special application under one annual crop of a dose calculated for three crops at once.
Timing
In different zones of the country, basic fertilizer is applied at times optimal for the given region. If deep plowing is carried out in autumn and surface tillage in spring, basic fertilizer is incorporated in autumn. Where, in addition to fall plowing, spring replowing is used, mineral fertilizers, except phosphorus fertilizers, should be applied in spring.
The choice of optimal application times is determined by soil properties, primarily particle-size distribution. Thus, on light soils and with sufficient moisture, most nutrients, especially nitrogen, will migrate through the soil profile beyond the root zone. Therefore, incorporation, primarily of nitrogen fertilizers, is carried out in spring.
Basic application of organic and phosphorus-potassium fertilizers is usually carried out in autumn, nitrogen fertilizers in spring before pre-sowing soil tillage in zones of sufficient moisture, or, under other conditions, in autumn before basic tillage in zones of insufficient moisture with incorporation by implements broadcast or locally. The effectiveness of deep incorporation of fertilizers before sowing increases with increasing soil moisture deficit and aridity of the climate.
Methods of Incorporation
Basic (before-sowing) fertilizer is incorporated with a plow during fall plowing.
In the zone of sufficient moisture and on heavy, slaking soils, fertilizers are applied in spring before replowing of fall-plowed land. Under these conditions, high fertilizer efficiency is noted with spring application before sowing followed by incorporation with a cultivator.
Incorporation of fertilizers applied before sowing with a cultivator is also permissible in the forest-steppe for winter cereals. Here, when harvesting late fallow-occupying crops and with a lack of moisture, to avoid drying out, they limit themselves to surface pre-sowing tillage, for example, disking, cultivation, deep stubble cultivation. In this case, fertilizers intended for basic application are applied after harvesting the predecessors of winter crops.
In almost all agricultural regions of Russia, an effect is noted from applying phosphorus and often potassium fertilizers in autumn followed by incorporation with a plow during fall plowing. Nitrogen fertilizers in zones of sufficient moisture, primarily on light soils, are applied in spring followed by incorporation with a plow during replowing of fall-plowed land or with a cultivator.
Localized application of basic fertilizer is effective — in bands, as a ribbon at the bottom of the furrow. With such methods, fertilizers are not mixed with soil, are closer to the feeding part of the root system, and are used by plants more efficiently. The increase in efficiency from band application of fertilizers is associated with the localization of phosphorus fertilizers. With this method, phosphorus fertilizers have less contact with soil, as a result of which water-soluble calcium phosphates convert less into sparingly soluble forms and are more fully assimilated by plants. Localized application of basic mineral fertilizer has a positive effect on the growth and physiological state of leaves, causes increased water-holding capacity, and increases photosynthesis productivity. The advantage of the localized method of fertilizer application is a higher fertilizer use coefficient compared with broadcast application. The fertilizer dose with localized application can be reduced by 30-50% compared with the broadcast method.
Table. Comparative assessment of fertilizer application methods.
| Crop | Yield, dt/ha | Increase from localization, dt/ha | ||
|---|---|---|---|---|
| without fertilizers | with fertilizer application (broadcast) | with fertilizer application (localized) | ||
| Chernozems | ||||
| Winter crops | 28.4 | 38.5 | 42.2 | 3.7 |
| Spring crops | 26.6 | 30.9 | 34.7 | 3.8 |
| Sugar beet | 331 | 386 | 410 | 24 |
| Sunflower | 21.3 | 24.4 | 25.6 | 1.2 |
| Sod-podzolic loamy soils | ||||
| Winter crops | 27.9 | 37.6 | 40.0 | 2.4 |
| Spring crops | 20.6 | 34.2 | 38.1 | 3.9 |
| Potato | 159 | 220 | 236 | 16 |
| Sod-podzolic sandy loam and sandy soils | ||||
| Winter crops | 15.8 | 24.2 | 27.3 | 3.1 |
| Spring crops | 15.2 | 22.1 | 25.2 | 3.1 |
| Potato | 137 | 206 | 217 | 11 |
More promising is two-layer localized application of fertilizers before sowing agricultural crops.
Two-layer localized application ensures intensive supply of nutrients throughout the entire vegetation period, which increases the effectiveness of this technique compared with both broadcast and localized application of fertilizers in one layer.
Table. Effectiveness of two-layer localized application of mineral fertilizers.
| Crop | Yields without fertilizer, dt/ha | Increase, dt/ha, from fertilizers applied | ||
|---|---|---|---|---|
| broadcast | localized in 1 layer | localized in 2 layers | ||
| Potato | 117 | 42 | 66 | 90 |
| Maize | 327 | 3.8 | 7.1 | 10.8 |
| Winter rye | 12.5 | 4.3 | 6.2 | 9.2 |
| Winter wheat | 12.7 | 7.1 | 11.9 | 14.2 |
| Barley | 11.5 | 7.9 | 9.8 | 12.8 |
| Oats | 12.2 | 7.8 | 10.7 | 12.7 |
| Sugar beet | 393 | 112 | 143 | 198 |
| Cabbage | 370 | 107 | 190 | 241 |
| Cucumbers | 313 | — | 103 | 158 |
Broadcast application is less effective but has been used in our country for decades. Basic fertilizer is applied with broadcast fertilizer drills, mineral fertilizer spreaders, and aerial spreaders.
When basic fertilizer is applied at calculated rates for grain crops, the effectiveness of the row application method decreases. Thus, on leached chernozem of the experimental field of Altai Agrarian University, row application of granulated superphosphate at a dose of 10 kg/ha against a background of basic fertilizer N60P60K60 did not provide a significant increase.
Ratio of Applied Fertilizers
For most crops under conditions of sufficient moisture or irrigated agriculture, the basic fertilizer accounts for 60-90% of the total dose; under conditions of insufficient moisture, 90-100%.
In the forest-steppe of the European part of Russia, where moisture conditions are best, 60-70% of the total fertilizer dose is used in the basic application, and the rest is applied in rows at sowing and in top dressing. For row crops in this zone, deep autumn plowing-in of fertilizers has an advantage over spring incorporation during cultivation of fall-plowed land.
In the zone of sod-podzolic soils, about 50% of the total rate is applied before sowing.
At-Sowing (Row) or At-Planting Fertilizer
At-sowing (row, or starter) or at-planting fertilizer is intended to meet the plant requirements for nutrients during the period from germination to full emergence. This technique was developed in Russia by A. E. Zaikevich in 1880. Fertilizers were first applied in rows when cultivating sugar beet; later, superphosphate began to be used when sowing cereals and other crops.
Due to granulation and localized application, the processes of retrogradation of superphosphate phosphoric acid proceed more slowly because of less contact with the soil absorbing complex. Due to the water-soluble form of P2O5 in superphosphate and its close location to the root system, it is actively used by plants. The utilization coefficient of P2O5 of superphosphate with localized application is 2-3 times higher than with broadcast application.
Table. Comparative effectiveness of granulated superphosphate when applied in rows and broadcast under a cultivator.
| Crop | Dose P2O5, kg/ha | Yield increase, dt/ha, with application of granulated superphosphate | Grain yield increase, in kg per 1 kg P2O5, with application | |||
|---|---|---|---|---|---|---|
| under cultivator | in rows | under cultivator | in rows | under cultivator | in rows | |
| Winter crops | 22 | 15 | 2.6 | 3.1 | 11 | 21 |
| Spring crops | 24 | 15 | 2.5 | 2.8 | 10 | 28 |
At a young age, plants are especially sensitive to a deficiency of nutrients. Favorable nutrition conditions at the beginning of growth allow young plants to develop a powerful root system in a shorter time, which subsequently makes it possible to better use the nutrients of the soil and basic fertilizer and to tolerate unfavorable conditions more easily. Water-soluble salts of nitrogen and potassium, as a rule, even in poor soils, are present in small amounts at the depth of seed placement, whereas water-soluble phosphorus salts are practically absent even in fertile soils. Consequently, small doses of superphosphate (10 kg/ha P2O5) are often effective as an at-sowing (at-planting) fertilizer for all crops and on all soils.
The high effectiveness of at-sowing fertilizer is confirmed by numerous data obtained in various regions of Russia and abroad. A high return on fertilizers applied in rows at sowing is also noted.
When the topsoil dries out in areas of insufficient moisture, the effect of such fertilizer decreases.
Application Methods
The most effective application method is localized: application simultaneously with sowing seeds in the form of a row (band) below them or to the side at a distance of 2-3 cm. The localized method increases the nutrient utilization coefficient.
Fertilizer doses with any application method, especially row application, must be optimal, since increased concentration of the soil solution and osmotic pressure can lead to thinning, and in excess, to death of crops and reduced overall productivity. Doses of at-sowing fertilizer are 5-10 kg each of nitrogen, phosphorus, and potassium per 1 ha. On soils with a low content of available phosphorus, row fertilization with superphosphate is carried out at a dose of 10 kg a.i./ha.
When fertilizers are applied with a combined drill, the seeds are separated from the fertilizers by a layer of soil. During germination, the seeds and young seedlings, very sensitive to increased salt concentration, do not come into contact with fertilizers. This sensitivity is usually higher in small-seeded plants.
Currently, there are special combined drills for simultaneous sowing of seeds and fertilizers. In this technique, fertilizer can be applied directly into holes when planting potatoes or seedlings.
Trace elements are introduced into the composition of the at-sowing complex fertilizer when the seed (planting) material has not been treated with trace elements.
Ratio of Applied Fertilizers
As a rule, the ratio of applied fertilizers does not exceed 2-10% of the total dose, although sometimes, when fertilizers are in short supply, they limit themselves to this.
Fertilizer Forms
Water-soluble phosphorus fertilizers are used more often, less often phosphorus-nitrogen or phosphorus-nitrogen-potassium fertilizers. Granulated superphosphate, ammophos, and nitrophoska are recommended as at-sowing fertilizer.
Post-Sowing Fertilizer (Top Dressing)
Post-sowing fertilizer, or top dressing, is used to obtain a high yield and improve its quality.
Importance
This technique makes it possible to strengthen plant nutrition during certain periods of development and supplements or improves the effect of basic fertilizer. The combination of these techniques makes it possible to ensure optimal plant nutrition during the vegetation period. The effectiveness of top dressing is influenced by natural conditions, moisture during the vegetation period, soil fertility and particle-size distribution, biological characteristics of crops, properties of fertilizers, and agronomic conditions.
Many crops, due to their biological characteristics, do not tolerate increased salt concentration, especially at the beginning of vegetation. Therefore, applying increased doses of mineral fertilizers before sowing can negatively affect initial development, while in subsequent periods an increased amount of nutrients is required. Therefore, top dressings make it possible to regulate plant nutrition by growth phases.
Top dressings are especially important on soils of light particle-size distribution, in areas of sufficient moisture. Thus, when cultivating winter cereals and row crops on sod-podzolic soil and in the northern forest-steppe, top dressings are effective on sandy loam soils with low absorption capacity, which require split fertilizer application. Applying the full fertilizer rate in these areas in the basic application leads to large nutrient losses due to leaching from the root zone, reducing fertilizer efficiency and increasing the negative impact on the environment.
In plants, there is an interconnection between all vital processes, including between root and foliar nutrition. Therefore, foliar top dressing, under certain conditions, increases the effectiveness of fertilizers applied to the soil and the efficiency of using soil fertility. The connecting link in this case is photosynthesis.
Foliar top dressings, by increasing the intensity of photosynthesis, ensure an influx of organic substances and energy material into the roots, which leads to increased respiration, rapid root growth, and an increase in their absorbing surface, which in turn leads to enhanced absorption of mineral substances. On the other hand, the entry of nutrients into leaves entails binding and retention of photosynthesis products at their site of formation, which should have a negative effect on root activity and lead to a decrease in yield. The negative effect of foliar top dressing on plant productivity is usually noted when it is used in the first half of vegetation, when synthetic processes predominate. A positive effect, especially on yield quality, is observed when top dressing is carried out after flowering, during the period when hydrolysis processes predominate.
The presence in plants after flowering of an increased amount of sugars allows more intensive assimilation of nitrogen applied to the leaves without harming nitrogen uptake by the roots. Considering that by this period the absorbing activity of roots decreases, competition for sugars as a product of photosynthesis between leaves and roots is weaker. Nitrogen that enters through the leaves is well distributed throughout the plant. Normal distribution of phosphorus between plant parts is possible when it enters through the roots.
Application Methods
Top dressing can be carried out superficially on the soil, into the soil during plant vegetation, and foliar, in which a fertilizer solution is applied directly to the vegetative parts of plants. Top dressings with nitrogen fertilizers are obligatory for winter cereals and perennial cereal grasses.
Surface top dressings are used mainly for solid-sown crops. Fertilizers are applied with fertilizer drills — by ground methods or by airplanes and helicopters specially adapted for this.
Late foliar top dressings of crops are carried out with fertilizer solutions.
Top dressing of sugar beet, cotton, maize, and potato has become widespread. Fertilizers are applied with cultivator-fertilizers or special attachments to inter-row cultivation implements.
Sometimes conditions for top dressing of row crops arise in areas of insufficient moisture: with sufficient soil moisture during spring-summer vegetation and insufficient fertilizer application in the basic technique.
Ratio of Applied Fertilizers
Top dressing accounts for 20-30% of the total dose.
Top dressing of row crops with nitrogen and potassium fertilizers on light soils under conditions of sufficient moisture and irrigation. The fertilizer dose for top dressing is N — 30-40 kg/ha, K2O — 30 kg/ha.
Fertilizer Forms
Ammonium nitrate, ammonium sulfate, and urea are used for top dressing.
References
- Yagodin B. A., Zhukov Yu. P., Kobzarenko V. I. (2002). Agrochemistry. Ed. by B. A. Yagodin. Moscow: Kolos.
- Evtefeev Yu. V., Kazantsev G. M. (2013). Fundamentals of Agronomy: A Textbook. Moscow: FORUM.
- Mineev V. G., Sychev V. G., Gamzikov G. P. et al. (2017). Agrochemistry. Textbook. Ed. by Mineev V. G. Moscow: Publishing House of VNIIA named after D. N. Pryanishnikov.
