Fertilizer application methods
The task of fertilizer application methods is to ensure optimal plant nutrition conditions during the growing season. When choosing the application methods it is necessary to take into account the crop’s need for nutrients by growth phase and the possibility of placing them in the zone of greatest contact with the root system. On the choice of methods of fertilizer influences the properties of fertilizers, their mobility, features of interaction with soil-absorbing complex, the presence of impurities in the fertilizer and the attitude of crops. The placement of fertilizers in the arable layer depends on the method of application and embedding.
Table. Distribution of fertilizers (%) at incorporation by different implements on stubble cereal cropsYagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
|Plow with skimmer, 20|
|Plow without skimmer, 20|
|Plow with skimmer, 30|
|Plow without skimmer, 30|
|Тяжелая дисковая борона в два следа, 20|
|Cultivator with universal tines, 20|
|Cultivator with spring tines|
When the harrow is applied, 75-98% of the fertilizer is located in the upper soil layer at a depth of up to 3 cm. This method can be effective in the area of sufficient moisture or with irrigation on light soils, as well as surface feeding of crops of continuous sowing, such as winter wheat, with soluble and mobile nitrogen fertilizers. In steppe areas with insufficient and unstable moisture this method of embedding is ineffective.
When closing the fertilizer with a plow with skimmer most of the fertilizer is embedded in the lower layers of the soil, where they work well and are used by plants with sufficient development of the root system. 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 fertilizers to provide nutrition to plants in the first phases of growth.
Table. Placement of fertilizers (in %) in the arable soil layer depending on the method of embeddingAgrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al. - M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, 2017. - 854 p.
When fertilizers are spread over the surface of the field, the incorporation of different tillage implements is unsatisfactory and does not meet the needs of crops. When cultivating even with the same implement, the distribution of fertilizers applied in a scattered manner over the soil profile depends on their physical properties.
The greatest effect under all crops is achieved when the local application of fertilizers to a given depth, which is usually not less than 8-10 cm for heavy soils and 12-15 cm for light soils with a granulometric composition. According to the summary of more than 20 years of the All-Russian Institute of Fertilizers and Agrochemistry, the yield of all crops from localization of equal doses of fertilizers increased by an average of 0.5-1.0 t / ha grain units, compared to scattered application, and more significantly under the intensive varieties of crops. At localization nutrients of fertilizers are more fully used by plants, their losses are reduced, doses of fertilizers can be reduced by 30-50% compared with a scattered application, thus increasing the fertilized area and efficiency by 2 times.
Fertilizer efficiency increases with the depth of embedding, with a decrease in moisture availability of crops. With the same moisture availability depends on the mobility of types and forms of fertiliser. Depth of embedding is important for organic and phosphorus, less – for potassium, nitrogen and micro fertilizers.
With sufficient precipitation the effectiveness of organic, phosphorus and potassium fertilizers, especially on sod-podzolic soils, increases with increasing embedding depth within the cultivated topsoil. At deeper treatment of such soils efficiency decreases as they are diluted with a large volume of soil poor in nutrients with unsatisfactory agrochemical and physical properties.
Fertilizer efficiency depends on the timing of the main tillage, especially for nitrogen fertilizers. For example, at late autumn tillage mineralization of root and crop residues because of the short period is minimal, so on such a background increases the effectiveness of nitrogen fertilizers.
The timing and methods of sowing (planting), the quality of seed (planting) material affect the efficiency of fertilizers. On cultivated fertile soils, yield losses when sowing is delayed by 1 day are 0.10-0.15 t/ha. The timing of sowing is primarily important in the southern regions of the country: optimal timing increases the resistance of crops to drought, dry weather, as well as early fall and late spring frosts. In the Non-Black Soil Zone, a delay in sowing for 10 days or more for most crops leads to lower yields, especially if there is a lack of moisture during the growing season.
The effect of fertilizers depends on the seed rate and the density of plant stand, i.e. on the feeding area of each plant. The optimum seeding rates and plant standings are given in reference books and depend on the cultivation of the soil. Within one plant species on the same soil, these rates vary depending on varieties, lodging resistance, and seed quality. Switching from high quality seeds of elite varieties to lower quality seeds reduces fertilizer efficiency.
Quality and timely work before sowing, at sowing, during the growing season and harvesting increases fertilizer efficiency. Creation of optimal conditions of plant nutrition by fertilizers and ameliorants increases their resistance to adverse factors, in particular to diseases, pests and weeds. Thus, mineral fertilizers increase resistance of barley to Swedish fly, winter wheat to Swedish and Hessian flies, all cereal crops, especially phosphorus, to root rot and brown rust. At the same time, nitrogen fertilizers, especially in their excess, can reduce the resistance of crops to diseases and pests.
Mutual influence of crop protection agents and fertilizers
Fertilizers in optimal rates and proportions reduce the activity of snow mold in winter crops and simultaneously increase the competitive ability of crops of continuous sowing, especially winter crops, in relation to weeds. Mineral fertilizers alone and in combination with organic fertilizers increase the resistance of potatoes to phytophthora, rhizoctoniosis and potato scab. Although the latter appears more often with liming of soils, it can be suppressed by boric fertilizers. Fertilizers do not replace plant protection by biological, chemical and agrotechnical means.
Weed infestation of crops reduces the yield of cultivated crops due to competition of weeds for nutritional conditions. Weeds, because of their different and greater need for nutrients than cultivated plants, change the populations of the predominant species when fertilizing crops. Therefore, the predominance of one or another type and form of fertilizer allows you to predict the predominant weed species and adjust the system of weed control measures.
Thus, the elimination of weeds by available methods indirectly affects the effectiveness of fertilizers.
It is possible to apply fertilizers and root herbicides together under the preplanting treatment. Treatment with herbicides is also combined with top dressing of winter cereals and perennial grasses with nitrogen fertilizers as well as with foliar dressing with nitrogen and microfertilizers combined with fungicides, insecticides and plant growth regulators.
In a series of field experiments with maize on sod-podzolic and gray forest soils summarized at the Agrochemistry Department of the Moscow Agricultural Academy, 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.
Herbicides also have a depressing effect on the protected crop, but the harm from weeds is more significant, so chemical weeding is very effective.
Optimization of rates and proportions of fertilizers for a particular crop increases competitiveness to weeds, to applied herbicides and other adverse environmental factors. Thus, under complex influence of doses of fertilizers (N43P33K74 and N86P66K148), simazine (before sprouts) and 2,4-D (on sprouts) on gray forest soils the corn green mass yield (the yield without fertilizers with one-time manual weeding was taken as 100%) was in fertilized variants without herbicides – total 83% and 115%, including milk-wax cobs 105% and 151%; the same + one manual weeding 131% and 124%, including cobs 170% and 186%; fertilizers + simazine 131% and 151%, 221% and 232%; the same + 2,4-D 160% and 164%, 307% and 230%. The most effective was the first dose of fertilizer combined with simazine before sprouting (2 kg/ha) and butyl ether 2,4-D after sprouting (0.6 kg/ha). The total weight increased by 1.6 times, the cobs by 3 times compared to the variant without herbicides.
A healthy plant not damaged by pests or other environmental factors responds better to improved nutritional conditions. Thus, according to the data of Rotamsted experimental station, the yield of grain of spring wheat damaged by nematodes and fungal diseases at N75 was 1.45 t/ha, and the soil treatment with formalin increased to 3.75 t/ha. Application of N225 without formalin provided a yield of 2.93 t/ha, and in combination with it – 4.49 t/ha.
Fertilizer efficiency depends on the type and yield of predecessors of fertilized crops, on the composition and scheme of alternation of crops in time and space, i.e. on crop rotation. Many crops have the ability to absorb nutrients from hard-to-reach compounds: legumes due to nitrogen fixation can provide their own nitrogen requirements by 50-97%, lupins, buckwheat, mustard have the ability to absorb phosphorus hard-to-reach phosphate soils and fertilizers.
After the mineralization of root and crop residues of these crops, the nutrients contained in them become available to subsequent crops that do not have similar biological characteristics. This is one of the reasons for the better assimilation of nutrients and the greater efficiency of the latter in crop rotations as compared to no-till crops. Cereal-grass-row (fruit-changing) crop rotation is one of the ways to increase nutrient cycling in a particular area and increase the productivity of cultivated crops.
Another reason of increasing efficiency of fertilizers under crops in crop rotations is improvement of phytosanitary condition of crops. The crop rotation creates better conditions for controlling weeds, diseases and plant pests.
According to the data of 86-year experience of the Department of Agriculture of the Moscow Agricultural Academy summarized by A.A. Alferov in 1978-1998, on average crop yields under different fertilization in crop rotations and in the sod-podzolic light loamy soil, the average yields of winter rye under no-tillage and in crop rotations were: without fertilization 1.29 and 2.51 t/ha, with the use of mineral fertilizers 2.33 and 2.97 t/ha, with a combination of mineral fertilizers with manure and lime 2.68 and 3.25 t/ha. Thus, the fertilizing value of crop rotation decreases when using mineral fertilizers, but the phytosanitary role constantly provides a higher efficiency of fertilizers.
The average yield of potato tubers was 8.3 and 9.2 t/ha without fertilizers, 19.1 and 19.1 t/ha using mineral fertilizers, 16.7 and 23.3 t/ha using a combination of mineral fertilizers, manure and lime, respectively. This crop can be cultivated without rotation, but the phytosanitary role of crop rotation manifested itself with a combination of lime, manure and mineral fertilizers maximum yield.
Average barley yields were, respectively, 0.39 and 0.31 t/ha without fertilization, 2.59 and 2.83 t/ha with mineral fertilization and lime, 2.79 and 3.25 t/ha with mineral fertilization, manure and lime. The phytosanitary role of crop rotation in this example is manifested in the increase of the effectiveness of increasing the saturation of fertilizer only against the background of lime.
The average clover hay yield was 1.95 and 3.60 t/ha without fertilizer, 5.55 and 6.66 t/ha with phosphorus-potassium fertilizer and lime, respectively, and 5.85 and 5.99 t/ha with mineral fertilizer, manure and lime combined. This example shows the fertilizing and phytosanitary role of crop rotation and the real ability of clover to meet the need for nitrogen.
As crop agronomy improves under the influence of fertilizers, yields increase both in crop rotations and in perennial crops; on both poor and cultivated soils. Different crops respond differently to fertilizers, cultivation in crop rotations and combinations of these factors.
According to the generalized data of the experiments of the Department of Agriculture of the Moscow Agricultural Academy, the contribution of crop rotation, fertilizers and their combination in the Non-Black Soil Zone to the total increase in yields, respectively, is:
- in winter wheat 57%, 32% and 11%;
- in oats – 56%, 36% and 8%;
- in potatoes 22%, 55% and 23%;
- in beets 10%, 69% and 21%;
- corn 6%, 81%, and 13%.
In cereals, more than 55% of the yield increase is due to crop rotations and only 32-36% to fertilizers, in row crops 55-81% to fertilizers and only 6-22% to crop rotations. This means that row crops should be placed in on-farm crop rotations, it is permissible to practice double cropping and cultivation in the lead fields. This becomes important under conditions of agricultural production intensification.
Under conditions of insufficient moisture, bare fallows in crop rotations improve moisture supply, enhance mineralization of organic matter and facilitate the fight against weeds. Therefore, under crops, followed by a bare fallow, the effectiveness of phosphorus-potassium and organic fertilizers increases, nitrogen – reduced. On seeded fallows efficiency of all fertilizers is usually higher than on bare.
After and one year after perennial grasses efficiency of organic and nitrogen fertilizers decreases, and phosphorus-potassium – increases.
Moisture availability of soils and crops is a factor of fertilizer efficiency. In zones of insufficient moisture and arid climate fertilizers are ineffective, applied in small quantities – up to 20-30 kg/ha a.s. In these conditions phosphate fertilizers are more effective, applied at the time of sowing in doses of 10-20 kg/ha a.s. Only with irrigation efficiency increases significantly, first of all nitrogen, then phosphorus and organic fertilizers.
In the Non-Black Soil Zone there are three regions with different need for hydromelioration:
- region of unstable moisture is represented by leached chernozems, gray forest and podzol soils. Rainfed agriculture is developed here for most crops in combination with irrigated agriculture for vegetable, fodder and other moisture-loving crops. Fertilizer efficiency under irrigation increases considerably here. So, on average for 18 years, according to data of All-Russian Institute of Fertilizers and Agrochemistry, increase of green mass of corn by fertilizers under irrigation increased by 15,6 t/ha, fodder beet – by 20,0 t/ha, buckwheat grain – by 0,35 t/ha.
- The region of sufficient moisture is represented by sod-podzolic soils, on which, first of all, low moisture soils, irrigation in combination with fertilization under vegetable and fodder crops is promising.
- The region of excessive moisture is represented by sod-podzolic soils and peatlands, on which drainage is required to increase fertilizer efficiency and only in some periods irrigation of vegetable and forage crops is applied. Potassium, copper, phosphorus and nitrogen fertilizers are effective on drained peat and mineral soils. Soil drainage system in this region should function if necessary in dry years or periods of short-term droughts, also as an irrigation system.
Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al. – M.: Publishing house of the All-Russian Scientific and Research Institute named after D.N. Pryanishnikov, 2017. – 854 с.
Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. – Moscow: Kolos, 2002. – 584 p.: ill.