- Fertilization system and soil-climatic conditions
- Zonal peculiarities of fertilizer systems
- Fertilizer efficiency depending on agrotechnical factors
- Efficiency depending on the amount and quality of fertilizer (Русская версия)
The effectiveness of fertilizers depends on the quantity (total rate) and quality (ratio of species, forms, methods and timing of application). The dependence is maintained as long as the lack of a nutrient remains a limiting factor for plant growth and development. With increasing the total rate and increasing soil fertility, the efficiency decreases.
Generalized A.I. Podkolzin (1998) for 30 years of long-term research in the Stavropol Territory with winter wheat confirms the decrease in fertilizer efficiency with increasing rates and fertility of black and chestnut soils.
Table. Winter wheat grain yield gains (t/ha) depending on fertilizer doses and soil nutrient supply
Application of fertilizers and ameliorants in dry conditions gives up to 20-30%, in conditions of insufficient moisture – up to 30-50%, and with sufficient moisture – up to 50-70% of total productivity of all cultivated crops.
By increasing the rates and improving the ratios (N:P2O5:K2O) the average annual yield of grain crops in some farms of the Moscow region increased from 1.1 to 4.6 t/ha. Only by improving the ratio of fertilizers corresponding to the needs of crops and soil fertility at 188 and 182 kg/ha a.s. yields increased by 0.6 t/ha, or 48%.
Even with optimal doses and ratios of nutrients, fertilizer efficiency depends on the forms, basic and associated elements, moisture content, solubility, granulometric composition, physiological and hydrolytic reactions.
With long-term use of organic and mineral fertilizers in crop rotations in equivalent doses of nutrients the productivity of crop rotations on chernozems, as a rule, is the same. On light sod-podzolic soils, organic fertilizers are more effective, on heavy and medium loamy – mineral. Maximum yields of vegetable, fodder and other crops are achieved with a combination of optimal doses of organic and mineral fertilizers, on acidic and alkaline soils also ameliorants.
The effect of once applied ameliorants, organic, phosphorus and, to a decreasing extent, potash and nitrogen fertilizers, depending on the rate, type and soil and climatic conditions is manifested for 4-5 years, sometimes at high rates – over 10 years.
On average, for 55 years on heavy loamy soils under cereal crops are more effective mineral fertilizers, under clover – manure, under potatoes – they are of equal value. By productivity of crop rotations the advantage of mineral fertilizers in experiment 1 (with pure fallow) and in experiment 2 (with clover fallow) is noted. The combination of half doses of manure and mineral fertilizers in the rotation with bare fallow (experiment 1) increases the productivity of crops in the rotation compared with the manure, bringing it closer to the variant with mineral fertilizers.
Table. Comparative efficiency of manure, mineral fertilizers and their combinations by crop rotation of sod-podzolic soil (summary by Hlystovsky, 1992)
|NPKCa (manure equivalent)|
|0.5 manure + 0.5 NPKCa|
Methods for evaluating fertilizer efficiency
Evaluation of the effectiveness of types, doses and combinations of fertilizers is carried out by the magnitude of additions, total crop yields and crop rotation productivity, the payback of 1 kg a.s. of fertilizers by yield increases and productivity of crop rotations. However, when the total doses are equal, but different types and ratios in obtaining equal increments or total yields of individual crops and productivity of crop rotations, as well as to determine the contribution of certain types of fertilizers in obtaining productivity, it is necessary to determine the use by crops of the nutrient elements of fertilizers. These estimates are calculated by different methods.
The isotopic method is the most accurate and shows the use of an element of the applied fertilizer. Based on the amount of labeled radioactive or stable isotope of an element delivered to the plants, the utilization factor is calculated from the total content in the applied dose of fertilizer:
where Kis – isotope coefficient of fertilizer use, %; Ris – economic, or biological, removal of labeled element isotope, mg/m2 or mg/unit; Dis – dose of labeled element isotope in fertilizer, mg/m2 or mg/unit; 100 – for conversion to %.
Isotope ratio is important in the study of the cycle, transformations and movements of fertilizer and soil elements in soil, plant, water, air, animals, as well as for an accurate assessment of the use of elements from fertilizers.
Fertilization increases the mobilization of soil nutrient reserves and plants absorb elements of the fertilizer applied and reserves in the soil. Therefore, along with the isotopic method, a more practically acceptable difference coefficient of fertilizer use is used.
The difference method is based on the results of field and production experiments with fertilizers and is suitable for determining optimum fertilizer doses and ratios. The difference coefficient of fertilizer use is the percentage ratio of the difference between the economic removals of elements in the fertilized (Rf) and not fertilized control (R0) variants to the fertilizer dose in the fertilized variant (Df):
Differential coefficients of use of elements of organic and mineral fertilizers in the first and subsequent years vary greatly even under the same crop and within the same field depending on the type, dose, ratios, form, timing and methods of application. With the same methods on the same soil, the coefficients of fertilizer use for crops with a poorly developed root system and a short growing season are lower than for plants with a more developed root system and a long growing season. Also under annual plants less than under perennials.
At local methods of fertilizer application under all crops in all soil and climatic zones the use of nutritive elements increases by 1.5-2.0 times in comparison with the scattered (continuous) method of application before sowing, before sowing and at root feeding. Phosphate water-soluble and complex fertilizers have higher rates of use from granular forms, and phosphate flour – with a finer grinding and thorough mixing with the soil.
The difference coefficients of fertilizer use (Kd) decrease for all crops when moving from poor to more fertile and cultivated soils, as well as when increasing fertilizer doses on all soils.
Thus, Kd under all crops, depending on conditions, can change: on average by 50-80% already in the first year after application. For practical purposes, it is sufficient to consider the effect of fertilizers for 3-4 years. In contrast to the one-year data Kd fluctuations in the total for 3-4 years is less due to the dissimilarity of weather conditions during these years and the biological characteristics of crops cultivated during this period.
Table. Differential coefficients of the use of nutrient elements of fertilizers (%) on medium fertile soils of the Central Black Earth RegionYagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
According to generalized long-term data, for medium-fertile soils of class 3-4 of the central regions of the Non-Black Soil Zone average differential coefficients of use of nutrients from organic and mineral fertilizers are applied.
Mineral and organic fertilizers, applied locally during planting or seeding, in the first year can be used by 50-80%.
The difference coefficients reflect the real consumption of the nutrient elements of fertilizer and soil by the fertilizer application by the crops. However, this consumption is compared with soil without fertiliser. Hence: the poorer the soil (without fertilizer), the higher the coefficients, the richer it is, the lower they are.
In reality, it takes more fertilizer to produce equal yields of any crop on poor soils than on cultivated ones, since on the former some of the fertilizer is absorbed by the soil and not by the crop or is lost. Endless exploitation of cultivated soils at low doses of fertilizer leads to impoverishment and loss of fertility. To prevent this, fertilizer application is controlled by using balance coefficients of nutrient use.
The balance method is based on determining the balance coefficient of fertilizer use (Kb):
where Rf is economic export of an element by the crop in the fertilized variant, in kg/ha, Df is the dose of fertilizer in kg/ha in this variant.
Balance coefficients are determined in experiments and production crops. They give an idea of the degree of assimilation by crops of nutrients from fertilizers and soil and possible changes in the provision of soils with these elements.
Table. Application and consumption of N, Р2O5, К2O in the crop rotation (bare fallow - winter crops - potatoes - oats) by DAOS on heavy loamy sod-podzol soils (average for 56 years on 4 fields; data of Khlystovsky, 1992)
Balance coefficients are higher than difference coefficients, and also higher on fertile soils than on poor soils, i.e. there are no disadvantages of difference and isotopic coefficients.
Balance results are also expressed in relative terms:
- return coefficient – the ratio of fertilizer dose to economic removal;
- intensity of the balance – the ratio of the dose to the economic removal, i.e. the return coefficient multiplied by 100.
The balance is expressed in absolute terms (kg/ha) as the difference between the dose and the economic removal of the element. Balance is positive if the dose exceeds removal or negative if the dose is less than removal. When the dose and removal are equal, the balance is called zero, or deficit-free, balanced.
Balance coefficient, return coefficient, and balance intensity are equal, respectively: 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 when the balance is zero, in other cases, the advantage remains for the balance coefficient, since its calculations are taken as the basis not dose of fertilizer, and economic removal, which characterizes the yield and product quality. Balance coefficients of fertilizer use can be determined for different years from the moment of application and to the end of the fertilizers, while the return coefficients and intensity of the balance – only at the end of the fertilizers, that is for most fertilizers – 4-5 years after application or during rotation of crop rotation, which is important for periodically applied fertilizers.
The use of balance coefficients allows to determine the optimum doses and ratios of fertilizers under individual crops and in crop rotations with simultaneous control and correction of soil provision with nutrients. Thus there is no need to calculate the balances of elements in fields, crop rotations, and farms.
For the Non-Black Soil zone of Russia recommended the following balance coefficients of mineral and organic fertilizers for soils of varying degrees of cultivation.
Table. Balance coefficients of mineral fertilizer use (%) on different fertility soils of Non-Black Soil zoneYagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
*The after-effect of nitrogen fertilizers is small, so they are taken into account in the 2nd-4th years in total
If mineral fertilizers are applied to all crops of the rotation, balance coefficients of mineral fertilizers in determining the optimal doses can not be taken into account by year, and take the sum for all years.
For organic fertilizers coefficients are selected taking into account the year of action, since these fertilizers are used, as a rule, not for all crops of the rotation.
Table. Balance coefficients of the use of elements of organic fertilizers (%) on soils of different fertility Non-Black Earth zone RussiaYagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. – Moscow: Kolos, 2002. – 584 p.: ill.