The maximum increase in yields of all crops from organic and mineral fertilizers, both in their separate and combined application, are achieved on the poorest soils. In the transition to more fertile and cultivated soils as limiting factors of growth and development of plants to a greater extent appear climatic and other conditions, so the effectiveness of fertilizers is most often reduced.
Such a decrease is observed in the transition from sod-heavy-podzolic, to medium and weak-podzolic, then from light to dark gray forest, then from podzolic and leached to common and southern black soils, then from dark to light chestnut soils.
Within one type and subtype, fertilizer efficiency is determined by the granulometric composition of the soil. In general, there is a pattern: the poorer the soil of lighter granulometric composition, the greater the relative yield gains from fertilizers. Although absolute gains in t/ha on more fertile soils are often higher than on less fertile ones.
Individual types of fertilizers also show different effectiveness: nitrogen fertilizers are more effective on sod-podzolic, gray forest soils, podzolized and leached chernozems, and on all irrigated soils. For podzolic loamy soils the following average security of crop yields by individual elements is typical: nitrogen – 38% of maximum productivity, phosphorus – 76% of maximum productivity, potassium – 82% of maximum productivity. With the improvement of moisture availability efficiency of nitrogen fertilizers increases on all types and varieties of soils.
Phosphate fertilizers are more effective in areas with insufficient moisture and arid climate on southern, ordinary chernozems, chestnut and brown soils, on poorly cultivated soils of other types. For example, on sod-podzolic uncultivated differences (1-2 class) they are more effective than nitrogen fertilizers.
Potassium fertilizers are more effective on peaty, then on sod-podzolic and gray forest soils. On gray soils, chernozems and chestnut soils, their effectiveness is reduced, often absent.
By granulometric composition on light soils of all types, the effectiveness of nitrogen, potassium and micro fertilizers increases on heavy – phosphorus. In the first case, it is associated with an easier leachability of elements in the second – with a greater binding of phosphorus in hard-to-reach compounds. If heavy soils are represented by minerals capable of fixing potassium and ammonium, potassium and nitrogen fertilizers are also effective on them.
The effectiveness of fertilizers on soils with an acid or alkaline environment depends on the crops being cultivated. Chemical reclamation should always precede the application of fertilizers. The effectiveness of all types of fertilizers and under all crops increases with the neutralization of acidic and alkaline soils, reaching a maximum at the optimal reaction for the cultivated crops. Thus, according to the generalized data of the experiments with barley on sod-podzolic soils the payback of 1 kg of fertilizer nitrogen by grain yield increase with pH of the salt extract less than 5 was 7.6-8.4 kg, with pH salt extract above 5.6 – 18.6-20.2 kg.
The effectiveness of each type of fertilizer decreases with increasing soil sufficiency of the respective elements available for plants and often disappears at high or very high (5-6th class) sufficiency.
According to the generalized L.M. Derzhavin (1992) data of experiments of agrochemical service (CINAO) with winter wheat on sod-podzolic medium-supplied potassium (100 mg/kg) soils, grain yield increases from 60 kg/ha P2O5 were: With a mobile phosphorus content of 50 mg/kg soil – 0.43 t/ha, 100 mg/kg – 0.36 t/ha and 150 mg/kg – 0.28 t/ha, and on leached chernozem – respectively 0.94 t/ha; 0.51 t/ha and 0.08 t/ha. From 60 kg/ha of K2O the yield increases of winter wheat were: on sod-podzolic soils with exchange potassium content of 50 mg/kg – 0.64 t/ha, 100 mg/kg – 0.33 t/ha and 150 mg/kg – 0.02 t/ha, and on medium phosphorus (125 mg/kg) dark gray forest soil and podzolic chernozem with exchange potassium content of 75 mg/kg – 0.49 t/ha, 125 mg/kg – 0.25 t/ha and 175 mg/kg – 0.02 t/ha.
Similar patterns of effectiveness of all types of mineral fertilizers are typical for all crops on any soils, but manifested with different intensity. Fertilizers and ameliorants simultaneously change agrochemical indicators and other properties of soils. For example, according to long-term stationary experience (since 1912) of the Department of Farming of the Moscow Agricultural Academy named after K.A. Timiryazev on sod-podzolic medium-loamy soils in the variant without fertilizers average potato yield for 1955-1972 years was 6.7 t/ha, in 1973, when applying N100P150K120 – 16.0 t/ha, while the soil had a pH of 3.83; content of humus 1.45%, mobile phosphorus and exchangeable potassium (by Kirsanov), respectively, 19 mg/kg and 41 mg/kg. In the variant of systematic application of fertilizers, the average potato yield in 1955-1972 was 15.4 t/ha, in 1973, at the same dose – 24.7 t/ha; soil pH 3.92, the content of humus 1.61%, mobile phosphorus and potassium, respectively, 100 mg/kg and 133 mg/kg. In the variant with the systematic use of mineral fertilizers, manure and periodic liming, the average potato yield in 1955-1972 was 19.1 t/ha; in 1973, with the same dose of fertilizers – 32.1 t/ha, the soil was 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 potatoes and other crops in other long-term experiments of different countries.
The mobile forms of nutrients accumulated by fertilizers and ameliorants are distributed over time throughout the root layer and prove to be most necessary under adverse conditions, when the application of fresh doses of fertilizers even in high doses with inevitable localization may be less effective.
Systematic agrochemical examination of soils carried out since 1965 in all farms, including homestead and garden plots, revealed the heterogeneity of agrochemical indicators within not only types, subtypes and varieties of soils, but also one field and field plot. This fact marked the need to take into account the existing differences in the classification of soils according to these indicators and in determining and adjusting the doses of fertilizers.
On the basis of relative indicators (classes, groups) of soils we correct the recommended doses of fertilizers for crops, in the absence of recommendations – we introduce correction factors. Correction factors to the doses must ensure that the planned yield of crops of good quality, while regulating the provision of soils with nutrients. When the average security of a particular crop, for example, for cereals, legumes and grasses – 3 class, for row crops – 4 class, for vegetables – 5 class, the correction factor to the dose is 1. When cultivating crops on soils poorer than the middle class, the correction factor is increased (more than 1), on more fertile than the middle class – less than 1. When changing by one class the dose of fertilizer on average for all crops should change by 20-30%, i.e. for soil poorer than average by one class the correction factor 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 indices the content of available forms of nutritious elements in soil is determined by the results of field experiments their part assimilated by the crop. This part is called the coefficient of utilization of soil nutrient element (CUE), determined by the formula:
where R0 – economic removal in the variant without fertilizers, kg/ha; S – stocks of mobile forms of the element, kg/ha; 100 – recalculation in percent.
Table. Yield and economic removal of nutrients by potatoes at different fertilization on sod-podzolic loamy sand soil (Vergey)
Example. Determination of potato CUE on sod-medium podzolic loamy sand soil with pH 4.8, Hg 3.5 and S 3 mg⋅eq/100 g, V 46.1%, phosphorus and potassium security according to Kirsanov 67 mg/kg and 102 mg/kg, hydrolysable nitrogen 50 mg/kg, humus content 1.5%. The arable soil layer (at its mass of 3 mln kg) contains:
- 201 (67⋅3) kg/ha P2O5,
- 306 (102⋅3) kg/ha K2O,
- 150 (50⋅3) kg/ha N.
Potatoes in the variant without fertilizer with an economic yield of 6.2 t/ha removal 94 kg N, 27 kg/ha P2O5 and 127 kg/ha K2O, therefore:
- КИП(N) = 94⋅100/150 = 63%;
- КИП(P2O5) = 27⋅100/201 = 13%;
- КИП(K2O) = 127⋅100/306 = 41%.
At the same time, you can determine the CUE in paired combinations where the appropriate fertilizer was not applied:
- by PK – CUE(N) = 110⋅100/150 = 73%;
- by NK – CUE(P2O5) = 37⋅100/201 = 18,1%;
- by NP – CUE(K2O) = 201⋅100/306 = 66%.
From the above calculations, it follows that the coefficients of use of nutrients change significantly under the influence of fertilizers, and determine them for all crops only in variants without fertilizers.
Generalization L.M. Derzhavin (1992) experimental data CINAO showed that even at the same initial provision, the CUE 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%, potatoes 63% and 85%, sugar beet 71% and 41%, couch flax 64% and 86%.
In the transition from low to high provision of soils with movable elements, the CUE of phosphorus and potassium decreased even more significantly: for winter wheat 4.6-5.7 and 2.7-3.4 times, winter rye 3.7-4.5 and 3.9 times, spring wheat 1.7-3.2 and 2.7-2.8 times, barley 3, 9-5.1 and 1.8-2.6 times, potatoes 3.8-4.4 and 2.9 times, sugar beet 4.9-6.4 and 2.3-2.6 times, flax 6.0 and 2.0-2.3 times.
Especially strong CUE of elements varies under the influence of weather conditions. According to the data summarized by the Department of Agrochemistry of the Moscow Agricultural Academy, the coefficients of mobile phosphorus use by crops depending on weather and agrotechnical conditions differ by 10-15 times, potassium – by 10 times.
Therefore, to correct and determine the doses of fertilizers on the results of the provision of soils with mobile forms of nutrients is better to use not absolute but relative indicators, that is classes and correction factors, as the above variability of absolute indicators leads not to increase but to decrease the effectiveness of fertilizers.
Climatic and weather conditions are often a determining factor in fertilizer efficiency.
The higher the light and moisture supply, the more carbohydrates are synthesized and the more nitrogen the plants can assimilate. Light affects plant nutrition not only through photosynthesis, but also through transpiration. As humidity increases, plant tolerance to increasing concentrations of nutrient solutions increases.
Soil temperature speeds transformation of nutrients and their absorption by plants. At 8-10 °C, the intake, movement and inclusion of nitrogen and phosphorus into the metabolism decreases, and at 5-6 °C the root consumption of nutrients is sharply reduced. At temperatures of 10-25 °C, the mobilization and absorption of soil nutrients and fertilizers by plants increases.
The optimum daytime temperature (23-25 °C) corresponds to 14-16 °C average daily temperatures. In the Non-Black Soil Zone, according to A.P. Fedoseyev, the average monthly summer temperature above 18.1 °C reduces the effectiveness of fertilizers, in the Black Soil Zone the increase of air temperature in May-July by 1 °C above the long-term norm reduces the increase of grain yields from fertilizers at doses of 120-180 kg/ha a.m. by 0.02 t/ha on average.
Increasing humidity deficit by 1 hPa in May reduces fertilizer efficiency by 40 kg/ha on average, in July by 4 kg/ha.
Reducing the annual norm of precipitation from north to south by 100 mm (100 l/m2) in the European part of Russia reduces the efficiency of average doses of fertilizers on average by 0.11 t/ha for all cereal crops and by 0.19 t/ha for winter crops. Reduction of moisture reserves in soil by 10 mm during vegetation of cereal crops reduces yield increases from fertilizers by 10-20 kg/ha on average. If the ratio of precipitation to evapotranspiration is taken as 100%, then each 10% increase in aridity reduces the fertilizer effect by 15%.
When moisture content increases to 90% of the smallest moisture content on soils with volumetric mass of 1.2-1.3 g/cm3 and to 80% on soils with 1.5-1.6 g/cm3 fertilizer efficiency increases. Further moistening of soils to 100-120% of the smallest moisture capacity on the first soils gradually, and on the second sharply reduces the effectiveness.
Excess moisture in soils of the Non-Black Soil Zone and in irrigated areas causes intra-soil and surface water runoff, which leads to leaching of nutrients. Calcium, sulfur, magnesium, nitrogen, carbon, sodium and potassium are leached from fertilizers and soils. The least leached is phosphorus. Maximum leaching occurs during spring floods and after harvesting in the fall.
On loamy and sandy loam soils of the Non-Black Soil area at saturation with fertilizers (N60P60K60) with precipitation washed out up to 50 kg/ha (on loamy) and 70-120 kg/ha (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 rates of mineral fertilizers (120-180 kg/ha a.s.) depending on moisture conditions in summer months can vary almost 2 times.
Table. Average NPK efficiency on soils of the Non-Black Soil zone depending on wetting conditions in May-July (summarized by Fedoseyev)
Fertilizer efficiency on loamy soils in years with insufficient or excessive summer precipitation decreases, and more significantly with insufficient precipitation. On light soils with excess of precipitation under wheat and spring crops efficiency remains high, and under rye – decreases.
According to the long experience of the Department of Agriculture of the Moscow Agricultural Academy, in years with dry June, with rainfall below 50 mm and temperature above 18 °C, normally moist June (50-90 mm and 16-18 °C) and wet (over 90 mm, temperature below 16 °C), the saturation of the crop rotation fertilizer (N50P75K60) paid 100 kg a. в. of fertilizers was: 0.35 t/ha winter rye grain; 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 efficiency of mineral fertilizers in years with dry June decreased on average by 36% (especially strongly under linen), and with wet June increased by 52% (especially under clover) compared with normally moist June. The combination of the same doses of mineral fertilizers with manure (10 t/ha) mitigated the negative effect of the lack of moisture in June; the efficiency of mineral fertilizers decreased by 27% on average.
On average in the Non-Black Soil zone the increase of grain yield from mineral fertilizers is 0.6 t/ha with fluctuations due to weather conditions ±40%, in the Central Black Soil zone – respectively, 0.52 t/ha and ±44%.
Scientifically justified use of fertilizers weakens the negative impact of adverse weather conditions (low temperatures, frosts) on crop productivity.
According to the data of 40 experiments summarized by A.P. Fedoseyev the number of winter rye and wheat plants which died during overwintering decreased from 42 (without fertilizers) to 27%; when combining phosphorous-potassium and optimal doses of nitrogen fertilizers before sowing the death of winter plants decreased to 18%.
The relationship of fertilizer efficiency with meteorological factors is characterized by correlation coefficients.
Table. Correlation coefficients between the effectiveness of average rates of mineral fertilizers and meteorological factors Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
|Central Black Earth|
Correlation coefficients developed by A.P. Fedoseyev (Institute of Experimental Meteorology) and regression equations to estimate fertilizer efficiency from meteorological factors show that weather-climatic conditions explain 25-60% of fertilizer efficiency variations in the Non-Black Earth zone and 35-70% in the Central Black Earth zone.
When determining the optimal and maximum doses of fertilizers it is necessary to be guided by the average for many years meteorological data of specific territories and annually adjust them to the forecast of the coming year. With increasing saturation of crops with fertilizers and the growth of crop productivity, the variation of yields depending on the meteorological conditions of a particular year in absolute values (t/ha) increases, and in relative (% to average) – decreases.
Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry/Under ed. B.A. Yagodin. – M.: Kolos, 2002. – 584 p.: ill.