Plant nutrition is the process of absorption from the environment, movement, accumulation and transformation of nutrients necessary for plant life. During this process, substances are exchanged between plants and the environment. Inorganic substances in the soil, atmosphere and water enter the plant and are used to synthesize complex organic compounds, some of the substances can be removed from the plant organism into the environment.
Green plants synthesize organic substances from carbon dioxide, water, and simple mineral salts during photosynthesis under the influence of sunlight, which in turn provide food for humans and animals. As a result of this process, all green vegetation releases large amounts of oxygen during the day, which is breathed by living organisms. Therefore, life on Earth is caused by the work of higher and lower plants. The scale and importance of this process in nature can be judged from the following data: green plants produce each year up to 400 billion tons of organic matter in the equivalent of glucose, of which 115 billion tons are on land, up to 170 billion tons of carbon dioxide is bound and 130 billion tons of water is decomposed during photolysis in plants, releasing 115 billion tons of oxygen.
Plants use up to 2 billion tons of nitrogen and 6 billion tons of ash elements globally to synthesize organic matter. Nitrogen reserves in the atmosphere are 4-1015 tons, but they do not determine the supply of nitrogen to crops because plants use this element from the soil, not the atmosphere.
The plant receives more than 95% of carbon dioxide through its leaves and can assimilate ash elements and nitrogen through foliar feeding from aqueous solutions. However, most of the nitrogen, water, and ash nutrients come from the soil through the root system.
Water is consumed by the plant and used in photolysis nutrition and in much larger amounts is evaporated by the leaves. Crops evaporate 300-400 kg of water to produce 1 kg of dry weight. Under unfavorable conditions water consumption increases 1.5-2 times, while under optimal conditions water consumption decreases by 15-20%.
Because of the relationship with weather and climatic conditions, regulation and optimization of plant nutrition and metabolism are not always possible. The content of nutrients in the soil in the form available to plants also depends on these conditions. Mobilization or immobilization of individual nutrients in the soil is also determined by the activity and direction of chemical, physico-chemical and microbiological processes, biological properties of the plant itself, the dynamics of absorption of individual cations and anions during the growing season.
The processes determining the growth and development of plants are strongly influenced by fertilizers. They change the salt content in the soil, the intensity and direction of chemical, physical, chemical and biological processes, the reaction and buffering capacity of the soil, the absorption capacity.
Types of plant nutrition
Autotrophic type of nutrition – the plant independently supplies its nutrient needs by absorbing inorganic substances from the soil and carbon dioxide from the atmosphere. It is characteristic of most plants. Autotrophic nutrient organisms also include some bacteria capable of photosynthetically or chemisynthetically assimilating carbon dioxide.
Symbiotrophic type of nutrition is a plant providing its nutrient needs at the expense of other organisms (symbionts). Symbiosis evolved in the course of evolutionary processes as a useful form of relationship for plants. In the symbiotrophic type of nutrition there is a mutual use of metabolic products for nutrition. The boundaries of symbiosis cannot always be precisely defined, because it is difficult to determine the benefit or harm brought by one organism to another.
Mycotrophic type of nutrition is the symbiosis of a higher plant with fungi. The mycorrhiza of the fungus provides water and dissolved mineral salts and other substances to the higher plant, the fungi use the organic compounds synthesized by the higher plant. The importance of mycorrhizal fungi is to increase the absorptive surface of the plant roots due to the mycelium of the fungus.
Mycorrhizal fungi have been discovered to improve plant nutrition with phosphorus. Further study of this symbiosis and its use in the practice of agriculture can be of great importance, as it allows to reduce the use of phosphorus fertilizers. For example, in a field experiment conducted in Wales, when liming and feeding with phosphorus, the yield of clover inoculated with mycorrhiza was 3 times higher in dry matter, shoot formation increased by 2 times, and rhizobium nodules by 5 times. Similar data were obtained in Tropical Africa, Brazil, Australia and Spain on soils poor in available phosphorus.
Bacteriotrophic type of nutrition is the symbiosis of higher plants with bacteria. The most striking example is the symbiosis of nodule bacteria with legumes. Under the conditions of intensification, chemicalization and ecologization of farming, the ability of leguminous plants and microorganisms to bind molecular nitrogen of the atmosphere is increasing in importance. Every year, 40-106 tons of nitrogen are fixed as a result of symbiosis between bacteria and legumes.
Plant nutritional conditions
Main article: Plant life factors: Nutrient regime of soils
Ensuring optimal nutritional conditions through the use of fertilizers allows a more economical use of moisture to create a unit yield. Transpiration coefficient in this case can be reduced by 15-20%. On the other hand, the economic efficiency of fertilizers with additional yield increases with good water supply to plants. There are numerous cases of lack of positive effect of fertilizers on acidic and saline soils.
In order to properly assess the effectiveness of fertilizer application, it is necessary to properly assess all factors limiting yield. For example, in the northern regions under conditions of sufficient moisture, factors of heat and soil nutrient supply become more important.
In the southern regions, especially on ordinary southern black earth and chestnut soils, characterized by high potential fertility, the limiting factor is more often the lack of moisture.
Kinds of plant nutrition
Main article: Plant nutrition: Air plant nutrition (photosynthesis)
Main article: Plant nutrition: Mineral (root) plant nutrition
Air plant nutrition is the carbon nutrition of plants carried out by assimilation of atmospheric carbon dioxide by green leaves in the process of photosynthesis.
Non-root (foliar) nutrition is the process by which nutrients enter plants through the above-ground organs. The discovery of this process has led to the development of foliar nutrition, which can improve yield and quality.
Root nutrition of plants – absorption of water and mineral salts from the soil, as well as in small amounts of some organic substances.
According to studies, the division into root and aerial nutrition is conditional, since the same substances can be absorbed by both roots and leaves. For example, carbon dioxide enters the plant through the roots as much as through the leaves. Sulfur enters the plant through the roots in the form of sulfates. Later, the ability of plants to absorb sulfur oxides from the air through the leaves was demonstrated through the use of radioisotope sulfur.
Root and foliar nutrition of plants are interrelated. Thus, a lack of nutrients in the soil leads to a delay in the formation of organic compounds in the leaves, which in turn inhibits plant development.
Plant nutrition in different periods of vegetation
Absorption of nutrients in ontogenesis, that is, during the growing season, is uneven, so the fertilizer system must take into account the needs of plants in different periods of the life cycle. Insufficient provision of nutrients in different periods of plant life leads to lower yields and deteriorating quality of plant products.
It is especially important to provide nutrients to plants during the critical period, when the lack of nutrition at this time sharply worsens growth and development. The same applies to the period of maximum absorption.
High sensitivity to the lack and to the excess of mineral nutrition is noted in plants in the initial period of growth.
Table. Influence of plant nutrition by phosphorus on barley yield[1]Yagodin B.A., Zhukov U.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
| A normal nutrition of phosphorus all the time | ||
| Without phosphorus for the first 15 days | ||
| Without phosphorus between 45 and 60 days | ||
The high demand of young plants in mineral nutrition is explained by the high intensity of synthetic processes with poorly developed root system. Thus, in cereal grains, the formation and differentiation of reproductive organs begins during the development of the first three to four leaves. Lack of nitrogen during this period leads to a reduction in the number of spikelets and a decrease in yield. Subsequent normal nutrition does not compensate the deficiency of nutrients in the initial stages of development.
Table. Nitrogen nutrition and barley yield, g per vessel[2]Yagodin B.A., Zhukov U.P., Kobzarenko V.I. Agrochemistry/ Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
| Nitrogen throughout the growing season | ||
| Without nitrogen for the first 15 days | ||
| Without nitrogen between 15 and 30 days | ||
| Without nitrogen between 30 and 40 days | ||
| Without nitrogen between 45 and 60 days | ||
| Without nitrogen after earing |
The intensity of nutrient consumption in different crops varies depending on the period of development. For example, sugar beet plants consume nitrogen, phosphorus and potassium 2 kg/ha in the first month, and N 96 kg/ha, P2O5 34 kg/ha and K2O 133 kg/ha in the second.
Grasses and sugar beets are characterized by a long period of nutrient consumption. Hemp, on the contrary, has a short period of intensive consumption – 75% of the total amount of nutrients is consumed from the phase of budding to the phase of flowering.
Spring cereals consume the greatest amount of mineral nutrients during the period from emergence to earing. During earing, wheat consumes about 76% of the maximum nitrogen, phosphorus and potassium, barley about 67% and oats 47%.
Table. Nutrient consumption by spring cereal crops, % of the maximum[3]Yagodin B.A., Zhukov Yu.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
| Spiking | |||||||||
| Flowering | |||||||||
| Full ripeness | |||||||||
Cereals are the most demanding to nitrogen nutrition during formation of assimilative apparatus and during differentiation of reproductive organs. Sugar beet needs sufficient potassium supply during sugar accumulation.
Table. Dynamics of nutrient elements consumption by cabbage, % of maximum[4]Yagodin B.A., Zhukov Yu.P., Kobzarenko V.I. Agrochemistry/ Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
| Sprouts (10.VI) | |||
| Shaping the head (27.VII) | |||
| Loose head (7.IX) | |||
| Commercial ripeness | |||
Flax is sensitive to a lack of nitrogen nutrition from herringbone to budding, to the level of potassium nutrition from budding to flowering.
Table. Dynamics of nutrient elements consumption by cabbage, % of maximum[5]Yagodin B.A., Zhukov Yu.P., Kobzarenko V.I. Agrochemistry/ Edited by B.A. Yagodin. - Moscow: Kolos, 2002. - 584 p.: ill.
| Sprouts (10.VI) | |||
| Shaping the head (27.VII) | |||
| Loose head (7.IX) | |||
| Commercial ripeness | |||
Table. Effect of nitrogen nutrition on flax
| Full nutrition for the entire period | |
| Without nitrogen from "herringbone" to budding | |
| Without nitrogen from budding to harvesting |
Table. Effect of potassium nutrition on flax
| Full nutrition during the whole vegetation period | |
| Without potassium for the first 22 days | |
| Without potassium between budding and harvesting |
Cucumber requires nitrogen nutrition during the formation of the assimilation apparatus and phosphorus nutrition before flowering. During the fruiting period, cucumber has higher requirements for nitrogen and potassium supply.
Increased nitrogen and partly phosphorus supply during budding and flowering leads to increased grain yield. Increased nitrogen supply during the formation of leaf mass and improved phosphorus-potassium supply later increases the yield of root and tuber crops.
The need for nitrogen nutrition in most crops decreases by the beginning of fruit formation, the role of phosphorus and potassium, on the contrary, increases. In general, the period of fruit formation is characterized by decreased consumption of nutrients, and vital processes in plants by the end of the growing season carried out mainly by the reutilization of accumulated nutrients.
In the fertilizer system, the main fertilizer must ensure plant nutrition throughout the growing season, so before planting all the organic and most of the mineral fertilizers. To provide plants with nutrients in the initial period, a pre-sowing fertilizer is applied.
The quantity and quality of the crop can be regulated by feeding at different times of the growing season. Fertilizing improves plant nutrition during the most critical periods or when a deficiency of a nutrient is detected.
Nutrient requirements also vary throughout the day. Daily periodicity is noted for almost all plant life processes.
Under artificial nutrition (on nutrient media), the composition and concentration of nutrient solution, the mode of its use during the growing season are important. For example, temporary deficiency of nutrients in external environment during certain periods of vegetation can enhance development of root system, and replacing nutrient solution with water can cause temporary starvation, thus stimulating tuber formation in potatoes, ovaries of fruits in tomatoes and achieve early ripeness by this method.
The daily periodicity of nutrient uptake manifests itself under variable and constant environmental conditions and has the character of an internal endogenous rhythm. Such a regulated diurnal periodicity of processes allows plants to adapt to changing environmental conditions. Endogenous diurnal and circadian (circadian) rhythms in constant artificial conditions tend to fade, but recover under changing conditions. The ability of plants to change circadian rhythms allows them to increase their survival.
Rhythms in plants come in annual, seasonal, and diurnal patterns. There are also rhythms of an impulsive nature, with periods ranging from a few seconds to hours. For example, such rhythms of short activity are noted in the absorbing and excretory activities of roots.
In conditions of artificial cultivation, the method of periodic feeding is of interest because it allows increasing plant productivity without increasing costs.
Diagnosis of plant nutrition
Main article: Plant nutrition: Diagnosis of plant nutrition
Diagnosis of plant nutrition is a complex of methods aimed at establishing the availability of plant nutrients.
The purpose of plant nutrition diagnostics is a constant monitoring of growing conditions and, if necessary, correction of plant nutrition during vegetation.
Methods of plant nutrition diagnostics:
- soil diagnostics – determining the quantitative content of nutrients in soils.
- plant diagnostics – determining the composition of chemical substances in the plant organism.
Sources
Agrochemistry. 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 с.
Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. – Moscow: Kolos, 2002. – 584 p.: ill.