Any fertilizer that uses organic matter (compounds containing carbon) is called organic fertilizer. Generally speaking, organic fertilizer consists of the remains of dead plants and animals, as well as animal excrement. Organic fertilizers are divided into commercial organic fertilizers and farmyard manure. Farmyard manure includes soil manure, stable manure, rotten manure, compost, green manure, and human urine and feces. So what are the advantages of organic fertilizer?
A. It can increase soil aggregate structure.
A soil aggregate structure is a structure in which several individual soil particles are bonded together to form aggregates. Small pores form between the individual particles, while larger pores form between the aggregates. Small pores retain water, while larger pores allow for ventilation. Soil with an aggregate structure ensures good root growth and is suitable for crop cultivation and growth. The effects of aggregate structure on soil fertility:
① It balances the balance between water and air;
② It balances the balance between nutrient consumption and accumulation in soil organic matter;
③ It stabilizes soil temperature and regulates soil thermal conditions;
④ It improves tillage properties and facilitates crop root expansion.
B. It improves soil air permeability and porosity.
Fruit tree leaves absorb carbon dioxide and exhale oxygen; their roots absorb oxygen and exhale carbon dioxide. For fruit trees to properly cycle nutrients, their shallow, surface-level breathing roots must have an adequate oxygen supply, which requires soil porosity and air permeability. Soil air permeability is proportional to soil particle size and is affected by factors such as soil moisture content, temperature, atmospheric pressure, and air temperature. Soil permeability, also known as soil aeration, refers to the exchange rate between soil air and the atmosphere, or the rate at which the atmosphere enters the soil. It is closely related to soil structure, particularly the porosity characteristics. Soils with a high total porosity or a high proportion of macropores have good air permeability. For example, well-structured soil has better air permeability than poorly structured soil; sandy soil is better than clay soil; soil with a moderate moisture content is better than excessively wet soil; and topsoil is better than subsoil.
C. It can improve soil and balance acidity and alkalinity.
The strength of soil acidity and alkalinity is often measured by pH. Soil acidity and alkalinity are due to the presence of small amounts of hydrogen ions and hydroxide ions. When the concentration of hydrogen ions is greater than the concentration of hydroxide ions, the soil is acidic; conversely, it is alkaline; and when the concentration is equal, it is neutral. The pH value of soils in my country generally ranges from 4.5 to 8.5, with the pH value increasing from south to north, creating a “south acid, north alkaline” pattern. Due to the climate differences between southern and northern my country, the south is humid and rainy, with acidic soils, while the north is dry and dry, with alkaline soils. Soil that is too acidic or too alkaline will reduce the availability of soil nutrients to varying degrees, making it difficult to form a good soil structure, severely inhibiting the activity of soil microorganisms, and affecting the growth and development of various crops.
D. It can improve the quality of agricultural products.
Changes in the main organic components of fruit:
a. Water. With the exception of nuts like chestnuts, walnuts, and other dried fruits, most fruits have a water content of 80% to 90%.
b. Sugar and acid. Sugar and acid content and the sugar-acid ratio are key indicators of fruit quality. Glucose, fructose, and sucrose are the most abundant sugars in fruit. Starch is found in young, green fruit. Different fruit varieties also vary in the type of sugar they contain. For example, grapes, figs, and cherries contain more glucose and fructose, while peaches, plums, and apricots contain more sucrose than reducing sugars. The main organic acids in fruit are malic acid, citric acid, and tartaric acid. Apples, pears, and peaches contain primarily malic acid, while citrus fruits, pomegranates, and figs contain primarily citric acid. Acid content in fruit is low in young fruit, increases as the fruit grows, and is broken down as a respiratory substrate nearing maturity.
c. Pectin. The internal factors contributing to fruit firmness are intercellular bonding, the mechanical strength of the cell’s constituent materials, and cell turgor pressure. Intercellular bonding is influenced by pectin. Protopectin in immature fruit is present in the middle gelatinous layer of the primary wall, connecting the cells. As the fruit matures, it transforms into soluble pectin and pectinates under the action of enzymes, softening the flesh. Cellulose and calcium content significantly influence fruit firmness.
d. Aroma and odor of the fruit. Aroma and odor are important factors in determining fruit quality. Many fruits have an astringent taste, primarily due to tannins. The main bitter component in citrus fruits is naringin. Fruits also contain vitamins. Vitamin A is found in yellow fruits rich in carotene, such as apricots, loquats, and persimmons. Vitamin C is relatively high in sea buckthorn, jujube, Chinese kiwifruit, and sea buckthorn. Chlorophyll is also present in high levels in young fruits. As the fruit matures, the absolute amount increases, but the content per unit fresh weight decreases. The content is higher in the peel than in the core, and higher on the sunny side than on the shady side.
e. Changes in pigments. Fruit color is determined by chlorophyll, carotenoids, anthocyanins, anthocyanins, and flavonoids. Carotenoids are tetraterpenes (C), of which there are 500 types. They are found in chloroplasts and plastids, bound to proteins, protecting cells from damage caused by strong light. As fruit ripens, chlorophyll decreases and carotene increases.
E. Contains various nutrients.
Organic fertilizers are not only rich in organic matter and organic acids, such as humic acid, amino acids, and fulvic acid, but also contain a variety of macro, medium, and trace elements. Although the content is low, they are relatively comprehensive. Generally speaking, nitrogen promotes leaf growth, phosphorus promotes flowering, and potassium promotes fruit growth; silicon maintains roots, calcium maintains fruit, magnesium maintains leaves, and sulfur maintains flavor; iron prevents yellowing leaves, copper prevents leaf drop, molybdenum prevents mosaic, zinc prevents leaf stunting, and boron prevents leaf curl.
F. Has a long-lasting effect.
True organic fertilizers must not dissolve, and cannot dissolve, because they contain large amounts of cellulose and lignin, which are insoluble in water. They must be broken down by soil microorganisms, converting them into amino acids and carbohydrates before they can be absorbed by fruit tree roots. This is a slow and ongoing process.
G. It has synergistic properties.
After decomposing, organic fertilizers provide energy and nutrients for soil microbial activity, promoting microbial activity and accelerating the decomposition of organic matter. The active substances produced promote crop growth and improve the quality of agricultural products, resulting in sweet melons and fragrant wheat. More importantly, the organic acids produced by microbial decomposition activate mineral elements fixed in the soil, allowing them to be fully absorbed and utilized.
H. It has water-retention properties.
Research data indicates that the humus in organic fertilizers contains fats, waxes, and resins. During the formation of highly fertile soils, these substances can soak into soil aggregates, making them hydrophobic. This reduces soil wetting and the rate of capillary water movement, reducing evaporation and increasing soil water retention, thereby improving soil moisture conditions.
Studies of the hydrophilicity and hydrophobicity of humic substances have shown that these properties are determined by the side chains on the edges of humic acid molecules. When the degree of polymerization of humic acid molecules is low, the amount of exposed side chain groups is greater, resulting in an inverse relationship between the two. The relationship between humic substances and water molecules, to a certain extent, determines the water properties of organic matter.
The aggregate structure is related to the soil organic matter content and the amount of organic fertilizer applied. A water-stable aggregate structure ensures the looseness of the soil surface, facilitating water permeability. This structure is characterized by loose aggregates and high non-capillary porosity, which reduces the height and speed of capillary water movement in the soil, thereby reducing evaporation from the soil surface. Soil particles with a good aggregate structure have a larger radius than those with a poorer structure, and the rate of capillary water rise is inversely proportional to the radius of the structural unit.
I. It has heat-retaining properties.
Organic fertilizers absorb heat and increase temperature, which is beneficial for the root germination and growth of fruit trees. During decomposition, organic fertilizer releases a certain amount of heat, raising soil temperature. Furthermore, organic fertilizer has a large heat capacity and excellent thermal insulation properties, making it less susceptible to external temperature fluctuations. It protects against freezing in winter and heatstroke in summer, making it highly beneficial for fruit tree root germination, growth, and overwintering.
J. Soil organic matter content is an important indicator of soil fertility.
Soil organic matter generally refers to the biogenic substances in the soil. A key component of the soil solid phase, soil organic matter is a primary source of plant nutrition. It promotes plant growth and development, improves soil physical properties, stimulates microbial and soil biota activity, facilitates the decomposition of nutrients in the soil, and enhances soil fertility and its buffering capacity. It is closely related to soil structure, aeration, permeability, adsorption, and buffering capacity. Generally, under similar or equal conditions, organic matter content is positively correlated with soil fertility within a certain range.
Soil organic matter content is an important indicator of soil fertility, and organic fertilizer can increase it.
