Seaweed extract is a bioactive substance derived from algae and is widely used in agriculture as a component of biostimulants. Extracts from red and brown algae are particularly valued because these organisms have evolved under diverse and often harsh environmental conditions, resulting in a high degree of stress tolerance. Their extracts act through natural signalling pathways to stimulate root development, nutrient uptake and transport, and photosynthetic activity. They also activate plant defence mechanisms against abiotic stress, enabling stable growth under adverse environmental conditions. In addition, seaweed extracts can enhance calcium uptake, thereby contributing to cell wall formation and proper plant development.
Secondary macronutrients are plant nutrients required in greater quantities than micronutrients but in smaller amounts than the primary macronutrients. They include calcium, magnesium, and sulphur. These nutrients perform essential functions in a wide range of plant physiological processes. Magnesium is the central atom of the chlorophyll molecule and is indispensable for photosynthesis. Sulphur is involved in the synthesis of amino acids and proteins, while calcium is essential for cell wall formation, the structural integrity of plant tissues, and the transport of substances within the plant
A soil aggregate is a cluster of soil particles of varying shapes and sizes that are bound together. Aggregates are formed through biological activity, soil shrink–swell processes, and soil cultivation. Depending on how the particles are bound, different types of soil structure can develop, including granular (crumb), blocky (polyhedral), and platy structures. Soil aggregates determine the overall soil structure and play a crucial role in regulating the movement of water and air through the soil.
Soil analysis is a laboratory method used to determine the chemical, physical, and biological properties of soil in order to assess its fertility and determine fertilization requirements. The results of soil analysis serve as a basis for developing fertilization recommendations and sustainable soil management practices.
Soil biota comprises all living organisms that inhabit the soil ecosystem. It includes bacteria, actinomycetes, fungi, and algae, which contribute to nutrient cycling through the decomposition of organic matter and the transformation of nitrogen compounds. Certain bacteria, such as species of the genus Azotobacter, fix atmospheric nitrogen, while nitrifying and denitrifying microorganisms are involved in nitrogen transformations within the soil. Soil fauna is commonly classified into macrofauna, mesofauna, and microfauna. Macrofauna, such as earthworms, improve soil structure and aeration, whereas mesofauna and microfauna, including mites and springtails, contribute to the decomposition and incorporation of organic matter. Soil biota plays a fundamental role in the mineralisation of organic matter, humus formation, and the maintenance of soil fertility.
Soil crusting refers to the formation of a thin, compacted, and relatively impermeable surface layer caused by the breakdown and subsequent compaction of soil particles following intense rainfall. During this process, soil particles become detached, transported, and deposited into soil pores, resulting in the blockage of larger pores. The resulting soil crust reduces water infiltration capacity and restricts soil aeration. Consequences may include increased surface runoff, enhanced soil erosion, and reduced root system development. Soil particles and nutrients transported by rainfall may accumulate in landscape depressions and enter surface waters, increasing the risk of water pollution and eutrophication. Therefore, soil crusting not only causes the loss of valuable soil particles but may also have negative environmental impacts.
Soil erosion is the process by which soil particles are detached and transported from their original location by natural forces such as heavy rainfall, storms, or wind. Agricultural soils are particularly vulnerable because soil lost through erosion is difficult to replace. The loss of fertile topsoil reduces soil quality and can lead to long-term declines in crop productivity. Consequently, soil erosion is a major environmental challenge that threatens both agricultural production and soil health.
Soil microorganisms are microscopic living organisms consisting of single cells or groups of cells. They include bacteria, yeasts, fungi, and algae. They are present in almost all natural environments, including soil, water, air, and the surfaces and internal tissues of other organisms. In soil, they play a fundamental role in organic matter decomposition, nutrient cycling, and humus formation. Soil microorganisms are essential for soil fertility and soil health because they decompose organic compounds and release nutrients in forms available for plant uptake.
Soil pH describes the degree of acidity or alkalinity of soil or a solution and is determined based on the concentration of hydrogen ions (H⁺). It is expressed on a scale from 0 to 14, where values below 7 indicate an acidic reaction, a value of 7 indicates a neutral reaction, and values above 7 indicate an alkaline reaction. Soil pH is an important factor influencing numerous soil properties and processes. It particularly affects nutrient availability to plants, soil microbial activity, and various chemical processes that determine soil fertility.
Soil reaction refers to the degree of soil acidity or alkalinity and is determined by measuring soil pH. Soil pH depends on the concentration of hydrogen ions (H⁺) in the soil. A pH value of 7 indicates a neutral soil reaction, values below 7 indicate an acidic soil reaction, and values above 7 indicate an alkaline soil reaction.
Soil structure describes the arrangement and organisation of soil particles into structural units known as aggregates. Several types of soil structure are recognised, including single-grain, massive, aggregate, and fragmental structures. Soil structure has a major influence on nutrient availability, root development, soil water and air regimes, and overall soil fertility. Well-developed soil structure promotes better soil aeration, improved water retention, and optimal conditions for plant growth.
Soil texture by feel (hand texturing) is a simple field method used to determine soil texture without laboratory equipment. The method evaluates the stickiness, plasticity, and cohesiveness of the soil to estimate the relative proportions of clay, silt, and sand. A small amount of soil is moistened and manipulated by hand to assess its physical behaviour. Depending on whether the soil can be rolled into a ribbon or thread, or whether it readily crumbles, the soil textural class can be estimated. Highly sticky and plastic soils indicate a high clay content, whereas loose, friable soils with a distinctly sandy feel indicate lower particle cohesion and a higher sand content.
Sulphur (S) is an essential secondary plant macronutrient involved in protein synthesis and quality. It plays an important role in nitrogen metabolism and contributes to the efficient utilisation of nitrogen within the plant. Sulphur promotes plant growth and development through its involvement in the synthesis of amino acids and enzymes. Sulphur deficiency may impair protein synthesis and lead to the accumulation of carbohydrates in plant tissues. Plants deficient in sulphur commonly exhibit chlorosis, particularly in younger leaves.
