Effective soil nutrient management is essential for optimising fertilisation strategies and maximising crop yield. By understanding how nutrients move within the soil, farmers can make data-driven decisions to improve plant health and soil fertility.
The ability of soil to supply plants with nutrients depends on multiple factors, including its chemical, physical, and biological properties. These factors influence nutrient availability, movement, and reserves, as well as the balance of soil moisture, air, and temperature. Additionally, soil nutrient management is affected by the presence of harmful substances or the limited availability of key nutrients.
While traditional soil analysis provides insights into nutrient content, it does not always indicate whether those nutrients are accessible to plants. Soil nutrient management requires an understanding of various uptake mechanisms to ensure efficient fertilisation. In this post, we explore how plants absorb nutrients, the role of real-time soil monitoring, and how farmers can optimise fertilisation strategies for better yield and sustainability.
Essential Nutrients for Soil Nutrient Management
Plants require specific chemical elements for growth and development, which cannot be substituted by others. In total, over 70 chemical elements have been found in plant composition, categorised as follows:
– Non-mineral elements: Hydrogen (H), Carbon (C), and Oxygen (O), which are obtained from water and carbon dioxide.
– Mineral elements: These are derived from the soil and can occur as anions (e.g., NO₃⁻, H₂PO₄⁻, SO₄²⁻, Cl⁻, BO₃³⁻, MoO₄²⁻) or cations (e.g., NH₄⁺, K⁺, Ca²⁺, Mg²⁺, Fe²⁺, Zn²⁺, Cu²⁺).
Nutrient Movement in Soil
Plants absorb nutrients through three primary mechanisms:
- Mass Flow – Nutrients move to the plant roots with water absorbed during transpiration. This process is especially important for the uptake of nitrates (NO₃⁻), sulphates (SO₄²⁻), calcium (Ca²⁺), and magnesium (Mg²⁺).
- Diffusion – Nutrients move from areas of higher concentration to areas of lower concentration, facilitating the efficient uptake of phosphorus (P) and potassium (K).
- Root Interception – Roots grow directly into contact with soil particles containing nutrients and absorb them. This mechanism is particularly relevant for calcium and magnesium uptake, though it plays a lesser role compared to mass flow and diffusion.
The actual transport of nutrients into the root cells can be:
Passive transport – Nutrients enter along with water, requiring no additional energy.
Active transport – Nutrients are transported into the root cells via specialised carrier proteins, using energy.
Macro and Micronutrients in Soil
The most important macronutrients required by plants in large amounts are nitrogen (N), phosphorus (P), and potassium (K). Secondary macronutrients, such as calcium (Ca), magnesium (Mg), and sulphur (S), are also essential. While their supplementation is not always necessary, certain soil types may require additional Ca and Mg supply.
The total concentration of macronutrients in the soil is often much higher than the amount accessible to plants. For example, potassium makes up approximately 1% of the soil composition, yet only 100–200 mg/kg is available for plant uptake, which accounts for just 1–2% of the total potassium reserves. The same principle applies to other essential plant nutrients.
Movement of Secondary Nutrients in Soil
The availability of calcium (Ca) and magnesium (Mg) is significantly influenced by soil moisture levels:
– Under high moisture conditions, these nutrients are primarily absorbed through mass flow.
– Under low moisture conditions, diffusion plays a more dominant role in their uptake.
Since Mg and Ca are exchangeable cations, their concentration in the soil solution remains relatively stable. Soil water acts as a buffer, maintaining consistent ion levels and preventing large fluctuations in soil electrical conductivity.
The Role of Electrical Conductivity in Soil Nutrient Assessment
Plant nutrition occurs through the soil solution, where dissolved nutrients influence electrical conductivity. As a result, the overall quantity of available nutrients can be assessed by measuring the electrical conductivity of the soil’s saturated extract.
It is important to note that:
– Phosphorus (P) is often bound to soil particles and does not dissolve in water, meaning its movement is not reflected in electrical conductivity measurements.
– The binding of potassium (K⁺), magnesium (Mg²⁺), and calcium (Ca²⁺) to soil particles depends on soil texture, cation exchange capacity (CEC), organic carbon content, temperature, and moisture levels.
– Sandy soils have a higher risk of nutrient leaching because they lack sufficient negatively charged surfaces to retain nutrient cations.
Turning Soil Insights into Action
Plant nutrition in soil occurs through various mechanisms, and understanding these processes is essential for effective fertilisation and yield optimisation.
While traditional soil analyses provide a snapshot of nutrient content, they do not always reflect real-time availability for plants. Paul-Tech’s system bridges this gap by continuously measuring electrical conductivity near the root zone, giving you immediate, data-driven insights to adjust fertilisation and irrigation strategies accordingly.
Why does this matter?
🌱 Reduce unnecessary fertiliser costs by applying nutrients only when and where they are needed.
🌱 Improve crop performance by ensuring essential nutrients are available at critical growth stages.
🌱 Minimise environmental impact by preventing nutrient leaching and optimising soil health.
Want to see how real-time soil data can transform your approach to fertilisation? Book a free demo today and start making data-driven decisions this season! Unlike traditional soil testing, Paul-Tech provides continuous real-time insights, ensuring your crops always get the nutrients they need.