Cultivated soil is earth deliberately managed to support plant growth by altering its natural state, forming the foundation of agriculture and gardening. This process creates a growing medium that is more productive than its uncultivated counterpart, enabling the consistent production of food and ornamental plants.
Defining Properties of Cultivated Soil
A defining characteristic of cultivated soil is its structure, or tilth. Well-structured soil has different-sized particles that clump into aggregates, creating a network of pore spaces for air and water movement. Organic matter, composed of decomposing plant and animal materials, binds these soil particles together. A higher concentration of organic matter leads to more stable and well-structured soil.
This structure improves aeration and water dynamics. The pore spaces ensure plant roots have access to oxygen for respiration and allow water to infiltrate the soil rather than running off. Well-cultivated soil holds a beneficial amount of moisture while allowing excess water to drain, preventing waterlogged conditions that can suffocate roots.
Cultivated soil is also characterized by high nutrient availability. The decomposition of organic matter releases a steady supply of nutrients for plants to absorb. This managed fertility distinguishes it from native soils, which may be deficient in elements required for vigorous plant growth.
Methods of Soil Cultivation
Creating cultivated soil involves a two-step process of primary and secondary cultivation. Primary cultivation is the initial digging or turning of the soil to break up compacted ground and bury existing vegetation. This can be done manually with tools like spades or mechanically with a rotavator to loosen the top layer of earth.
Following the initial turning, secondary cultivation prepares the soil surface for planting by refining it into a finer tilth. Rakes and hoes are common tools for breaking down large clumps to create a smooth, level seedbed. During this phase, initial soil amendments are incorporated to build a fertile foundation.
Adding materials like compost, aged manure, or peat moss is a common practice. These amendments improve the soil’s physical properties and boost its organic matter content. For instance, incorporating compost into the topsoil enhances its structure, water-holding capacity, and nutrient levels, creating a productive garden bed.
Sustaining Soil Fertility
Maintaining the health of cultivated soil is an ongoing process. One technique is using cover crops, or “green manure,” which are plants like legumes or grasses grown to protect and enrich the soil between main seasons. When tilled back into the ground, these crops decompose and add organic matter and nutrients.
Crop rotation is another practice for long-term soil fertility. Growing the same plant in one location can deplete specific nutrients. By rotating different plant families, such as following heavy-feeding corn with nitrogen-fixing beans, nutrient imbalances are avoided. This practice also helps disrupt the life cycles of pests and diseases specific to certain crops.
Regularly applying top-dressings of organic matter also sustains the soil. This involves spreading a layer of compost or leaf mold on the surface, allowing nutrients to slowly work into the soil. This process mimics natural nutrient cycling and replenishes the organic matter consumed by soil life and plants.
Risks of Soil Degradation
Poor management can lead to the degradation of cultivated soil, compromising its productivity. Soil erosion occurs when a bare surface is exposed to wind and rain. Without plant cover or mulch, wind and water can dislodge topsoil particles, carrying them away and leaving less fertile subsoil behind.
Compaction is another risk, resulting from pressure on the soil surface from foot traffic or heavy machinery. This pressure squeezes soil particles together, destroying the pore spaces needed for aeration and water movement. Compacted soil restricts root growth and reduces water absorption, leading to increased runoff and a stressful environment for plants.
Continuous planting without adequate replenishment can lead to nutrient depletion. Each harvest removes nutrients from the soil that the plants used to grow. If these nutrients are not replaced through organic matter or fertilizers, the soil’s fertility declines, resulting in weaker growth and reduced yields.