Cultivation is the mechanical manipulation of soil to create optimal conditions for plant growth. This process involves using various tools to disturb the soil surface and subsurface, altering the physical environment where seeds germinate and roots develop. The primary goal is to prepare a suitable seedbed, manage competing vegetation, and enhance the overall productivity of the land. The act of turning and loosening the earth sets off physical, chemical, and biological changes that directly impact the health of the soil and the crops it supports.
Defining the Action of Cultivation
Cultivation methods are categorized based on the depth and timing of the soil disturbance.
Primary Cultivation
Primary cultivation is the initial, deep operation, often involving tools like plows or deep tillers that break up the soil to depths between 15 and 75 centimeters. This action is intended to shatter tough ground, incorporate plant residue, and create large soil clods. The resulting rough surface is generally too uneven for immediate planting.
Secondary Cultivation
Secondary cultivation follows to refine this rough surface, preparing a final seedbed that is finer and more level. This shallower work, typically affecting the top 5 to 15 centimeters, uses implements like harrows or rakes. Traditional tillage involves deeper turning and inversion, while cultivation often refers to a shallower, more frequent disturbance used to manage weeds between crop rows.
How Cultivation Affects Soil Structure
The most immediate effect of cultivation is the creation of soil “tilth,” a loose, porous, and friable condition conducive to plant establishment. Mechanical disruption breaks apart large, dense clods, reducing the soil’s bulk density. This loosening introduces a greater volume of air into the topsoil, a process known as aeration, which is necessary for the respiration of plant roots and beneficial microorganisms.
Increasing the number of soil pores allows water to move more freely into the ground, improving infiltration and drainage. A cultivated surface absorbs rainfall more effectively than compacted soil, reducing the potential for surface erosion. This enhanced porosity allows developing roots to penetrate the soil more easily, establishing a stronger structure to access water and nutrients. However, excessive cultivation, especially when the soil is too wet, can destroy stable soil aggregates and lead to a collapse of this desirable structure.
Cultivation as a Tool for Weed Management
One primary benefit of cultivation is the suppression of weeds, which compete with crops for light, water, and nutrients. Cultivation can be used preemptively through the “false seedbed” technique. Here, the soil is tilled once to encourage weed seeds to germinate, and then a subsequent shallow cultivation kills the emerged seedlings before the cash crop is planted, depleting the surface weed seed bank.
Once crops are growing, shallow cultivation between rows physically dislodges and uproots young weed seedlings. These exposed plants quickly dry out and die from desiccation. Alternatively, the cultivator can bury small weeds deep enough beneath the soil surface, preventing them from accessing light. This mechanical control is effective against annual weeds and is a cornerstone of organic and integrated pest management strategies.
Increasing Nutrient and Water Availability
Cultivation enhances the chemical and biological activity that makes nutrients available to plants. Aeration stimulates microbial activity by supplying oxygen, which speeds up the decomposition of organic matter, such as crop residues and dead roots. This accelerated breakdown, known as mineralization, rapidly converts complex organic nutrients, like nitrogen and phosphorus, into simpler, plant-available inorganic compounds.
The physical act of cultivation also conserves moisture by managing the soil surface. Breaking up a hard surface crust prevents the formation of capillaries that wick moisture from deeper soil layers up to the surface where it is lost to evaporation. By creating a layer of loose, dry soil at the very top—a dust mulch—the cultivator acts as an insulating barrier that slows the rate of water loss from the lower root zone. This moisture conservation, combined with improved root access, means that existing water is used more efficiently by the crop.