Companion planting involves growing two or more plant species together in the same field to create a mutually beneficial relationship, moving beyond the simple monoculture approach. In wheat cultivation, this sustainable strategy leverages plant interactions for improved field ecology and overall productivity. By strategically choosing plant partners, farmers can enhance soil health, manage pest populations naturally, and reduce reliance on synthetic inputs like fertilizers and herbicides. This biological diversification creates a more resilient and balanced growing environment, supporting a stable and higher-quality grain yield.
Nitrogen-Fixing Companions for Soil Enrichment
Leguminous plants are widely used as companions to wheat because they capture atmospheric nitrogen and convert it into a form plants can use. This process, known as nitrogen fixation, is facilitated by a symbiotic relationship with Rhizobium bacteria, which live within specialized structures called nodules on the legume’s roots. Species such as field peas, crimson clover, and hairy vetch are highly effective in this role.
The nitrogen fixed by these companions reduces the need for synthetic nitrogen fertilizers, which are costly and can contribute to environmental run-off. When the companion plants senesce or are terminated, the nitrogen stored in their biomass is released into the soil, becoming available to the wheat crop. This improves the long-term structure and organic matter content of the soil, supporting healthier root development. Incorporating these legumes can enrich the soil by 50 to 150 pounds of nitrogen per acre, depending on the species and growing conditions.
Repellent and Trap Crops for Pest Management
Managing insect pests is a primary goal of wheat companion planting, achieved through two distinct strategies: repulsion and attraction. Repellent companion plants interfere with a pest’s ability to locate its host by releasing volatile chemical compounds that mask the wheat’s scent or are irritating to the insect. Strong-smelling herbs such as coriander (Coriandrum sativum) or dill can deter pests like aphids and mites by confusing their olfactory sensors. Certain Brassica species, like mustard, release glucosinolates, which act as natural deterrents against various insect feeding patterns.
Trap crops are species that are deliberately more attractive to specific pests than the wheat itself, diverting the insect population away from the cash crop. For example, the wheat stem sawfly (Cephus cinctus) is highly attracted to rye grass and brome grass, which can be planted along the field borders. These trap plants serve as a sacrifice, drawing in the pests where they can be concentrated and managed, often through early termination of the trap crop. The success of this strategy relies on the trap crop’s superior attractiveness to the target pest, effectively reducing the overall infestation pressure on the wheat.
Ground Covers for Weed and Moisture Control
Using specific plants as living ground covers is a physical method of resource management that benefits the wheat crop by suppressing competing weeds and stabilizing soil conditions. These low-growing, non-competitive species form a dense canopy that functions as a living mulch. This physical layer blocks the sunlight necessary for the germination and growth of weed seeds, out-competing them for light and space.
Ground covers help to conserve soil moisture by reducing direct evaporation from the soil surface, which is particularly beneficial during dry periods. This moisture retention also helps to moderate soil temperature, preventing extreme fluctuations that can stress the wheat roots. Cereal rye and buckwheat are common choices; the decomposing residue of some species, like cereal rye, releases allelopathic compounds that naturally inhibit the growth of certain weed seedlings.
Integration and Timing of Companion Crops
Successfully integrating companion crops into a wheat system requires careful logistical planning regarding planting time, seeding rates, and management. Companion species must be chosen to avoid excessive competition with the wheat, which is the primary crop. For winter wheat, companion crops like winter beans or linseed can often be drilled simultaneously, sometimes using a single hopper by mixing the seeds.
Timing is often adjusted to give the wheat an initial competitive advantage; for instance, clover used as a living mulch is typically broadcast or inter-row drilled into the standing wheat in the spring, well after the wheat has established. Management of the companion crop is crucial, as it may need to be terminated before harvest. Many companions are naturally removed by the application of broad-leaved herbicides in the early spring, or they are mowed or chemically terminated to prevent them from competing for moisture and nutrients during the final stages of the wheat’s growth.