A major tenet of sustainable agriculture is to mimic diversity that is commonly found in natural ecosystems but may be lost in agricultural terrain, says Annette Wszelaki, plant specialist at the University of Tennessee.
"Organic cropping systems promote a diverse, balanced ecosystem as a practice to enrich the soil and prevent weed, insect pest and disease problems," Wszelaki says. "Crop diversity, crop rotations, intercropping, cover cropping, conservation tillage and incorporation of organic matter are all important components of farm biodiversity."
She says benefits of biodiversity include improved soil quality; enhanced insect, weed and disease control; the encouragement of beneficial organism; and the spread of economic risk.
Wszelaki says diverse crop rotations improve soil, increase farm biodiversity and boost crop yields. High-quality soils encourage dense populations of microorganisms, enhance natural biological control of pathogens, slow turnover of nutrients, encourage communities of beneficial insects and improve soil aeration and drainage.
Here are strategies to increase onfarm biodiversity, according to Wszelaki.
Crop rotation refers to the sequence of crops and cover crops grown in a specific field. Rotation designs should include multiple crop families, managing short- and long-term crop fertility needs, reducing weed pressure, disrupting weed and disease cycles and optimizing crop production.
Two or more crops grown in close proximity can produce beneficial interactions. Intercropping can be achieved by growing crops in alternating rows (row intercropping), growing crops in larger alternating strips (strip intercropping), growing crops together with no distinct row arrangement (mixed intercropping) or by planting a second crop into a standing crop at the reproductive stage (relay
Special attention should be given to the spatial arrangement, plant density and expected maturity dates of selected crops.
Cover crops are used to protect the soil from erosion during times when a field is not under production. Crops that are easy to plant, establish and control or kill should be selected. Suitable varieties provide reliable ground cover and have no negative impact on the following crop.
It's important to evaluate rooting depth and crop characteristics, such as weed and disease suppression, nitrogen fixation and the attraction of pollinators and natural enemies. Planting dates and climate requirements are also important for consideration, as suitable crops vary by geography and climactic conditions.
Conservation tillage requires minimal soil disturbance, keeping at least 30% of the soil covered by crop residue. After harvest, crop residues are left or cover crops are established until the next crop is planted.
Several methods of conservation tillage have been established. No-tilling uses
specialized equipment, disturbing only a small area where the seed or transplants are set. Strip-till or zone-tillage creates a tilled seedbed 5 to 7 inches wide
along the plant-rooting zone, leaving the rest of the field undisturbed.
Incorporation Of Organic Matter
Increasing organic matter provides harbors for soil microbes and intensifies soil biological activity, helping to lessen the risk of disease. The breakdown of organic matter by soil microbes returns nutrients to the soil removed during crop production.
Animal manures, cover crops, crop residues and organic amendments can be incorporated into the soil to increase organic matter content over time.
Plant Species Diversity
Increasing within-field biodiversity can be achieved through planting crop mixtures and multiple crop varieties. The establishment of diverse plantings at
field margins should also be considered.
Planting strips of beneficial flowers, incorporating perennials, establishing hedgerows (a row of trees or shrubs separating fields) and leaving areas of land
uncultivated are methods of increasing diversity on noncropped land.
To increase diversity of native pollinators, establish nest blocks and allow access to areas of soil, such as soil piles, for nesting. Branches of trees and shrubs, such as those in hedgerows, will also provide nesting sites for pollinators.