Adoption of Direct Seeding Improves Soil Quality
Starting in the early 1980’s, prairie farmers gradually switched from conventional tillage to adopt direct seeding, the seeding of crops directly into undisturbed or cultivated soil.
Direct seeding of crops has improved soil quality, increased soil organic matter and improved nutrient supplying power of the soil. Generally, over a period of years of direct seeding, not only has soil organic matter increased, but there are other improvements in soil quality such as better soil tilth.
“No-till leaves more crop residue on the soil surface to protect surface soil from the damaging forces of wind and rain,” says Dr Ross McKenzie, senior research scientist – agronomy with Alberta Agriculture and Rural Development.
“Elimination of tillage means less oxygen is added to the soil, which stimulates microorganisms that break down and decompose residue. Crop residue on the soil surface reduces contact with the soil organisms that decompose residues. As a result, surface residue and remaining root material stay in the organic form longer. This contributes to increased soil organic matter.”
Prairie farmers are using more diverse crop rotations with cereals, oilseed and pulse crops in their rotation. This generally results in higher crop yields by interrupting the life cycle and impact of some weeds, insects and diseases.
More diverse crop rotations and increased crop yield means more surface residue and root material is returned to the soil to improve soil organic matter. In a long-term crop rotational study initiated in 1992 at Bow Island, in Alberta’s Brown Soil Zone, McKenzie has been comparing traditional wheat fallow rotations with extended rotations that include more diversified crop systems. Soil quality, including soil organic carbon, was measured 6, 12 and 18 years after the trials were initiated.
“There was a significant increase in soil organic carbon, a reflection of organic matter, in the first six years,” says McKenzie.
“The increased organic matter has continued after 12 years and 18 years; however, the increase has flattened out as the soil organic matter levels have approached an equilibrium or steady state.”
Organic matter acts like a glue to bind soil mineral particles together. Using low disturbance direct seeding systems not only improves soil organic matter, but other benefits include improved soil structure, which in turn improves water infiltration into soil. When the only soil disturbance occurs at seeding, there is less disturbance of root and earthworm channels. This also increases the water infiltration rate of rain water into soil and reduced water runoff.
The more water that can penetrate and be stored in soil, the greater the crop yield potential. Direct seeding contributes to increased crop water use efficiency. This is particularly important in the drier soil regions in southern and south central Alberta. Increased crop water use efficiency results in more stable crop yields and farm income.
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