Trends toward early corn planting and conservation tillage systems increase the risk of reduced and uneven stands and subsequent yield loss.
Soil temperatures at planting typically are well below the optimal temperature for corn emergence, which is about 85°F.
Soils under heavy residue typically are wetter and cooler than bare soils in the early spring, adding extra cold stress and disease pressure.
In addition to moisture and temperature disparities within the seedbed, uneven residue also can cause variations in planting depth, all con- tributing to uneven emergence and runt plants (plants at least one leaf stage behind most others).
To improve stand establishment, it is critical to mitigate these risks with good management practices:
• Hybrid selection is crucial to establishing productive stands and achieving high yields. Pioneer annually conducts early planted emergence trials in high-residue fields to evaluate hybrid performance under early season stress.
• Pioneer stress emergence and high-residue suitability ratings give guidance to growers selecting hybrids for early planting and reduced-tillage systems.
• In stressful, high-residue environments, Pioneer® brand hybrids with higher stress emergence scores establish higher stands, on average, than ones with lower scores.
• Pioneer hybrids with highly suitable (HS) and suitable (S) high-residue suitability ratings produced higher and more uniform stands in high-residue locations than hybrids with a poorly suited (X) rating.
• High-residue environments are more commonly associated with non-uniform emergence and “runt” plants due to uneven planting depth, temperature and moisture vari- ability, and physical residue impediments.
• The use of row cleaners and other planter modifications can improve seed-to-soil contact, promote soil warming and help reduce runt plants.
• Planting at soil temperatures above 50°F or prior to a warming trend promotes rapid and uniform emergence in high-residue fields.
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