Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2000
Publication Date: N/A
Interpretive Summary: Intensified crop rotations and reduced tillage increase the likelihood that seed will be placed near large amounts of residue from the previous crop. The effects of residue on seedling health are difficult to measure in the field, and can be positive or negative depending on the position of the residue relative to the seedling. This greenhouse study examined the effect of different residue placements produced by different seeding methods. Wheat seedling growth was stunted if roots intercepted fresh wheat residue placed below the seed. This information helps to explain some of the problems that have been encountered when planting into fresh residues. Producers and cropping system researchers can use this knowledge in developing no-till and reduced tillage systems. Planting systems that place fresh residues below the seed should be avoided.
Technical Abstract: Unweathered crop residues can produce growth-inhibiting substances, stimulate pathogen growth, and immobilize nutrients. The location of seed relative to residue may be an important factor in the early health of a crop. This greenhouse study simulated sowing conditions typical of annual dryland winter wheat (Triticum aestivum L.) to evaluate the likelihood of inhibitory effects. We placed newly harvested, unweathered winter wheat residue on the soil surface, mixed with the seed, immediately above the seed, or 3 cm below the seed. Treatments using a plastic residue substitute and treatments using pasteurized soil and residue provided comparisons to the natural soil and wheat residue. Residue mixed with or placed above the seed caused a temporary delay in emergence. Since this occurred with both wheat and plastic residue, the delay is explained by the physical impedance of coleoptile growth. Wheat residue 3 cm below the seed dreduced the height and rate of wheat plant development, indicating a biological inhibitory effect of the wheat residue. This reduction in height and development rate at 20 days after planting did not occur when the soil and residue were pasteurized. We conclude that winter wheat seedling growth can be inhibited if roots encounter unweathered residues.