|Iqbal, Muhammad - IOWA STATE UNIVERSITY|
|Zuo, Yueming - VISITING SY, P.R. CHINA|
|Marley, Stephen - IOWA STATE UNIVERSITY|
Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: July 16, 1996
Publication Date: N/A
Interpretive Summary: Corn plants sometimes emerge poorly when seeds are planted into no-tillage conditions. The reason for poor emergence is not clear but seems to be caused by smearing of soil in the sides of the furrow into which corn seeds are placed. There are inadequate methods to measure soil smearing or to control planters to avoid smearing. In a laboratory experiment, a fiber-optic sensor gave a voltage output related to the amount to which a soil surface was smeared. Smearing increased with an increase in pressure applied to soil by a metal disc, moved with a rotary motion over the soil surface to simulate action of a planter furrow opener. As smearing increased, fewer corn roots were able to penetrate the soil surface. This research shows that, to improve corn growth, planters should be designed to reduce smearing of the seed furrow. In addition, a fiber-optic sensor showed potential for use in instruments to measure smearing and for use to control planters to reduce smearing.
Technical Abstract: Soil smeared by planter furrow openers may reduce crop seedling emergence. Smearing of a clay loam soil as affected by soil moisture content and bulk density and by surface preparation (no-smearing, surface fully smeared with a spatula, or smearing done by a coulter loaded to apply either 7, 13, or 18 kPa pressure to the soil surface) was evaluated in a laboratory experiment. Output voltage of a fiber-optic structure sensor, percentage of corn roots penetrating the prepared soil surface, and corn shoot height were measured to evaluate smearing. Root penetration decreased in conditions for which the mean output voltage of the structure sensor increased. Mean sensor output values were not significantly effected by the initial soil moisture levels evaluated, but a significantly greater percentage of roots penetrated the wetter soil. Initial soil bulk density did not significantly effect sensor output voltage or percentage of roots penetrating the soil. The magnitude of pressure applied by the coulter used to apply surface smearing treatments significantly affected root penetration, shoot height, and sensor output voltage. The no-smearing treatment resulted in greatest root penetration into the soil, greatest average shoot height, and lowest sensor output. The most severe smearing treatment caused least root penetration, resulted in shortest plants, and produced the greatest sensor output voltage. For best corn emergence it is important to operate furrow openers to minimize soil smearing. The fiber-optic sensor has potential for measuring the degree to which a soil surface is smeared.