Submitted to: Electronic Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2009
Publication Date: N/A
Citation: Interpretive Summary: Being able to accurately determine the depth of compacted soil allows producers to precisely set their in-row subsoiling depth. The best method that we currently have is the soil cone penetrometer which is inserted vertically down from the soil surface. A problem that currently exists with the use of this device is that soil drying may cause the depth of the compacted soil layers to appear to be too shallow. This study examined the effect of soil drying on the depth of the compacted soil layers and found that for all practical purposes, this depth only changed by less than 1 inch. The soil cone penetrometer can continue to be used to establish in-row subsoiling depth without regard for soil moisture considerations.
Technical Abstract: Site-specific detection of a soil hardpan is an important step in precision farming. Different methods have been developed including the ASAE standard soil cone penetrometer to detect the hardpan layer. Most of the newly developed methods use results obtained by a soil cone penetrometer as a reference to validate their potential. Soil factors, mainly soil moisture and bulk density, may influence the cone index measurement and the prediction of the relative strength and depth of the hardpan layer. The effects of soil drying on hardpan characterizing attributes of peak cone index, depth to the peak cone index and depth to the top of the hardpan layer were studied for three compaction levels on a Norfolk Sandy Loam soil in a soil bin. The soil bin was wetted to near saturation and then subjected to four levels of soil drying. A multiple-probe-soil-cone-penetrometer (MPSCP) was used to measure soil cone index. The results showed that soil drying had a significant effect on peak cone index for the single pass compaction (1.78 Mg m-3 within hardpan) and the double pass compaction (1.83 Mg m-3 within hardpan). The predicted depths to the hardpan indicated from the depth to the peak cone index and the depth to the top of the hardpan showed a statistically significant decreasing trend for the single pass compaction; however, the differences were practically small (< 2 cm) to justify varying prescription tillage depth due to soil drying.