Submitted to: Korean Journal of Soil Science and Fertilizer
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2006
Publication Date: 4/1/2006
Citation: Jung, W., Kitchen, N.R., Sudduth, K.A. 2006. Relationship of soil profile strength and apparent soil electrical conductivity to crop yield. Korean Journal of Soil Science and Fertilizer. 32(2):109-115.
Interpretive Summary: Claypan soils of the U.S. are common in north-eastern Missouri and southern Illinois. These soils have a distinctive sub-surface “claypan” that results in very slow water infiltration and low water storage relative to other Midwest soils. Infiltration is particularly slow during wet periods when the clay particles “swell”. The degree to which this claypan affects infiltration and water storage, which in turn has a great impact on plant growth, is controlled by the depth at which the “claypan” horizon is found in the soil profile. The challenge is that this depth is not the same within fields. The depth of the claypan can be as little as a few inches below the soil surface or as deep as three or four feet. Farmers and watershed managers are interested in having tools that allow them to characterize and map the differences of claypan soils within fields. This investigation was conducted to relate two different in-field sensor measurements with grain crop yield on a claypan soil field. One sensor used was “cone penetrometer” that measured the force required to push it through the soil as an indicator of soil strength. The second field sensor measures soil electrical conductivity (EC) and has generally been used as an indicator of soil texture, but can be affected by several different soil properties. We found soil strength at the 6 to 18 inch depth and soil EC were significantly correlated to crop yield. This means that these two sensors could replace more expensive soil sampling and lab analysis for estimating and mapping variations of critical soil properties that affect grain yield on claypan soil fields. Characterizing claypan soil properties and how they vary within fields will provide a basis for farmers to consider improved management strategies for more efficient food and forage production systems.
Technical Abstract: Understanding characteristics of claypan soils has long been an issue for researchers and farmers because the high-clay subsoil has a pronounced effect on grain crop productivity. The claypan restricts water infiltration and storage within the crop root zone, but these effects are not uniform within fields. Conventional techniques of identifying claypan soil characteristics require manual probing and analysis which can be quite expensive; an expense most farmers are unwilling to pay. On the other hand, farmers would be very interested if this information could be obtained with easy-to-use field sensors. Two examples of sensors that show promise for helping in claypan soil characterization are soil profile strength sensing and bulk soil apparent electrical conductivity (EC). Little has been reported on claypan soils relating the combined information from these two sensors with grain crop yield. The objective of this research was to identify the relationships of sensed profile soil strength and soil EC with nine years of crop yield (maize and soybean) from a claypan soil field in central Missouri. A multiple-probe (five probes on 19-cm spacing) cone penetrometer was used to measure soil strength and an electromagnetic induction sensor was used to measure soil EC at 55 grid site locations within a 4-ha research field. Crop yields were obtained using a combine equipped with a yield monitoring system. Both soil strength at the 15 to 45 cm soil depth and soil EC were significantly correlated to crop yield. Estimated crop yields from apparent electrical conductivity and soil strength were validated with an independent data set. Using measurements from these two sensors, standard error rates for estimating yield ranged from 9 to 16%. In conclusion, these results showed that the sensed profile soil strength and soil EC could be used as a measure of the soil productivity for grain crop production.