|Sudduth, Kenneth - Ken|
Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/18/2005
Publication Date: 11/1/2005
Citation: Chung, S., Sudduth, K.A., Tan, J. 2005. Variability structure of on-the-go soil strength sensor data. Proceedings of the American Society of Agricultural Engineers Annual International Meeting. Paper No. 051090.
Interpretive Summary: Precision agriculture attempts to minimize costs and environmental damage caused by agricultural activities and also to optimize crop yield and maximize benefits, all based on information collected at within-field locations. One factor that can vary considerably within fields and can also greatly affect crop yields is soil strength, or compaction. Because of this, a quick and inexpensive compaction measurement device is needed by farmers and consultants. In previous research, we developed an on-the-go sensor to meet this need. This paper reports on analysis of data from that sensor and investigates the spatial patterns of soil strength we found in lab and field tests. The results showed that soil movement caused by the sensor traveling through the soil was a cyclic process. Soil forces increased and decreased as blocks of soil broke free and were moved aside or compacted by the sensor. In lab tests, the size of soil blocks indicated by the sensor data was confirmed by video recordings of the soil surface. Field tests also showed a cyclic pattern in soil strength, repeating at distances from 10 to 50 feet. This means that to capture the variation encountered in the field, a soil strength sensor needs to collect data at least every 3 to 5 feet. These results will benefit other researchers working in the field by providing them with data on which to base sensor designs, and may benefit future users of the sensor technology based on those designs.
Technical Abstract: As agricultural machinery has become larger and tillage practices have changed in recent decades, compaction as a result of wheel traffic and tillage has caused increasing concern. If strategies to manage compaction, such as deep tillage, could be applied only where needed, economic and environmental benefits would result. For such site-specific compaction management to occur, compacted areas within fields must be efficiently sensed and mapped. We previously developed an on-the-go soil strength profile sensor (SSPS) for this purpose. The SSPS measures within-field variability in soil strength at five soil depths up to 50 cm. Determining the spatial structure of SSPS data is useful in site-specific field management since the variability structure determines the required spatial intensity of data collection and is related to the delineation of compaction management zones. In this paper, soil bin and field data were analyzed by spectral and variogram analysis techniques to determine the variability structure of the SSPS data, and to investigate causes and implications of this variability. In the soil bin, we observed a repeating pattern due to soil fracture with an approximate 12- to 19-cm period, especially at the 10-cm depth. In the field, variograms at 10- and 20-cm depths were similar between the two sites, while sill variances were higher at 30- and 40-cm depths and lower at the 50-cm depth in sandy soils than in finer-textured soils. Spatial periods between 3 and 15 m were predominant, due to soil strength variability within transects. These findings will facilitate interpretation of soil strength data and enhance application of the SSPS.