1. Anazodo, U. G. N., Onwualu, A. P., & Watts, K. C. (1991). Evaluation of alternative tillage systems in the absence of herbicides for maize production in a savannah loamy sand. Journal of Agricultural Engineering Research, 49, 259–272.
2. Carter, L. M., & Tavernetti, J. R. (1968). Influence of precision tillage and soil compaction on cotton yields. Transactions of the ASAE, 11(1), 65–0067.
3. Clay, D. E., Carlson, C. G., Brix-Davis, K., Oolman, J., & Berg, R. (1997). Soil sampling strategies for estimating residual nitrogen. Journal of Production Agriculture, 10, 446–452.
4. Clay, D. E., Kitchen, N., Carlson, C. G., Kleinjan, J. L., & Tjentland, W. A. (2002). Collecting representative soil samples for N and P fertilizer recommendations. Crop Management, 1(1), 0–0.
5. Everitt, J. H., Escobar, D. E., Alaniz, M. A., & Davis, M. R. (1989). Using multispectral video imagery for detecting soil surface conditions. Photogrammetric Engineering and Remote Sensing, 55(4).