10 Dick, R.P., Thomas, D.R., and Halvorson, J.J. (1996). Standardized methods, sampling, and sample pretreatment. In J.W. Doran, and A.J. Jones (Eds.) Methods for assessing soil quality (p. 107–121). Soil Sci. Soc. Am. Spec. Publ. No. 49. Madison, WI: SSSA.
11 Ellert, B.H., and Bettany, J.R. (1995). Calculation of organic matter and nutrients stored in soils under contrasting management regimes. Can. J. Soil Sci. 75, 529–538.
12 Franco, H.H.S., Guimarães, R.M.L., Tormena, C.A., Cherubin, M.R., and Favilla, H.S. (2019). Global applications of the visual evaluation of soil structure method: A systematic review and meta‐analysis. Soil Till. Res. 190, 61–69.
13 Gringal, D.F., Bell, J.C., Ahrens, R.J., Boone, R.D., Kelly, E.F., Monger, H.C., and Sollins, P. (1999). Site and landscape characterization for ecological studies. In G.P. Robertson, D.C. Coleman, C.S. Bledsoe, and P. Sollins (Eds.) Standard soil methods for long‐term ecological research (p. 29–52). New York: Oxford Univ. Press.
14 Harris, R.F., and Bezdicek, D.F. (1994). Descriptive aspects of soil quality/health. In J.W. Doran, D.C. Coleman, D.F. Bezdicek, and B.A. Stewart (Eds.) Defining soil quality for a sustainable environment (p. 23–35). Soil Sci. Soc. Am. Spec. Publ. No. 35. Madison, WI: ASA and SSSA.
15 Kravchenko, A., and Robertson, G.P. (2014). Whole‐profile soil carbon stocks: The danger of assuming too much from analyses of too little. Soil Sci. Soc. Am. J. 75, 235–240.
16 Liebig, M.A., Varvel, G.E., and Honeycutt, C.W. (2010). Sampling protocols. Chapter 1. Guidelines for site description and soil sampling, processing, analysis, and archiving. In R.F. Follett (Ed.), GRACEnet Sampling Protocols (p. 1‐1 to 1‐5). Available at https://www.ars.usda.gov/anrds/gracenet/gracenet‐protocols (accessed 26 July 2019).
17 Liebig, M., Carpenter‐Boggs, L., Johnson, J.M.F., Wright, S., and Barbour, N. (2006). Cropping system effects on soil biological characteristics in the Great Plains. Renew. Agric. Food Systems 21, 36–48.
18 Magdoff, F., and Van Es, H. (2009). How good are your soils? Field and laboratory evaluation of soil health. In Building soils for better crops: Sustainable soil management (p. 257–266). 3rd ed. Handbook Series Book No. 10. Washington, DC: Sustainable Agriculture Research & Education (SARE), Nat. Inst. Food Agric., USDA.
19 Mikha, M.M., Vigil, M.F., Liebig, M.A., Bowman, R.A., McConkey, B., Deibert, E.J., and Pikul, J.L., Jr. (2006). Cropping system influences on soil chemical properties and soil quality in the Great Plains. Renew. Agric. Food Systems 21, 26–35.
20 Mueller, L., Schindler, U., Shepherd, T.G., Ball, B.C., Smolentseva, E., Hu, C., Hennings, V., Schad, P., Rogasik, J., Zeitz, J., Schlindwein, S.L., Behrendt, A., Helming, K., and Eulenstein, F. (2012). A framework for assessing agricultural soil quality on a global scale. Arch. Agron. Soil Sci. 58, S76–S82.
21 Mulla, D.J., and Schepers, J.S. (1997). Key processes and properties for site‐specific soil and crop management. In F.J. Pierce, and E.J. Sadler (Eds.) The state of site‐specific management for agriculture (p. 1–18). Madison, WI: ASA, CSSA, and SSSA.
22 Munkholm, L.J., and Holden, N.M. (2015). Visual evaluation of grassland and aerable management impacts on soil quality. In B.C. Ball, and L.J. Munkholm (Eds.). Visual soil evaluation: Realizing potential crop production with minimum environmental impact (p. 49–65. Oxfordshire, UK: CABI.
23 Peerlkamp, P.K. (1959). A visual method of soil structure evaluation. Meded. v.d. Landbouwhogeschool en Opzoekingsstations van de Staat te Gent. 24, 216–221.
24 Pellant, M., Shaver, P.L., Pyke, D.A., Herrick, J.E., Lepak, N., Riegel, G., Kachergis, E., Newingham, B.A., Toledo, D., and Busby, F.E. (2020). Interpreting indicators of rangeland health, Version 5. Tech Ref 1734‐6. Denver, CO: U.S. Department of the Interior, Bureau of Land Management, National Operations Center.
25 Peterson, R.G., and Calvin, L.D. (1986). Sampling. In A. Klute (Ed.) Methods of soil analysis, Part 1 (p. 33–51). 2nd ed. Agrono. Monogr. 9. Madison, WI: ASA and SSSA.
26 Pikul, J.L. Jr., Schwartz, R.C., Benjamin, J.G., Baumhardt, R.L., and Merrill, S. (2006). Cropping system influences on soil physical properties in the Great Plains. Renewable Agric. Food Systems 21, 15–25.
27 Reeves, J.L., and Liebig, M.A. (2016). Depth matters: Soil pH and dilution effects in the northern Great Plains. Soil Sci. Soc. Am. J. 80, 1424–1427.
28 Romig, D.E., Garlynd, M.J., and Harris, R.F. (1996). Farmer‐based assessment of soil quality: A soil health scorecard. In J.W. Doran and A.J. Jones (Eds.) Methods for assessing soil quality (p. 39–60). Soil Sci. Soc. Am. Spec. Publ. No. 35. Madison, WI: SSSA.
29 Sarrantonio, M., Doran, J.W., Liebig, M.A., and Halvorson, J.J. (1996). On‐farm assessment of soil quality and health. In J.W. Doran, and A.J. Jones (Eds.) Methods for assessing soil quality (p. 83–105). Soil Sci. Soc. Am. Spec. Publ. No. 49. Madison, WI: SSSA.
30 Schepers, A., Shanahan, J.F., Liebig, M.A., Schepers, J.S., Johnson, S.H., and Luchiari, A., Jr. (2004). Appropriateness of management zones for characterizing spatial variability of soil properties and irrigated corn yields across years. Agron. J. 96, 195–203.
31 Scotland’s Rural College. (2019). Visual evaluation of soil structure. Available at: https://www.sruc.ac.uk/info/120625/visual_evaluation_of_soil_structure (accessed 24 July 2019).
32 Seybold, C.A., and Herrick, J.E. (2001). Aggregate stability kit for soil quality assessments. Catena 44, 37–45.
33 Smith, J.L., Halvorson, J.J., and Papendick, R.I. (1993). Using multiple‐variable indicator kriging for evaluating soil quality. Soil Sci. Soc. Am. J. 57, 743–749.
34 Soil Science Division Staff. (2017). Soil survey manual. C. Ditzler, K. Scheffe, and H.C. Monger (Eds.). USDA Handbook 18. Washington, DC: U.S. Government Printing Office.
35 Sun, S.‐Q., Cai, H.‐Y., Chang, S.X., and Bhatti, J.S. (2015). Sample storage‐induced changes in the quantity and quality of soil labile organic carbon. Sci. Rep. 5, 17496. doi:10.1038/srep17496.
36 Thomasson, J.A., Sui, R., Cox, M.S., and Al–Rajehy, A. (2001). Soil reflectance sensing for determining soil properties in precision agriculture. Trans. Am. Soc. Agric. Eng. 44, 1445–1453.
37 USDA‐NRCS. (2004). Compliant cavity (3B3). In R. Burt (Ed.) Soil survey laboratory methods manual (p. 98–100). Soil survey investigations report no. 42, version 4.0. Lincoln, NE: USDA‐NRCS National Soil Survey Laboratory.
38 USDA‐NRCS. (2001). Soil quality test kit guide. Available at: https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_050956.pdf (accessed 24 July 2019).
39 USDA‐NRCS. (19990. Soil quality card design guide: A guide to develop locally adapted conservation tools. Available at: https://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/assessment/ (accessed 22 July 2019).
40 Wang, X., Jelinski, N.A., Toner, B., and Yoo, K. (2019). Long‐term agricultural management and erosion change soil organic matter chemistry and association with minerals. Sci. Total Environ. 648, 1500–1510.
41 Wienhold, B.J., Pikul, J.L., Liebig, M.A., Mikha, M.M., Varvel, G.E., Doran, J.W., and Andrews, S.S. (2006). Cropping system effects on soil quality in the Great Plains: Synthesis from a regional project. Renew. Agric. Food Systems 21, 49–59.
42 Wills, S.A., Burras, C.L., and Sandor, J.A. (2007). Prediction of soil organic carbon content using field and laboratory measurements of soil color. Soil Sci. Soc. Am. J. 71, 380–388.
43 Wuest, S.B. (2015). Seasonal variation in soil bulk density, organic nitrogen, available phosphorus, and pH. Soil Sci. Soc. Am. J. 79, 1188–1197.
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