1.Ball, D.F. 1964. Loss-on-ignition as an estimate of organic matter/organic carbon in non-calcareous soils. J. Soil Sci. 15:84–92.
2.Barber, S.A., Mackay, A.D., Kuchenbuch, R.O., and Barraclough, P.B.. 1988. Effects of soil temperature and water on maize root growth. Plant Soil 111:267–269.
3.De Willigen, P., and Van Noordwijk, M.. 1987. Roots, Plant Production and Nutrient Use Efficiency. Wageningen Agricultural University, The Netherlands.
4.JrDouds, D.D., Janke, R. R., and Peters, S.E.. 1993. VAM fungus spore populations and colonization of roots of maize and soybean under conventional and low-input sustainable agriculture. Agric., Ecosystems and Environment 43:325–335.
5.Jackson, R.B., and Caldwell, M.M.. 1989. The timing and degree of root proliferation in fertile-soil microsites for three cold-desert perennials. Oecologia 81:149–153.
6.Jackson, R.B., Manwaring, J.H., and Caldwell, M.M.. 1990. Rapid physiological adjustment of roots to localized soil enrichment. Nature 344:58–60.
7.Kaspar, T.C., Brown, H.J., and Kassmeyer, E.M.. 1991. Corn root distribution as affected by tillage, wheel traffic, and fertilizer placement. Soil Sci. Soc. Amer. J. 55:1390–1394.
8.Kovar, J.L., Barber, S.A., Kladivko, E.J., and Griffith, D.R.. 1992. Characterization of soil temperature, water content, and maize root distribution in two tillage systems. Soil Tillage Research 24:11–27.
9.Kuchenbuch, R.O., and Barber, S.A.. 1987. Yearly variation of root distribution with depth in relation to nutrient uptake and corn yield. Communications in Soil Sci. and Plant Analysis 18:255–263.
10.Kuchenbuch, R.O., and Barber, S.A.. 1988. Significance of temperature and precipitation for maize root distribution in the field. Plant Soil 106:9–14.
11.Kurle, J.E., and Pfleger, E.L.. 1994. Arbuscular mycorrhizal fungus spore populations respond to conversions between low-input and conventional management practices in a corn-soybean rotation. Agronomy J. 86:467–475.
12.Liebhardt, W.C., Andrews, R.W., Culik, M.N., Harwood, R.R., Janke, R.R., Radke, J.K., and Rieger-Schwartz, S.L.. 1989. Crop production during conversion from conventional to low-input methods. Agronomy J. 81:150–159.
13.Mackay, A.D., and Barber, S.A.. 1986. Effect of nitrogen on root growth of two corn genotypes in the field. Agronomy J. 78:699–703.
14.Maizlish, N.A., Fritton, D.D., and Kendall, W.A.. 1980. Root morphology and early development of maize at varying levels of nitrogen. Agronomy J. 72:25–31.
15.Mengel, D.B., and Barber, S.A.. 1974. Development and distribution of the corn root system under field conditions. Agronomy J. 66:341–344.
16.Newell, R.L., and Wilhelm, W.W.. 1981. Conservation tillage and irrigation effects on corn root development. New Phytologist 88:160–165.
17.Passioura, J.B. 1983. Roots and drought resistance. Agric. Water Management 7:265–280.
18.Peters, S., Janke, R.R., and Bohlke, M.. 1992. Rodale's farming systems trial: 1986–1990. Research report. Rodale Institute Research Center, Kutztown, Pennsylvania.
19.Robertson, W.K., Hammond, L.C., Johnson, J.T., and Boote, K.J.. 1980. Effects of plant-water stress on root distribution of corn, soybeans, and peanuts in sandy soil. Agronomy J. 72:548–550.
20.Sahs, W., and Lesoing, G.. 1985. Crop rotations and manure vs. agricultural chemicals in dryland grain production. J. Soil and Water Conservation 40:511–516.
21.SAS Institute. 1985. SAS User's Guide: Statistical Methods. 7th ed. Cary, North Carolina.
22.Scheffe, H. 1959. The Analysis of Variance. John Wiley & Sons, New York, N. Y.
23.Smucker, A.J.M. 1990. Quantification of root dynamics in agroecological systems. Remote Sensing Review 5:237–248.
24.Smucker, A.J.M., McBurney, S.L., and Srivastava, A.K.. 1982. Quantitative separation of roots from compacted soil profiles by the hydropneumatic elutriation system. Agronomy J. 74:500–503.
25.Snedecor, G.G., and Cochran, W. G.. 1980. Statistical Methods 7th ed.Iowa State Univ. Press, Ames, Iowa.
26.St. John, T.V., Coleman, D.C., and Reid, C.P.P.. 1983. Growth and spatial distribution of nutrient-absorbing organs: Selective exploitation of soil heterogeneity. Plant Soil 71:487–493.
27.Voorhees, W.B., Johnson, J.F., Randall, G.W., and Nelson, W.W.. 1989. Corn growth and yield as affected by surface and subsoil compaction. Agronomy J. 81:294–303.