References
- Welch , L. F. 1971 . More nutrients are added to soil than are hauled away in crops . Illinois Research , 14 ( 1 ) : 3 – 4 .
- Ross , G. L. , Dillon , J. E. and Graffis , D. W. 1971 . 1971 performance of commercial corn hybrids in Illinois , Univ. of Illinois Agr. Extension . Circ. 1048
- Horwitz , W. , ed. 1960 . Official Methods of Analysis. , 9th ed. , Washington, D.C. : Association of Official Agricultural Chemists .
- Viets , F. G. Jr. and Domingo , C. E. 1948 . Yields and nitrogen content of corn hybrids as affected by nitrogen supply . Soil Sci. Soc. Amer. Proc. , 13 : 303 – 306 .
- Kurtz , L. T. and Smith , G. E. 1966 . “ Nitrogen fertilizer requirements ” . In Advances in corn production: principles and practices , Edited by: Pierre , W.H. , aldrich , S. R. and Martin , W. P. Ames, Iowa : Iowa State Univ. Press .
- Lang , A. L. , Pendleton , J. W. and Dungan , G. H. 1956 . Influence of population and nitrogen levels on yield and protein and oil contents of nine corn hybrids . Agron. J. , 48 : 284 – 289 .