References
- Bremner , J. M. 1965 . Methods of soil analysis , Edited by: Black , C. A. vol. 2 , 1185 – 1191 . Madison, Wise, , USA : Am. Soc. Agron. Inc. . 1205, and 1339–1341, Ser. Agron. No. 9
- Clement , C. R. and Williams , T. E. 1967 . Leys and organic matter, II. The accumulation of nitrogen in soils under different leys . J. Agric. Sci. Camb. , 69 : 133 – 138 .
- Gasser , J. K. R. and Williams , R. J. B. 1963 . Soil nitrogen, VII. Correlations between measurements of nitrogen status of soils and nitrogen % and nitrogen content of crops . J. Sci. Fd Agric. , 14 : 269 – 277 .
- Gasser , J. K. R. 1969 . Available soil nitrogen—its measurement, and some factors affecting its correlation with crop performance . Welsh Soils Discussion Group Report No. 10. ,
- Gasser , J. K. R. 1970 . “ Some effects of soil-N status on crop growth and yield. ” . In Agricultural Chemistry Symposium , 174 – 188 . University of Leeds . 1970
- Henriksen , A. and Selmer-Olsen , A. R. 1970 . Automatic methods for determining nitrate and nitrite in water and soil extracts . Analyst , 95 : 514 – 518 .
- Huntjens , J. L. M. 1971 . The influence of living plants on mineralization and immobilization of nitrogen . Plant and Soil , 35 : 77 – 94 .
- Jenkinson , D. S. 1965 . Studies on the decomposition of plant material in soil. I. Loss of carbon from 14carbon labelled ryegrass incubated with soil in the field . J. Soil Sci. , 16 : 104 – 115 .
- Keeney , D. R. and Bremner , J. M. 1966 . A chemical index of soil nitrogen availability . Nature , 211 : 892 – 893 .
- Keeney , D. R. and Bremner , J. M. 1966 . Comparison and evaluation of laboratory methods of obtaining an index of soil nitrogen availability . Agronomy J. , 58 : 498 – 503 .
- Last , P. J. and Draycott , A. P. 1971 . Predicting the amount of nitrogen fertilizer needed for sugar-beet by soil analysis . J. Sci. Fd Agric. , 22 : 215 – 220 .
- Lyngstad , I. 1971 . Nitrate studies in arable soils , 101 – 109 . NLH : Lie .
- Munson , R. D. and Stanford , G. 1955 . Predicting nitrogen fertilizer needs of Iowa Soils: IV. Evaluation of nitrate production as a criterion of nitrogen availability . Soil Sci. Soc. Amer. Proc. , 19 : 464 – 468 .
- Olsen , R. J. , Hensler , R. F. , Attoe , O. J. , Witzel , S. A. and Peterson , L. A. 1970 . Fertilizer nitrogen and crops rotation in relation to movement of nitrate nitrogen through soil profiles . Soil Sci. Soc. Amer. Proc. , 34 : 448 – 452 .
- Selmer-Olsen , A. R. 1971 . Determination of ammonium in soil extracts by an automated indophenol method . Analyst , 16 : 565 – 568 .
- Solberg , P. and Braadlie , O. 1957 . Nitrat- og ammoniuminnhold i dyrket jord med og uten plantevekst. Orienterende undersokelser . Forskn.fors. landbr. , 8 : 329 – 367 .
- Technicon Auto Analyzer Methodology . 1965 . N-3c with some small modifications , New York : Technicon Ardsley . 10502
- Waring , S. A. and Bremner , J. M. 1964 . Ammonium production in soil under waterlogged conditions as an index of nitrogen availability . Nature , 201 : 951 – 952 .