TABLE S4. N:P ratios for W < 2 Mg ha-1 from dataset B with references to the sources of data

Species / No of observations / %N / S.E each observation / W / S.E each observation / N:P ratio / S.E each observation / Reference
Wheat / 10 / 4.58 / 0.57 / 0.87 / 0.61 / 9.59 / 1 / Bergman, 1992 p343 & p361; Tcierling, 1978
Maize / 6 / 2.97 / 0.67 / 1.05 / 0.61 / 9.76 / 1.78 / Karlen & Camp, 1982; Karlen et al.,1987; Plenet et al. ,1992, a & b
Winter rye / 2 / 4.4 / - / 1.2 / - / 8 / - / Tcierling, 1978, adequate nutrition
Oat / 2 / 4.95 / - / 0.96 / 6.11 / Tcierling, 1978, adequate nutrition
Timothy / 2 / 4.47 / - / 1.58 / 11.05 / Belanger & Richards, 1995;1999
Alfalfa / 1 / 4.25 / - / 1.32 / 9.41 / Bergman, 1992, p343
Spinach / 1 / 4.4 / - / 1.13 / 8.8 / Bergman, 1992, p343
Sugar beet / 1 / 3.69 / - / 0.47 / 9.33 / Houba, 1973
Weighted mean / 4.14 / 1.02 / 9.29
Weighted mean excluding Winter rye and Oat / 9.72

References for Table S3

Belanger G, Richard JE. 1995. Growth analysis of timothy cultivary differing in maturity. Canadian Journal of Plant Science 75: 643-648.

Belanger G, Richard JE. 1999. Relationships between P and N concentrations in timothy. Canadian Journal of Plant Science 79: 65-70.

Bergman W. 1992. Nutritional disorders of plants. Development and, visual and analytical diagnosis. Jena Germany: Gustav Fischer,

Houba VJG. 1973. Effect of nitrogen dressings on growth and development of sugar beet. Agricultural Research Reports 791 Wageningen, The Netherlands: Pudoc Centre for agricultural publishing and documentation.

Karlen DL, Camp CR. 1982. N, P and K accumulation in high yielding irrigated maize grown on typic paleudult in the southeastern U.S. In: Scaife A, ed. Proceedings of the ninth international plant nutrition colloquium, University of Warwick, Volume 1.). Slough, UK: Commonwealth Agricultural Bureau, 262-267.

Karlen DL, Flannery RL, Sadler EJ. 1987. Nutrient and dry matter accumulation rates for high yielding maize. Journal of Plant Nutrition 10: 1409-1417.

Plenet D, Lubert E, Esvan JM. 1992 Effects of N level on dry matter and nitrogen accumulation for high yielding maize. In: Scaife A, ed. Proceedings of the second congress of the European Society of Agronomy. Warwick UK: ESA UK Congress Office, 294-295.

Plenet D, Lubert E, Esvan JM, Soyer JP. 1992. Effects of long term phosphorus applications on continuous maize cropping and soil P status. In: Scaife A, ed. Proceedings of the second congress of the European Society of Agronomy. Warwick UK: ESA UK Congress Office, 296-297.

Tcierling VV. 1978. Agrochemical fundamentals of diagnostics of crop mineral nutrition. Moscow: Nauka. (in Russian)

Церлинг В.В. Агрохимические основы диагностики минерального питания сельскохозяйственных культур. М.: Наука, 1978. 216 с.