1. De Willigen P and Van Noordwijk M 1987 Roots, Plant production and Nutrient Use Efficiency. PhD thesis Agricultural University, Wageningen.
2. Jensen C R, Luxmoore R J, Gundy S D and Stolzy L H 1969 Root air space measurements by a pycnometer method. Agron. J. 61, 474–475.
3. Int. Symp. Gumpenstein 1982, Irdning;H Konings,1983
4. Kozinka V 1979 Conditions for ‘internal aeration’ in the seminal root system of Zea mays L. Biologia (Bratislava) 34, 531–539.
5. Weast R C (Ed.) 1975 Handbook of Chemistry and Physics, 56th ed. The chemical rubber Co., Cleveland.