Samples were air-dried, sieved < 2mm and a sub-sample ground < 0.5 mm. Determination of pH, NaHCO3-soluble P, exchangeable cations were carried out on < 2mm sample; organic C and total N on < 0.5 mm sub-sample.
The following methods were used for the analysis of the 1987 and 1988 samples.
2.5:1 water-soil suspension. pH by glass electrode.
Dichromate digestion; modified Tinsley. Kalembasa, S.J. & Jenkinson, D.S. (1973) J.Sci.Food Agric. 24,1085-1090
Kjeldahl Method. Bremner.J.M (1965) In: Methods of Soil Analysis (C.A.Black, Ed.) Vol2 pp1149-1178. American Society of Agronomy.
|Exchangeable Cations K, Ca, Mg and Na||Metson, A.J.(1956) New Zealand Soil Bureau, Bulletin No12.|
|NaHCO3 Soluble Phosphorus||Olsen, S.R., Cole, C.V., Watanabe, F.S. & Dean L.A (1954) USDA Circular No 939, 19pp.|