Prior to the experiment, soil was thoroughly sieved < 2 mm.
In the present experiment, soil tillage has been done almost at the same time for all treatments.
In the pot experiment, soil nitrate concentration was also monitored by using anion exchange membranes inserted directly into the soil.
At the beginning of experiment, soil was sampled at 0 15 cm depth and analyzed for pH, N, P, K, C, Ca and Mg.
At the end of the experiment, soil samples were collected with the assistance of a probe-type 50 mm PVC auger, at the 0 20 cm soil layer, air-dried, and sieved in a 2 mm sieve.
At the end of experiment, soil sub-samples were taken from each pot and analyzed for pH in saturated paste, OM (Jackson 1958), NO3 N (Bremner and Keeney 1965), and DTPA-extractable Fe, Mn, Zn, Cu, Cd, and Pb (Lindsay and Norvell 1978).
At the beginning and end of the experiment, soil was sampled at 0 15 cm depth and analysed for pH, Ca, Mg, K, C, N and P. End of the 2000/2001 short rains (SR) season and 2001 long rains (LR) season, soil samples were taken at 0 30, 30 100 and 100 150 cm for nitrate and ammonium analysis.
In October 2006 and 2012, i.e. after 18 and 24 years of the start of NT or 12 and 18 years after lime re-application (beginning of the experiment), soil samples were taken at each 1 cm depth up to 10 cm layer, each 2.5 cm depth up to 10 to 25 cm layer, and each 5 cm depth from 25 to 60 cm layer.
