Aw. Bekker et al., EFFECTS OF LIMING, K-FERTILIZATION AND LEACHING ON K-RETENTION, NUTRIENT-UPTAKE AND DRY-MATTER PRODUCTION OF MAIZE GROWN ON A SAMOAN OXIC INCEPTISOL, Fertilizer research, 38(2), 1994, pp. 123-130
Effects of coralline lime and leaching on dry matter production and nu
trient uptake by maize (Zea mays) were studied in 21 cm deep leaching
columns/pots filled with an Oxic Inceptisol (12 kg) from Alafua, Weste
rn Samoa. Ground (< 0.25 mm) coralline material containing approximate
ly 80% CaCO3 was used as lime. There were 12 treatments, factorially a
rranged: 4 liming rates (0, 10.5, 21.0 and 31.5 g pot-1) which were ap
plied to the top 5 cm of the pots, and 3 K applications (0, 0.69 1.38
g pot-1) which were applied after the initial leaching period of 10 da
ys (3 1 pot-1 day-1) following the lime applications. Leaching continu
ed for 15 more days, using 1 1 pot-1 day-1, after K fertilizations. Du
ring the initial leaching period, liming intensified K losses. The app
lied Ca-ions displaced the exchangeable K which was subsequently leach
ed out of the pots. During the second leaching period, liming increase
d K retention only when K concentrations in the soil were high (treatm
ent receiving 1.38 g K pot-1). These effects of liming and leaching on
K retention were not detectable in the nutrient uptake of maize grown
for 50 days after the second leaching period. This may have been beca
use the leaching losses made up only approximately 2% of the K-turnove
r in the pots. A calculated nutrient balance for the pots showed that
a large portion of K taken up by maize came out of a pool of nonexchan
geable K. The Alafua soil had 0.45 % (11.5 cmol(+)kg-1) total-K, indic
ating a relatively large K reserve. Since mineralogical studies failed
to detect the presence of any known 2:1 minerals, the K reserve of th
e Alafua soil might be located in amorphous material.