Effects of liming, K fertilization and leaching on K retention, nutrient uptake and dry matter production of maize grown on a Samoan Oxic Inceptisol

Abstract

Effects of coralline lime and leaching on dry matter production and nutrient uptake by maize (Zea mays) were studied in 21 cm deep leaching columns/pots filled with an Oxic Inceptisol (12 kg) from Alafua, Western Samoa. Ground (<0.25mm) coralline material containing approximately 80% CaCO3 was used as lime. There were 12 treatments, factorially arranged: 4 liming rates (0, 10.5, 21.0 and 31.5 g pot−1) which were applied 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 days (3 1 pot−1 day−1) following the lime applications. Leaching continued for 15 more days, using 1 1 pot−1 day−1, after K fertilizations. During the initial leaching period, liming intensified K losses. The applied Ca-ions displaced the exchangeable K which was subsequently leached out of the pots. During the second leaching period, liming increased K retention only when K concentrations in the soil were high (treatment 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 because the leaching losses made up only approximately 2 % of the K-turnover 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 nonexchangeable K. The Alafua soil had 0.45 % (11.5 cmol(+)kg−1) total-K, indicating a relatively large K reserve. Since mineralogical studies failed to detect the presence of any known 2:1 minerals, the K reserve of the Alafua soil might be located in amorphous material.