caa a22 4500 386326185 CHVBK 20180307111653.0 cr unu---uuuuu 161130e198904 xx s 000 0 eng 10.1017/S0014479700016719 doi S0014479700016719 pii (NATIONALLICENCE)cambridge-10.1017/S0014479700016719 Obi A. Olu Department of Soil Science, University of Ife, Ile-Ife, Nigeria Long-term Effects of the Continuous Cultivation of a Tropical Ultisol in Southwestern Nigeria [Elektronische Daten] [A. Olu Obi] Continuous cropping of a tropical Ultisol with or without nitrogen fertilizer increased soil acidification and reduced soil organic matter and productivity. Addition of nitrogen fertilizer failed to increase yields. This was apparently due to the decline in soil pH, an increase in the amount of soluble aluminium, and consequent inefficient utilization of added nutrients. Continuous use of ammonium sulphate as a nitrogen source hastened the development of both surface and subsoil exchange acidity. Copyright © Cambridge University Press 1989 Experimental Agriculture Cambridge University Press 25/2(1989-04), 207-215 0014-4797 25:2<207 1989 25 EAG https://doi.org/10.1017/S0014479700016719 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S0014479700016719 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Obi A. Olu Department of Soil Science, University of Ife, Ile-Ife, Nigeria NATIONALLICENCE 773 0- Experimental Agriculture Cambridge University Press 25/2(1989-04), 207-215 0014-4797 25:2<207 1989 25 EAG CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge