Soil organic amendments and mineral fertilizers: options for sustainable lowland rice production in the forest agro-ecology of Ghana Rectification organique des sols et engrais chimiques: options pour la production durable du riz dans les terrains bas dans l'agro-ecologie des forets du Ghana

Abstract

The “sawah” technology (bunded and leveled irrigated rice field) was introduced to some farmers within the forest agro-ecology of Ghana. To improve the productivity of their soils and also to minimize expenditure on mineral fertilizers, the effect of three organic amendments on rice yield was evaluated. Poultry manure, cattle manure and rice husk were used either solely or in combination with mineral fertilizer on rice at three different locations within the forest agro-ecological zone at Potrikrom, Biemso No. 1 and Biemso No. 2. Sole organic amendments were applied at a rate of 7.0 t ha^-1 and sole mineral fertilizer was applied as N-P-K at 90-60-60 kg ha^-1. The N source was either urea or sulphate of ammonia, P source was triple super phosphate and K source was muriate of potash. Combinations were half rate (organic amendments + mineral fertilizer). Results showed that organic amendments, mineral fertilizer and their combinations significantly contributed to the growth and grain yield of rice. A combination of poultry manure (half rate) and mineral fertilizer (half rate) gave significantly greater grain yield than all the treatments except mineral fertilizer (full rate) at two out of the three locations. Rice grain yields were 6.2, 7.3 and 3.7 t ha^-1 for half rate poultry manure + half rate mineral fertilizer at Potrikrom, Biemso No. 1 and Biemso No. 2 respectively, while full rate mineral fertilizer gave 6.6, 7.3 and 3.9 t ha^-1 at the three sites respectively. In addition, a combination of organic amendments with mineral fertilizer out-yielded sole organic amendments at all the three sites. Organic amendments applied solely performed in the order: poultry manure > cattle manure > rice husk.

Keywords: agro-ecology, forest, organic amendments, “sawah”, sustainability

Agricultural and Food Science Journal of Ghana Vol. 3 2004: 237-248