Improving the productivity of lowland soils for rice cultivation in Ghana The role of the ‘Sawah’ system

2011

English

Lowlands constitute one of the largest and appropriate environments suitable for rice cultivation in Ghana. However, environmental degradation and declining soil productivity, leading to low crop yields are major concerns. Some reasons leading to such concerns may be traced to lack of proper management of our soil resources and possible unsuitable crop production systems and practices. Effective nutrient and water management in addition to suitable land preparation options are key factors for the effective and sustainable utilization of these inland valley ecosystems. Proper and meaningful management strategies therefore need to be developed in a way as to enable and encourage farmers to accept and easily adopt them. Designing and implementation of comprehensive and integrated soil management programs that will not only improve and maintain soil fertility but also make maximum use of available water are necessary. While research has shown that these environments vary considerably in soil type, water holding capacity and nutrient retention, it has been further observed that soils of most valleys are dominant in low activity clay minerals which have low nutrient and water holding capacities. Adoption of the “Sawah” system will enhance and sustain production. The "Sawah" system is characterized by nutrient replenishing mechanisms with intrinsic resistance to erosion (better water control and nutrient management). Rice responds better to fertilizer (mineral and organic) under the "Sawah" system than the traditional system of rice production in Ghana. Rice cultivation under the “Sawah” system in inland valleys in Ghana has lead to significant improvement in soil and water management. There has been a gradual and significant increase in rice grain yield in the order: farmers practice < only bunded < bunded and puddled < bunded, puddle and leveled (“sawah”), across locations and varieties. An integration of available farm manures with mineral fertilizer resulted in significant increases in paddy grain yield across locations, thus reducing the over reliance of famers on mineral fertilizers to improve soil fertility. From a significant initial increase (from less than 1.0 t ha-1 to over 4.5 t ha-1), mean paddy grain yield under the “Sawah” system consistently and continuously increased annually and currently stands at over 6.0 t ha-1 among farmer groups. Mean net income generated per hector under the “sawah” system also ranged from US $1,500 to US $2,800 over the same period among farmer-groups. There was also a gradual build up of total carbon and exchangeable bases (K, Ca, Mg) leading to improved nutrient levels, even though there was a net loss of both total Nitrogen and available Phosphorus over the same period. Ghana (possibly West Africa) has the potential to increase local rice production by over 300% when the “Sawah” system is adopted.

Buri, M. M.; Iassaka, R. N.; Wakatsuki, T.; Kawano, N.