Evaluation of sawah rice management system in an inland valley in southeastern Nigeria. I: Soil chemical properties and rice yield

Abstract

Failures in agricultural development in parts of West Africa may have been caused by the inability of the farmers to develop the abundant inland valleys for cultivation of such crops like rice, using appropriate water management systems. An inland valley in southeastern Nigeria was used to evaluate the influence of sawah and non-sawah water management using inorganic and organic soil amendments on the soil chemical properties and rice grain yield. Soil chemical properties tested were soil organic carbon, total nitrogen, pH, exchangeable K + , Ca 2+ and Mg 2+ . Others were CEC, percent base saturation and exchangeable acidity while the grain yield of rice was also measured. The soils are loose, low in pH and poor in plant nutrient elements. In spite of that, the sawah-managed system was able to improve the pH of the soil by raising it slightly both in the first and second year of planting. Generally, essential plant nutrients such as exchangeable K + , Ca 2+ and Mg 2+ , including fertility index like the CEC, were improved within sawah management within the period. Also, rice grain yield increased significantly (5.62 and 6.25 tons/ha in the first year and 5.32 and 6.53 tons/ha in the second year for non-sawah and sawah, respectively) with sawah system such that about 11 and 23% yield increases were obtained in sawah over the non-sawah in the two years, respectively. Although organic carbon can be used to explain the variation in total grain yield in the first year, it was the CEC that explained the total grain yield in the second year. The study revealed the superiority of sawah over non-sawah in the production of lowland rice in an inland valley in southeastern Nigeria.

Long-term effects of lowland sawah system on soil physicochemical properties and rice yield in Ashanti Region of Ghana

“…The sawah systems could thus be a means of coping with the low fertility status of inlandvalley soils. Nwite et al (2008) also reported higher soil exchangeable bases under sawah compared to nonsawah systems in a lowland soil in southeastern Nigeria. Owing to the positive correlation between SOC and exchangeable bases in West African inland valleys (Issaka et al, 1997), the NSP would by virtue of its high SOC content be expected to also be rich in exchangeable bases.…”

“…Apart from not conforming to any specific textural attribute, West African lowlands exhibit diverse hydrological conditions. Yet, the sawah technology enhances rice yield under such scenarios in the region (Asubonteng et al, 2001;Buri et al, 2008;Nwite et al, 2008). Attempts to edaphologically explain such yield benefits due to the sawah system focused only on other beneficial attributes of the system, such as enhancement of soil chemical and fertility properties and good water control (Nwite et al, 2008;Issaka et al, 2009).…”

“…Yet, the sawah technology enhances rice yield under such scenarios in the region (Asubonteng et al, 2001;Buri et al, 2008;Nwite et al, 2008). Attempts to edaphologically explain such yield benefits due to the sawah system focused only on other beneficial attributes of the system, such as enhancement of soil chemical and fertility properties and good water control (Nwite et al, 2008;Issaka et al, 2009). It has been shown under Asian conditions that paddy soils exhibit a dynamic soil-water system which is driven by puddling, duration of ponding, and age of the paddy (Lennart et al, 2009), but such has yet to be checked for the increasingly popular sawah system in West Africa.…”

Puddling Intensity for Late-season Sawah Systems Based on Soil Hydrophysical Conditions and Rice Performance

“…The superiority of sawah systems over traditional rice (Oryza sativa L.) culture in West Africa is no longer debatable (Nwite et al, 2008;Obalum et al, 2012;Ofori et al, 2005). Sawah is a term adopted from Indonesia referring to an ecologically engineered lowland rice field, one that is properly demarcated using bunds, puddled, leveled and rowtransplanted to a high-yielding variety and, thereafter, kept under regulated flooding and routine fertilization.…”

“…Lately, the research has been focused on reducing the cost of the system for enhanced acceptability to farmers. However, most of the studies in this regard concentrated on alternative fertilization strategies (Buri et al, 2004(Buri et al, , 2008Nwite et al, 2008Nwite et al, , 2011. Under the sawah system, land preparation using a hand-operated power tiller is routinely done.…”