Effect of Different Land Preparation Methods for Sawah System Development on Soil Productivity Improvement and Rice Grain Yield in Inland Valleys of Southeastern Nigeria

The development of agriculture in inland valleys of Southeastern Nigeria could not be realized merely due to inability of the farmers to develop these potential and abundant inland valleys for such water loving crops like rice using appropriate water management systems.

In an attempt to replicate the successful Japanese Satoyama watershed management model in the African agro-ecosystems, sawah rice cultivation technology has been introduced to farmers’ fields. A study was conducted in an inland valley at Akaeze, Ivo Local Government Area of Ebonyi State, Southeastern Nigeria, in 2012, 2013 and 2014 cropping seasons using the same watershed and treatments, to assess the effects of different tillage environments and different amendments in sawah water management system on soil chemical properties and rice grain yield. Sawah described as an Indo-Malaysian word for padi, refers to leveled rice field surrounded by bunds with inlets and outlets for irrigation and drainage. A split- plot in a randomized complete block design was used to evaluate these two factors. The four tillage environments (complete sawah tillage- bunded, puddled and leveled rice field (CST); farmers tillage environment- no bunding and leveling rice field (FTE); incomplete sawah tillage- bundding with little leveling and puddling rice field (ICST) and partial sawah tillage- bunding with no puddling and leveling rice field (PST)) for rice growing served as main plots. The amendments, which constituted the sub-plots, were applied in the following forms: 10 t ha-1 rice husk ash, 10 t ha-1 of rice husk, 400 kgha-1 of N.P.K. 20:10:10, 10 t ha-1 of poultry droppings, and 0 t ha-1 (control). The additive residual effects of the amendments were not studied in the course of this research. A bulk soil sample was collected at 0-20 cm depth in the location before tillage and amendments for initial soil characteristics. At each harvest, another set of soil sample was collected on different treated plots to ascertain the changes that occurred in the soil due to treatments application. Selected soil chemical properties analyzed include; soil pH, OC, total nitrogen, exchangeable bases (Na+, Ca2+, Mg2+ and K+) and CEC, while the rice grain yields was also measured at each harvest. The soil amendments were analyzed for N, P, K, Ca, Mg, Na, and organic carbon. Data collected were subjected to statistical analysis using Genstat 3 7.2 Edition. Results showed that the soil pH, organic carbon (OC) and total nitrogen (TN) including the exchangeable bases were significantly (p < 0.05) improved by different tillage parameters for the three years of study. CEC was significantly (p < 0.05) improved by the tillage environments on the 2nd and 3rd year of studies. Soil amendments significantly (p < 0.05) improved the soil pH, OC, TN and all the exchangeable bases within the periods of study. The interaction significantly (p < 0.05) improved the soil exchangeable Ca2+ and Mg2+ on the third year of study. The result showed a significant improvement on the rice grain yield by the tillage environments and amendments within the periods of study. It was also obtained that all the sawah adopted tillage environments positively improved both the soil parameters and rice grain yield relatively higher than the farmers’ tillage environment.