**1. Introduction**

Low inherent soil fertility has been identified as a major cause for low rice yield in Sub-Sa‐ haran Africa (Buri et al., 2004; Senayah, et al., 2008; Buri et al., 2009; Issaka et al., 2009; Abe et al., 2010). The problem is compounded because farmers are not able to purchase fertilizer due to relatively high cost and therefore rely mostly on natural soil fertility which is low and declining. However, there are various organic materials that have the potential and can ef‐ fectively contribute to improving soil fertility within the region. JIRCAS (2010) reported the quantity, quality and distribution of various organic materials that are available and suitable for supplementing soil fertility in Ghana. In this report, Rice straw (RS), Cow dung (CD), and Human excreta (HE) were evaluated in the Northern region which is located within the Guinea savanna zone and found them effective materials that can contribute in reducing chemical fertilizer application, and to improve soil fertility. RS, Poultry manure (PM), and Saw dust (SD) were evaluated in the Ashanti region located within the Equatorial forest zone. These two climate zones are common agricultural zones where lowland rice is culti‐ vated in Africa.

RS, the commonest material within the two regions, is one of the most accessible materials to resource poor peasant farmers, because RS is produced in rice fields itself and therefore does not need to be transported. Therefore, the development of proper and improved manage‐ ment techniques of this material is essential for Ghanaian rice production.

© 2012 Nakamura et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Nakamura et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

In the Northern region, CD and HE were selected as regional materials for agricultural use. These materials have been evaluated and used in some Asian countries as having high fertilizer effects (e.g. Austin et al., 2005, Matsui, 1997). However, in Ghana, these materials are considered as non-accessible resource because of lack of proper management technology, and psychologi‐ cal reasons (Coffie et al., 2005). In Ghana, it seems that gathering plant materials in the Northern region is more difficult than in the Ashanti region. Human and/or animal resource could be col‐ lected in settlement ecosystem through some life style or system innovations.

Rock (PR) on rice yield was also investigated by setting-up three levels of phosphorus i.e. CON as control (0 kgP2O5 ha-1), BRP as (Burkina Faso phosphate rock) applied at 135kg P2O5 ha-1, and TSP as mineral fertilizer (135kg P2O5 ha-1). 36 treatments (3 x 4 x 3) and withoutorganic material (WOM) application plot at 3 levels of P application and three replication.,

Improvement of Soil Fertility with Use of Indigenous Resources in Lowland Rice Systems

http://dx.doi.org/10.5772/53209

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The quantities of the three types of organic materials applied were maintained as 3.2 kg P2O5 ha-1 at the Northern site, and applied directly to the soil surface. Compost was purchased from the market because there was not enough compost at that time. In Ashanti region, 3.2 kg P2O5 ha-1 of organic materials were applied as direct application, and 1 t ha-1 of materials were applied for pretreated organic materials. For all treatments, 30 kg N ha-1 and 30 kg K2O

Rice varieties in our trials were selected GR18 in Northern region, and Sikamo in Ashanti region. GR18 is reported to be one of the most popular varieties in Northern Ghana (Ghana Seed Company, 1988). Sikamo was recommended by Crops Research Institute (CRI), and was an improved variety for rain-fed lowlands rice cultivation, demonstrated in the 1990s

A 3-way analysis of variance (ANOVA) for rice grain yield under 36 treatments was con‐ ducted to verify the effect of organic matter application at each site, and to clarify the effect of interaction between three factors, i.e. type of organic material, pretreatment, and PR ap‐ plication. In this analysis, rice yield without organic matter application was excluded. The results of the 3-way ANOVA for rice grain yields did not show any significant difference between treatments and their interaction (Tables 1 and 2). Even though, all treatments were replicated three times, but it might not be enough to avoid specific variance of land condi‐

The plant density was at a recommended rate of 20 cm × 20cm in each site.

This gave a total of 117 plots in each station.

ha-1 was applied as basal dressing.

tion for elucidation of statistical difference.

**Table 1.** 3-way ANOVA for rice grain yield in the Northern region

by Ghana rice project.

**3. Results**

In the Ashanti region, PM and SD were selected. These materials are considered as having high agronomical potential especially in the Ashanti region. Commercial poultry farmers are generally concentrated in the Greater Accra and Ashanti regions hence almost 50% of poultry manure is produced in these two regions (Quarcoo, 1996). So poultry manure is par‐ ticularly accessible and available for rice production in the Ashanti region. SD is a byprod‐ uct material of lumbering industry which is popular in Ghana. Hence, its disposal has lately become a major problem for the government and timber industry.

This study therefore investigated the application effect of these selected organic materials on rice yield, and their proper processing methods for each organic matter application. The various processing (referred here as pre-treatment) include the following four treatments i.e. (i) ashing, (ii) charring, (iii) composting, and (iv) direct application. The effect of these four treatments on rice growth and yield were investigated. Organic materials have various forms, and each form has some advantages and disadvantages, as far as crop nutrition is concern. Therefore, this study investigated the best organic matter management option for rice production in Ghana, through the comparison of rice yield under four types pretreated i.e. ashed (ASH), charred (CH), composted (CO), or non-treated raw material (RW) organic materials application.
