**2. Materials and methods**

#### **2.1. Research site**

Ghana has several agro-ecological zones but these can be broadly categorized into forest and savannah. The experiments were conducted at the University of Development Studies (UDS; N 09°24'19", W 000°58'14") located in the Northern region which lies within the Guinea sav‐ annah agro-ecological zone, and at the CSIR - Soil Research Institute (SRI; N 06°45'18", W 001°35'30") which is in the Ashanti region and within the forest agro-ecological zone of the country. At UDS, the effect of rice straw (RS), cow dung (CD), and human excreta (HE) ap‐ plication on rice yield were investigated. At the CSIR-SRI, the effect of RS, poultry manure (PM), and saw dust (SD) application on rice production was evaluated.

#### **2.2. Treatments**

Three types of organic materials that are potentially available were selected, for study site. Each of the organic material was applied to rice on the fields after pretreatment into ash (ASH), charr (CH), compost (CO), and untreated raw material (RW). The effect of Phosphate 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., This gave a total of 117 plots in each station.

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 ha-1 was applied as basal dressing.

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 by Ghana rice project.

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