**4. Conclusions and recommendations**

The application of poultry manure resulted in higher yield except ASH and CH under CON treatment. However, ASH-PM showed low yield (5.20 t ha-1) under CON treatment, but

Under the SD application, RW-SD produced a lower value compared with other SD application. RW-SD under all three P treatments showed a similar yield as WOM (Effectiveness against WOM: 1.05 at CON, 0.95 at BRP, 0.98 at TSP). Only the RW-SD did not show the positive effect of organic matter application on rice yield. The RW-SD in Ashanti region was direct application of woody material for submerged condition. So, decomposition rate and plant nutrient release rate

**3.3. The combination effect of various organic materials and phosphate rock application**

The agronomic efficiencies to TSP under various organic matter applications are shown in Table 5. Agronomic efficiency was calculated from the difference in grain yield (t ha-1) of PR to those of TSP treatment. This efficiency can be considered as the indicator of BRP being a possible alternative to TSP. According to FAO (2004), BPR direct application showed 97% of

Under this study and within the Northern region in Ghana, the agronomic efficiency of BPR direct application against TSP was relatively lower in WOM, RW-RS, ASH-HE (54, 66, 62%, respectively). Treatments of ASH-RS, RW-CD, CO-CD, CH-HE, CO-HE showed efficiency of over 120%, suggested that combined application of PR and organic materials was effective in PR application. It is well known that organic matter application is one of the effective techniques to solubilize PR. This may be so due to PR dissolution in organic acids produced by microorganisms, through decomposition of easily decomposable organic substances.

On the other hand, within the Ashanti region, only CO-SD showed a lower value (71%). The other treatments including WOM gave similar trend with higher values that ranged from 84% to 118%. This result shows that agronomic efficiency did not increased by organic mat‐ ter application. These results do not only indicated that BPR can be use directly as alterna‐ tive fertilizer, but also indicated that there are not clear positive effects of organic matter

RS: rice straw, CD: cow dung, HE: human excreta, PM: poultry manure, SD: saw dust, WOM: without organic material,

**Table 5.** Effect of various organic material application on changes of agronomic efficiency (%) in BPR direct

showed high yield under BPR and TSP treatments (6.83 and 7.20 t ha-1), respectively.

seemed to be extremely slow, and thus causing nitrogen starvation for the treatment.

agronomic efficiency in lowland rice cultivation.

40 Soil Fertility

application on PR agronomic efficiency enhancement.

ASH: ashing, CH: charring, CO: composting, RW: raw material directly applied

application against TSP application

Rice grain yields generally increased with the application of the various organic matters. Grain yields under organic matter application showed approximately 1.5 to 1.6 times higher than those of WOM in Northern region, and 1.1 to 1.2 times higher than WOM in Ashanti region. However in some case e.g. RW-SD, did not show any positive effect of application on rice yield, and so the proper pretreatment for each organic resources need to be selected.

### **4.1. Suggestion for indigenous organic material application in Northern region, for rainfed lowland rice cultivation in Savannah zone**

The best promising organic material for agricultural use in Northern region is rice straw (RS). CO-RS and RW-RS treatment showed high positive effect on rice yield in the Northern region trial. It seems adequate amount of mineral plant nutrients were supplied due to de‐ composition of RS and that soil physical and biological properties were enhanced. On the other hand, CH-RS and ASH-RS also showed positive effect on rice yield, however, it should be considered that charring needs input of labor and capital, and that ashing will im‐ pact the environmental negatively. Moreover, ashing process can reduce effectiveness of soil physical and biological properties observed under CO and RW application.

CD application showed high yield in all pretreated plots. It is well known that CD appli‐ cation is effective for rice production. In the Northern region, however, it is far from rec‐ ommended materials because of difficulty in material gathering. Most of CD in this region was produced by cattle grazing, that means farmer needs to collect CD scattered through‐ out savannah forest. This study indicated that CD has similar effect on rice yield com‐ pared with other organic materials. The use of CD in rice cultivation can be as popular as RS due to both availability and accessibility. While RS is readily available in the rice fields extra labour is require to search and collect CD. However, after using CD as fuel CH-CD and ASH-CD can be used in rice production since these materials increased rice yield sig‐ nificantly.

Rice yields average of HE application was almost same as those of CD. Improvement of crop productivity has been reported by many existing studies. However it also has been men‐ tioned that HE usage has difficulty to diffuse for farmers because of hygienic risk and psy‐ chological avoidance. These obstacles can be resolved by either combustion process such as CH and ASH, or composting process. CO-HE indicated highest yield among four pretreat‐ ment in HE treatments, the yield was almost twice higher than WOM.

According to the results from Northern region trial, authors suggest that CD and/or HE composting based on RS usage should be well examined as the effective and affordable technical options for farmers. HE composting still have the difficulty of gathering, but technology introduction on collecting and separating urine and feces, such as Eco-San toi‐ let, will open the way for proper management of HE, especially in Northern region. More‐ over CD and HE composting based RS can be expected to increase RP application effect on rice yield.

#### **4.2. Suggestion for indigenous organic material application in Ashanti region, under water controlled lowland rice cultivation in Equatorial forest zone**

**Author details**

Satoshi Nakamura1

Satoshi Tobita1

Ibaraki, Japan

Tamale, Ghana

**References**

Mohammed Moro Buri2

, Roland Nuhu Issaka2

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1 Japan International Research Center for Agricultural Sciences (JIRCAS), Ohwashi, Tsukuba,

3 University for Development Studies (UDS) Faculty of Agriculture, Department of Agronomy,

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

Similar to what was observed in Northern region, the use of RS is considered as an effective resource for rice production in Ashanti region, because of its high accessibility. However, unlike the Northern region, RW-RS in Ashanti region showed a smaller effect on rice pro‐ duction than the other treatments. Most rice fields in Ashanti region are irrigated and can be used to cultivate throughout the year. Therefore, rice fields are generally maintained under submerged condition for long periods hence decomposition rate of organic matter will be relatively slow. Hence, RW-RS application is discouraged because its effect on rice yield is not pronounced, and a possible risk of nitrogen starvation.

Poultry manure with every pretreatment showed high positive effect on rice yield enhance‐ ment, especially in CO-PM. Poultry manure is a popular organic material that is an effective P source, and that is highly accessible in the Ashanti region.

In the SD treatment, RW-SD showed lower value (5.47 t ha-1) than WOM of rice yield (5.52 t ha-1). Similar to RW-RS, direct application of SD generally has the problem due to its high C/N ratio. Moreover SD composting is also difficult because SD consist of woody material that contains resistant organic matter. To avoid plant damage by organic acids and/or nitrogen starvation, SD composting needs to take a long time for decomposition and fermentation. Combustion treatment, which take shorter time and is easy to practice (CH and ASH) is affordable and effective for agricultural usage in Ashanti region. The possibility of composting through inoculation with microorganisms should not be exclud‐ ed from future investigation.

In the organic material application in Ashanti region, all treatment except direct application of RS and SD showed positive effect on rice grain yield. It is suggested that ASH-RS, CH-RS, ASH-SD, CH-SD, and composting RS or SD combined with PM, and also RW-PM, are evalu‐ ated as promising technical options that are accessible and effective for rice cultivation in Ashanti region. These selected options showed relatively high value not only in rice yield but also in agronomic efficiency of BPR application. The effect of organic material applica‐ tion on enhancement of PR solubility was smaller compared with the effect observed in Northern region. However, direct application of PR in this region indicated high agronom‐ ical efficiency to TSP application, and means PR has possibility of alternative usage against TSP. Further investigation need to be conducted on the effect of RP combined with organic material application on rice yield.
