Optimal P fertilization using low-grade phosphate rock-derived fertilizer for rice cultivation under different ground-water conditions in the Central Plateau of Burkina Faso

ABSTRACT

Previous studies have reported two major methods of increasing PR solubility; calcination and partial acidulation. In addition, soil water condition would influence the solubility of P fertilizers. However, the effects of local P fertilizers, namely calcined PR (CPR) and partially acidulated PR (PAPR) on rice yield under different soil water conditions have not been explored comprehensively. The aims of the present study were to evaluate the effects of local P fertilizers produced from PR in Burkina Faso under different soil water conditions and to propose local fertilizers with optimal application rates for different soil water conditions. The field experiments were conducted at four farmers’ fields with different ground-water levels (GWL). CPR, PAPR, and superphosphate were applied at rates of 0, 7.6, 15.3, and 30.5 kg P ha⁻¹, respectively. Superphosphate mostly consists of water-soluble P fraction (WP), PAPR of WP and alkaline ammonium citrate-soluble P fraction (SP), and CPR of SP and 2% citric acid-soluble P fraction (CP). The solubility is in the order of WP > SP > CP. The GWL was monitored during the growing season, and yield components were observed. Results of multiple regression analysis showed that WP influenced grain yield under all soil water conditions, whereas SP only influenced grain yied at mean GWL > −24.7 cm. Therefore, PAPR with high WP has an advantage over CPR in the field with GWL > −18.7 cm, and both CPR and PAPR are effective in fields with GWL > −6.5 cm. The optimal application rate was 14.4 kg P ha⁻¹ as WP in the field with low GWL (mean −29.2 cm), 15.2–15.9 kg P ha⁻¹ as WP + SP in the field with middle GWL (mean −24.7 to −18.7 cm), and 11.1 kg P ha⁻¹ as WP + SP in the field with high GWL (mean −6.5 cm). According to the results, the optimal fertilizer types and application rates differ according to the soil water conditions.

KEY WORDS:

• Lixisols
• Ground-water level
• Rice
• Local phosphate fertilizer
• Optimal fertilization

Acknowledgments

The authors thank local farmers and technical staff members (Mr. Mohamed Ouedraogo and Mr. Kafando Serge Placide) for supporting our field trials, as well as JIRCAS’s Soil Team for soil chemical analysis. Soil sample was imported with plant phytosanitary certificate of Ministry of Agriculture, Forestry and Fisheries.

Disclosure of potential conflicts of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was financially supported by the Science and Technology Research Partnership for Sustainable Development (SATREPS), Japan Science and Technology Agency (JST)/Japan International Cooperation Agency (JICA) (Project on establishment of the model for fertilizing cultivation promotion using Burkina Faso phosphate rock).