Solubility and application effects of African low-grade phosphate rock calcinated with potassium carbonate |
| |
| Authors: | Satoshi Nakamura Takashi Kanda Toshio Imai Jacques Sawadogo Fujio Nagumo |
| |
| Institution: | 1. Japan International Research Center for Agricultural Sciences (JIRCAS), Crop Livestock and Envrionment Division, Tsukuba, Japannsatoshi@affrc.go.jp;3. Japan International Research Center for Agricultural Sciences (JIRCAS), Crop Livestock and Envrionment Division, Tsukuba, Japan;4. Central Research Laboratory, Taiheiyo Cement Corporation, Sakura, Japan;5. l’Institut de l’Environnement et de Recherches Agricoles (INERA) INERA/Kamboinse, Ouagadougou, Burkina Faso |
| |
| Abstract: | This article indicates solubility improvement of African low-grade phosphate rock (PR) through calcination with potassium carbonate. We showed calcination with potassium carbonate made its citric acid solubility up to 100%, and reinforcement of its application effect. In sub-Saharan Africa, although many phosphate deposits have been found, farmers are facing high prices of P fertilizers because of the low solubility of the African PRs. We previously reported PR calcination with Na carbonate improves the solubility, but their application produced limited crop growth, especially in upland conditions. It was speculated soil Na accumulation caused plant growth inhibition. Therefore, we tried to elucidate the effect of calcination with potassium carbonate on PR solubility and its application effects for lowland rice and maize through pot experiments. We used Kodjari PR produced in Burkina Faso for the calcination. Powdered PRs were mixed with K2CO3 in five doses to achieve the target K2O compositions of 200, 250, 300, 350, and 400 g kg-1. The pelletized PR-K2CO3 mixtures were calcined at 900, 1000, 1050, and 1100 °C for 10 min. The pot experiments were conducted for 56 days, monitoring the growth of rice and maize under several application rates. Calcination with K carbonate generated K-rhenanite (KCaPO4) and kaliophilite (KAlSiO4), and the solubility reached about 100% in 20 g L-1 citric acid and about 40% in water. This shows that K carbonates behave like Na carbonate in the solubilization of Kodjari PRs. Although the calcinated Burkina PR (CB) application significantly reduced plant growth when it was applied at an excessive rate, reduced application rates yielded comparable plant growth to that of triple super phosphate (TSP). K carbonate calcination deterred Na accumulation in the soil, and it was effective for plant growth. However, CB easily causes plant damage in excessive application, and it may contain phytotoxicant substances. |
| |
| Keywords: | Burkina Faso calcination fertilizer maize rice |
|
|
