Enhancement Effect of Cassava Starch Manufacturing Wastes on Availability and Fate of P from Thai Phosphate Rocks in Sandy Typic Paleusults: An Incubation Study

ABSTRACT

Direct application of phosphate rock (PR) can be an alternative to phosphorus (P) fertilizer in highly weathered tropical soils, but the low solubility of PR obstructs its use. The use of cassava peel (CP) and cassava starch waste (CSW) to enhance two Thai PRs (Kamphaeng Phet, KP-PR; 20.3% P₂O₅ and Lamphun, LP-PR; 14.7% P₂O₅) was investigated for P availability in two sandy Typic Paleusults in laboratory. Both PRs had low reactivity but similar dissolution behavior as most P dissolved in 2% formic acid (22.2% and 19.0%, respectively, of total P₂O₅). The CP promoted better PR solubility than did the CSW, resulting in significantly more available P in the soils but P majorly occurred in moderately labile and chemically relatively stable fractions. The labile fraction was still lower than other forms of soil P, especially NaHCO₃-Po, but both wastes, especially CP, increased NaHCO₃-Pi and -Po to some extent while the soluble Pi (NH₄Cl-Pi) became more soluble after 4 months. The relative distributions of the Pi and Po fractions varied over the incubation period with no definite trends detected, but the PR and wastes were correlated variably in all P fractions.

KEYWORDS:

• Cassava peel
• cassava starch waste
• organic waste
• phosphate rock dissolution
• red tropical soils

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was mainly supported by the Kasetsart University Research and Development Institute (KURDI), Kasetsart University (FF(KU)5.65), and partly funded by a Graduate Scholarship for International Publication, Kasetsart University, and the Thai Challenging Fund for Natural Resource and Environment Development.