Evaluation of agro-industrial by-products as nutrient source for plant growth

Abstract

Nutrient leaching from dry (COD) and wet (COW) coffee, sisal (SIS), brewery barley malt (BEB) and sugar cane (FIC) by-products, and linseed (LIC) and niger seed cakes (NIC), and uptake by maize were studied in a pot experiment with tropical Alfisol. After three months, soils were leached to recover labile plant nutrients, and root and shoot biomass was harvested. The leachate from FIC-amended soil had the highest concentration of inorganic P (0.90 μmol L⁻¹), whereas the highest concentrations of potassium (K) (48,088 μmol L⁻¹) and calcium (2566 μmol L⁻¹) were determined in leachates from COD and BEB treatments, respectively. The amendments significantly increased K uptake by maize proportional to the amount of K applied, but the effects for other plant nutrients were small. The results indicated that pre-decomposition of agro-industrial by-products may increase the nutrient release in tropical soils.

Keywords:

• nutrient uptake
• nutrient leaching
• phosphorus
• tropical soil
• maize

Acknowledgements

The German Academic Exchange Service (DAAD) provided a fellowship for W. Negassa. We are grateful to Dr A. Schlichting, and Mrs M. Hopp, Institute for Land Use, University of Rostock, for their technical support during experimental set up and laboratory analyses. We also acknowledge two anonymous reviewers for their constructive comments and suggestions.