Amending triple superphosphate with chicken litter biochar improves phosphorus availability

Headnote

Article Info

Received : 09.07.2017

Accepted : 18.09.2017

Abstract

The reaction of H₂PO₄^2- and HPO₄^- with Al and Fe in acid soils to form a precipitate reduces P availability. Chicken litter biochar has been used to improve soil P availability for maize production but with limited information on optimum rates of biochar and Triple Superphosphate (TSP) to increase P availability. This study determined the optimum amount of chicken litter biochar and TSP that could increase P availability. Different rates of chicken litter biochar and TSP were evaluated in an incubation study for 30, 60, and 90 days. Selected soil chemical properties before and after incubation were determined using standard procedures. Soil pH, total P, available P, and water soluble P increased in treatments with 75% and 50% biochar. Total acidity, exchangeable Al³⁺, and Fe²⁺ were significantly reduced by the chicken litter biochar. The chicken litter biochar also increased soil CEC and exchangeable cations (K, Ca, Mg and Na). The use of 75% and 50% of 5 t ha^-1 biochar with 25% TSP of the existing recommendation can be used to increase P availability whilst minimizing soil Al and Fe content. This rates can be used to optimize chicken litter biochar and TSP use in acid soils for crop production especially maize and short term vegetables.

Keywords: Incubation period, interaction, optimization, phosphorus fertilizers, phosphorus fixation, tropical acid soils.

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Introduction

Orthophosphates are essential macronutrients which when taken up by plants as soluble inorganic P regulate protein synthesis (Mkhabela and Warman, 2005). Phosphate availability and use efficiency is poor in acid soils (Oxisols and Utisols) because of Al and Fe ions. Aluminium and Fe ions have been implicated in P fixation (Adnan et al. 2003; Ch'ng et al. 2014a,b, 2016a,b,c). The reaction of H₂PO₄^2- and HPO₄^- with Al and Fe ions to form a precipitate reduces diffusion of P into plant roots (Adnan et al., 2003) and conventionally, large amounts of lime and P fertilizers such as triple super phosphate (TSP) and rock phosphates are applied to acid soils to saturate Al and Fe ions (Ch'ng et al. 2014a;...