An Investigation Into the Short-Term Effects of Biochar on Nitrate Leaching From Artificial Columns of Sand

Daniel Sombo

doi:10.5539/jas.v10n5p24

Abstract

Leaching of NO3 has been shown to be a major problem in coarse-textured sandy soils. It has been suggested that biochar application to sandy soils could reduce leaching of NO3. However, how biochar could be used to provide short-term NO3 leaching reduction in sandy soils has received little research attention. Therefore, the aim of this study was to determine if and how biochar could be used to reduce NO3 leaching from artificial columns of sand (sandy soil). To achieve this, a simple assay was developed in a controlled temperature room to assess the short-term impacts of biochar on NO3 leaching from a column containing sand. The capacity to pick-up variations in NO3 leaching pattern from the sand columns based on the concentrations of the NO3 solutions used to perfuse the sand columns, as well as, the rate at which these solutions were perfused through the sand columns using this approach was initially established. A pulse chase experiment showed that the NO3 was very mobile, and once the supply was removed, the column of sand rapidly lost the NO3. The exception appears to the inclusion of biochar where this process is slowed down, but eventually the sand column lost all the NO3. When oak biochar produced through high temperature pyrolysis (500-600 oC) by a commercial producer (Humko, d.o.o., Bled Sheenjek, Slovenija) was applied to the sand columns at a rate of 10% (w/w), the pattern of NO3 leaching was modified. Biochar appeared to delay NO3 leaching from the sand. The extent of this delay, and how it may influence NO3 availability in the soil for plant uptake requires further research.

Highlights

Nitrogen is one of the most essential elements that supports all life in the biosphere (Bernhard, 2010)
The aims of this study are intended to answer the following research questions: 1) can biochar be used to reduce NO3 leaching in coarse-textured sandy soils? and 2) can biochar offer short-term NO3 leaching reduction in coarse-textured sandy soils when N fertilizers are applied during high rainfall seasons such as in the winter? The objective of this study is to contribute to the expansion of our knowledge and understanding on how biochar may offer short-term NO3 leaching reduction in coarse-textured sandy soils
The concentration of the NO3 in the leachates from the sand only columns declined rapidly (0.04 mmol L-1 minute-1) (Figure 4 and Table 3) from about 2.20±0.03 mmol L-1 on the 25 minute to about 0.04±0.02 mmol L-1 on the 60 minute when these NO3 saturated sand columns were perfused with deionised water at a rate of 7.7 ml min-1

Summary

Introduction

Nitrogen is one of the most essential elements that supports all life in the biosphere (Bernhard, 2010) It is an essential constituent of most biological molecules in plants and animals, including RNA and DNA, ATP, chlorophyll, proteins, enzymes and hormones (Vitousek et al, 2002; Rachmilevitch, 2004; Pidwirny, 2006; Bernhard, 2010). In the atmosphere, it is the most abundant gas (78%), but in most soils, it is the most limiting element for plant growth (Bernhard, 2010). Applications of nitrogen fertilizers are used to supplement the plants’ nitrogen requirement in the soil (Cameron et al, 2013)

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