Effectiveness of neem materials and biochar as nitrification inhibitors in reducing nitrate leaching in a compost-amended Ferric Luvisol
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Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
Frontiers in Soil Science
Abstract
The nitrates produced after mineralization from compost may be prone to
leaching, especially in tropical sandy soils, because of the increased rate of
nitrification and the porous nature of such soils. This may result in low nitrogen
(N) use efficiency and adverse environmental effects. Inorganic nitrification
inhibitors are costly and mostly unavailable in Ghana. Research on simple but
effective local materials for use as nitrification inhibitors is therefore a priority.
Two such materials are neem materials and biochar. Neem materials can
suppress nitrifying bacteria due to their antimicrobial properties. Biochar can
hold ammonium in the soil, making it temporarily unavailable to nitrifying
bacteria. This study aimed to determine the efficacy of neem materials and
biochar as nitrification inhibitors and their influence on nitrate leaching. In
preliminary studies: 1) pot incubation was conducted for 60 days to estimate
the nitrification rate with manure, compost, and NH4Cl as the N source (150 kg
N/ha) in one set and neem seeds, bark, and leaves (1.25 µg azadirachtin/g) in
another set, using nitrate concentrations; and 2) the ammonium sorption and
desorption capacities of sawdust, rice husk, and groundnut husk biochar were
determined. In the main study, pot incubation with compost as the N source
but treated with milled neem seeds or bark (1.25 µg azadirachtin/g) or sawdust
biochar (20 t/ha) was conducted for 60 days, in which the nitrification inhibition
was determined using nitrate concentrations. A leaching experiment in
columns with similar treatments and maize sown was then conducted to
quantify the nitrate in leachates. A high nitrification rate was recorded in
compost-amended soil, almost half that of the standard (NH4Cl). The use of
sawdust biochar, which showed the highest ammonium sorption and
desorption capacity, resulted in 40% nitrification inhibition that lasted the
entire incubation period. The use of neem seeds with an azadirachtin
concentration of 3.92 mg/g resulted in a similar nitrification inhibition, but this only lasted 40 days. Inhibition caused by both materials resulted in about a
60% reduction in nitrate leached. Thus, neem seeds (498 kg/ha) and sawdust
biochar (20 mt/ha) could be used to control nitrate leaching for short-duration
and long-duration crops, respectively
Description
Research Article
Keywords
leaching, nitrification, azadirachtin, inhibition
Citation
Abeka H, Lawson IYD, Nartey E, Adjadeh T, Asuming-Brempong S, Bindraban P and Atakora WK (2022) Effectiveness of neem materials and biochar as nitrification inhibitors in reducing nitrate leaching in a compost-amended Ferric Luvisol. Front. Soil Sci. 2:1023743. doi: 10.3389/fsoil.2022.1023743