Abstract

Highly weathered tropical acidic soils are characterized by low pH, low organic matter, and aluminium and iron toxicity. These factors pose a challenge to achieving sustainable agriculture. The continued increase in the human population with the accompanied increasing food demand have negatively impacted the global N cycle partly because of excessive use N fertilizers particularly urea which is commonly used in agriculture. Ammonia volatilization from urea as an example, negatives the environmental quality. This study focuses on soil-N availability, pH, exchangeable acidity, Al3+, and H+ of a highly weathered acid soils (Bekenu series) through the combined use of charcoal, sago bark ash, and urea. To this end, an incubation study was conducted for 90 days through the combined use of charcoal, sago bark ash, and urea to determine if this approach could improve soil N availability and pH at the same time reducing exchangeable acidity, and Al3+, and H+ toxicity. The amount of urea used was fixed at 100% as the recommended rate. Charcoal and sago bark ash were varied by 25%, 50%, 75%, and 100%, respectively of the recommended rate. Selected soil physico-chemical properties were determined using standard procedures. This study revealed that combined use of charcoal, sago bark ash, and urea increased soil pH and base cations simultaneously the approach also reduced exchangeable acidity, exchangeable Al3+, and exchangeable H+. There were no significant differences in soil total N, exchangeable NH4+, and available NO3− for the combined use of charcoal, sago bark ash, and urea and urea alone because of the acid neutralizing effect of the amendments. Apart from the sago bark ash’s liming effect, the high affinity of the functional groups of the charcoal for Al3+ might have impeded Al3+ from undergoing hydrolysis to produce more H+ because a complete one mole of Al3+ hydrolysis produces three moles of H+. Thus, the combined use of charcoal and sago bark ash can mitigate soil acidity and aluminium toxicity, although this approach has minimal effect on-N.

Highlights

  • Ammonium is the predominant source of N which is commonly available for plant nutrition the average of NH4 + concentration of soils is often lower than nitrate (NO3 − ) [4]

  • It was hypothesized that the combined use of sago bark ash, charcoal, and urea could improve soil pH and urea-N availability through reduction exchangeable acidity, Al3+, and H+

  • There were no significant differences in the total C for soil60 only (S0), U1, and A1 regardless of the incubation period

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Summary

Introduction

Adsorption of NH4 + ions on bark ash exhibits intermediate adsorption capacity compared with charcoal, it has the potential to reduce nutrient loss in addition to being ideal for highly weathered acidic soil because of its acid neutralizing properties. This present study attempts to answer the question of whether amending urea with charcoal and sago bark ash could significantly improve soil pH and N availability in addition to reducing exchangeable acidity, Al3+ , and H+ of highly weathered acid soils. It was hypothesized that the combined use of sago bark ash, charcoal, and urea could improve soil pH and urea-N availability through reduction exchangeable acidity, Al3+ , and H+

Materials and Methods
Selected physicochemical properties ofused the soil used in the incubation
Characterization of Charcoal and Sago Bark Ash
Incubation Study Set Up
Experimental Design and Statistical Analysis
Results
Amending
12. Treatments
Effects of Treatments on Selected Soil Physicochemical Properties
Conclusions
Full Text
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