Using Biochar To Reduce Leaching And Enhance Nitrogen Uptake In Two Ghanaian Soils

Abstract

In recent times the use of biochar as soil amendment has been proposed as one of the ways for reducing nitrogen leaching particularly in sandy soils because it has the potential to retain cations and anions. Three different biochar types (sawdust, rice husk and corn cob) pyrolysed at 400°C were tested in the laboratory to investigate their retention capacity for NO3- and NH4+. One hundred and fifty grams (150 g) of each biochar was packed into acrylic cylinders to create biochar column. The soluble cations in these biochar types were then leached out completely. Three nitrogen fertilizer solutions (ammonium sulphate, potassium nitrate and ammonium nitrate) prepared at 1.36 g N per litre were allowed to pass through the column and leachate collected to determine NO3-N and NH4+N. Results from the column leaching experiment showed that the sawdust biochar had superior retention capacity for NO3- and NH4+. This could be due to its relatively higher surface area when compared to the other biochar types. In another experiment in the screen house, the sawdust and rice husk biochar types were applied at 0, 20 and 40 t/ha and treated with different N sources (cow dung and ammonium sulphate; 265 N kg/ha) in two soils, Keta series (Quartzi Psamment) and Nyankpala series (Plinthic Acrisol) and maize was grown for five weeks. During the growth period the treated soils were leached at 14 and 28 days after planting to determine the quantity of available nitrogen (N) leached out. Biochar amendment of the soils reduced leaching of NO3-N and NH4-N, indicative of their ability to retain N in the soils. The amendment also enhanced dry matter production and N uptake by maize, therefore biochar amendment is recommended for reducing leaching. It was also recommended that the experiment should be conducted under field condition.