Protein content was determined by the Micro-Kjeldahl method
in triplicate, using a factor of 6.25 for transformation of total nitrogen into proteins as recommended by the AOAC (2010).
Moisture, ash, crude fat and crude fibre were determined in accordance with AOAC (2012), while nitrogen was determined by the micro-kjeldahl method
and the percentage of nitrogen was converted to crude protein by multiplying by 6.25.
The centesimal composition was determined in triplicate by means of the following analyses: Moisture; Total nitrogen, according to the micro-kjeldahl method
; Total lipids, by Soxhlet, and ash (AOAC, 2010).
Total Kjeldahl nitrogen (TKN) and total organic carbon (TOC) were estimated by using a Micro-Kjeldahl method
(21) and partial-oxidation method (22) respectively.
The samples were wet digested and then analysed for nitrogen using the micro-kjeldahl method
, phosphate using sodium molybdate and bases using 2.5% EDTA method.
The total N content was measured by the micro-Kjeldahl method
; while the phosphate determination was carried out by the vanadomolybdate phosphoric acid color method; and an atomic absorption spectrophotometer was used to measure the potassium after wet digestion with HN[O.sub.3].
Protein content was estimated by Micro-Kjeldahl method
and oil content was determined by the Soxhlet extraction method using petroleum ether (BP 40-60[degrees]C).
The percent of total nitrogen in the soil, determined by the micro-Kjeldahl method
, was 0.22.