Effects of NPK and biochar fertilized soil on the proximate composition and mineral evaluation of maize flour

Abstract

Series of farming practice methods have been employed to increase maize production but there is no adequate information on the effect of these methods on the nutritional and mineral content of organically grown maize. This study investigated the effects of inorganic and biochar fertilized soils on the proximate composition and mineral content of maize. Maize seeds were planted on organically fertilized soil (sawdust and gliricidia biochar), chemically fertilized soil Nitrogen Phosphorus and Potassium (NPK fertilizer), and soil without any amendment as control. The proximate compositions (protein, ash, crude fat, carbohydrate, and moisture) and mineral contents (Na, Mg, K, Ca, Fe, and Zn) of the maize flour samples were determined using standard methods. The results showed that protein content ranged from 4.58% to 7.24% (protein), ash 0.82% to 1.09%, crude fat 3.84% to 4.61%, moisture 9.76% to 10.60%, and carbohydrate 76.85% to 80.31%. There was no significant (p ≤ 0.05) difference among the proximate compositions except for protein and carbohydrate. Maize planted on NPK fertilized soil had the highest crude protein content of 7.24%. Other results obtained included sodium (55.65 mg/100 g), magnesium (35.87 mg/100 g), and iron (6.78 mg/100 g). Maize from soil without amendments was significantly higher than maize from NPK fertilized and biochar fertilized soils. Also, maize from control plot had the highest calcium content value of 48.95 mg/100 g. We concluded that maize planted with NPK fertilizer had higher nutrient than those planted with biochar application. Also, the mineral content of maize planted in control plot was higher than those on the amended soil.

Keywords: NPK fertilizer; biochar (sawdust and gliricidia biochar); maize; mineral evaluation; proximate composition.

Figure 1

Flowchart of maize flour preparation from maize grains