Efficacy of Fortified Molasses Waste-Water as Hydroponic Nutrient Solution for Growing of Spinach and Barley

Abstract

Muhoroni Sugar Processing Industry is a significant sugar factory in western part of Kenya. It produces huge volumes of molasses waste-water which poses challenges of pollution of water bodies and affects plant life and other organisms. Molasses wastewater is known to have substantial amounts of nutrients and has been suggested as an alternative to commercial hydroponic fertilizers. However, its efficacy as a nutrient solution has not been evaluated scientifically. This study therefore aimed at investigating its efficacy as a hydroponic solution for growing vegetables and fodder crops in a greenhouse. Greenhouse experiments were carried at the Christian Industrial Training Centre – Kapsabet in Nandi County (0.2030° N, 35.0978°). Macro-nutrients present in molasses waste-water were determined and the deficiencies remedied by fortifying with appropriate amounts of nitrogen, phosphorous and potassium (NPK) fertilizer. The standard Walkey black rapid titration was used to determine total organic carbon. Potassium and calcium were determined using flame photometry. Nitrogen and phosphorous were determined by colorimetric analysis. Magnesium was analysed using atomic absorption spectroscopy. Uv/vis spectrophotometry was used to determine the presence of sulphur.The study established that molasses waste-water has greater levels of potassium, calcium, sulphur, magnesium and carbon of 230.0 ± 1.00 mg/L, 25.9 ± 0.39 mg/L, 4.4±0.07 mg/L, 0.04 ± 0.01 mg/L and 37.3 ± 0.67%, respectively compared to commercial hydroponic nutrient solutions. Low nitrogen and phosphorus content in molasses waste-water was improved to 74.3 ± 0.18 and 47.6 ± 0.01 mg/ L, respectively. The greenhouse experiments were set up in triplicate using a Complete Randomized Block Design (CRBD). The hydroponic nutrient solutions used included molasses waste-water (MW) and fortified molasses waste-water (FMW) with commercial hydroponic nutrient solution (HN) as the control experiment. Barley was grown by improvised nutrient film (NFT) technique whereas spinach was grown in static solution culture using sand growing media. Plant growth parameters which include plant height, stem girth and leaf length were measured every after 2 days in barley and every after 7 days in spinach. The levels of macro-nutrients in plant tissues were determined in the harvested crops. The plants grown in fortified molasses waste-water showed the highest growth parameters; mean plant height of 13.0± 0.38cm, mean stem girth of 9.23 ± 0.43 mm and mean leaf length of 5.6±0.17cm in barley, mean plant height of 20.97 ± 0.18 cm, mean stem girth of 16.2±0.12 cm and mean leaf length of 13.0±0.38 cm in spinach. Mean fresh weight of 0.6±0.06 kg for spinach and 12.0 ± 0.57 kg for barley grown in fortified was obtained. Crops grown in fortified molasses waste-water also recorded the highest values of macro-nutrients at 210.6± 0.07 and 205.9 ± 0.14 mg/kg nitrogen, 94.9 ± 0.01 and 90.7± 5.79 mg/kg phosphorus, 3.3 ± 0.05 and 6.4 ± 0.01mg/kg magnesium, 632.7± 7.54 and 616.5± 2.30 mg/kg potassium, 48.8±0.71 and 38.0±0.34 mg/kg calcium and 15.8±0.04 and 15.8±0.05 mg/kg sulphur in spinach and barley, respectively. Organic carbon content was also highest in spinach and barley grown in fortified molasses waste-water at 84.0 ± 1.15 and 82.7 ± 0.67% respectively. The results show that molasses waste-water contains adequate amounts of potassium, calcium, sulphur and magnesium macro-nutrients essential for plant growth but lacks sufficient nitrogen and phosphorus. Appropriate amendments in the amounts nitrogen and phosphorus macro-nutrients make it efficacious for application as a hydroponic solution for growing crops and, therefore, a possible alternative to commercial hydroponic nutrient solution.