NPK-Liquid Fertilizer Based on Humic-Like Substances Extracted from Spent Coffee Grounds: Extraction, Preparation and Application to Maize

Abstract

Reuse of agricultural waste materials is a smart solution for reducing their environmental impacts and increase economic value. Spent coffee grounds (SCG) is worldwide generated in tremendous amounts. The objectives of this study were to optimize a method to extract humic-like substances (HLS) from SCG using KOH extractant, prepare a liquid organic-mineral fertilizer enriched with N and P in addition to K, and to evaluate this fertilizer on growing maize (Zea mays L.). HLS extracted from SCG increased with KOH concentration up to 3 N and with extraction ratio up to 1:10 at room temperature. Increasing the temperature to 50 and 80 °C and contact time up to 3 h, significantly enhanced HLS recovery. Therefore, the optimum conditions for maximum HLS extraction were; 2 N KOH, SCG-to-extractant ratio of 1:10, 3 h of contact time, and 80 °C. Adjusting the pH of the alkaline K-HLS supernatant to pH 6 was achieved using a mixture of HNO 3 and H 3 PO 4. The prepared NPK mineral-organic fertilizer (NPK-HLS) was dark brown containing 2.0/5.8/8.6 as N/P 2 O 5 /K 2 O and 5.1 %w/v HLS. The produced fertilizer was evaluated for its effect on maize plants grown in a calcareous soil low in available nutrient using a CRBD pot experiment. Two application rates of NPK-HLS (NPK-HLS1 and NPK-HLS2) based on P rates, 125 and 250 mg P pot-1 , with and without a basic fertilizer (BF) were applied. Both NPK-HLS1 and NPK-HLS2 rates significantly increased shoot dry matter, NPK uptake and availability in soil compared to the control, but did not significantly affect root dry matter. Increasing the application rate to NPK-HLS2 did not further increase dry matter or NPK uptake. No significant effect was found for BF for all measured variables. Results of this study showed that the extraction of HLS from SCG and its incorporation into a liquid fertilizer could be an alternative solution to the reuse of SCG.

Effect of Potassium Humate Application on Yield and Nutrient Uptake of Maize Grown In a Calcareous Soil

“…The effects of humic materials on plant growth are well reported in many studies (Chen and Aviad, 1990;Fagbenro and Agboda, 1993;Ihsanullah and Bakhashwain, 2013). The enhancement in nutrient uptake due to applying humic materials was also reported in numerous studies (Chen and Aviad, 1990;David et al, 1994;Kamh and Hedia, 2018).…”

Advances in Production of Hydroxycinnamoyl-Quinic Acids: From Natural Sources to Biotechnology

“…The extraction of HCQAs results in large amounts of the residual plant material. Aiming for the sustainable circular economy and resource conservation, these residues can be utilized for combustion [ 112 ], as a biofuel (e.g., biodiesel, bioethanol, biochar and liquid pyrolysis product production) [ 113 , 114 , 115 ] or other applications [ 60 , 113 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 ] ( Figure 4 ), which allows for reducing the solid waste amount and/or covering up to 100% of phytoremediation cost [ 124 , 125 ].…”

Maize Growth and Yield Response to Different Rates of Humic Acid and Zinc

“…Dowswell (2019) reported that average maize grain yield in developed and developing countries are (6.2 and 2.5 t/ ha), respectively, and this discrepancy may be due to technological, environmental and organization of crop. Many researchers such as Tahir et al (2011) and Al-Mahdi et al (2021), Kamh and Hedia (2018) and Humintech (2012) reported that humic acid is very important for plant growth, mineral nutrition, uptake of macro and micronutrients and reducing the uptake of some toxic elements. Humic acid, also could counteract abiotic stress conditions as pH, salinity and unfavourable air temperature (Masciandaro et al, 2002).…”