COMPARISON OF EFFECT OF STRUVITE PREPARED FROM SOURCE-SEPARATED HUMAN URINE WITH INORGANIC FERTILIZER ON AMARANTHUS CAUDATUS

Abstract

In Nigeria, use of urine for fertigation has been limited because of its liquid form, odour and the unsanitary disposal methods. This poses great hazard to man and the environment. Converting urine into dry fertilizer product (struvite) helps extract nutrients contained in urine and also eliminates handling problems. The study was aimed at converting urine to struvite and comparing its effectiveness on plant growth with inorganic fertilizer (NPK).

The study involved the extraction of struvite from human urine and its use as fertilizer for raising Amaranthus caudatus in a screen house. Fourteen students selected randomly from the students' hostel at the University College Hospital produced 100 litres of urine which was stored for three months in order to reduce the microbial load. Triplicate samples of fresh and stored (stale) urine collected from the same set were analyzed for physico-chemical [pH, ammonia (NH3), nitrogen (N), phosphate (PO43-) and potassium (K)] parameters using standard methods at the point of collection and three months after. Magnesium Chloride (MgCl2) with concentrations: 1.2M, 1.5M and 1.8M was added to 20 litres of stale urine to produce struvite of varying concentrations. Amaranth vegetable seeds were planted in 15 pots (of three replicates each) containing 2kg of soil treated with struvite and inorganic fertilizer while soil without either struvite or inorganic fertilizer was used as control. Plant height and stem width were measured and number of leaves were counted the second week of planting. Plants were harvested after the fourth week; with the wet and dry weight of the leaves, stem and root taken. Data were analyzed using descriptive statistics, t- test and ANOVA at p=0.05.

Mean pH of fresh and stored urine were 6.50±0.10 and 9.03±0.15 respectively. Mean concentration (mg/l) of NH3, N, PO43- and K were: 0.26±0.20, 1080.33±145.22; 46.00±1.00, 32.00±3.00; and 29.66±4.72, 1358.66±183.90, 45.66±3.05 and 35.33±0.57 for fresh and stored urine respectively. Mean concentration (mg/l) of N, PO43-, K present in struvite were 193.33±56.5, 471.66±61.71 and 34.56±2.18, with PO43-being significantly different when compared with stored urine. Mean plant height (cm) for control, struvite produced from 1.2M, 1.5M, 1.8M of MgCl2 solution and inorganic fertilizer at the fourth week were 20.00±0.90, 20.16±4.36, 29.08±0.87, 28.00±0.86 and 20.00±7.76 respectively. Mean stem width (cm) of control, struvite 1.2M, 1.5M and 1.8M and inorganic fertilizer were 0.34±0.02, 0.39±0.07, 0.48±0.02, 0.46±0.03 and 0.40±0.21 respectively while the mean numbers of leaves were 13.00±0.50, 12.50±1.50, 15.16±0.76, 15.16±0.76 and 13.00±2.64 respectively. Plant height and stem width of struvite 1.5M and 1.8M treated vegetable were significantly (p=0.05) higher and thicker respectively when compared with other treatments. Mean wet and dry weights (g) were: 11.58±2.77 and 1.76±0.38 (control), 14.90±11.09 and 2.39±2.19 (struvite 1.2M), 32.11±5.35 and 5.85±0.77 (struvite 1.5M), 28.81±3.84 and 5.45±0.92 (struvite 1.8M), 9.97±8.87 and 1.34±1.24 (inorganic fertilizer) respectively. Weights of struvite-treated vegetable were significantly higher when compared with other treatments.

The highest dry weight (5.85 ± 0.77) was obtained with Amaranthus caudatus planted on struvite-treated soil. Struvite production and use in agriculture should be explored on a larger scale and could be employed as organic fertilizer to improve plant yield and indirectly improving environmental sanitation.