The effects of urine and urine-separated plant nutrient sources on growth and dry matter production of perennial ryegrass (Lolium perenne. L)

Abstract

The use of urine, and urine-derived products can supplement chemical fertilisers. There is little information on the use of urine products in agriculture particularly in South Africa. A laboratory incubation experiment was conducted to determine effects of urine-derived sources on nitrogen (N) release in soil. A 5 × 2 factorial in a completely randomised design was used with two soils, differing in clay and carbon contents, and five nitrogen (N) sources; unamended control, urine, struvite effluent, stuvite + struvite effluent, nitrified urine concentrate. A follow up tunnel pot trial was conducted to determine effects of the urine-derived N sources on dry matter production of perennial ryegrass. The experiment was conducted with the Cartref soil as a 6 × 2 factorial in a completely randomised design, with the same N sources as in the incubation experiment, applied either once-off or split, replicated three times. In the Cartref soil (lower clay and C), ammonium- N declined from 1000 to about 3 mg/kg from day one to day 70, while nitrate- N increased significantly from 0.3 mg/kg to about 400 mg/kg during the same period. Conversely, ammonium-N declined from 100 mg/kg to 8.5 mg/kg in the Inanda soil (higher clay and C), while nitrate- N did not significantly increase. Split application of urine derived N sources resulted in higher cumulative dry matter (873–993 kg/ha) than once-off application (602–727 kg/ha). When split applied only struvite effluent resulted in higher drymatter than struvite effluent + struvite, while once-off application resulted in higher drymatter in the NUC (725 kg/ha) and urine (707 kg/ha) than struvite effluent (602 kg/ha) and struvite effluent + struvite (663 kg/ha). The study indicate that urine derived nitrogen sources, particularly nitrified urine concentrate, can release nitrogen in soil and increase drymatter production of perennial ryegrass, particularly with split application.