Submitted to: Agro-Environment Symposium
Publication Type: Proceedings
Publication Acceptance Date: 6/30/2006
Publication Date: 8/15/2006
Citation: Norton, L.D. 2006. Reducing runoff phosphorous loss using by-product gypsum and composted waste paper. In: Proceedings of the International Symposium Agro-Environ. Agricultural constraints in the soil-plant-atmosphere continuum. September 4-7, 2006, Ghent, Belgium. p. 163-169. 2006 CDROM.
Technical Abstract: Contamination of surface runoff with phosphorous (P) from agricultural non-point sources is a major environmental concern causing off-site eutrophication of water bodies and in the USA contributes to the hypoxia zone at the mouth of the Mississippi River. This problem is intensified when agricultural fields are either over fertilized with phosphate based materials or when manures have been over applied and an erosive rainfall occurs. We conducted a four year field rainfall simulator study on a soil that had received long-term additions of effluent from a secondary lagoon at a poultry operation. The field had soil test P levels as high as 5,000 mg/kg. The soil was a Zulch clay loam (thermic Udertic Paleustalf) near Kurten, Texas, USA containing a considerable amount of smectitic clay on a 2-5 percent slope. We compared the use of by-product gypsum (GP), and a new waste paper product (PP) on reducing P runoff, to the high P control using rainfall simulation. Rates were 5 Mg/ha GP and 24.4 Mg/ha PP. The PP was incorporated to a depth of 10 cm prior to rainfall whereas gypsum was surface applied to the freshly tilled soil. Soil loss and runoff was collected at 5-minute following initiation of runoff until steady state runoff was achieved. Rainfall rate was a constant target rate of 64mm/hr using deionized water applied with a programmable simulator equipped with 80-100 veejet nozzles. Actual rainfall amount was measured and soil loss and runoff normalized to the target rate. Soil loss was measured gravimetrically from a 1-liter sediment sample taken and runoff rate was calculated based on the mass and time to collect. A smaller P sample was collected and frozen until analyzed colorimetrically for soluble reactive P (SRP) and total Bray P1 extractable P in sediment (TP). The control contained significantly greater runoff, soil loss, SRP and TP than both the treatments. When comparing treatments, PP reduced the total runoff at this rainfall intensity greater than did the GP, however, the gypsum reduced the concentration of the SRP in addition to significantly reducing runoff volume therefore having the least overall loss of total SRP. Both PP and GP treatments significantly reduced TP in sediment from the control. GP had less TP in sediment than PP, but the difference was not significant. The addition of both amendments were highly effective in reducing P losses. The advantage of the gypsum treatment was that it only needed to be surface applied, whereas, the PP needed incorporation. The GP provided equal protection to the PP but was much easier to apply. The significance of this work is to show that contaminated agricultural land can be protected to reduce the movement of P offsite through the use of low cost recycled waste materials.