EFFECT OF DRYING AND RAINFALL INTENSITY ON CYROMAZINE LOSS FROM SURFACE-APPLIED CAGED-LAYER MANURE

Most poultry manure is surface applied as pasture fertilizer. Cyromazi ne (N cyclopropyl-1,3,5 triazine 2,4,6 triamine), a feed through larvi cide used to control house dies (Musca domestica), is often a manure c omponent in caged layer (Gallus gallus domesticus) systems. Since cyro mazine is quite soluble and stable in water, the objective of this stu dy was to quantify cyromazine in runoff and soil water from pasture tr eated with caged-layer manure. Plots of uniform slope were bordered to isolate runoff and planted in fescue (Festuca arundinacea Schreb). Ma nure was analyzed for cyromazine content and applied at 0, 4.4, and 17 .7 Mg ha(-1) (dry basis). Rain was applied by simulator at 50 and 100 mm h(-1). Runoff was analyzed for cyromazine and its metabolite, melam ine (1,3,5-triazine-2,4,6 triamine). A high manure application rate in creased runoff volume and cyromazine concentration. High rain intensit y increased total cyromazine runoff loss but provided enough runoff vo lume to reduce the concentration. Mean cyromazine concentration in run off was as high as 101 mu g L(-1), and mean cyromazine loss was as hig h as 23.7%. Pan lysimeters monitored soil water in the vadose zone for 1 yr after the manure application, but cyromazine and melamine were n ot detected. In a follow-up study, plots received manure at 3.76 Mg ha (-1), were allowed to dry for either 1 or 7 d, and then received rain at 50 mm h(-1) for 30 min of runoff. The 7-d drying time decreased cyr omazine loss, apparently by reducing both runoff volume and cyromazine concentration in the runoff.