EFFECTS OF FRESH VERSUS COMPOSTED MANURE ON HYDROLOGIC RESPONSE FROM CROPLAND

Abstract

A two-year (1999-2000) study examined the hydrologic response of cropland amended with fresh manure andcomposted manure using a rainfall simulator. We hypothesized that composted manure would increase infiltration anddecrease runoff compared to fresh manure because of its more uniform and finer particle size. The dry-weight application ratesof both fresh and composted manure from straw-bedded pens were low (14 Mg ha-1), medium (42 Mg ha-1), and high (83 Mgha-1), plus an unamended control. Amendment type treatment effects depended on their interaction with rate and year.Interactions of amendment type and rate were observed for initial abstractions in 2000 and for average runoff rates and runoffcoefficients in 1999. Initial abstraction in 2000 was generally higher for the high rates of fresh and composted manure andfor the medium rate of fresh manure. Initial abstractions were also lower in 1999 (4 to 21 mm) than in 2000 (10 to 115 mm).Runoff rates and runoff coefficients were generally lower for the high and medium rates of fresh manure. For all seventreatments, runoff rates when runoff volumes reached 10 L varied between 36 and 55 mm h-1, and runoff coefficients variedbetween 0.12 and 0.53. Based on the results of our two-year study, application of composted manure or fresh manure tocropland at rates up to 83 Mg ha-1 should have similar impacts on hydrologic response. However, longer-term effects areunknown and should be examined to better understand potential hydrological and water quality differences.