Rainfall simulations to evaluate pathogen and nutrients Runoff loss under controlled conditions

Abstract

Soil fertilizing the old-fashioned way, with raw manure, is a well-known procedure to increase land productivity. However, the fertilization value of organic amendment to the soil depends among others, on the composition of manure and manure application rates, timing and placement. When a rainfall event occurs soon after organic fertilizer application, it might help increase nutrient and pathogen concentrations in superficial runoff, carrying out negative consequences on water quality. The aim of this research was to study the effect of variable rates of poultry manure application and landscape slope on bacterial pathogens, nutrients and sediment transport with surface runoff. Experimental assays were performed with an indoor rainfall simulator; a constant 25 mm. h-1 intensity was applied for 2.5 hours. We evaluated interactions between slopes (2%, 4% and 9%) and application rates of poultry manure. Trial conditions tested tend to reproduce the typical farming practices applied in the central area of Iowa State, which is part of the productive area known as the Corn Belt (USA). Nutrient present in surface runoff showed a positive correlation with manure application rates. Also, when manure application rate was doubled, E. coli FCU increased correspondingly. This study emphasized the need for proper manure management (rate and timings of application) in order to optimize fertilization efficiency and to avoid negative impacts on downstream water quality of productive areas and on the ecological systems surrounding them.