Effects Of Nitrogen Fertilizer and Reclaimed Water Application Rate On Nitrate Leaching From ‘Floratam' St. Augustinegrass.

Abstract

Reclaimed water (RW) is increasingly viewed as a resource for supplying irrigation water and nutrients for landscape plants growing in urban environments. Proper management of the irrigation system is important to minimize the risks to leaching of fertilizer N or the N supplied with the reclaimed water. The objective of this research was to evaluate nitrogen (N ) leaching and turf response to N fertilizer application and reclaimed water irrigation rate in ‘Floratam' St. Augustinegrass. This one-year greenhouse study was conducted on the University of Florida campus. Nitrogen (N) was applied in two treatments: a 1X fertilizer treatment based on the recommended N application rate for turfgrass in northern Florida and one-half of the recommended rate.  Irrigation treatments consisted of 5 rates of RW: 200, 300, 400, 600, 800 mL per lysimeter tub per day, corresponding to 1.0, 1.5, 2.0, 3.0, and 4.0 cm per week, respectively. Irrigation rates significantly affected the turfgrass clippings yield and tissue TKN concentrations (p<0.001, p<0.05) and subsequently affected the N uptake by turf. Lowest dry matter yields were found with the 200 mL/tub daily irrigation rate, which can be explained by lack of water. The one-half recommended fertilizer rate resulted in similar growth compared with the full N application. There was no leaching with the two lowest irrigation rates.  Leaching increased with irrigation rate and was greater with the 1X compared with the 0.5 X fertilizer rate. Leaching across all treatments was negligible. From the results of leaching loss and plant growth, the optimum daily irrigation rate was determined to be 300-400 mL/tub which is equal to 1.5-2 cm of irrigation weekly.