Nitrogen Removal and Nitrate Leaching for Two Perennial, Sod-Based Forage Systems Receiving Dairy Effluent

Abstract

major contributing source of nitrate (Katz and DeHan, 1996;Berndt et al., 1998). There are 44 000 dairy cows in In northern Florida, year-round forage systems are used in dairy four Florida counties that border the Lower Suwannee effluent sprayfields to reduce nitrate leaching. Our purpose was to River (Florida Agricultural Statistics Service, 2002). quantify forage N removal and monitor nitrate N (NO Ϫ 3 -N) concentration below the rooting zone for two perennial, sod-based, triple-In the LSRW, the types of soils and underlying hydrocropping systems over four 12-mo cycles (1996-2000). The soil is an geology make the UFA vulnerable to nitrate contaminaexcessively drained Kershaw sand (thermic, uncoated Typic Quartziption. Most of the soils are excessively to moderately samment). Effluent N rates were 500, 690, and 910 kg ha Ϫ1 per cycle. drained, deep, sandy Entisols. Also, the UFA is rela-Differences in N removal between a corn (Zea mays L.)-bermudatively close to the surface and layers above it are thin grass (Cynodon spp.)-rye (Secale cereale L.) system (CBR) and cornand unconfined (Andrews, 1992). These characteristics, perennial peanut (Arachis glabrata Benth.)-rye system (CPR) were coupled with relatively high annual rainfall (1310primarily related to the performance of the perennial forages. Nitro-1460 mm), increase the possibility that nitrate from inorgen removal of corn (125-170 kg ha Ϫ1 ) and rye (62-90 kg ha Ϫ1 ) was ganic and organic fertilizer sources will contaminate relatively stable between systems and among cycles. The greatest N removal was measured for CBR in the first cycle (408 kg ha Ϫ1 ), with ground water. The Suwannee River is also vulnerable the bermudagrass removing an average of 191 kg N ha Ϫ1 . In later because during low flow, it is supplied with water from cycles, N removal for bermudagrass declined because dry matter (DM) the UFA through springs and bottom seeps (Andrews, yield declined. Yield and N removal of perennial peanut increased 1992). over the four cycles. Nitrate N concentrations below the rooting zone Most of the dairies in the LSRW keep their milking were lower for CBR than CPR in the first two cycles, but differences herds in confinement lots. Typically, manure effluent is were inconsistent in the latter two. The CBR system maintained low applied in sprayfields where forages are grown year-NO Ϫ 3 -N leaching in the first cycle when the bermudagrass was the round. Several double and triple cropping systems with most productive; however, it was not a sustainable system for longannual and perennial forages have been used, but the term prevention of NO Ϫ 3 -N leaching due to declining bermudagrass yield in subsequent cycles. For CPR, effluent N rates Ն 500 kg ha Ϫ1 most common combination consists of two sequentially yr Ϫ1 have the potential to negatively affect ground water quality.

Impacts of fertilizer practices on environmental risk of nitrate in semiarid farmlands in the Loess Plateau of China

“…The leaching (or downward movement) of nitrate in soil profiles is generally regulated by soil moisture conditions, as well as the balance between the mineralization of soil organic N and N uptake by the crop (Hartemink et al 1996;Woodard et al 2003;Randall and Vetsch 2005). At our experimental site, most of the precipitation (>70% of the annual total) occurred between July and September (Fig.…”

Agro-ecological nitrogen management in soils vulnerable to nitrate leaching: a case study in the Lower Suwannee Watershed

“…Studies have shown that soil water NO 3 -N concentration likely to pose ecological problems is primarily the NO 3 -N that escapes plant uptake and moves past the root zone (Woodard et al 2002(Woodard et al , 2003. Despite the differences in the total annual precipitation in 2009 and 2010 (1,044 and 1,222 mm, respectively; Fig.…”

“…Since N uptake efficiency from this treatment was *42%, the data suggest that *58% of the applied N escaped plant uptake, but considering the N application rate it is unlikely that the amount of leached N would significantly contaminate the percolating water. Studies have shown that NO 3 -N leaching is a common occurrence in the sandy soils of southeastern United States, particularly in intensive forage production systems where high N fertilization are used (Woodard et al 2002(Woodard et al , 2003Zotarelli et al 2007;Fan andLi 2009). Fruh (1967) showed that N is one of the most limiting nutrients that causes eutrophication and, consequently, freshwater quality deterioration.…”

“…Nutrient management in croplands and grasslands, particularly in nutrient sensitive watersheds, has become critical in many production systems and is a major environmental issue that could undermine the long-term sustainability of agriculture in many watersheds (Woodard et al 2002(Woodard et al , 2003. Nitrogen and phosphorus (P) are essential nutrients for sustainable crop production, but if the supply of N and P exceed quantities taken up by crops, the residual soil content could be of environmental concern.…”

“…For example, agricultural operations in many watersheds in southeastern United States have come under scrutiny in terms of N and P management in recent times. The Lower Suwannee Watershed, in particular, has received an increased attention because soils in the watershed are mostly coarse-textured sandy soils, and the underlying hydrogeology could result in nitrate leaching to contaminate the Upper Floridan Aquifer (Woodard et al 2003). Andrews (1992) showed that the Upper Floridan Aquifer underlying the soils in the Lower Suwannee Watershed has unconfined layers with karstic features.…”