Nitrogen fertilization and nitrate leaching into groundwater on arable sandy soils

Abstract

Nitrate leaching depending on N fertilization and different crop rotations was studied at two sites with sandy soils in N Germany between 1995 and 2000. The leaching of NO À 3 was calculated by using a numerical soil-water and N model and regularly measured N min values as input data. Also the variability of N min values on the sandy soils was determined along transects. They reveal the high variability of the N min values and show that it is not possible to confirm a significant N min difference between fertilizer treatments using the normal N min -sampling intensity. Nitrate-leaching calculations of five leaching periods showed that even strongly reduced N-fertilizer applications did not result in a substantially lower NO À 3 leaching into the groundwater. Strong yield reductions of even more than 50%, however, were immediately measured. Mean NO À 3 concentrations in the groundwater recharge are >50 mg L -1 and are mainly due to mineralization from soil organic matter. Obviously, the adjustment of the N cycle in the soil to a new equilibrium and a reduced NO À 3 -leaching rate as a consequence of lower N inputs need a much longer time span. Catch crops are the most efficient way to reduce the NO À 3 concentrations in the groundwater recharge of sandy soils. Their success, however, strongly depends on the site-specific development possibilities of the catch crop. Even with all possible measures implemented, it will be almost impossible to reach NO À 3 concentrations <50 mg L -1 in sandy soils. The only way to realize this goal on a regional scale could be by increasing areas with lower nitrate concentrations in the groundwater recharge like grassland and forests.

The effect of different forms of nitrogen fertilizers on nitrogen leaching

“…In autumn, 37.1-45.4% of the annual amount of nitrogen is leached, so the rainier is the autumn the higher nitrogen content is leached from the upper soil layer. The established pattern confirms scientists' recommendations to reduce the infiltration from agricultural soils through autumn period by cultivating cover crops (Vos, van der Putten, 2004;Köhler et al, 2006;Jayasundara et al, 2007).…”

Rural Development Program measures on cultivated land in Europe to mitigate greenhouse gas emissions – regional “hotspots” and priority measures

“…It concurs with published literature as a potential issue throughout Europe, including the northern and central case study MSs: the UK [46], Sweden [47], Poland [48], France [49], northern Spain [50,51] and Germany [52]. Italy [53,54] and Greece [55] in the south also report NO 3 ¡ leaching from cultivated land, a factor further influenced by irrigation during drier periods of the year [56].…”

Biomass Production with Willow and Poplar Short Rotation Coppices on Sensitive Areas—the Impact on Nitrate Leaching and Groundwater Recharge in a Drinking Water Catchment near Hanover, Germany

“…According to model calculations of Springob et al [14] and Springob and Kirchmann [15], it was estimated that it might take up to 100 years for the soils to achieve a new equilibrium under the present conditions. Under these conditions, Köhler et al [16] concluded that the only way to reduce the N output to groundwater is to convert the arable land into forests or back into continuous grasslands, while setting aside the land will not reduce the risk of nitrate leaching in the long run. However, another promising land-use for fallow grounds to meet the requirements of groundwater protection might be the establishment of SRC with fast-growing trees like poplar or willow.…”