Very Low Nitrogen Leaching in Grazed Ley-Arable-Systems in Northwest Europe

Abstract

High input dairy farms that are located on sandy soils in northwest Europe are predisposed to substantial nitrate leaching during a surplus of winter precipitation. Leys within integrated crop-livestock systems play an important role in soil fertility, soil C sequestration and soil N mineralization potentials. Therefore, leys are a feasible option that can be utilized to reduce local N losses to the environment, especially following maize grown for silage. We hypothesize that grass-clover leys ensure low nitrate leaching losses even when grazed intensively. The extent to which NO3-leaching occurred across seven different pasture management systems in terms of their sward composition, cutting, grazing, fertilization and combinations thereof was investigated in integrated animal-crop grazing systems over three winter periods (2017/2018, 2018/2019 and 2019/2020). The observed grazed systems were comprised of cut-used- and grazed grass-clover swards (0, 1 and 2 years after establishment following cereals), a catch crop grazed late in the year as well as a cut-used permanent grassland for comparison. Overall, all treatments resulted in nitrate leaching losses that did not exceed the WHO-threshold (25 mg nitrate/L). The highest level of NO3-leaching was observed in the catch crop system and the lowest in cut-used permanent grassland, with NO3-N losses of 19.6 ± 5.3 and 2.1 ± 0.3 kg NO3-N ha−1 year−1. Annual herbage yields were in the range of 0.9 to 12.4 t DM ha−1 and nitrogen yields varied between 181 ± 51 and 228 ± 66 kg N ha−1 during the study period. The highest herbage-N-yields were observed from the 1- and 2-year-old grass-clover leys. The highest N-field-balance was observed for the grazed leys and the lowest for the cut-used permanent grassland. However, no correlation was found between the highly positive field-N-balance and the amount of NO3-leached. This indicates a high N carry-over from grass-clover swards to the subsequent cash crop unit instead of increasing the risk of groundwater contamination from grazed leys in integrated animal crop-systems and underlines the eco-efficiency of dairy farming based on grazed ley systems.

Species-Enriched Grass-Clover Mixtures Can Promote Bumblebee Abundance Compared with Intensively Managed Conventional Pastures

“…The research presented here is part of the superior topic "Eco-efficiency of pasturebased milk production" at Lindhof experimental farm of Kiel University, analysing a wide range of ecosystem services and ecological footprints of low-input dairy farming as a complementary approach to typical highly intensive confinement dairy systems [18,55,56] in Northwest Europe. Compared with high-input confinement milk production systems, based on grass and maize silage, pasturing grass-clover leys results in comparably high milk yield performance per hectare [54]; however, there are very low methane emissions [55], N 2 O emissions [68] and nutrient losses via leaching [56], and thus very low carbon and nitrogen footprints per unit of milk produced [18], while enhancing yield stability [69]. Furthermore, combining L. perenne and P. lanceolata, as in the multispecies mixture in this experiment, enhances soil microbial activity [70].…”

“…The study took place in 2019 at the Lindhof experimental farm of Kiel University, in Schleswig-Holstein, Germany (WGS 84, 54 • 28 N; 9 • 58 E), in the frame of the topic "Eco-efficiency of pasture-based milk production" [54][55][56]. In 2019, the mean temperature of the study area was 10.24 • C (mean annual temperature of 9.35 • C between 1990 and 2019) and the annual precipitation was 745 mm (mean annual precipitation of 775 mm between 1990 and 2019).…”

Eco‐efficiency of leys—The trigger for sustainable integrated crop‐dairy farming systems

“…This mounting concern has spurred the implementation of various regulations, including the European Union Nitrate Directive. The findings from 3 years of field measurements at Lindhof (Smit et al, 2021) offer valuable insights into nitrate leaching across different grassland systems. The outcomes reveal that fertilised permanent grasslands and grazed grass‐clover swards exhibited relatively low (<10 kg N ha −1 ) and medium (10–28 kg N ha −1 ) levels of nitrate leaching, respectively (Figure 2).…”

“…Average nitrate leaching losses (kg NO 3 N ha −1 ) of the different systems (permanent grassland (PG with no fertilisation), PG240N is PG receiving 240 kg N ha yr −1 ; GC (with no fertilisation) is grass‐clover swards; 0, 1, 2 years old; CC60N is catch crop fertilised with 60 kg slurry N ha −1 ); Permanent Grassland (PG), Grass clover (GC), cover crop (CC) (annual ryegrass); (Smit et al, 2021). N load of 30 kg N ha −1 is equivalent to the threshold exceeding 50 ppm nitrate concentration in the leachate (275 mm of percolated water)–EU limit in drinking water is 50 ppm.…”

Assessing and Mapping the Environmental Impacts of Best Management Practices in Nitrate-Vulnerable Areas

“…In addition, the intensive practice scenarios were the most problematic, while the others, based on effective agricultural practice guidelines, were not. Considering this, it is important to note that, as much as grassland land use is usually considered an excellent option for nitrate-vulnerable areas [3,44,45] when it is not managed following effective agricultural practice, the nitrate footprint is not any better than that of the typical arable land use.…”