Catch Crops in Lower Saxony—More Than 30 Years of Action against Water Pollution with Nitrates: All in Vain?

Abstract

Intensive animal production, vast amounts of biogas plants, and the spreading of manure and digestates, exerts strong pressure on water quality in the German federal state of Lower Saxony. Catch and cover crop (c&c) cultivation is seen as one measure to inhibit nitrate leaching into soils, and to prevent water pollution with nitrates. A document analysis was carried out, covering the time span of 1992 to 2020, and the findings were combined with available quantitative data of the same period, and with GIS analysis. From 1994 to the year 2020, the acreage of subsidized c&cs increased from ca. 10,000 ha to ca. 380,000 ha. In addition, there was an acreage of unsubsidized c&cs of about 100,000 ha declining to 50,000 ha. In comparison, the acreage of arable land remained at approximately 1,880,000 ha. We found that c&cs did not contribute substantially to water protection for the following reasons: the design of the measure, control of farmer’s actions, and the antagonistic trend due to the increase in animal numbers and biogas plants. The development of c&cs over time and space reveals that frame conditions and management requirements of cultivating c&cs need to be well designed to be effective and efficient (with regard to N reduction and reduction of costs). It is vital to coordinate all programs and schemes in one region. From our evaluation, we conclude that a measure such as c&c cultivation, which is simple to introduce and easy to control, should be implemented over winter as a mandatory measure in order to achieve a greater uptake. Additionally, result-based measures could complement this scheme, as there is a strong link between subsidy level and the success of the measure.

Groundwater springs in the German Wadden Sea tidal flat: A fast-track terrestrial transfer route for nutrients and dissolved organic matter

“…Furthermore, the high concentrations of nitrate in the intertidal springs suggest a shallow groundwater source since nitrate sources occur on or near the soil surface. Like most parts of Northern Germany, the Sahlenburg area is extensively used by agriculture with chronically high nitrate concentrations particularly in the shallow groundwater as documented by local authorities (Klages et al, 2022) and evidenced by our data from the Sahlenburg monitoring well (Supplementary Table 1). In the Sahlenburg springs, the high average concentrations of nitrate, and lower concentrations of nitrite and ammonium are indicative of an oxygenated system where there is little denitrification (Tamborski et al, 2020), in line with elevated dissolved oxygen concentrations.…”

Definition of hot-spots to reduce the nitrogen losses from agricultural land to groundwater in Slovakia

“…Nitrogen capture by winter crops or catch crops in hot-spot areas for reducing agricultural N-balance surpluses (Bowles et al, 2018;De Notaris et al, 2018;Hansen et al, 2017;Hérivaux et al, 2013;Kühling et al, 2021) can be considered as a suitable complementary action to the reduction of nitrogen inputs, because in Central Europe the nitrogen leaching usually takes place during the autumn-spring period (Buczko, Kuchenbuch, 2010;Haberle et al, 2009;Stark, Richards, 2008). Klages et al (2022) consider the compulsory cultivation of winter catch crops where necessary and appropriate. In addition, the summer drought or inter-annual weather/drought variability also affects the cultivation of winter catch crops in warm lowland areas (Bowles et al, 2018;Kühling et al, 2022;Texeira et al, 2016).…”

Strategies of Climate Change Mitigation in Agriculture Plant Production—A Critical Review

“…Its general role is the prevention of nitrogen leaching, while the main role of cover crops is to protect soils from erosion, the decrease of organic matter and weed suppression. Leguminous crops are mainly used as green manure, in order to improve the N supply for succeeding crops [168]. Catch crops are mainly plants with a short growing seasons, used during the vegetative or in the initial period of generative plant growth.…”