Aspects of peat conservation and water management

Abstract

An extended water regime model was used for calculating the evapotranspiration, groundwater recharge, and peat mineralization (CO2 and N release) for various fen locations with grassland utilization in dependence on the groundwater level. The results show that an increasing groundwater level leads to a strong decline of the actual evapotranspiration Et. For example, increasing the groundwater level from 30 to 120 cm diminishes the Et by up to 230 mm a—1. A positive groundwater recharge only takes place at groundwater levels of 90 cm and more. At smaller distances the capillary rise into the rooting zone during the summer months is greater than the water seepage during the winter months, so that a negative groundwater recharge‐balance is reached in the course of a year. The CO2‐ and the N‐release, as well as the annual decline in peat thickness, increase significantly with rising groundwater levels. The results show, that varying the groundwater level can influence the water regime and the peat mineralization significantly. The lower the groundwater level the less is the peat decomposition. The demand for a groundwater level as small as possible is, however, limited by an agricultural utilization of the fens. Choosing the optimum groundwater level should consider the aims (1) peat mineralization, (2) gas emission (CO2, CH4, N2O), and (3) crop production. If a grassland utilization is supposed to be made possible and all three aims above are given equal importance, the groundwater level should be maintained at 30 cm. At this distance, about 90 % of the optimum plant output can be reached. The peat mineralization can be reduced to 30 to 40 % of the maximum peat mineralization. The gas emission amounts to 50—60 % of the maximum value.

Influence of water table level and soil properties on emissions of greenhouse gases from cultivated peat soil

“…Mäkiranta (2009) found that the instantaneous effect of water level followed a Gaussian form with the highest respiration with a water level of 61 cm. Renger et al (2002) showed that CO 2 emissions doubled with the groundwater level at 80 cm depth compared with 30 cm depth. The influence of water table level was questioned by Joosten & Clarke (2002), who found that the highest mineralisation rate was observed with the groundwater level at 80-90 cm depth, but that a groundwater level at 17-60 cm still had 80% of the maximum mineralisation rate.…”

“…In the middle of the summer, with temperatures between 15-20 o C, the emission rates were higher from WT@40 cm compared to WT@80 cm. Contrary to our results, many investigations have reported increasing CO 2 emissions following lowering of the groundwater level (Eggelsman, 1976;Renger et al, 2002;Wessolek et al, 2002). Findings supporting our results, with a higher emission rate at intermediate groundwater levels compared with low (dry soil), have been reported by Davidson et al (1998), Chimner and Cooper (2003) and Kechavarzi, C. et al (2007).…”

The contribution of mineralization to grassland N uptake on peatland soils with anthropogenic A horizons

“…Van Kekum (2004) reported annual N uptakes from unfertilized experimental fields on peatland soils in the Western part of the Netherlands that ranged from 176 kg N ha −1 for wet peatland soils to 302 kg N ha −1 for drained peatland soils. Schothorst (1977) even reported annual N uptakes from nonfertilized peatland soils exceeding 400 kg N ha −1 increase in the annual N supply (Hacin et al 2001;Renger et al 2002), which is most apparent in the first years after the start of drainage. Apart from N uptake, nitrous oxide emissions through denitrification are also considered to be a major pathway of N removal from intensively managed grasslands on peat soil (Regina et al 2004;Van Beek et al 2004).…”

Short-term effects of biogas digestate and cattle slurry application on greenhouse gas emissions affected by N availability from grasslands on drained fen peatlands and associated organic soils

“…Various studies reported an annual N supply through peat mineralization of 70 to 292 kg N ha −1 yr −1 (Schothorst, 1977;Flessa et al, 1998;Sonneveld and Lantinga, 2011). It can be assumed that at a comparable aeration status and temperature, mineralization processes are more intensive at peatlands that were recently drained (Hacin et al, 2001;Renger et al, 2002;Sonneveld and Lantinga, 2011) or contain higher amounts of SOM. As expected from the literature, the biogas digestates differed in their physical and chemical properties from the cattle slurries.…”