Individual study: Effects of delayed hay removal on the nutrient balance of roadside plant communities in the Netherlands
Schaffers A.P., Vesseur M.C. & Sýkora K.V. (1998) Effects of delayed hay removal on the nutrient balance of roadside plant communities. Journal of Applied Ecology, 35
Cutting and hay removal is a common form of road verge management. Apart from traffic safety, the objective usually is either to conserve or to develop more diverse plant communities. One important effect of cutting is the removal of nutrients. Removal of cuttings and atmospheric deposition are the most important components of the nitrogen balance in unfertilized Dutch grasslands under a hay management regime, and likewise probably for other macronutrients such as phosphorus and potassium. Soil impoverishment thus can only be achieved when removal of nutrients exceeds atmospheric input.
In this study, mass losses and nutrient losses from fresh roadside cuttings in middle and eastern Holland were studied in the field over a six week period.
Study sites: The field experiment was carried out at eight roadside locations situated in the middle and eastern parts of the Netherlands. Seven locations were selected, involving two grassland plant communities: the Ranunculo-Alopecuretum geniculati and the Arrhenatheretum elatioris. An eighth contrasting grass-heath community was also selected.
Experimental design: On each roadside verge a 1.50 × 0.75 m plot was established. The experiment took place between 24 May and 6 July 1993. At different locations, the start and finish dates were different. For the seven grassland plots the experimental duration was 5–6 weeks, the grass-heath plot was only 4 weeks duration as its low productivity led to less available biomass.
Between 24 May and June 8 the plots were cut at 1 cm above the soil surface. Long stems were reduced to pieces of 10 cm length at most. Half of the fresh cut vegetation of each plot was evenly distributed between 25 litterbags (20 for the grass-heath plot), each 15 × 15 cm, with a mesh size of 1 mm (allowing soil microflora and microfauna and most of the soil mesofauna to enter). The litterbags were laid out in the plot, evenly spread between the remaining cut material.
At 1–2 week intervals during the next 5–6 weeks, sets of five litterbags per plot were randomly collected. The first set was collected on the day of cutting. After collection, the content of each bag was dried at 70 °C for 48 h, weighed and stored for later chemical (nitrogen, phosphorus and potassium) analysis.
Weather: At a weather-station near some of the plots 75 mm of rainfall was measured over the 43 days of the experiment (30-year average for this period ±96 mm). Slight differences among plots and between plots could not be avoided. The average air temperature was ±16 °C (30-year average for this time of year ±15 °C).
In terms of both mass and nutrient content, large amounts (over 50%) appeared to be lost from the cuttings over the six weeks of the study period. The losses were positively related to initial nutrient concentrations. Mass and nitrogen losses were best explained by the initial C:N ratio, phosphorus and potassium losses by the initial phosphorus concentration.
Losses of potassium were particularly large (up to 90%). Potassium is mainly lost by leaching whereas the major nitrogen, phosphorus and mass losses were most probably caused by rapid microbial decomposition of readily soluble substances. All or most of the losses were assumed to return to the underlying soil system.
Conclusions: When soil impoverishment is a desired outcome, for example in the conservation of flower-rich roadside verge communities, cuttings should be removed within 1 to 2 weeks in most plant communities. If removal is delayed longer, the amounts of nutrients removed will often fall below the annual atmospheric input. In plant communities where annual above-ground production of nitrogen and phosphorus are lower than the annual atmospheric deposition already, rapid removal of the cuttings may be the only way to maintain at least potassium at a limiting level.
Note: If using or referring to this published study, please read and quote the original paper. The original paper can be viewed at: http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-2664.1998.00316.x