Using fertilization rates in semi-natural grasslands to produce seed for ecological restoration

To produce seeds of native species for ecological restoration, cultivating semi-natural grasslands can be a strategy that avoids the environmental impacts of conventional seed propagation and favours the conservation of speciesrich grasslands. In a lowland grassland in northern Italy, the effects of three mineral fertilisation treatments (0–0–0, 0–54–108, and 192–108–216 kg ha􀀀 1 year􀀀 1 of N, P2O5, and K2O; abbreviations: 000, 0pk, and NPK) on seed production were studied in a fully randomised block design. Fertile shoots of flowering species were collected and analysed for seed content, and species phenology was recorded during field observations. The grassland environmental quality was described based on soil analyses and indices of natural (plant and insect richness) and aesthetic (flower colour) value. NPK produced the highest viable seed amount (59,375 m􀀀 2 year􀀀 1). The seed mixture was composed mostly of grasses (97%) and included the lowest species number (34). NPK also had the lowest environmental value. In 0pk, the nitrogen from legume rhizobial fixation allowed the production of an intermediate viable seed amount (28,485 m􀀀 2 year􀀀 1) with an intermediate forb seed percentage (14%) and the highest species number in the vegetation (42) and collected as seeds. In 000, the seed amount was the lowest (8310 m􀀀 2 year􀀀 1), but the species number (40) and forb percentage in the seed mixture (39%) were high. The natural and aesthetic values did not significantly differ between 0pk and 000. The P soil content increased strongly in NPK, whereas decreases or insignificant increases in P and K were recorded in 0pk and 000. Mineral 0pk fertilisation allows for relatively high seed production with high legume and forb richness by avoiding the distribution of nitrogen fertilisers that potentially impact the environment. This strategy seems to be a good option for producing environmentally friendly seed mixtures of many native species from semi-natural grasslands.