Effects of nitrogen, phosphorus and potassium fertilization on field performance ofDactylorhiza majalis

Abstract

SUMMARY The effects of nitrogen, potassium and phosphorus fertilization on performance of Dactylorhiza majalis (Rchb.f.) Hunt & Summerh. were studied in a Juncus acutiflorus‐dominated hayfield. Frequency, total shoot biomass and flowering incidence decreased as a result of both nitrogen and phosphorus application. Nutrient additions also affected yields of species showing positive and negative association with orchid performance. These changes were sufficient in explaining the nitrogen and phosphate response of orchid shoot biomass and extent of flowering. The most important competitors in this respect were Rumex acetosa and Holcus lanatus. The negative overall N‐ and P‐effect on orchid frequency seemed to be independent of changes in the surrounding vegetation however. The relative importance of nutrient limitations and additions is discussed in relation to the species decline in frequency and to its reappearance in grasslands under restoration management with decreasing nutrient availability.

Axenic in vitro nitrogen and phosphorus responses of some Dutch marsh orchids

“…In Calthion palustris hay lands fertilizing with nitrogen and phosphorus decreased the frequency of D. majalis, an effect that could not be accounted for solely by vegetation changes due to nutrient application (Dijk & Olff, 1994). The pronounced negative N-efTect observed in the field can only be related partly to the growth depression due to nitrogen levels, since inhibition of axenic growth was not pronounced.…”

“…Low rates of fertilization reduced the number of flowering individuals of Orchis morio in Centaurea nigra-Cynosurus cristatus hay meadows (Silvertown et al, 1994). The frequency of Dactylorhiza majalis decreased in Calthion paiustris hay fields as a result of nitrogen and phosphorus application, whereas potassium addition did not affect orchid growth; these effects were not determined solely by vegetation changes brought about by the fertilizer regime (Dijk & Olff, 1994).…”

The effects of fertilizer and root competition on seedlings of Orchis morio and Dactylorhiza fuchsii in chalk and clay soil

“…In the experiment of Silvertown et al, (1994) 400 g m"^ of P was thought to be toxic to the orchids, whereas in my experiment only 6-4 g m~^ of P and 48 g m"^ of N were applied close to the plant (calculations based on 1 cm radius application). This lower dose, however, did bring about a decrease in the growth of D. fuchsii and was similar to the dose which brought about a decrease in density in D. majalis in field trials (Dijk & Olff, 1994). Thus, it is clear that at this stage in development O. morio is fairly tolerant of moderate doses of fertilizer, at least in the short term.…”

“…Increases in nitrogen concentration can also have a negative effect on the growth of juvenile symbiotic orchids m vitro (Dijk, 1989). The 'improvement' of traditionally * E-mail: S.L.McKendrick(gSheffield.ac.uk managed meadows by fertilizer has long been implicated in the decline of orchid species (Wood, 1989), yet it is onh^ recently that the application of fertilizer has been demonstrated to have an adverse effect on natural orchid populations (Dijk & Olff, 1994;Silvertown et al, 1994). The application of 25 g N m-^ yr-i (as NH^NOg) and/or 8 g P m"" yr-( as NaH2PO4) w^as sufficient to decrease the frequency, total hiomass and flowering of Dactylorhiza majalis in a Juncus acutiflorus-doxmnQX^d hayfield in the Netherlands (Dijk & Olff, 1994).…”

“…The 'improvement' of traditionally * E-mail: S.L.McKendrick(gSheffield.ac.uk managed meadows by fertilizer has long been implicated in the decline of orchid species (Wood, 1989), yet it is onh^ recently that the application of fertilizer has been demonstrated to have an adverse effect on natural orchid populations (Dijk & Olff, 1994;Silvertown et al, 1994). The application of 25 g N m-^ yr-i (as NH^NOg) and/or 8 g P m"" yr-( as NaH2PO4) w^as sufficient to decrease the frequency, total hiomass and flowering of Dactylorhiza majalis in a Juncus acutiflorus-doxmnQX^d hayfield in the Netherlands (Dijk & Olff, 1994). The decrease in yield and flowering rate w^as correlated with the increased biomass of competing species, but the effect on the density of the orchids could not be explained by vegetation-mediated effects and was more likely to be caused directly by the fertilizer.…”