N, K and P deficiency in chronosequential cut summer-dry grasslands on gley podzol after the cessation of fertilizer application

Abstract

With the intensification of agricultural practices, formerly species rich marginal grassland communities of high botanical value in the Netherlands have been fertilized or manured since the first part of the twentieth century. This type of land use resulted in a dramatic decrease of the original plant species-richness. In the early 1970's yearly nutrient input to many of these grasslands was ceased as a nature management practice, while hay-cropping was continued. This type of grassland management is carried out to decrease overall nutrient supplying ability of the soil to plant cover in order to restore their original high botanical richness. The effect of this management on the type and the extent of nutrient deficiency was studied by comparing the short-term shoot responsiveness of undisturbed turfs to added nutrients and the nutrient status of fieldgrown dominants of four hay-field communities which were not fertilized for 3, 7, 20 or 25 years.Contrary to expectation, hay-cropping without input of additional nutrients did not impose an increase of species-richness of grassland on gley podzol. During early vegetation change strong inadequacy of N supply and moderate inadequacy of K supply by the soil regulate (shoot) growth. P-deficiency was not established. Prolonged discontinuation of fertilizer application caused concomitant inadequate supplies of N, K and P. In the last field (25 years unfertilized), nutrient deficiencies could not be detected by shoot growth responses to added nutrients but only by a low nutrient status. It appeared that during this type of vegetation change N-deficiency is the most pronounced and that K-deficiency developes much more rapidly than P-deficiency. The strong decline in total aerial pool sizes of N, K and P also emphasizes these simultaneously occurring shifts.We conclude that cut grassland composition on gley podzol soil is regulated by co-deficiencies of at least the soil phytoavailable macronutrients nitrogen, potassium and phosphorus. The absence of change in plant species number is likely not regulated by the nutrient supplying ability of the soil. Seed dispersal from elsewhere seems to be the most important factor.

Restoration of a Cirsio‐Molinietum Fen Meadow on an Agriculturally Improved Pasture

“…In Experiment 2 the phosphorus yield in the dry matter from the topsoil removal treatment plots was comparable to that harvested from the Cirsio‐Molinietum . The ratio of nitrogen/phosphorus in the harvested dry matter from the topsoil removal treatments was 15.2, which in light of the studies of Koerselman and Verhoeven (1995) and Pegtel et al (1996) would indicate that phosphorus availability severely limited phytomass production.…”

Responses of wetland graminoids to the relative supply of nitrogen and phosphorus

“…With all other species, relationships between biomass and N:P supply ratios ͑Figure 2, Figure 3͒ were intermediate between those depicted in Figure 1a and Figure 1e: biomass either increased monotonically with increasing N:P ratio ͑N-limitation͒ or reached a maximum at a N:P ratio of 15 or 45 ͑Nlimitation below this threshold and P-limitation above͒. The finding that growth was generally N-limited at a N:P ratio above 15 contrasts with the suggestion that the optimal N:P ratio for vascular plant growth is 10-15 ͑Duarte 1992; Koerselman and Meuleman 1996;Pegtel et al 1996͒, but it concurs with the results of other growth experiments, which all found N limitation at N:P supply ratios higher than 15 ͑Veerkamp et al 1980;Shaver and Melillo 1984;Thornton 1991;Ryser and Lambers 1995;Romero et al 1999͒. Various reasons may cause the N:P ratio separating N from P limitation to be higher in growth experiments than in the field. First, all N and P supplied in the experiments could be taken up directly by plants.…”

Biomass N:p Ratios as Indicators of Nutrient Limitation for Plant Populations in Wetlands

“…The higher N:P ratios of P-limited populations compared to others were due to both higher N concentrations and lower P concentrations. Thus, the tendency of nutrient ratios to reflect resource accumulation as well as resource scarcity, sometimes put forward as an argument against their use to indicate nutrient limitation (Wassen et al 1995, Pegtel et al 1996, was an important reason why ratios were related to limitation in our study. It is possible that the importance of nutrient accumulation in determining the N:P ratio may reflect patterns of nutrient use characteristic of plant species adapted to nutrient stress and might therefore be different in other vegetation types.…”

“…Still other authors questioned whether N:P ratios can provide any indication of nutrient limitation or nutrient availability at all because they may reflect the accumulation of the nonlimiting nutrient rather than the scarcity of the limiting one (Wassen et al 1995, Pegtel et al 1996 or, more generally, because inherent regulation in uptake or interactions with other factors would weaken any relationships between nutrient contents and nutrient availability (Hayati and Proctor 1991). Thus, McJannet et al (1995) found considerable variation in the biomass N:P ratios of 41 wetland species grown at exactly the same nutrient supply.…”