Interactions between nitrogen, phosphorus and potassium determine growth and N2-fixation in white clover and ryegrass leys

Abstract

Variations in yield, N 2 fixation and above-ground accumulation of nitrogen (N), phosphorus (P) and potassium (K) in white clover and ryegrass grown separately or in mixture were investigated under field conditions over two consecutive years at different supplies of N, P and/or K. Ryegrassclover mixtures consistently out-yielded the pure stand clover and pure stand ryegrass in terms of dry matter. Improved N supply favoured ryegrass, and ryegrass in mixture with clover accumulated substantially higher amounts of N, P and K than ryegrass in pure stand. Conversely, the growth of white clover in mixture with grass was significantly depressed by N application, particularly when P and K were also applied. Plots of dry matter, N, P and K in white clover versus ryegrass in mixtures followed lognormal relations demonstrating the superior responsiveness of ryegrass to improved availability of N, P and/or K. Although competition for P and/or K reduced the N 2 fixation rate in the mixture, the effect on the total above-ground N accumulation was insignificant. The proportions of P and K in the shoot dry matter of ryegrass in pure stand were only half of those of ryegrass in mixture with clover, while white clover co-cultivated with ryegrass had lower P concentration in dry matter, showing a P deprivation of clover growing in mixture with grass. Na was able to replace K under the competitive conditions in the mixture. In conclusion, the results show that growth and nutrient acquisition of clover and ryegrass interact in a complex manner involving competition, facilitation and complementarity.

Robustness in the mineral supply from temporary grasslands

“…The variation in soil fertility is often related to below-ground species richness that may influence the function of ecosystems via nutrient supply (Naeem et al, 1995;Ekschmitt & Griffiths, 1998) which in turn influences the botanical composition (Høgh-Jensen & Schjoerring, 2010;Rasmussen et al, 2007). Increasing the supply of N to temporary grassland was shown by Mudd (1970) to decrease herbage Mn, which is confirmed in this study (data not shown).…”

“…One of them may lie in the release of these nutrient elements from the various species and organs, not to mention cell fractions (Whitehead et al, 1985;Ibrahim et al, 1990). Another may lie in nutrient interactions, for example N, P and K interaction, which Høgh-Jensen and Schjoerring (2010) demonstrated to determine the competitive ability in a two-species mixture. A third may be that some systems favour productivity and resource-use efficiency, which may give lucerne, red clover and festulolium an advantage, 88 H. Høgh-Jensen & K. Søegaard while others may favour persistence to grazing which may give ryegrass and white clover some advantages.…”

“…Such comparisons are relevant to evaluate through yield density functions or with-and-without individual species in grassland (Goldberg & Scheiner, 1993;Sackville Hamilton, 2001). Evaluating measurements of the species in mixtures represent difficulties as the individual indices of performances may not be independent (Pearce & Gilliver, 1978;Høgh-Jensen & Schjoerring, 1997;Høgh-Jensen & Schjoerring, 2010). …”

Recovery efficiency of nitrogen from liquid and solid fractions of pig slurry obtained using different separation technologies

“…No increase of the P concentration was observed after application of slurry or slurry fractions. Similar P concentration values in ryegrass were observed by Høgh‐Jensen and Schjoerring (2010), while Starnes et al (2008) reported values considerably higher.…”

“…The N concentration values in dry biomass, observed in the first cut, were in the range of values reported in other studies ( Høgh‐Jensen and Schjoerring , 2010; Grigatti et al, 2011) and can be considered as adequate according to the classification from Reuter and Robinson (1997). However, N concentrations in the materials harvested at the second cut were all very low and indicated N deficiency.…”