Effects of nitrogen and phosphorus fertilisers on yield and on inorganic and organic composition of italian ryegrass grown on phosphorus‐deficient soil

Abstract

Italian ryegrass (Lolium rnultiflorum) S22, grown in a greenhouse in phosphorusdeficient soil in pots was given 40 and 160 mg N/kg of soil (as ammonium nitrate) and 5, 25 and 100mgP/kg of soil (as calcium tetrahydrogen diorthophosphate). Giving more nitrogen increased yields only when adequate phosphorus was applied. A significant response to added phosphorus was obtained when ryegrass dry matter contained about 0.15 % P or less. Nitrogen increased the amount of sugars but decreased that of fructosan. Phosphorus increased the production of both sugars and fructosan. Protein N (expressed as a percentage of total N) increased with increasing amounts of phosphorus given. The largest values for protein N were obtained when grass contained about 0.3 % Pin the dry matter. In phosphorus-deficient grass nitrate-N accumulated and the predominant compounds within the free amino acid fraction were asparagine and glutamine. Adding phosphorus decreased the concentrations of both nitrate-N and the amides. The amino acid composition of the grass protein was not affected by the nitrogen and phosphorus treatments.

Dietary nitrogen - definitions, digestion, excretion and consequences of excess for grazing ruminants

“…About 20-30% of the nitrogen content in fresh forages is in the form of non-protein N (NPN) (Mangan 1982), represented by nitrates, free amino acids, peptides and secondary metabolites. Fertilisation with N will increase N concentration in the DM of forage, but the increase will be greater if N is not the first limiting nutrient for plant growth (Nowakowski & Byers 1972;Nowakowski et al 1977). In addition to the increase in total N, nitrogenous fertiliser usually increases the proportion of NPN in the forage (up to 45% of the total N: Table 3) and this can affect nutrition, production and health of the animal.…”

Effects of nitrogen fertiliser and urine on pasture performance and the influence of soil phosphorus and potassium status

“…Interactions of Nand P fertiliser have been demonstrated (Dev 1964, Lambert & Toussaint 1977, Nowakowski et al 1977, Soon & Miller 1977. However, these relate to combined applications of N and P, and the interaction is attributable to the influence of N fertiliser on P availability through changes in soil chemistry and/or plant physiology (Cope & Hunter 1968).…”

Can pasture‐fed livestock farming practices improve the ecological condition of grassland in Great Britain?

“…Significant positive relationships between soil P and Lolium cover for both the PFLA plots and the CS Improved Grassland plots (where the relationship was unimodal) indicated that some of the PFLA member farms may retain characteristics of conventional systems, perhaps reflecting a recent transition and legacy effects on existing swards and soils or, in some cases, continued management with P fertilizers. The relationship reflects positive (and agriculturally desirable) impacts of soil P on Lolium growth established decades ago (Nowakowski et al., 1977). Despite similarities in these relationships, Lolium cover was significantly lower in PFLA grassland than in CS Improved Grassland.…”