Agronomical and physiological responses of white clover(Trifolium repens)and perennial ryegrass(Lolium perenne)to nitrogen fertiliser applied in autumn and winter

Abstract

Mixed pastures of white clover and ryegrass are profitable and widely used. However, loss of clover is common with time due to N fertiliser applications in late winter. The factors that cause this loss have yet to be determined. This work investigated reasons for the competitive disadvantage suffered by white clover relative to ryegrass in autumn and winter. White clover (Trifolium repens cv. 'Grasslands Huia') and ryegrass (Lolium perenne cv. 'Grasslands Nui') were sown in March in Canterbury, New Zealand, and grown as single plants in silica sand. Nitrogen (N; 0.5 mol m -3 N); was applied daily simulating an unfertilised soil; solution N concentration was increased to 5.0 mol m -3 N for treatments in autumn (May) or winter (August), simulating fertiliser treatment. Net photosynthesis was measured before each harvest and over a diurnal period at 123 days after sowing. Plants were destructively harvested six times (33-185 days after sowing) and plant dry weight and N concentration (%) measured. White clover had a significantly (P < 0.05) lower dry weight than ryegrass. Extra N applied from May significantly increased (P < 0.05) dry weight of ryegrass. No significant changes in shoot N concentration were found. Except at the last harvest, net photosynthesis was significantly lower (P < 0.05) in white clover than in ryegrass; this was also apparent for diurnal net photosynthetic rates 123 days after sowing. Results indicated that white clover growth was limited by temperature, whereas ryegrass growth was limited by N supply.

Long‐term time series of legume cycles in a semi‐natural montane grassland: evidence for nitrogen‐driven grass dynamics?

“…In other systems less limited by nitrogen, grasses can successfully suppress the legumes (Haynes ; Elgersma, Schlepers & Nassiri ; Castle et al . ). However, this happens typically in fairly nutrient‐rich systems where nutrients are provided by some external source (e.g.…”

“…However, this does not need to be a universal finding: our system is only one example of a semi-natural grassland (for which fortunately we have long-term data). In other systems less limited by nitrogen, grasses can successfully suppress the legumes (Haynes 1980;Elgersma, Schlepers & Nassiri 2000;Castle et al 2002). However, this happens typically in fairly nutrient-rich systems where nutrients are provided by some external source (e.g.…”

A Novel Approach to Grass–Legume Management

“…Johnson and Morrison (1997) in a study of spring fertilizer N on ryegrass-white clover swards grazed by beef cattle reported that there was no effect of spring fertilizer N on white clover proportion in the sward over the season as a whole and the use of extra N did not have a significant effect on white clover plants leaf area. Further, white clover dry weight and total shoot and root proportion did not respond to an application of N (Castle et al, 2002). Further evidence to support these claims on a general negative correlation of mineral N use on clover swards has been documented.…”

Clover and ryegrass are tolerant species to ammonium nutrition

“…Thus, there is a great range of plant responses to NH 4 + nutrition; there are some species that are tolerant to high NH 4 + doses, such as rice (Wang et al, 1993), and some very sensitive species, which are almost unable to live under NH 4 + nutrition, such as tomato or barley (Magalhaes and Huber, 1989;Britto et al, 2001). Reports about the nitrogen form effect in grassland species are rare and, in general, are focused on high and low availability of nitrate (Castle et al, 2002;MacDuff et al, 2002;Collins et al, 2003). Tolerance to NH 4 + -based nutrition could be expected in these species because intensive grazing process leads to urea deposition in grasslands and, consequently, maintained NH 4 + availability in the soil.…”