SUMMARYThe response of two cultivars of white clover (Aberystwyth SI 84 and New Zealand Grasslands Huia), grown under laboratory and field conditions, to inoculation with two endophytes (Glomus mosseae LI and Glomus etunicatus) was investigated in two hill soils with various amounts of added phosphate.In the experiment with the deep peat soil in the laboratory, inoculation with either endophyte increased infection from 2 % to up to 70 %, the increase being less the higher the amount of added P. Shoot growth of white clover was significantly increased (P < 0-05) by inoculation at the 0 and 20 kg P ha"' level and decreased at the highest level of added P (200 kg P ha~'). Both endophytes produced similar effects. With the brown earth soil, total infection of roots with indigenous endophytes ranged from 30 to 50 % and this was significantly (P < 0-05) increased by inoculation only at 40 kg P ha"'. However, the introduced coarse endophytes had replaced between a quarter and a half of the predominantly fine indigenous endophyte at each level of added P. This change of endophyte was without significant effect on dry wt of shoots and roots although there was a general trend for inoculation, and with Glomus etunicatus more than with Glomus mosseae LI, to increase shoot and root dry wt. Inoculation also tended to increase the P content of shoots and roots but this was statistically significant only at 40 kg P ha~'.In the field experiment with the deep peat soil, inoculation with Glomus mosseae LI doubled the amount of infected root from 18 to 42 % but there was no effect on shoot growth or the concentration of P. With the brown earth soil, although the amount of infection was not increased, the introduced coarse endophytes had become established in the roots but no effect on shoot growth was observed in the year of sowing. However, in the first harvest year, in the presence of 40 kg P ha~', clover inoculated with Glomus etunieatus produced double the amount of dry shoot per hectare produced by uninoculated plants and 75 % greater than that produced with Glomus mosseae LI.These observations encourage the view that inoculation with mycorrhizal fungi of white clover for improved hill pastures might have a practical role if the responses could be made more predictable. It is concluded that further work is justified to understand the ecology of mycorrhizal fungi in hill pastures and how the symbiosis functions, to select suitable endophytes and to develop methods of inoculation appropriate for use in routine field practice.

No abstract

The benefits to establishment and growth of white clover cvs Aberystwyth S.184 and Grasslands Huia of inoculation with three strains of Rhizobium trifolii, using the peat or liquid inoculum techniques, were investigated during 1975-8 on improved hill soils ranging from brown earth through dry and wet peaty podzol to deep peat.Inoculation induced positive response in either number of seedlings, plant cover or dry-matter production in 18 out of 139 comparisons, had no effect in 118 and produced a negative response in three. Most of the positive responses to inoculation were at sites with wet peaty podzol or deep peat soils but of the five sites where increase in clover D.M. production was found in the first harvest year one was a brown earth. The positive agronomic responses occurred only when the proportion of plants with nodules was high and where a substantial proportion ( > 50 %) of the latter contained introduced Rhizobium strains at least in the year of sowing. The three negative responses were in numbers of seedlings on one brown earth and two dry peaty podzol soils and with the Huia cultivar only. Despite lack of statistical significance at individual sites the dominant overall trend was for inoculation to enhance seedling establishment and the early growtli of white clover in all soil types.On one brown earth and one dry peaty podzol soil there was some evidence that spraying the Rhizobium on to emerging white clover seedlings was more beneficial, at least in microbiological terms, than the customary peat inoculum procedure.The incorporation of even a small amount of nitrogen (30 kg/ha) into the seed bed at the time of sowing adversely affected germination, establishment and growth of white clover in some soils. Sometimes the effects of this nitrogen persisted into the first harvest year.

No abstract

The responses in dry matler (DM) production and changes in nutrient concentration in the shoots of white clover (cv. New Zealand Grasslands Huia) to additions of lime, N, P, K and Mg were investigated in pot and field experiments in a deep peat soil and to additions of N, P, K in two other hill soils in pot experiments. DM production and nutrient concentrations were assessed also for perennial ryegrass in the field experiment. There was no response by white clover to N, but in all soils, and in particular a deep peal, production of shoot DM was increased greatly by lime. P and K, and slightly by Mg. Interactions between lime and P and between P and K were observed. Critical concentrations of nutrients {g kg"') for whitecloverappeared toheabout 20for P. 10-15 for K and 20 for Ca. Herbage production and nutrient contents of ryegrass and white clover grown on a deep peat in the field suggests that critical concentrations may possibly help to diagnose the need for maintenance fertilizer dressings.