Spring barley (Hordeum vulgare cv. Triumph) was grown hydroponically over a 6-week period. Two treatments were incorporated either into the hydroponic solution or sprayed onto the plants at rates of 1 ml per 3 litres. The treatments applied were: (i) a seaweed concentrate prepared from Ascophyllum nodosum (L.) Le Jolis (marketed as Maxicrop Triple), (ii) a 'Trace element' treatment incorporating the micro and macro nutrients added to the seaweed extract base to produce the formulated product Maxicrop Triple and (iii) a control treatment. Irrespective of the mode of application, plants treated with Maxicrop Triple grew faster than plants under either of the two other treatments. Elevated growth rates were also found for the 'Trace element' treated plants when incorporated into the hydroponic solution. At the final harvest, plants with Maxicrop Triple incorporated into the hydroponic solution showed increases from 56-63% over the control treatment for the growth characteristics measured. 'Trace element'-treated plants produced increases of between 25-45 %. When the treatments were sprayed the effect was less pronounced. Maxicrop Triple increased growth characters by 35-38% and the 'trace element' treatment gave increases in the range of 2-13%.
Timothy [S. 50], meadow fescue [S. 53], perennial ryegrass [S. 23], Italian ryegrass [S. 22] and cocksfoot [S. 143] were grown together in all possible pair combinations at two levels of fertility, in a pot experiment. Dry weight of herbage and tiller counts were determined at 136 and 198 days from sowing. The data were analysed for competitive effects by the application of the diallel analysis technique of Durrant (1965). The competitive effects were largely compensatory in type with dominant species such as Italian ryegrass and perennial ryegrass increasing in mixtures, relative to their pure stand values, more than species such as timothy and meadow fescue declined. This resulted in a tendency for the mixture means to exceed their mid-constituent values.The competitive effects on the reciprocal differences were seen to be predominantly of the alpha type; that is, there was a constant increase or decrease in one or more species when grown with others. The alpha values were found to be correlated with the unmixed species values so that 5, the mean effect, was appropriately calculated from alpha. The over-all value of 5 was -1-216, which means that for each gram difference in weight between the species when grown by themselves there was 2-452 g increase in difference between the species when grown in mixtures, the larger species increasing and/or the smaller species decreasing. There were significant differences in 5 values between harvests, the 5 competitive effects being approximately twice as large in the more mature plants. Although the alpha competitive effects increased in magnitude with time the species order remained relatively constant, and in terms of competitive ability the species could be placed in the ascending order, meadow fescue, timothy, cocksfoot, perennial ryegrass and Italian ryegrass.Tiller number showed a similar pattern, but the 5 values were smaller, and not significant. Nevertheless competition had differential effects upon the plant weight/ tillering relationship and it is possible that the resultant morphological changes would influence the re-growth quality of the species.The conclusions derived from the analysis of reciprocal differences in this work is compared with earlier examples.
Graphical and statistical analyses based on the methods of DURRANT (1965) are applied to data on plant competition experiments previously presented by WILLIAMS (1962) and MCGILCHRIST (1965) and to new data from a comparable experiment in barley.The primary objectives of the analysis are to determine: 1. whether the differences between species grown together are a function of the differences between them when grown separately (beta competition), (2) whether the individual species are uniformly increased or decreased when grown with the other species (alpha competition), (3) which species influence the other species most and which species are influenced most by other species, (4) to what extent the change of one species results in a compensating change in the species grown with it, (5) whether the mixtures give more or less yield than the unmixed species.Data from both experiments are similar in showing large competitive effects in their reciprocal differences which are compensating, the larger species increasing and the smaller decreasing, but whereas the one could be interpreted in terms of beta competition and the mixture means tended to the smaller species, the other could only be interpreted in terms of alpha competition, and the mixture means tended towards the larger species. It is possible that the differences may be a reflection of the environmental differences imposed by the pot culture of the first, and the field plot conditions of the second. INTRODUCTIONThe plant breeder is required to evaluate the performance of species and species combinations on the field scale, his ultimate aim being the successful exploitation of environmental resources for crop and stock production. He is particularly concerned with the manipulation of density in order to obtain optimum yields in pure stands and also in the performance of mixtures of different varieties from the same, or from different species, in studying the interactions of mixed populations it has been customary to grow the species or varieties together in pairs or higher groupings and to compare their performance in mixtures with that of the components grown alone. A most useful layout from an experimental standpoint is to grow the varieties or strains in all possible pair combinations. Such a competition "diallel" may be likened to a genetic diallel table where the species grown alone e.g. A and B correspond to the parental genotypes, and the species grown in mixtures, e.g. AB, correspond to the F 1 crosses. In each mixture both the difference between A and B (the reciprocal
The relative uptake of P was measured in two varieties of Lolium perenne using radioactive tracer techniques. Tbe diploid cv. Hora and the tetraploid cv. Terhoy were sown as pure stands and as 50:50 mixtures at both high and low density. Uptake from four depths 10, 20, 30 and 40 cm was examined. The results showed tbat: in pure stands the diploid uptake at 10 cm exceeded that of tbe tetraploid altbougb at deeper levels the uptake pattern was similar; in mixtures the uptake of the tetraploid variety increased markedly at 10 cm while that of the diploid variety decreased. The diploid compensated for its decreased uptake at 10 cm by a suhstantiai increase in uptake at 20 cm; overall the tetraploid variety had a deeper pattern of uptake tban the diploid; in general, uptake at high density was greater than that at low density; the mixture showed a greater degree of P utilization than pure stands in the upper layers of the soil; when these two varieties are grown together in 50:50 mixtures the tetraploid is relatively more efficient in taking up P.
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