Turfgrass (Cynodon dactylon L.) sod production on sandy soils: I. Effects of irrigation and fertiliser regimes on growth and quality

The effects on growth, quality and N uptake by turfgrass (Cynodon dactylon L.) during sod production of four fertiliser types applied at three application rates (100, 200 or 300 kg N ha⁻¹ per ‘crop’) under two irrigation treatments (70% and 140% daily replacement of pan evaporation) were investigated. The fertiliser types were: water-soluble (predominately NH₄NO₃), control-release, pelletised poultry manure, and pelletised biosolids; and the experiment was conducted on a sandy soil in a Mediterranean-type climate. Plots were established from rhizomes, with the turfgrass harvested as sod every 16–28 weeks depending upon the time of the year. Four crops were produced during the study. Applying water-soluble and control-release fertilisers doubled shoot growth and improved turfgrass greenness by up to 10% in comparison with plots receiving pelletised poultry manure and pelletised biosolids. Nitrogen uptake into the shoots after four crops (averaged across irrigation treatments and N rates) was 497 kg N ha⁻¹ for the water-soluble fertiliser, 402 kg N ha⁻¹ for the control-release, 188 kg N ha⁻¹ for the pelletised poultry manure and 237 kg N ha⁻¹ for the pelletised biosolids. Consequently, the agronomic nitrogen-use efficiency (NAE, kg DM kg⁻¹ N applied) of the inorganic fertilisers was approximately twice that of the organic fertilisers. Increasing irrigation from 70% to 140% replacement of pan evaporation was detrimental to turfgrass growth and N uptake for the first crop when supplied with the water-soluble fertiliser. Under the low irrigation treatment, inorganic N fertilisers applied at 200–300 kg N ha⁻¹ were adequate for production of turfgrass sod. Section Editor: P. J. Randall     

A comparative study of growth strategies in two varieties of Arrhenatherum elatius

Growth strategies of the two varieties of Arrhenatherum elatius were studied. The two varieties studied were: onion couch, which produces bulbous swollen internodes and is an arable weed of local importance, whilst tall oat-grass is more widely distributed. An experiment in which the two varieties were grown at different densities in monoculture and were harvested at intervals, highlighted various aspects of the competitive relation between the two varieties and an annual crop. Significant and consistent differences were found between the two varieties for most of the attributes measured during the two growing seasons. Tall oat-grass allocated a greater proportion of its whole shoot dry weight to producing vigorous aerial tillers, whereas onion couch allocated a greater proportion of its whole shoot dry weight to the development of basal internodes. The regulation of tiller number as a reaction to increasing density in tall oat-grass is achieved by high tiller mortality, whereas in onion couch, this stress is expressed by small tiller mortality. Growth pattern shown by the two varieties of A. elatius reflect the adaptive strategies evolved by them in two different habitats and are due to the genetic factors which determine the presence or absence of their characteristic basal internodes.     

Using RAPD markers to identify genets of an arable grass weed, Arrhenatherum elatius ssp. bulbosum

RAPD (Random Amplified Polymorphic DNA) markers were used to identify genets within a weed infestation of Arrhenatherum elatius ssp bulbosum (“onion couch”). Three selected primers could discriminate between 18 sexually-derived plants of A. elatius ssp. elatius. Using these primers, RAPD phenotypes were obtained for ramets of ssp. bulbosum from a population of unknown sexual derivation, i.e. predominantly sexual or vegetative. Thirty three RAPD phenotypes were observed amongst 65 plants. Ramets with identical RAPD phenotypes were termed “genets”. Some genets of ssp. bulbosum were found in localised patches, whereas others had much wider ranges, indicating long-distance dispersal by farm machinery. RAPD markers provide a useful tool for discriminating between genets within an established plant population.