Annual ryegrass (Lolium rigidum) reduces the uptake and utilisation of fertiliser-nitrogen by wheat

Abstract

The effect of timing of annual ryegrass (Lolium rigidum) emergence on the uptake and utilisation of N by wheat was investigated in a field trial on a duplex soil at Katanning, Western Australia, and in a glasshouse study in which 15N-fertiliser was applied. Three treatments were used to investigate the effect of timing of annual ryegrass emergence on the uptake and utilisation of N by wheat: simultaneous sowing of wheat and annual ryegrass, sowing of annual ryegrass 1 week before wheat, and sowing of the annual ryegrass 1 week after wheat. A control treatment, consisting of wheat sown alone, was also included. Plant densities during the field trial were 105 and 140 plants/m2 for wheat and annual ryegrass, respectively, whereas in the glasshouse they were 105 plants/m2 for wheat and 155 plants/m2 for annual ryegrass. Fertiliser-N was applied at seeding of wheat at 50 kg N/ha in the field trial and 60 kg N/ha in the glasshouse. The introduction of annual ryegrass into the wheat system reduced the production of biomass and the grain yield of wheat. The earlier the annual ryegrass was introduced into the system, the greater the reduction in the biomass and grain yield of wheat. Poor tillering and slow rates of growth were accountable for the reduction in biomass, whilst the reduction in wheat grain yield was caused by the reductions in ear number, kernels per ear, and kernel size. Grain N content and hence grain protein was also reduced by the introduction of annual ryegrass into the wheat system. Irrespective of the timing of introduction of annual ryegrass, the low N uptake of wheat resulted from a reduction in the uptake of both soil and fertiliser-N. This indicates that annual ryegrass competed with wheat not only for the fertiliser-N that was applied at seeding of wheat, but also for mineralised soil N. The competition for N reduced the total recoveries of fertiliser-N in the wheat plant. Total recoveries of fertiliser-N in the wheat plant suggest that 59% of the fertiliser-N was not taken up by wheat when annual ryegrass was sown 1 week earlier than wheat or at the same time as wheat, whereas only 32% was not taken up by the wheat when annual ryegrass was sown 1 week later than wheat. More competitive wheat genotypes would be those with better efficiency in the uptake of N and its utilisation in maintaining yield and grain protein under infestations of annual ryegrass.

Understanding Lolium rigidum Seeds: The Key to Managing a Problem Weed?

“…Lolium rigidum is now a major weed of cropping systems worldwide, particularly in regions with a Mediterranean climate, and the cost of infestation in Australian agriculture is estimated to be hundreds of millions of dollars annually. The highly competitive nature of L. rigidum for the nutrients applied to crop fields leads to decreases in the number of fertile tillers and spikelets of the crop, resulting in significantly lower yields [3][4][5]. The success of L. rigidum as a weed is due to its high genetic variability, adaptability and fecundity, with reports of 45,000 seeds m −2 being produced in infested wheat fields [6].…”

Multiple herbicide‐resistant Lolium rigidum (annual ryegrass) now dominates across the Western Australian grain belt

“…Lolium rigidum Gaudin (annual or rigid ryegrass) is the most widespread and problematic weed of crops in southern Australia. Originally widely planted as a pasture plant (Kloot, ), L. rigidum is now present across most of the southern Australian cropping region (Gill, ) and is a major crop weed which competes with the crop for nutrients and water (Palta & Peltzer, ). Control of L. rigidum has been achieved by the use of herbicides since the 1970s.…”

Addressing the yield gap in rainfed crops: a review

“…Fischer and Wall (1976), Evans (1987) and Passioura (2006) have discussed physiological characters such as developmental patterns in relation to sowing times and length of season, Reynolds et al (2012) and Semenov et al (2014) assessed physiological and biochemical traits in relation to radiation and nitrogen use efficiency in some detail, and others placed emphasis on the synergies that exist between breeding and agronomy or management (Hochman et al 2009;Passioura and Angus 2010;Richards et al 2014;Sadras and Lawson 2011). Improved transpiration efficiency (Evans 1987;Passioura and Angus 2010), competitive ability against weeds (Lemerle et al 2001;Palta and Peltzer 2001), nutrient use efficiency (Anderson and Hoyle 1999) and suitability for dual purpose use (grazing and grain recovery, e.g. Anderson 1985;Virgona et al 2006) have also been suggested as traits likely to contribute to yield increases.…”