Crop competition is an important component of weed management in modern cropping systems. A large number of wheat genotypes varying in early vigour were evaluated over multiple sites and seasons to identify differences and stability of competitive ability. Several of these experimental high vigour lines showed consistently greater weed suppression than commercial cultivars. A strong association between genotype mean weed suppression and stability across four environments provides evidence for opportunities in the selection of improved weed competitive ability in wheat.

Genetic relations between morphotypes of the endemic native legume Vigna lanceolata were studied using a complete diallel cross. It was concluded that genetic incompatibilities will preclude all morphotypes being used in a single breeding program. Two options drawing on subsets of morphotypes are suggested: a tuberous-rooted, amphicarpic perennial for use as a pasture legume, and a freely seeding, fibrous-rooted, amphicarpic annual for use as a ley legume.

Tropical dairies use high rates of nitrogen fertiliser and there have been few studies into how fertiliser-use efficiency might be improved. This 1-year study on a dairy farm in tropical North Queensland found that urea application rates could be halved without reducing pasture growth if the urea was coated with a nitrification inhibitor (DMPP). The findings indicate good potential for farmers to maintain productivity and profitability while reducing losses of nitrogen to the environment.

The present study has established a set of GrassMaster II probe calibration equations, whereby it is possible to estimate green matter and dry matter yield for typical Mediterranean pastures based on the corrected meter reading at different phenological stages and pasture moisture contents. The accuracy and the reliability of the probe show that it can be associated with a GPS receiver providing the means for in-situ evaluation and monitoring of pasture development patterns.

Information pertaining to GE interaction especially for native genotypes under irrigation conditions is very limited. This study aimed to analyse and understand the complex G × E interactions in three groups of tall fescue genotypes using the AMMI model analysis. The graphical presentation has brought out the complexity in the dataset and has clearly aided in the identification of stable and superior genotypes in some environments.