This paper reviews the interactions between water and nitrogen from physiological, agronomic, economic, breeding and modelling perspectives. Our primary focus is wheat, the main crop in Australia; forage crops, sorghum and legumes, are considered where relevant aspects of water–nitrogen interactions have been advanced. The paper concludes with suggestions for future research on water-nitrogen interactions.

Barley yellow dwarf virus is one of the most ubiquitous pathogens in cereal crops that cause significant yield losses. The most effective and sustainable protection against the virus to date is the use of resistant/tolerant cultivars. The results describe in this article include the incidence of BYDV in winter cereal crops in the Czech Republic and a comprehensive analysis of resistance in numerous wheat and barley cultivars (breeding lines) to this disease.

Some of 100 winter and facultative wheat entries from the International Winter Wheat Improvement Program were resistant against PST-17, 44%; PST-37, 32%; PST-43, 45%; PST-45, 49%; PST-116, 18%; PST-100, 17%; and PST-127, 8%. Molecular markers were positive for genes Yr9, Yr17, and Yr18 and negative for Yr5, Yr10, and Yr15. Sixteen entries were shown to have high-temperature adult-plant (HTAP) resistance and resistance–moderately resistance.

Field experiments were conducted under two different (arid and semi-arid and cool) climatic conditions to indicate how wheat light properties may be affected by different plant and environmental parameters including wheat genotypes, planting dates and N chemical fertilisation. The results indicated that the right wheat genotype, planted at the right planting date using the proper rate of N chemical fertilisation resulted in the highest plant response to light, and hence the highest wheat grain yield.

Moisture deficit is a major challenge to the future maize production. As the development of drought tolerant genotypes is an important aim in maize breeding, therefore the selection indices based hybrids suitable for drought prone area were identified. Cultivation of identified drought-tolerant hybrids would be useful to enhance maize productivity in drought-stress environments.

Soybean genotypes that release more carbon compounds into the rhizosphere are capable of mining fixed soil P, and hence are more efficient in P acquisition. This paper evaluates the use of isotope (¹⁴C) labelling to identify genotypes with improved P-acquisition efficiency. Genotypes with high root exudation index (REI) performed equally well at sufficient and low soil P availability, and therefore, REI may be used to screen efficient genotypes from a large set of diverse germplasm.

Fodder legumes are of major importance for crop rotations as well as for fodder production in agriculture, but fungal diseases such as southern anthracnose can cause severe losses and reduce productivity of grassland and arable feed crop production. A test for resistance against southern anthracnose was performed in the greenhouse with different fodder legumes, and species with high resistance were identified. Thus, species which remain productive when the disease occurs can ensure forage yield and nutrient supply.

We conducted two greenhouse experiments to explore the response of AMF to heterogeneous P by creating P-enriched patches of different P supply levels or P forms. Our results indicated that AMF improved the plant growth but the response of AMF to P-enriched patches was complex and both the form and amount of P supplied should be considered. This may provide a mechanism by which AMF can maintain diversity in intensive agricultural ecosystems.