Assessment of plant height is an important factor for agronomic and breeder decisions; however, current field phenotyping, such as visual scoring or using a ruler, is time consuming, labour intensive, costly and subjective. For agronomists and plant breeders, the most common method used to measure plant height is still a meter stick. In a 3-year study, we have adopted a herbometre similar to a rising plate meter as a reference method to obtain the weighted plant height of barley cultivars and to evaluate vehicle-based ultrasonic and laser distance sensors. Sets of 30 spring barley cultivars and 14 and 60 winter barley cultivars were tested in 2013, 2014 and 2015, respectively. The herbometre was well suited as a reference method allowing for an increased area and was easy to handle. The herbometre measurements within a plot showed very low coefficients of variation. Good and close relationships (R² = 0.59, 0.76, 0.80) between the herbometre and the ultrasonic distance sensor measurements were observed in the years 2013, 2014 and 2015, respectively, demonstrating also increased values of heritability. Hence, both sensors were able to differentiate among barley cultivars in standard breeding trials. For the sensors, we observed a 4-fold faster operating time and 6-fold increase of measurement points compared with the herbometre measurement. Based on these results, we conclude that distance sensors represent a powerful and economical high-throughput phenotyping tool for breeders and plant scientists to estimate plant height and to differentiate cultivars for agronomic decisions and breeding activities potentially being also applicable in other small grain cereals with dense crop stands. Particularly, ultrasonic distance sensors may reflect an agronomically and physiologically relevant plant height information.

Evaluation of genetic diversity within germplasm collections and identification of trait-specific germplasm is a basic requirement for plant breeders. A total of 221 Indian pearl millet collections from the National Genebank were characterised and evaluated for 27 agro-morphological descriptors. Considerable variation was observed for all characters. Frequency distribution analysis showed predominance of cylindrical and compact spike, grey seeds, earliness (less than 40 days to spike emergence). Hierarchical clustering method was used for classifying 221 pearl millet accessions based on agronomic and disease resistance traits, which resulted into three clusters. Clusters 1, 2 and 3 comprised 91, 54 and 76 accessions respectively. There was high correspondence between the geographic collection sites of accessions and their inclusion in particular clusters. In addition, principal component analysis was used for data reduction and generating biplot. First four principal components explained 66.43% of total variability. Among the traits analysed, plant height, nodes/plant, days to spike emergence, number of tillers, leaf width and leaf length are major contributor towards phenotypic diversity. Further the trait-specific germplasm were identified for agronomic traits, disease resistance, popping and antioxidants activity, namely for earliness (IC343664, IC343689, IC343661, IC309064), spike girth (IC283693, IC283842, IC367638), dual purpose with high grain and fodder yield (IC283705, IC283745, IC283885 and IC335901 and so on). Four accessions of pearl millet germplasm viz., IC309064, IC393365, IC306465 and IC283866, were observed as multiple disease resistant. This study suggested that application of appropriate techniques and their interpretations provide more efficient way to identify potential accessions and improve the utilisation of germplasm collections in plant breeding.

The expression and heritability of quantitative traits were examined in four hybrid mungbean populations, developed by crossing two cultivars, Kiloga and Berken, with two Australian wild accessions, ACC 1 and ACC 87. Phenological, morphological, agronomic and pod and seed traits were measured in the parental, F₁, F₂, and two F₁ × parent backcross progeny generations. Plants were grown in large pots on benches, in autumn in the field at Townsville, Australia. The two cultivars were both early flowering (∼5 weeks) and short duration, with short, thick stems, few branches, large leaflets, pods and seeds, and high harvest index. There were greater differences between the two wild accessions. ACC 1 was very late flowering (>12 weeks) even under the short days of autumn, and strongly indeterminate, with prostrate habit, prolific branching, thin stems, small leaflets and tiny seeds. The perennial type ACC 87 was intermediate in flowering (∼6 weeks), with more robust, albeit still branched and twining growth habit, and larger leaflets, flowers, pods and seeds. Flowering in all crosses was conditioned by additive gene action with some dominance effects (with lateness recessive to earliness). The responses suggested that the extreme lateness of ACC 1 was due to the cumulative additive effects of multiple lateness genes. For most other traits, there were broad consistencies in trait expression in hybrid progeny and heritability between the different crosses, indicating general similarities in genetic control. Although broad-sense heritability for most traits was high, narrow-sense heritability was high to very high for twice as many traits in the ACC 87 as in the ACC 1 crosses, indicating higher levels dominance effects in the latter crosses. Several genetic and phenotypic correlations were identified between various traits, as well as associations between quantitative traits in this study and previously reported qualitative traits from the same populations. There were no gross genetic incompatibilities between the wild and cultivated accessions. However, irregularities in the segregation patterns in the progeny generations for seeds per pod suggested that there may have been cryptic hybrid breakdown effects at the gametic or zygotic level. The results of this study indicated that ACC 1 and ACC 87 are genetically distinctive, with the perennial form ACC 87 actually less distant from the domesticated mungbean than is ACC 1. The research provides yet further evidence that the Australian wild accessions add significant diversity to the mungbean primary germplasm.

Despite the potential productivity benefits, intercrops are not widely used in modern, mechanised grain cropping systems such as those practised in Australia, due to the additional labour required and the added complexity of management (e.g. harvesting and handling of mixed grain). In this review we investigate this dilemma using a two-dimensional matrix to categorise and evaluate intercropping systems. The first dimension describes the acquisition and use of resources in complementary or facilitative interactions that can improve resource use efficiency. The outcome of this resource use is often quantified using the land equivalent ratio (LER). This is a measure of the relative land area required as monocultures to produce the same yields as achieved by an intercrop. Thus, an LER greater than 1 indicates a benefit of the intercrop mixture. The second dimension describes the benefits to a farming system arising not only from the productivity benefits relating to increased LER, but from other often unaccounted benefits related to improved product quality, rotational benefits within the cropping system, or to reduced business risks. We contend that a successful intercrop must have elements in both dimensions. To date most intercropping research has considered only one of these two possible dimensions.

Intercrops in large, mechanised, rain-fed farming systems can comprise those of annual legumes with non-legume crops to improve N nutrition, or other species combinations that improve water use through hydraulic redistribution (the process whereby a deep-rooted plant extracts water from deep in the soil profile and releases a small proportion of this into the upper layers of the soil at night), or alter disease, pest or weed interactions. Combinations of varieties within cereal varieties were also considered. For our focus region in the southern Australian wheatbelt, we found few investigations that adequately dealt with the systems implications of intercrops on weeds, diseases and risk mitigation. The three main intercrop groups to date were (1) ‘peaola’ (canola-field pea intercrops) where 70% of intercrops (n = 34) had a 50% productivity increase over the monocultures, (2) cereal-grain legume intercrops (n = 22) where 64% showed increases in crop productivity compared with monocultures and (3) mixtures of cereal varieties (n = 113) where there was no evidence of a productivity increase compared with the single varieties.

Our review suggests that intercropping may have a role in large rain-fed grain cropping systems, based on the biophysical benefits revealed in the studies to date. However, future research to develop viable intercrop options should identify and quantify the genotypic differences within crop species for adaptation to intercropping, the long-term rotational benefits associated with intercrops, and the yield variability and complexity-productivity trade-offs in order to provide more confidence for grower adoption. Farming systems models will be central to many of these investigations but are likely to require significant improvement to capture important processes in intercrops (e.g. competition for water, nutrients and light).

Technologies such as minimum tillage and new herbicides have enabled the use of early and dry sowing in Western Australia (WA). Although there is a sowing date that maximises yield of individual fields, on-farm sowing dates are constrained by the availability of machinery and labour. It was hypothesised that farms with a larger crop area would begin sowing earlier and be more likely to dry sow than smaller farms because they would take longer to sow. Current sowing dates and the extent of dry sowing in WA were explored using multiple analytical approaches, such as analysis of farm records, survey data and historical weather records, and simulation modelling. Field records from seven farms showed that sowing date of the first cereal crop on-farm had advanced markedly in recent years. The timeline of this advanced cereal sowing date differed across sites but was prominent from 2010 for most sites. In a larger survey, conducted between 2011 and 2014, of 805 grain farms across all rainfall zones in the WA grain belt, the mean first crop sowing date was 29 April and half the farms used dry sowing. Farms with larger cropped areas tended to begin sowing crops earlier and were more likely to dry sow. Only 26% of small farms (<1000 ha crop) used dry sowing compared with 71% of large farms (>5000 ha crop). A larger proportion of lupin (34%) and canola (43%) was sown dry than wheat (16%) or barley (10%; P < 0.001). Simulation modelling demonstrated that the optimum time to begin sowing at the farm level was often well before the break of season (the first autumn rainfall of sufficient volume to ensure subsequent successful crop germination and establishment), but this was dependant on the size of the cropping program. Early and dry sowing will continue to expand, and research to understand how other agronomic management interacts with this change should be a priority. This may include cultivars with appropriate traits, such as longer duration to flowering, changes in weed management practices, management practices that accumulate soil moisture at sowing, interactions with water repellent soil and the interaction with dual purpose cropping.

Remote sensing through Unmanned Aerial Vehicles (UAV) can potentially be used to identify the factors influencing agricultural yield and thereby increase production efficiency. The use of UAV remains largely underutilised in tropical agricultural systems. In this study we tested a fixed-wing UAV system equipped with a sensor system for mapping spatial patterns of photosynthetic activity in banana plantations in Costa Rica. Spatial patterns derived from the Normalised Difference Vegetation Index (NDVI) were compared with spatial patterns of physical soil quality and banana fruit production data. We found spatial patterns of NDVI were significantly positively correlated with spatial patterns of several metrics of fruit yield and quality: bunch weight, number of hands per bunch, length of largest finger, and yield. NDVI was significantly negatively correlated with banana loss (discarded due to low quality). Spatial patterns of NDVI were not correlated with spatial patterns of physical soil quality. These results indicate that UAV systems can be used in banana plantations to help map patterns of fruit quality and yield, potentially aiding investigations of spatial patterns of underlying factors affecting production and thereby helping to increase agricultural efficiency.

Helicoverpa armigera was once considered the most important insect pest to Australian cotton production. The introduction of genetically modified cotton altered this status and made this insect pest control less chemically dependent, but resistance to the insecticidal compounds expressed in genetically modified cotton has evolved in laboratory-reared H. armigera populations and is shown to exist in natural populations. Preventing the development of resistance in field populations is complicated by the over wintering of potentially resistant individuals in the soil. Biocontrol may assist in reducing the population of resistant individuals. Several projects investigating the ecology of Australian cotton highlighted the existence of several native organisms with ability to limit the growth or utilise H. armigera as a host. The work reported here set about establishing the presence of such organisms in Australian cotton soils by recovering them from soil and farm-collected H. armigera that exhibited abnormal growth, disease or death. The recovered organisms were identified as the fungi Lecanicillium lecanii, Actinomucor elegans and several Aspergillus species. L. lecanii was subsequently shown to reduce moth emergence to 56% of the larvae to which it was applied. We also identified a species of Rhabditis nematode, which killed 34% of the larvae to which it was applied and reduced moth emergence to 28%. In light of these observations these organisms are reported as potential candidates for biological control of H. armigera.

Organic amendments not only improve soil conditions but also affect belowground biological processes. This study used a split plot design to investigate the effects of cotton straw management, inorganic fertiliser, and manure amendment on (i) soil nutrient content, (ii) soil microbial properties, and (iii) cotton root growth in a drip-irrigated cotton field. Straw return significantly increased soil inorganic nitrogen (N), N transformation rates, organic carbon (C), and urease activity. Straw return, however, had no significant effect on either root growth or activity. Inorganic fertiliser and/or manure amendment significantly increased inorganic N, N transformation rates, organic C, microbial biomass C, urease activity, and invertase activity. Inorganic fertiliser and/or manure also significantly increased fine root growth, triphenyltetrazolium chloride-reducing capacity, and specific root length. Moreover, the inorganic fertiliser plus manure treatment had the greatest soil inorganic N concentrations, N mineralisation rate, total carbon dioxide efflux, C mineralisation rate, soil organic C concentration, microbial biomass C concentration and enzyme activity, as well as root biomass, fine root : coarse root ratio, root triphenyltetrazolium chloride-reducing capacity and specific root length. Straw return to inorganically fertilised soil increased inorganic N concentrations by 11%, net N mineralisation rate by 59%, net nitrification by 59%, gross nitrification by 14%, denitrification by 39%, and urease activity by 25% compared with inorganic fertiliser alone. Taken together, the results indicated that straw return and manure application significantly promoted soil microbial activity and soil N transformation in the presence of inorganic fertiliser. The manure amendment enabled the crop to develop a more extensive root system, primarily by increasing the number of fine roots. Thus, organic amendments may improve the acquisition efficiency of inorganic fertiliser in drip-irrigated cotton fields.

Intensely pigmented potato tubers are desired for the speciality potato market because of the health-promoting effects of pigments and other related compounds. Although highly coloured potatoes show higher concentrations of carotenoids and anthocyanins and higher antioxidant capacity, the phytochemical composition is highly dependent on environmental factors. Thus, the effects of genotype, environment and genotype × environment interactions on monomeric anthocyanins, soluble phenolics, carotenoids and hydrophilic antioxidant capacity were evaluated in a set of cultivars selected on the basis of the contrasting flesh colour of tubers. Twenty-one tetraploid potato genotypes were grown in three different field trials at Arkaute and Iturrieta for 2 years. Genotype, environment and genotype × environment interactions were significant for all of the studied parameters (P ≤ 0.01). However, most of the variation was accounted for by clonal variation. Broad-sense heritabilities (and their 95% confidence intervals) were 0.947 (0.832–0.981) for total monomeric anthocyanins, 0.917 (0.852–0.952) for total soluble phenolics, 0.950 (0.911–0.975) for total carotenoids, and 0.887 (0.799–0.945) and 0.850 (0.734–0.927) for hydrophilic antioxidant capacity measured by ABTS and DPPH methods, respectively. Although certain instabilities were recorded for all of the studied traits, the high estimates of heritability support the main role of genetics in phytochemical composition and suggest that sufficient heritable genetic variation exists in tetraploid potato germplasm for the breeding of advanced clones with improved bioactive properties.