Beverley A. Orchard

Grapevine (Vitis vinifera) roots and leaves represent major carbohydrate and nitrogen (N) sources, either as recent assimilates, or mobilized from labile or storage pools. This study examined the response of root and leaf primary metabolism following defoliation treatments applied to fruiting vines during ripening. The objective was to link alterations in root and leaf metabolism to carbohydrate and N source functioning under conditions of increased fruit sink demand. Potted grapevine leaf area was adjusted near the start of véraison to 25 primary leaves per vine compared to 100 leaves for the control. An additional group of vines were completely defoliated. Fruit sugar and N content development was assessed, and root and leaf starch and N concentrations determined. An untargeted GC/MS approach was undertaken to evaluate root and leaf primary metabolite concentrations. Partial and full defoliation increased root carbohydrate source contribution towards berry sugar accumulation, evident through starch remobilization. Furthermore, root myo‐inositol metabolism played a distinct role during carbohydrate remobilization. Full defoliation induced shikimate pathway derived aromatic amino acid accumulation in roots, while arginine accumulated after full and partial defoliation. Likewise, various leaf amino acids accumulated after partial defoliation. These results suggest elevated root and leaf amino N source activity when leaf N availability is restricted during fruit ripening. Overall, this study provides novel information regarding the impact of leaf source restriction, on metabolic compositions of major carbohydrate and N sources during berry maturation. These results enhance the understanding of source organ carbon and N metabolism during fruit maturation.

Eight rice experiments were established at two sites in the Riverina district of south-eastern Australia in the 2012–13 and 2013–14 seasons. Two semi-dwarf rice varieties were drill-sown and nitrogen (N) fertiliser (urea) was applied at different rates at the 4-leaf stage before permanent water (pre-PW) and at panicle initiation (PI). The research assessed the impact of timing of N application on grain yield, compared the apparent N recovery of N fertiliser applied at the two stages, and determined an application strategy for N to obtain consistently high grain yields for current, semi-dwarf rice varieties when drill-sown. The apparent N recoveries achieved were 59% for N applied pre-PW and 25% for N applied at PI, averaged across years, sites, varieties and N rates. Grain yield increased significantly with increased rate of N applied at both stages, but the rate of increase from N applied at PI decreased as the rate of N applied pre-PW increased. The grain yield increase for N applied pre-PW was due to increased number of panicles at maturity and increased number of florets per panicle. Nitrogen applied at PI increased dry matter at maturity and number of florets per panicle. Application of N at PI increased grain yield over that when no N was applied; however, at low PI N-uptake levels, application of N at PI is not enough to achieve high grain yields. Therefore, sufficient N should be available to the crop from a combination of soil- and pre-PW-applied N for the crop to reach a level of N uptake at PI whereby high yields can be achieved. Nitrogen applied at PI did not appear to increase the potential for cold-induced floret sterility as much as pre-PW-applied N. Further research is required to confirm this in other seasons and for other rice varieties.

April sowing of canola is considered optimal for grain yield in many regions of Australia; however, there is often insufficient rainfall in April to sow seed into moisture at the ideal depth of 15–30 mm. We report a series of experiments that investigated the seed characteristics (cultivar type and seed size) that would facilitate successful canola emergence from relatively deep sowing (>30 mm). Ten canola cultivar by sowing depth experiments, each with three hybrid and three open-pollinated cultivars, found hybrid cultivars were able to maintain higher emergence rates and grain yield compared with open-pollinated cultivars from deep sowing. Further investigations in the glasshouse showed that the emergence advantage of the hybrid cultivars was largely due to their inherently large seed size, as increased seed size also improved emergence of open-pollinated canola. Early biomass accumulation also improved with larger seeds. In a field experiment, larger seed size of both hybrid and open-pollinated canola increased early biomass accumulation and final grain yield. Simulation modelling in New South Wales demonstrated the importance of timely sowing of canola, as delayed sowing caused a larger reduction in grain yield than reduced plant population. Although ‘moisture-seeking’ (placing seed into moist soil below a layer of dry soil) reduced the emergence rate of canola, the reduction could be offset by planting large seed (>2 mm diameter). This practice of ‘moisture-seeking’ large-seeded canola should be considered as a strategy to improve the timeliness of establishment and subsequent grain yield of canola when rainfall for crop establishment is marginal yet there is moisture available deeper in the seedbed.

The feed quality of a variety of native shrub and herbaceous legume species from the Riverina area of southern New South Wales was determined to provide an indication of their potential use in livestock grazing systems. Fifteen species were sampled from each of two locations (chiefly low fertility roadsides or travelling stock reserves) at four times within a 12-month period viz. August, November, February and May according to the most likely plant parts to be consumed by grazing animals for each species. Digestibility was estimated using an in vitro rumen fluid digestion assay and crude protein was estimated from nitrogen analysed using the Dumas combustion method. Digestible organic matter in the dry matter (DOMD) was greater than 550 g/kg dry matter (DM) for seven of the native legume species and was highest for Daviesia spp. (D. latifolia 696.2 ± 15.0, D. leptophylla × latifolia 642.5 ± 15.1 and D. leptophylla 622.7 ± 15.4), Glycine spp. (G. clandestina 628.2 ± 18.1, G. tabacina 621.9 ± 28.0 and G. canescens 580.4 ± 25.4) and Indigofera australis (617.8 ± 15.3). Crude protein content was greater than 80 g/kg DM for all species analysed, suggesting that these plants are able to fix nitrogen under low phosphorus fertility conditions. Studies examining grazing management as well as nitrogen fixation and nitrogen transfer to companion grasses are required in order to optimise the management of these plants in grazing systems.

This field trial investigated the effect on vineyard nematodes of organic soil amendments: poultry-litter (PL) biochar, composted cow manure, composted green waste and un-composted rice hulls. To investigate their effects on disease suppression, we chose a vineyard containing healthy grapevines proximal to grapevines with fungal root disease (caused by Ilyonectria spp.). Spring and winter surveys showed that nematodes did not interact with Ilyonectria root disease. Plant-parasitic citrus and ring nematodes predominated in deep soil (10–20 cm), whereas Rhabditis spp. (bacterial-feeder) and omnivorous Dorylaimidae (excluding plant-parasitic and predators) predominated in shallow soil (0–10 cm). After 2 years, the amendments generally decreased the total plant-parasitic nematode (TPPN) populations while increasing the total (non-plant-parasitic) free-living nematodes (TFLN), thus increasing the TFLN : TPPN ratios. PL biochar caused the greatest TPPN decreases (8.5- and 12.9-fold for diseased and asymptomatic grapevines, respectively). The changes caused by the organic amendments were less favourable in a drier season and for diseased grapevines, indicating the importance of seasonal conditions and initial disease status for interpretation of soil organic amendment trial results. This is the first vineyard investigation comparing the impact of PL biochar and other organic soil amendments on parasitic and non-parasitic nematodes.

Most soils in eastern Australian contain abundant soil potassium (K) reserves, and it is often assumed that there are no problems with soil K status. However, soil K deficiency has been reported in selected locations, and for viticulture, there are potential problems with high soil K concentrations due to the application of winery wastewater. This study investigated different soil K variables and plant variables for six soils with distinctive properties from across central and southern New South Wales to determine the presence of soil K deficiency and to understand the effect of adding K on the dynamics of soil K availability. A glasshouse experiment compared the selected soils under three fertiliser K rates with forage kale as the test species. Highly significant differences (P < 0.001) were found for soil and fertiliser K rate effects for three measures of soil K (solution K, soln K; exchangeable K, exch. K; tetraphenyl borate K; TBK). Significant soil and fertiliser rate effects were detected (P < 0.001 and P = 0.04 respectively) for the plant shoot (stem and leaf) biomass and nutrient uptake efficiency (UPE) index, but no plant K deficiency was detected; in fact, luxury K consumption was likely. Quantification of K efficiency indices (UPE and utilisation efficiency, UTE) demonstrated significant differences between the soils in the ease with which K was removed. This was illustrated by the negative correlation between both UPE and UTE with final exch. K. From soil properties potentially related to soil K variables, a significant linear regression relationship (P = 0.05) was found for TBK with illite and clay content. By contrast, a linear regression relationship between exch. K and illite content only was weaker (P = 0.09). These relationships show how soil properties (especially mineralogy) can predict soil K variables. A significant positive log–log relationship was found between exch. K or TBK for 37 Queensland soils and the same soil K measures from this study, consistent with this relationship. This relationship indicates that TBK can be effectively predicted from measuring exch. K for a wide range of soils across eastern Australia, but more research is required to understand the value of TBK to predict soil K availability.

The sterile insect technique (SIT) is a non-chemical approach used to control major pests from several insect families, including Tephritidae, and entails the mass-release of sterile insects that reduce fertility of wild populations. For SIT to succeed, released sterile males must mature and compete with wild males to mate with wild females. To reach sexual maturity, the Queensland fruit fly,Bactrocera tryoni(Froggatt) (Diptera: Tephritidae), must obtain adequate nutrition after adult emergence; however, in current SIT programs sterileB. tryonireceive a pre-release diet that lacks key nutrients required to sustain sexual development. The chief objective of this study was to determine whether pre-release yeast hydrolysate (YH) supplements affect the persistence and abundance of sexually mature sterile maleB. tryoniunder field conditions. Experiments were run in outdoor cages under conditions of low and high environmental stress that differed markedly in temperature and humidity, and in the field. Under low environmental stress conditions, survival of sterileB. tryoniwas monitored in cages under three diet treatments: (i) sugar only, (ii) sugar plus YH or (iii) sugar plus YH for 48 h and sugar only thereafter. Under high environmental stress conditions survival of sterileB. tryoniwas monitored in cages under four diet treatments: (i) white sugar only, (ii) brown sugar only, (iii) white sugar plus YH and (iv) brown sugar plus YH. In a replicated field study, we released colour-marked sterileB. tryonifrom two diet regimes, YH-supplemented or YH-deprived, and monitored abundance of sexually mature males. In the low-stress cage study, there was no effect of diet, although overall females lived longer than males. In the high stress cage study, mortality was lower for YH-fed flies than YH-deprived flies and females lived longer than males. In the field, YH supplementation resulted in higher abundance of sexually mature sterile males, with 1.2 YH-fed flies trapped for every YH-deprived fly trapped. Under field conditions, YH supplementation can increase over-flooding ratios and hence may improve the effectiveness of SIT programmes.

For many years, the poor physical and hydraulic properties of the soils in south-western Victoria have restricted crop production due to waterlogging. In this region of predominantly winter rainfall, raised beds have become popular with farmers to overcome these difficulties; however, little has been reported on the hydrology of raised beds compared with other tillage systems for cropping in the rain-fed environment of south-western Victoria. This study measured rainfall characteristics, runoff volumes, and soil properties such as the soil water content, bulk density, and hydraulic conductivity for three tillage treatments (raised beds, conventional cultivation, and deep cultivation) over 6 years on a Sodosol at a field site near Geelong, Victoria. Runoff was regressed against rainfall variables such as the amount per event, hours of rainfall, rainfall intensity, and maximum rainfall intensity to determine the significance of any differences between the treatments. The relationship between runoff and rainfall amount was best described with an exponential model. Raised beds significantly increased the amount of runoff relative to the other treatments when above-average rainfall was received, but there was little difference in runoff in years of below-average rainfall. No consistent effect of runoff on crop biomass was detected nor could any differences in runoff be attributed to differences in soil water content, hydraulic conductivity, and bulk density between treatments. The most important factor appeared to be the furrows between the raised beds, which acted as conduits for the flow of surface water during the larger storm events. During such events, runoff is an important hydrological process in cropping land in south-western Victoria.

Maize production in the Democratic People's Republic of Korea is limited by soil infertility. Trials were established at two cooperative farms to quantify the yield response of maize to fertilizer and to vetch green manure. Crop land is precious so the vetch had to be integrated either by a short growth period prior to the crop in spring, or risking an autumn sowing for growth over winter. Maize grain yield was linearly related to the amount of vetch incorporated before maize at an annualized rate of 77–121 kg grain per fresh weight ton of vetch manure. The N fertilizer substitution value was about 60 kg N ha⁻¹ as urea. This response may be increased by adopting more cold-tolerant vetch (or alternative legumes), and safeguarding vetch from villager's livestock.