Lindsay C. Campbell

Canola response to high and moderately high temperature stresses during seed maturation

Canola is a valuable oilseed crop worldwide. Temperature during the post-anthesis period plays an important role in determining the final yield and seed composition. Experiments were conducted in climate-controlled growth cabinets to test the effect of two high temperature regimes following a 24-h acclimation period on three canola cultivars differing in their thermotolerance. A long, moderately high temperature treatment of 28°C/23°C (day/night) was applied for 10 d from 20 to 30 d after flowering (DAF) and a short, very high temperature regime of 28°C/23°C (day/night) including a peak of 38 °C reached for 5 h around midday for 5 d from 25 to 29 DAF. Very high temperature for 5 d reduced yield on the main stem by up to 52% for a sensitive cultivar by reducing seed weight. This treatment also decreased the oil/protein ratio, but had a lesser effect on fatty acid composition. The moderately high temperature treatment for 10 d had only affected yield of one cultivar and increased the oil/protein ratio of al...

A review of the phosphorus content of dry cereal and legume crops of the world

When food scarcity increases, instability in society increases. The majority of food consumed is from cereals and legumes. Phosphorus is essential for crop plant growth and soils are depleted as this element is removed from crop lands with harvested grains/seeds. To sustain yields, inputs of nutrients are required to balance losses. On global and continental/regional bases, we assembled nine years data on: total dry cereal grain and total dry legume seed production, production of barley, maize, rice, soybean and wheat grains/seeds, yields, area farmed, the tonnage of phosphorus and phytic acid removed in these crops and the elemental phosphorus applied as mineral fertilizers to all plant crops. Some significant imbalances were found that may affect food security. Asia consumes significantly more mineral P fertilizer in proportion to crop production than any other region – a potential environmental, economic and social problem. Approaches which could address nutrient (P) imbalances are discussed.

Nitrate and nitrite in Australian leafy vegetables

A market survey of Australian leafy vegetables and a winter and spring experiment with Swiss chard were conducted to examine nitrate and nitrite levels in leaves. The relationship between growth response to nitrogen (N) supply and light level and accumulation of N in leaves was of particular interest. The survey that included 7 types of lettuce and endive (Asteraceae), 6 leafy Asian vegetables (Brassicaceae), and Swiss chard and spinach (Amaranthaceae) showed that fresh leafy vegetables available during a 6-month period on the Australian market can range in nitrate-N from 12 to 1400 mg/kg fresh weight and nitrite-N from 0 to 37.5 mg/kg. Some samples exceeded the limits for nitrate and nitrite based on international food safety standards. The response of Swiss chard to N supply and light was investigated. The accumulation of nitrate in Swiss chard was primarily influenced by increasing N supply and not by light level. Light conditions for all treatments in both the winter and spring experiments exceeded the critical level (~200 μmol/m2.s) required to increase leaf nitrate. Growth and leaf nitrate concentration were higher for spring, associated with average minimum to maximum temperatures of 18–39°C, compared with 14–28°C for winter. Treatment effects on nitrite-N in Swiss chard could not be determined because nitrite was only detected in one-third of plants. The importance of N supply in affecting nitrate accumulation in vegetables is highlighted by the Swiss chard experiments. It confirmed that nitrate accumulation occurs at optimal to supra-optimal nitrate supply, emphasising for growers the undesirable effect of excessive fertiliser use.

Response of ornamental Eucalyptus from acidic and alkaline habitats to potting medium pH

Abstract Seedlings of 35 Eucalyptus species were grown in a peat-based growing medium amended with limestone and dolomite (1:1) to provide an experimental pH range of 5.1–8.9. The species were largely of the multi-stemmed (mallee) growth habit, relatively new to commercial cultivation, and known to occur naturally on alkaline, neutral or acidic soils. Growth was generally greater under acidic (pH 5.1–5.6) than under more alkaline conditions in all species, regardless of natural soil occurrence of the parent trees. Above pH 5.6, species showed a range in the degree of response to pH, from those that were unaffected even at pH 8.9 (e.g. E. erythrocorys and E. extensa), to those for which growth was reduced at pH 6.8. There was generally good correspondence between pH response and the pH of the soil in which parent plants occurred naturally, i.e. accessions from trees growing on alkaline soils tended to exhibit less growth reduction at high pH. Leaf elemental analyses of selected species indicated that tolerance of high pH was associated with an ability to maintain relatively low Ca/Mg and P/Fe concentration ratios (

Micropropagation of Telopea speciosissima R. Br. (Proteaceae). 2: Rhizogenesis and acclimatisation to ex vitro conditions

Conditions affecting rhizogenesis in vitro and ex vitro and subsequent acclimatisation of Telopea speciosissima (waratah) were investigated. Clonal selections were successfully rooted in vitro in agar, on filter paper bridges or using crushed quartz-sand, the last substrate resulting in superior growth of roots. The in vitro substrates were impregnated with half-strength MS, 7.5 gl-1 sucrose and various concentrations of IBA. For the quartz-sand, an IBA concentration of 50 μM was optimal, 70% of microcuttings were rooted. No plantlets rooted in vitro were acclimatised to ex vitro conditions (using mist, fog or humidity tent regimes). Microcuttings (25–45 mm in length) were rooted ex vitro in a fog humidity regime (droplet size <10 μm) using an IBA powder dip (3 g IBA kg-1). Neither a mist nor a humidity-tent regime was suitable for rooting of waratah microshoots ex vitro. A peat and perlite mixture was superior to crushed quartz-sand or potting mix for the rooting of microshoots; this appeared to be related to the air-filled porosity (>20%) of the mixture, measured after the medium was saturated and then drained for 24h. Plantlets must be left under the high humidity regime until shoot growth resumes (four to eight weeks) otherwise plant mortality increase significantly. In vitro-produced leaves abscised between eight and 12 weeks after transfer to ex vitro conditions, indicating that these structures did not acclimatise ex vitro.

Differences in yield among annual forages used by the dairy industry under optimal and deficit irrigation

While perennial forages dominate the feed base on Australian dairy farms, poor persistence of perennial ryegrass (Lolium perenne L.) and relatively poor forage nutritive value of kikuyu (Pennisetum clandestinum Hochst. ex. Chiov.) and paspalum (Paspalum dilatatum Poir.) has led to an increasing interest in growing annual forages. Thus, this study was conducted to identify annual forage species that are more productive than the commonly used perennial pasture species. Seventeen annual forages were investigated under ‘optimal’ irrigation and two deficit irrigation treatments (nominally 66 and 33% of irrigation water applied of the optimal level) over 3 years at Camden, New South Wales, on a brown dermosol in a warm temperate climate. The forages evaluated were: Italian ryegrass (Lolium multiflorum Lam.), oats (Avena sativa L.), triticale (Triticosecale rimpaui Wittm), wheat (Triticum aestivum L.), balansa clover (Trifolium michelianum Savi), berseem clover (Trifolium alexandrinum L.), maple pea (Pisum sativum L.), Persian clover (Trifolium resupinatum L. var. majus Boiss.), subterranean clover (Trifolium subterraneum L.), forage rape (Brassica napus L.), forage radish (Raphanus sativus L.), maize (Zea mays L.), Japanese millet [Echinochloa esculenta (A. Braun) H. Scholz], pearl millet [Cenchrus americanus (L.) Morrone], sorghum [Sorghum bicolor (L.) Moench], cow pea [Vigna unguiculata (L.) Walp.] and lablab [Lablab purpureus (L.) Sweet]. There was more than a 4-fold range in annual yield between forages, but the length of the growing season and season of growth made direct comparisons difficult. Under optimal irrigation, maize produced the highest mean yield of 29.0 t DM/ha in only 125 days, which was over three times greater than cow pea (9.2 t DM/ha) grown in the same season yet requiring 190 days. Of the cool season annuals, wheat had the highest mean yield of up to 20.6 t DM/ha in 230 days, which was more than three times the yield of the lowest yielding forage, subterranean clover, at only 6.5 t DM/ha in 215 days. The forages which require harvesting generally had higher yields within a growing period of similar length than those that were defoliated to reflect being ‘grazed’. Combining annual forages in an annual cycle (e.g. maize and wheat) had the potential to produce up to 47 t DM/ha. Deficit irrigation reduced annual yield of all warm season-grown forages ranging from 8% for sorghum up to 48% for maize. In contrast, annual yield reductions were generally smaller for cool season forages, there being no reduction for forage rape, subterranean clover or oats, but up to 35% for Persian clover. However, while yield is an important criterion for choosing dairy forages, it is only one factor in a complex system, and choice of forages must be considered on a whole-farm basis and include water use efficiency, nutritive value, cost of production and risk.

Studies on depth of placement of urea on nitrogen recovery in wheat grown on a red-brown earth in Australia

Field and greenhouse experiments were carried out at the University of Sydneyto examine the influence of depth of placement of urea on crop nitrogen (N) uptake and N recovery in wheat grown on a red-brown earth in Australia. In the greenhouse, an 15N source of urea was used in examining the pattern of N availability, while field experiments using an unlabelled urea assessed the usefulness of deep placement of urea as a tool for improving N use by wheat.Placement at a depth of 15 cm slightly delayed the accessibility of N to the plant only in the early stages of growth, i.e., about 12 days after sowing. Large differences in N content and N concentration observed as a result of placement was only transient and disappeared later in the season. Total N recovery was 93.8% in the deep placement and 79.9% in the shallow placemen, but these differences were due to differences in soil N recovery, as crop N recovery was approximately 48% in both treatments.In the field, there was very little advantage in the deep placement compared with the shallow placement. Also, no residual benefit was observed as a result of increased depth of placement. Thus deep placement may not be an important strategy for increasing N uptake over a conventional shallow depth of 3–5 cm.

Micropropagation of Telopea speciosissima R. Br. (Proteaceae). 1: Explant establishment and proliferation

Axillary bud explants of 11 selected mature waratah clones were established in vitro on a modified Murashige & Skoog medium. Adequate proliferation of axillary shoots was achieved by optimisation of the growth regulator status of the culture medium. For the majority of clones, a three to six times rate of proliferation was achieved with 1.25 μM BA and 1.0 μM GA3 without the occurrence of abnormalities. The white flowering clone did not respond favourably to the addition of GA3 to the medium.

Plant and soil analysis: An Australian perspective

Abstract Cropping, horticultural industries, and pastoral enterprises based on improved pastures occupy only a small percentage of Australias land mass. The major part of Australian agriculture is confined to limited zones, usually within 500 km of the coast, due to rainfall and limited irrigation potential. This is in stark contrast to the United States with its productive mid‐west agricultural belt. Soil testing and plant analysis are services which have not been widely used by the horticultural, floricultural, cropping, or improved pastoral enterprises. Perhaps only 2% of the market has utilized these services. The ratio of soil tests to plant tests is about 5:1. Regular crop or soil monitoring is rarely practised. The general economic state of agriculture seems not to influence this markedly. Is this a function of farmer education or a matter of the quality of the information obtained by the farmer? Once a soil test is developed, commercial laboratories tend to be reluctant to adopt a better or multi...

Beneficial impact of precision nutrient management on the environment and future needs

Abstract The necessity for precision nutrient management has arisen from a decline in agricultural commodity prices, the advent of new technology, and demographic changes resulting in increased urbanization. Community perceptions and attitudes to agriculture, food quality and the environment are often negative: thus management of essential and beneficial nutrients as well as agriculturally undesirable ions is progressing at a more rapid pace than would be dictated by economic and technological factors alone. Some of the main agronomic reasons for developing precision nutrient management are: the potential for ground water pollution particularly nitrate; heavy metal pollution; salinity including rising water tables; nutrient run‐off into streams and rivers from cropping, pastoral, intensive livestock and horticultural enterprises; suitable crop, pasture or other ground cover to minimize soil erosion; and the introduction of new cultivars of plants. Opportunities for developing more precise nutrient managem...