Influence of vesicular-arbuscular mycorrhiza fungi on growth and uptake of various nutrients as well as uptake ratio of fertilizer P for lucerne (Medicago sativa)

Summary Lucerne plants were inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungus,Glomus caledonius andRhizobium meliloti and grown in pots in voliére. Treatments were 0,1 and 2 mg P added to 100 g of a soil with low P-fertility. Plants were harvested after 6, 9, 13 and 18 weeks, allowing shoots to regrow between harvests. VAM-infection was determined after 6 and 18 weeks, dry weight, concentration and uptake of P and concentrations of N, K, Ca, Mg, Cu and Zn were determined at all harvests. VAM-inoculation increased growth of shoots, P-concentration and P-uptake at all soil-P levels and the increase was most pronounced at the lowest soil-P level. P-fertilization also increased growth, P-concentration and P-uptake. VAM-inoculation showed tendency to increase N-and K-uptake and decreased Ca-, Mg- and Zn-concentrations in shoots. The uptake ratio of fertilizer-P was increased by VAM.     

Use of synthetic pheromone traps to time control of the lucerne leafroller,Merophyas divulsana

Catches of maleMerophyas divulsana (Walker) (Lepidoptera: Tortricidae) in pheromone traps showed seven peaks per year in lucerne (Medicage sativa L.) between September and April at approximately five week intervals. The trap catches can be used to predict the occurrence of specific stages of the life cycle and periods of damage. By using trap catches to time both harvesting and the application of insecticide, damage to a lucerne crop was reduced. Harvesting was considered to be the more acceptable control strategy.     

Ion accumulation in lucerne plants regenerated from salt-adapted suspension cultures compared with recultured cells from these plants

Lucerne (Medicago media cv. Rambler) plants, regenerated from cell suspension cultures adapted to 200 mm NaCl, and cell cultures derived from the leaflets of regenerated plants showed enhanced Na⁺ exclusion compared with the unselected plants and cell cultures. There was a decrease in the K⁺ concentration in response to NaCl treatment but the selected plants and cell cultures maintained a significantly higher K⁺ concentration and showed much lower Na⁺/K⁺ ratios than unselected plants and cell cultures. The proline concentration increased in the shoots and cell cultures in response to NaCl stress but the selected plants and cell cultures showed a significantly higher proline concentration than unselected plants and cell cultures. Received: 10 December 1996 / Revision received: 28 February 1997 / Accepted: 25 August 1997     

Cycling of nitrogen in modern agricultural systems

Summary Agro-ecosystems have developed from mixed- and multiple-cropping systems with relatively closed N cycles to intensively managed monocultures with large N inputs in the form of commercial fertilizers. Cultivation of increasingly larger areas of land has resulted in substantial losses of soil organic matter and N. Also, the move from slash and burn agriculture to intensively ploughed systems has resulted in losses through increased erosion.The use of N fertilizers has increased rapidly toca. 60 Tg N yr^–1 (1980/81), which is equivalent to at least 40% of the N fixed biologically in all terrestrial systems and 36% more than is fixed in all croplands. On a global scale, the major losses of N from agro-ecosystems are estimated to be: harvest, 30 Tg; leaching, 2 Tg; erosion, 2–20 Tg; denitrification 1–44 Tg; and ammonia volatilization, 13–23 Tg. However, the data base is very crude and several estimates may be wrong by as much as one order of magnitude.Additions of N fertilizers have both direct and indirect effects on soil microorganisms. The possible importance of such effects is briefly discussed and a specific example is given on long-term effects on soil microbial biomass and nitrification rates in 27-year-old cropping systems with different N additions: (i) 0 kg N ha^–1 yr^–1, (ii) 80 kg N ha^–1 yr^–1, (iii) farmyard manureca. 80 kg N ha^–1 yr^–1.Few detailed N budgets exist for agro-ecosystems, despite its major importance as a limiting plant nutrient and the large losses of N from such systems. In conclusion, preliminary nitrogen budgets for four cropping systems (barley receiving 0 or 120 kg N ha^–1 yr^–1; meadow fescue ley with 200 kg N ha^–1 yr^–1 and a lucerne ley) are presented, with special attention to N flow through the soil organisms.Keynote address     

Field measurement of symbiotic nitrogen fixation in an established lucerne ley using15N and an acetylene reduction method

Summary Lucerne is an important forage legume in the south and south-east of Sweden on well-drained soils. However, data is lacking on the apparent amount of nitrogen derived through N₂ fixation by field-grown lucerne. This report provides basic information on the subject. The experiment was performed in a lucerne ley grown 40 km north of Uppsala. The input of nitrogen through fixation to the above-ground plant material of an established lucerne (Medicago sativa L.) ley was estimate by¹⁵N methodology during two successive years. The amount of fixed N was 242 kg N ha^–1 in 1982 and 319 kg N ha^–1 in 1983. The proportion of N derived from the atmosphere (%Ndfa) was 70% and 80% for the two years respectively. The first harvest in both years contained a lower proportion fixed N. Both N₂ fixation and dry matter production were enhanced during the second year, particularly in the first harvest. The Ndfa was 61% in the first harvest in 1982, compared to 72% Ndfa during the same period in 1983. This demonstrates the strong influence of environment on both dry matter production and N₂ fixation capacity of the lucerne.In addition anin situ acetylene reduction assay was used in 1982 to measure the seasonal distribution of the N₂ fixation and in 1983 to study the effect of soil moisture on the N₂ fixation process. The seasonal pattern showed great dependence on physiological development and harvest pattern of the lucerne ley. The maximum rate of N₂ fixation occurred at the bud or early flower stage of growth and was followed by a rapid decline as flowering proceeded. After harvest the nitrogenase activity markedly decreased and remained low during at least two weeks until regrowth of new shoots began. Irrigation doubled the nitrogenase activity of the lucerne in late summer 1983, when soil moisture content in the top soil was near wilting point. No changes in nitrogenase activity did occur in response to watering earlier during the summer, when the soil matric potential was around –0.30 MPa.     

Observations on root hair production by lucerne,maize and perennial ryegrass grown in a sandy loam

Summary Root hair production by young plants of lucerne, maize and perennial ryegrass grown in a sandy loam was assessed by examining roots growing at a soil-glass interface. Results are given for the percentage frequency distribution of root hair lengths and the numbers of root hairs produced per mm root. The mean lengths of root hairs observed on lucerne, maize and perennial ryegrass roots were 0.35, 0.90 and 1.12 mm respectively. Lucerne produced an average of 105 root hairs per mm of root, whereas maize produced 161 and perennial ryegrass produced 88. The total length of root hairs per mm length of root was estimated to be 37, 146 and 99 mm for lucerne, maize and perennial ryegrass resp. Letcombe Laboratory     

Effect of Alfalfa Meal in diets of laying quails on performance,egg quality and some serum parameters

This study was conducted to investigate the effects of increasing levels of alfalfa meal in the diet of laying quails on egg production, feed consumption, feed efficiency, egg quality, egg yolk cholesterol and selected serum parameters. In this study, 192, 10-week old quails (Coturnix coturnix japonica) were evenly distributed to four groups with four replicates of 12 quails each. The control group was fed a basal diet containing 0% alfalfa meal and the remaining groups received 3, 6 or 9% alfalfa meal for 12 weeks. Live weight, feed consumption, and egg production were recorded and feed efficiency were calculated. Eggs were examined for interior and exterior quality and egg yolk cholesterol content. At the end of the experiment, blood samples were collected and sera were analysed for serum Ca, inorganic P (P_i), Mg, triglycerides and total cholesterol. Any level of alfalfa meal had no effect on live weight, egg production, feed consumption, feed efficiency, egg weight, and egg yolk index. Six percent and 9% alfalfa meal increased specific gravity of whole egg and eggshell thickness as well as serum P_i levels. Nine percent alfalfa meal reduced serum triglycerides, total cholesterol levels and egg yolk cholesterol content. The results of this experiment indicated that addition of 9% alfalfa meal into the laying quail diet may improve eggshell quality and reduced serum triglycerides and serum and egg yolk cholesterol without any adverse effect on performance.     

Alfalfa,Medicago sativa L., in highly weathered,acid soils

Summary Rooting into acid subsoils would be a desirable trait for alfalfa which should result in better water extraction and yield. In this study, the rooting depth into acid subsoils and top yield of alfalfa plants selected for acid tolerance were investigated in a repacked profile with a limed, fertile topsoil, but unamended, acid subsoil. The effects of subsoil modification by CaCO₃ and CaSO₄·2H₂O addition on alfalfa rooting, top growth, and water extraction were also studied. Plants from acid selections rooted deeper into acid subsoil when compared to control plants (selected under limed conditions). However, the reverse response was found in the CaSO₄·2H₂O treated subsoil. There were no differences among selections for total top yield for any subsoil treatment. Water extraction from the lower subsoil and top growth yield (data pooled by selections) were improved mainly in the subsoil treatment containing the highest addition of CaCO₃.     

The profile of tropical alfalfa in Indonesia: A review

Alfalfa (Medicago sativa L.), or lucerne, is a subtropical plant popularly known as the “Queen of Forages”. It has a superior nutritional profile that includes high levels of crude protein, secondary metabolites, as well as macro and micro minerals, making it one of the best feed fodders in the world. Alfalfa is also highly adaptable to both warm and cold climates in addition to being highly nutritious. These features have led to the cultivation of alfalfa in tropical areas, such as Indonesia. Studies have been conducted on the vegetative and generative aspects of alfalfa cultivation in tropical regions to increase crop yield and sustainability. Progress in the cultivation and use of alfalfa in tropical regions has been encouraging and has led to the potential emergence of a new stock, namely tropical alfalfa, which is now a high-quality green forage source in tropical regions. Cultivation of tropical alfalfa provides breeders with a high-quality feed, leading to significant improvement in the condition and health of livestock and an increase in the production of meat, milk, and eggs. This review will be very important source of information not only for researchers but also for businessman who have a concern to develop alfalfa tropic either for feed or food (growth characteristic, function and nutrient content).     

Does Bdellodes lapidaria (Acari: Bdellidae) have a role in biological control of the springtail pest, Sminthurus viridis (Collembola: Sminthuridae) in south-eastern Australia?

Throughout southern Australia, the lucerne flea, Sminthurus viridis (Collembola: Sminthuridae), is an important pest of a variety of winter grain crops and pastures. The predatory mite, Bdellodes lapidaria (Acari: Bdellidae), co-occurs with S. viridis and is reported to be a biological control agent of this pest. Using laboratory bioassays and field experiments, we assessed the susceptibility of B. lapidaria to several pesticides and investigated its impact in controlling S. viridis. In the laboratory, B. lapidaria was found to be susceptible to the synthetic pyrethroids, α-cypermethrin and bifenthrin, but relatively tolerant to the avermectin, abamectin, and organophosphorous chemicals, omethoate and chlorpyrifos. In field experiments, B. lapidaria was not adversely affected by applications of either bifenthrin or omethoate. Despite strong intraspecific interactions, we found no detectable impact of B. lapidaria on S. viridis numbers in the field. These results indicate that B. lapidaria has a relatively high tolerance to several pesticides, perhaps partly through behavioural avoidance, but little impact as a biological control agent on S. viridis in south-eastern Australia.