Short-term Rotation Research Articles

Medical Students' Attitudes:

Although education in the care of the elderly is widely recommended for all medical students, the specifics of this aspect of pressional education are widely variable and their effects unclear. This study evaluated the effects of a short-term interdisciplinary clinical rotation in geriatrics on medical student attitudes toward elderly patients, as well as attitudes toward non-physician health professionals. We also evaluated whether assignment to long-term care facilities as geriatrics clinical sites had a deleterious effect on attitudes of medical students taking this rotation. Our analysis demonstrated no measurable beneficial effects of the week-long geriatrics rotation on medical student attitudes toward elderly patients. The brief rotation did improve student attitudes toward the importance of non-physician health professionals in patient care; at the end of the course the students had more positive attitudes toward social workers, psychologists, and occupational therapists. Assignment to long-term c...

Suppression of Foliar and Soilborne Peanut Diseases in Bahiagrass Rotations

Florunner peanut was grown after 1, 2, or 3 years of Tifton 9 bahiagrass and in alternating years with bahiagrass. Continuous peanut was grown in nontreated plots and in plots treated with flutolanil (4.48 kg/ha). In continuous peanut, stem rot (Sclerotium rolfsii) incidence was 4, 18, 19, and 44% during 1990 to 1993, respectively, without flutolanil and 0, 4, 10, and 17% with flutolanil. In 1993, stem rot incidence was 39, 29, 17, and 23% in the third, second, first, and alternating year of peanut, respectively. Rhizoctonia limb rot severity was low to moderate and not affected by crop rotation. Leaf spot diseases caused by Cercospora arachidicola and Cercosporidium personatum were present each year and were more severe in the short-term rotations. Pod yield of peanut was 3,044, 3,616, 4,547, and 3,922 kg/ha during the third, second, first, and alternating year of peanut, respectively. Compared to continuous peanut, longer rotations or treatment with flutolanil increased peanut grades and reduced percent damaged kernels (seeds). Population densities of Rhizoctonia solani and Pythium spp. in the soil generally were low and not altered by crop rotation. Rotation had little effect on root-knot (Meloidogyne incognita), ring (Criconemoides curvatum), or lesion (Pratylenchus brachyurus) nematodes.

Long term effects of rotation, tillage and stubble management on wheat production in southern NSW

A long term field experiment began in 1979 at Wagga Wagga, N.S.W., to compare the sustainability of a range of rotation, tillage and stubble management systems on a red earth. This paper reports yield, yield components and grain protein of wheat for 1979-90. Rotations considered were alternating lupin-wheat (LW), lupin-wheat-wheat (LWW), continuous wheat (WW) with and without N fertilizer (100 kg N/ha), and alternating sub-clover-wheat (CW). Soil N supply at the start of the experiment was high following many years of sub-clover based pasture. From 1979 to 1983, there was a negative grain yield response to N fertilizer and no response to a legume in rotation except in the drought of 1982 when low yields were recorded from LW. Thereafter, a positive grain yield response was usually produced to N fertilizer in WW rotations, until 1989 and 1990, when these crops displayed aluminium toxicity sym ptoms. Overall, average grain yields from legume rotations were higher than WW with added N fertilizer. Since 1983, LW rotations consistently produced higher mean grain yields than CW, but mean grain protein and total N uptake were lower. Yields and N uptake by the second wheat crop in a LWW rotation indicated little carryover of benefits from the lupins. Slightly higher mean grain yield and harvest index, but lower mean grain protein, were produced by direct drilling, compared with cultivation before sowing, following lupins or sub-clover. However, retaining stubble rather than burning in autumn consistently reduced grain yields. There was no evidence that early burial of wheat stubble following summer rain, rather than incorporation in autumn, improved grain yield or total N uptake. The build-up of giant brome grass and diseases, particularly where stubble was retained and crops direct-drilled, casts some doubt on the long term sustainability of these short term rotations in this environment.

A comparison of the persistence of Medicago truncatula cv. Paraggio with other annual medics in the Victorian Mallee

The annual medic Medicago truncatula cv. Paraggio has been widely sown in pastures throughout the Victorian Mallee region; however, its ability to persist in cereal pasture rotations is not known. Seed permeability and production, and plant regeneration of Paraggio, were studied in the field over 4 years, and the changes in its seed reserve were examined under 3 different cereal-pasture rotations. When compared with medic cvv. Parabinga, Harbinger, and Jemalong, Paraggio had up to twice the level of permeable seed over the summer-autumn period in 2 years (7-36% v. 2.5-19%). Paraggio produced 336-928 kg/ha of seed over 3 years, and after seed production was halted, it regenerated at densities of 150-1438 plants/m2 over the next 4 years. These results were generally the same as, or better than, the other cultivars. When seed set occurred in 1 and 2 years in the pasture phase of a 2- and 3-year rotation, respectively, Paraggio seed reserves were maintained at >4000 seeds/m2. This study demonstrated that Paraggio resulted in superior plant densities when grown in a number of typical rotations. It persisted satisfactorily and is expected to improve agricultural productivity in shor-tterm cereal-pasture rotations.

Pine Resin Midges (Diptera: Cecidomyiidae) in Monterey Pine Plantations: Control Decisions and Perception of Aesthetic Injury

Two insecticides (dimethoate and fenpropathrin) applied monthly, every other month or every third month to plantation-grown Monterey pines, Pinus radiate D. Don, did not reduce the number of active feeding sites of a complex of pine resin midges during the 6-mo period when the insects were active. Trees that were wounded each month to simulate natural growth cracks were significantly more heavily infested than the insecticide-treated or untreated trees. A consumer preference study suggested that the aesthetic injury caused by the resin midges was not a factor in purchasing a choose-and-cut tree. Thus, although the insect damage was recognized by the producers, was difficult to reduce through applications of chemical insecticides, and was exacerbated by wounding, it may not be an economic problem during the short-term rotation of Christmas tree production because consumer choice is not adversely affected by injury caused by the insects.

The conservation of arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia: II. The loss of trees with hollows and its implications for the conservation of leadbeater's possum Gymnobelideus leadbeateri McCoy (marsupialia: petauridae)

Leadbeater's possum, Gymnobelideus leadbeateri McCoy, a rare and endangered arboreal marsupial inhabiting the montane ash forests of the Central Highlands of Victoria, is dependent on hollows in mature and dead trees. The number of trees with hollows that had collapsed between 1983 and 1988 was assessed at 32 sites located in ash-type forests in the Central Highlands of Victoria, south-eastern Australia. The extent of decay amongst standing trees with hollows was also determined. A simple stochastic model of the decline and collapse of these trees was calculated from the data. The model was applied to data on trees with hollows collected from 497 other sites within the study region to predict their future abundance and availability over the next 75 years. Almost 18% of the total measured population of trees had collapsed in the 5-year interval between assessments. A subjective categorization of the form of the trees was the best predictor of the susceptibility to collapse. More senescent trees were those most vulnerable to collapse and they also exhibited the highest rates of decay. Stochastic models based on transition probabilities of trees with hollows predict that very few of the sites surveyed will support such trees in 50 years time and imply a severe future shortage of trees containing suitable nest hollows for wildlife until at least the end of the next century. Silvicultural practices which result in ash-type forests being clear-felled on a short-term (80–120 year) rotation will further accelerate and exacerbate the anticipated shortage. The implications of these effects for wildlife, particularly G. leadbeateri, are discussed.

Effect of Depth and Duration of Seed Burial on Ripgut Brome (Bromus rigidus)

The influence of depth (0 to 30 cm) and duration (1 to 24 months) of burial on the deterioration, germination, and viability of ripgut brome seed was studied in the field. Both surface-sown and buried ripgut brome seed were depleted within 15 months. Persistence of surface-sown seed declined relatively slowly during the first year, falling from 83 to 62 to 23% after 1, 9, and 12 months, respectively. Seed covered by soil, however, germinated more rapidly, with less than 10% of the initial population ungerminated after 1 month at all depths. The mode of seed disappearance was closely related to whether or not the seed was covered with soil. Seed loss at depths of 1 to 30 cm was primarily due to germination in situ, with little effect from viability loss or enforced or induced dormancy. In contrast, the persistence of surface-sown seed was due primarily to induced dormancy for up to 12 months, with viability loss and enforced dormancy becoming important thereafter. Tillage practices aimed at providing favorable germination conditions may reduce ripgut brome seed survival in the soil. Because seed is relatively short lived, seed supply in soil may be reduced by short-term rotation to a crop that allows for effective control of ripgut brome.

Rotational chaos in dissipative systems

An investigation is made into chaotic attractors arising from a quasiperiodic transition to chaos, using a quantity called the rotation interval. The rotation interval describes the short term rotation rates available to the attractor. We present algorithms to calculate it given an appropriate map, differential equation or time series. We find that the rotation interval has a very robust parameter dependence: its endpoints are almost always phase locked. Our numerical ideas are based on the theory of dissipative twist maps, which is reviewed. This theory is also used to prove a theorem about the non-existence of certain strange attractors in nearly conservative systems. Finally, an investigation is made into the relationship between the rotation interval and topological entropy, and the breakup of invariant circles.

Effect of preceding legume or cereal on barley grain and nitrogen yield

SummaryTwo separate short-term rotation experiments were conducted during 1982–5 in order to study the production and effect on subsequent barley of legumes grown in Cyprus. The treatment crops, seven legumes and three cereals, were grown in 1982–3 and in 1983–4 growing seasons and barley was grown in the subsequent growing seasons (1983–4 and 1984–5).Among the treatment crops, cereals gave equal or higher dry-matter yields, but equal or lower nitrogen yields compared with legumes. Barley, the test crop, which followed the treatment crops, gave lower grain and nitrogen yields when following cereals than after legumes. There were differences among legumes in their residual effect on the subsequent crop.

Legumes: Their potential role in agricultural production

AbstractThe energy crisis of the late 1970's has raised the question of the wisdom of depending upon fertilizer nitrogen as the primary source of N input into crop production systems. While present and past price structures have favored fertilizer-N over biologically fixed N, there are a number of other benefits of legumes in a cropping system in addition to their effects on N availability. Among these are less potential for environmental degradation and improved soil physical conditions and water relations, but it is difficult to assign economic value to many such benefits. In addition to the economics of the present price structure, disadvantages of using legumes could include reduced total production and increased need for livestock in a farming enterprise (these could be considered assets from some aspects). Legumes are presently used in shortterm rotation, such as corn-soybean, or in continuous corn with a legume winter cover crop. These systems are finding widespread use and offer the producer many benefits, as well as helping to solve several major environmental problems associated with N use in agriculture.

Nitrogen nutrition of cereals in a short-term rotation. I. Single season treatments as a source of nitrogen for subsequent cereal crops

The residual effects of one season of five cultural treatments common in southern Australian dryland farming were examined with respect to soil water and nitrogen, and the production of cereals in the next two years. The initial treatments were medic or subterranean clover pasture, faba beans, oats or bare fallow. In the second year barley, wheat and triticale were grown on the same plots, with 0,30,60 or 90 kg ha-1 of fertilizer nitrogen. Wheat was sown over the whole area for the third season. The medic and subterranean clover pastures contributed approximately 100 kg ha-1 of nitrogen in top growth, but this remained on the surface until cultivation. Oats and fallow plots declined in total soil nitrogen by about 70 kg ha-1. The nitrogen content of the faba bean stubble showed that this crop has the potential of providing equivalent nitrogen to a good legume pasture. At the beginning of the second season the previous plots of fallow, beans, subterranean clover and medic had 36,27, 14 and 12 mm more water in the top metre of soil than oat plots. Cereals after oats apparently did not respond to fertilizer nitrogen because of the dry conditions, but on other plots the yield response was not proportional to the additional water. Although first year treatments affected growth of the three cereals in the second season, the new cereal, triticale, showed no evidence of different adaptation to growing conditions than wheat or barley. The effects of first and second year treatments carried through to the wheat crop in the third season. There were marked differences in nitrogen availability, but evidence that the second crop was depleting soil nitrogen reserves. Nitrogen from first year legume residues was available earlier in the season than second year fertilizer nitrogen which had been leached from the surface soil.

Nitrogen nutrition of cereals in a short-term rotation. II. Stem nitrate as an indicator of nitrogen availability

The effect of cultural treatments and fertilizer nitrogen on nitrate nitrogen concentration of cereal steins and the relation between nitrate nitrogen and cereal production were examined in a three-year experiment. Five cultural treatments in the first year were medic or subterranean clover pasture, field beans, oats or bare fallow. These were oversown in the second year with barley, wheat and triticale, with 0, 30, 60 or 90 kg ha-1 of fertilizer nitrogen. Wheat was sown over the whole area in the third season. There were marked differences in nitrate nitrogen concentrations in the second year cereals as a result of the previous cultural treatments and the current application of fertilizer nitrogen. For cultural treatments the concentrations were highest after fallow, intermediate after legumes, and lowest after oats. There was an asymptotic increase in nitrate nitrogen as fertilizer nitrogen increased. The second year had low rainfall, and there was little correlation between nitrate nitrogen concentration and production, but measurements of nitrate nitrogen clearly indicated relative availability of nitrogen. In the third season's wheat crop the residual effects of first year subterranean clover gave highest nitrate nitrogen, but effects of fallow were almost as high. Second year fertilizer had less effect than first year cultural treatments. Grain yield of wheat in the third year was closely related to nitrate nitrogen concentration during early growth stages. This was a year with good rainfall. Measurement of nitrate concentration in plant stems could be useful for determining the need for fertilizer nitrogen.

Solar rotation measurements at Mount Wilson

We examine the background velocity fields of the sun as observed at Mount Wilson. The method of velocity reduction of the full-disk Mount Wilson data is outlined. We describe a number of tests that have been carried out in order to find an instrumental origin for short-term rotation variations and a large-scale background line-shift - the ears. No instrumental cause can be found for this ear effect, although such a cause cannot yet be ruled out.

American Physicians in Other Nations

To the Editor.— Lest the medical profession (and other health workers) be seduced into a tranquil venture of international service, I would like to bring some reality to the correspondence of Charles Failmezger, MD, On Volunteer Physicians in the Developing Nations (241:132, 1979). He encourages short-term rotations (which in his case become even more abbreviated, with an average of less than two months spent in each country) while at the same time advising extensive prior preparations that he does not seem to include in his length of duty. I have been working for nearly 18 months in the same urban region of northeast Brazil, and even with on-site language training and experiences concerning local customs, I am just now at the periphery of understanding the people and environs here. The language problems should not be minimized. Whereas one may learn common expressions that help basic survival, involvement at a university

Effects of initial clover seeding rate and length of ley on pasture production, soil nitrogen and crop yields in a ley farming system

Several factors relating to the use of subterranean clover (Trifolium subterraneum) in a ley farming system were studied at Kojonup in the south-west of Western Australia viz; the effect of seeding rates of clover on the botanical composition and herbage production of a grazed pasture over five years; the build-up of soil nitrogen over this period, and the effect of 5, 8 and 11 years of clover on wheat yield and on subsequent regeneration of the pasture. In the final year (year 12) the effects of lime on mineralization of soil nitrogen and on crop yields were also studied. Seeding rates of clover in excess of 6 kg ha-1 affected botanical composition in the first year, and yield of pasture in the first two years only. Build-up of soil nitrogen over the first five years (when all plots were grazed) was significantly greater (P < 0.05) where clover had been sown at the higher rates (< 6 kg ha-1) but this did not result in increased wheat yields at the end of this period. In the 12th year, when all plots were cropped, there were no significant differences in grain yield between treatments cropped for the first time (after 11 years of clover) and those cropped either once or twice in the preceding six years. Cropping reduced pasture production in the early part of the post crop year but the proportion of clover in the pasture increased. The application of lime (in year 12) resulted in a significant increase in grain, and straw yields and nitrogen uptake on all treatments. The results suggest that crop yields can be sustained in short term rotations provided there is sufficient clover present in the pasture phase.

Short-term Jovian rotation profiles, 1970–1972

Approximately 1300 measurements of the positions of 101 features in Jupiter's atmosphere have been made using blue-light photographs of the planet obtained by the International Planetary Patrol from 1970 to 1972. The longitudinal positions of features were read directly with orthographic grids superimposed on optically projected images of Jupiter. For each feature, least-squares linear fits were made on plots of the longitude measurements as a function of time, in order to derive drifts rates relative to System I or II. Drift rates were used to compute rotation periods; and, by combining the data from various latitudes, short-term rotation profiles were constructed. These short-term profiles are compared with a “mean” multiple-year profile, and differences in detail are evident. Slightly shorter rotation periods were found near the edges of the equatorial jet than at its center in 1970 and 1971. In 1972, one feature at +37° north was found to exhibit an abrupt change in period amounting to an increase of 95.1 seconds.

Studies on Improvement of Field Soil by Short Term Pasture Rotation : I. Effect of clover rotation on chemical properties of soil : II. Effect of clover rotation on physical properties of soil

For the purpose of clearing up the effects of clover rotation on the chemical and physical properties of field soil, this study was carried out. The results obtained are as follows: 1) Short term rotation of clover increased humus content remarkably and adjusted the soil reaction in surface soil compared with the common cropping system (growing wheat and sweet potato alternately). 2) Formation of water stable soil aggregates was promoted remarkably by clover rotation, particularly that of larger aggregates as 3.0 mm < diameter. 3) It seems that "Summer withering" of clover may be caused by the dry condition, under which clover cultivation reduced liquid phase of surface soil and produced so much hard greater clods in subsoil.