Estimates of nitrogen fixations by legumes in alternate cropping systems at Warra, Queensland, using enriched - 15N dilution and natural 15N abundance techniques

1995 ◽  
Vol 46 (3) ◽  
pp. 493 ◽  
Author(s):  
SA Hossain ◽  
SA Waring ◽  
WM Strong ◽  
RC Dalal ◽  
EJ Weston
Keyword(s):  
Dry Matter ◽  
Cropping Systems ◽  
Management Strategies ◽  
Dilution Method ◽  
Similar Amount ◽  
Rhodes Grass ◽  
15N Dilution ◽  
A Value ◽  
Annual Medics

Nitrogen fixation was measured using two isotopic techniques over 2 years as part of a long-term field experiment established to test alternative management strategies for restoring fertility in a vertisol at Warra, Southern Queensland. Treatments containing legumes were: grass- legume ley (purple pigeon grass and Rhodes grass, lucerne and annual medics) for 4 years followed by 4 years of wheat; a 2-year rotation of lucerne and wheat; a 2-year rotation of medic and wheat; and a 2-year rotation of chickpea and wheat. For the enriched-15N procedure, the proportion of N derived from air (% Ndfa) for the grass-legume and lucerne and medic leys ranged from 67 to 97%, and averaged 85%, with little evidence for effects of season, pasture establishment, time or species. The % Ndfa for chickpea was significantly lower (62%). Values for the natural abundance 15N procedure were mostly lower and more variable than for the enriched method, ranging from 62 to 91% for the grass-legume, lucerne and medic leys, and averaged 76%. It was concluded that the enriched procedure provided more reliable estimates of N2 fixed by the legumes. N2 fixation measured by the enriched-15N dilution method in the grass-legume ley averaged 80 kg N ha-1 during 2 years. A similar amount of N was fixed by the lucerne ley during 1 year (83 kg N ha-1 but medic ley fixed less (56 kg N ha-1 The amount of N2 fixed by chickpea was 72 kg N ha-lyear-1. The dry matter yield of the legumes in leys, mainly lucerne, was closely associated with the amount of N2 fixed, with a value of 28 kg of N2 fixed for each tonne of dry matter produced.

Long-term Productivity of Intensive Rice Cropping Systems on the Central Plain of Thailand

1977 ◽  
Vol 13 (4) ◽  
pp. 305-315 ◽  
Author(s):  
J. J. Walcott ◽  
M. Chauviroj ◽  
A. Chinchest ◽  
P. Choticheuy ◽  
R. Ferraris ◽  
...  
Keyword(s):  
Grain Yield ◽  
Short Duration ◽  
Nitrogen Uptake ◽  
Nitrogen Fertilizer ◽  
Dry Matter ◽  
Cropping Systems ◽  
Dry Season ◽  
Multiple Cropping ◽  
Rice Cropping Systems

SUMMARYThe productivity of seven multiple rice-cropping systems, utilizing a short-duration cultivar under irrigation, were assessed over 5 years. Systems of one, two and three crops a year were compared. Multiple cropping reduced grain yield, panicles m-2, total dry matter and nitrogen uptake per crop. However, the unfertilized three-crop-per-year system averaged 9·1 t grain, 17·1 t DM and 126 kg N ha-1 per annum, without showing a long term decline in productivity. Recovery and utilization of nitrogen fertilizer were generally low compared to other experiments, and were highest for the early dry season cropping period.

U.S. Farmer Awareness of Glyphosate-Resistant Weeds and Resistance Management Strategies

2009 ◽  
Vol 23 (2) ◽  
pp. 308-312 ◽  
Author(s):  
William G. Johnson ◽  
Micheal D. K. Owen ◽  
Greg R. Kruger ◽  
Bryan G. Young ◽  
David R. Shaw ◽  
...  
Keyword(s):  
North Carolina ◽  
Weed Control ◽  
Cropping Systems ◽  
Management Strategies ◽  
Resistance Management ◽  
Genetically Engineered ◽  
Effective Strategy ◽  
Weed Science ◽  
Evolution Of Resistance

A survey of farmers from six U.S. states (Indiana, Illinois, Iowa, Nebraska, Mississippi, and North Carolina) was conducted to assess the farmers' views on glyphosate-resistant (GR) weeds and tactics used to prevent or manage GR weed populations in genetically engineered (GE) GR crops. Only 30% of farmers thought GR weeds were a serious issue. Few farmers thought field tillage and/or using a non-GR crop in rotation with GR crops would be an effective strategy. Most farmers did not recognize the role that the recurrent use of an herbicide plays in evolution of resistance. A substantial number of farmers underestimated the potential for GR weed populations to evolve in an agroecosystem dominated by glyphosate as the weed control tactic. These results indicate there are major challenges that the agriculture and weed science communities must face to implement long-term sustainable GE GR-based cropping systems within the agroecosystem.

Soil treatment, plant species and management effects on improved pastures on a solodic soil in the semi-arid subtropics. I. Dry matter and botanical composition

1985 ◽  
Vol 25 (2) ◽  
pp. 367 ◽  
Author(s):  
JS Russell
Keyword(s):  
Dry Matter ◽  
Nitrogen Deficiency ◽  
Treatment Plant ◽  
Hydrated Lime ◽  
Grass Species ◽  
Botanical Composition ◽  
Nitrogen And Phosphorus ◽  
Rhodes Grass ◽  
Annual Medics ◽  
Semi Arid

Pastures of Rhodes grass (Chloris gayana), temperate legumes (annual medics) and a tropical legume (siratro) were established on a solodic soil in 1973-74 at Kogan in the semi-arid subtropics of southern Queensland. The effect of soil treatments, sown pasture species and cattle stocking rates on dry matter yields and botanical composition were measured during 1974-79. Nitrogen deficiency was a key factor limiting herbage production. Increased nitrogen in the ecosystem applied as fertilizer increased mean presentation dry matter of Rhodes grass pastures from 990 to 3443 kg/ha. Use of hydrated lime and gypsum (HLG) and annual medics with Rhodes grass increased dry matter yields from 990 to 1773 kg/ha. Where HLG had been applied, the annual medics re-established from seed each autumn and early winter throughout the period studied. Siratro established well at sowing and contributed initially to herbage production but then declined to almost zero. Deep subsoiling had no significant effect on dry matter yields or siratro persistence. Applied phosphorus at 48 kg Plha at establishment significantly increased herbage yields of Rhodes grass compared with 24 kg P/ha but no significant effects at either rate were found with a further 60 kg P/ha applied as 12 kg P/ha.year. Rhodes grass, which is tolerant of high soil sodium and magnesium status, maintained frequencies above 90% in treatments where the levels of nitrogen and phosphorus were high and when grazed at 0.62 steers/ha. However, deterioration occurred where nitrogen and phosphorus were lower or grazing pressure was higher, resulting in an ingress of native grasses. Twenty-five volunteer grass species were identified, the main genera being Eragrostis and Chloris. The need for a self-regenerating annual summer-growing legume in this environment is discussed.

SIMULATING RESPONSE OF MAIZE TO NITROGEN FERTILIZER IN SEMI-ARID ZIMBABWE

2002 ◽  
Vol 38 (1) ◽  
pp. 79-96 ◽  
Author(s):  
Z. Shamudzarira ◽  
M. J. Robertson
Keyword(s):  
Smallholder Farmers ◽  
Cropping Systems ◽  
Management Strategies ◽  
N Fertilizer ◽  
Research Centre ◽  
Price Ratio ◽  
Systems Simulation ◽  
N Use ◽  
Semi Arid

Data from a long-term trial on rates of fertilizer nitrogen (N) application to maize (Zea mays) were used to validate a cropping systems simulation model (APSIM) and then to apply the model to explore the risk associated with N fertilizer use by smallholder farmers and management strategies to minimize that risk. On average, maize growth and development in response to N was simulated with a degree of accuracy that justified its use in analysis of risk associated with N use in these semi-arid regions of Zimbabwe. APSIM was then configured to simulate the response to N over a 46-year climate record in order to assess the long-term risks associated with N use. The simulated long-term distribution indicated that negative responses to N could be expected in 15% of years, whereas no negative response to N was recorded in the experiments at the Makoholi Research Centre. Median responses were 20–30 kg maize grain kg−1 N for observed and simulated results. In terms of return on fertilizer investment, the observed and simulated distributions were also similar: in about 20% of years, a negative return could be expected, while in the best 20% of years a return of $Z5000 or more could be expected given the grain:fertilizer price ratio which, at March 2000, was about 1:7. The model analysis has suggested moderate rates (approximately 30 kg N ha−1) of N fertilizer would give greater responses per unit N applied than smaller rates (15 kg N ha−1). There was no evidence that conditional fertilizer strategies based on early-season rainfall would offer significant benefits over fixed application strategies. Early sowing at recommended population densities gave higher responses to N than were achieved for late sown or low-density crops.

Connecting Crop Nutrient Use Efficiency to Future Soil Productivity

2018 ◽  
Vol 102 (4) ◽  
pp. 8-10
Author(s):  
Fernando García ◽  
Andrés Grasso ◽  
María González Sanjuan ◽  
Adrián Correndo ◽  
Fernando Salvagiotti
Keyword(s):  
Nutrient Management ◽  
Nutrient Use Efficiency ◽  
Management Strategies ◽  
Crop Productivity ◽  
Soil Productivity ◽  
Nutrient Use ◽  
Grain Crop ◽  
Wide Scale ◽  
Use Efficiency

Trends over the past 25 years indicate that Argentina’s growth in its grain crop productivity has largely been supported by the depletion of the extensive fertility of its Pampean soils. Long-term research provides insight into sustainable nutrient management strategies ready for wide-scale adoption.

Petroclival meningiomas: long-term outcomes of multimodal treatments and management strategies based on 30 years of experience at a single institution

2020 ◽  
Vol 132 (6) ◽  
pp. 1675-1682 ◽  
Author(s):  
Jin Wook Kim ◽  
Hee-Won Jung ◽  
Yong Hwy Kim ◽  
Chul-Kee Park ◽  
Hyun-Tai Chung ◽  
...  
Keyword(s):  
Adjuvant Treatment ◽  
Management Strategies ◽  
Local Tumor Control ◽  
Tumor Control ◽  
Years Of Experience ◽  
Local Tumor ◽  
Long Term Outcomes ◽  
Single Institution ◽  
Petroclival Meningiomas

OBJECTIVEA thorough investigation of the long-term outcomes and chronological changes of multimodal treatments for petroclival meningiomas is required to establish optimal management strategies. The authors retrospectively reviewed the long-term clinical outcomes of patients with petroclival meningioma according to various treatments, including various surgical approaches, and they suggest treatment strategies based on 30 years of experience at a single institution.METHODSNinety-two patients with petroclival meningiomas were treated surgically at the authors’ institution from 1986 to 2015. Patient demographics, overall survival, local tumor control rates, and functional outcomes according to multimodal treatments, as well as chronological change in management strategies, were evaluated. The mean clinical and radiological follow-up periods were 121 months (range 1–368 months) and 105 months (range 1–348 months), respectively.RESULTSA posterior transpetrosal approach was most frequently selected and was followed in 44 patients (48%); a simple retrosigmoid approach, undertaken in 30 patients, was the second most common. The initial extent of resection and following adjuvant treatment modality were classified into 3 subgroups: gross-total resection (GTR) only in 13 patients; non-GTR treatment followed by adjuvant radiosurgery or radiation therapy (non-GTR+RS/RT) in 56 patients; and non-GTR without adjuvant treatment (non-GTR only) in 23 patients. The overall progression-free survival rate was 85.8% at 5 years and 81.2% at 10 years. Progression or recurrence rates according to each subgroup were 7.7%, 12.5%, and 30.4%, respectively.CONCLUSIONSThe authors’ preferred multimodal treatment strategy, that of planned incomplete resection and subsequent adjuvant radiosurgery, is a feasible option for the management of patients with large petroclival meningiomas, considering both local tumor control and postoperative quality of life.

Influence of Long-term Cropping Systems on Soil Physical Properties Related to Soil Erodibility

2003 ◽  
Vol 67 (2) ◽  
pp. 637 ◽  
Author(s):  
Achmad Rachman ◽  
S. H. Anderson ◽  
C. J. Gantzer ◽  
A. L. Thompson
Keyword(s):  
Physical Properties ◽  
Cropping Systems ◽  
Soil Physical Properties ◽  
Soil Erodibility

Investigation of a New Approach to Predict Water Quality Extremes with a Case Study of Chemical Determinands in Stream Water

1991 ◽  
Vol 24 (6) ◽  
pp. 25-33
Author(s):  
A. J. Jakeman ◽  
P. G. Whitehead ◽  
A. Robson ◽  
J. A. Taylor ◽  
J. Bai
Keyword(s):  
Water Quality ◽  
Stream Water ◽  
Probability Distributions ◽  
Management Strategies ◽  
Hybrid Modelling ◽  
Trend Model ◽  
Environmental Extremes ◽  
Modelling Approach

The paper illustrates analysis of the assumptions of the statistical component of a hybrid modelling approach for predicting environmental extremes. This shows how to assess the applicability of the approach to water quality problems. The analysis involves data on stream acidity from the Birkenes catchment in Norway. The modelling approach is hybrid in that it uses: (1) a deterministic or process-based description to simulate (non-stationary) long term trend values of environmental variables, and (2) probability distributions which are superimposed on the trend values to characterise the frequency of shorter term concentrations. This permits assessment of management strategies and of sensitivity to climate variables by adjusting the values of major forcing variables in the trend model. Knowledge of the variability about the trend is provided by: (a) identification of an appropriate parametric form of the probability density function (pdf) of the environmental attribute (e.g. stream acidity variables) whose extremes are of interest, and (b) estimation of pdf parameters using the output of the trend model.

scholarly journals Contributions to Management Strategies in the NE Atlantic Regarding the Life History and Population Structure of a Key Deep-Sea Fish (Mora moro)

Biology ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 522
Author(s):  
Régis Santos ◽  
Wendell Medeiros-Leal ◽  
Osman Crespo ◽  
Ana Novoa-Pabon ◽  
Mário Pinho
Keyword(s):  
Population Structure ◽  
Life History ◽  
Deep Sea ◽  
Management Strategies ◽  
Size Composition ◽  
Large Size ◽  
The Common ◽  
Fishing Impacts ◽  
Sea Fish

With the commercial fishery expansion to deeper waters, some vulnerable deep-sea species have been increasingly captured. To reduce the fishing impacts on these species, exploitation and management must be based on detailed and precise information about their biology. The common mora Mora moro has become the main deep-sea species caught by longliners in the Northeast Atlantic at depths between 600 and 1200 m. In the Azores, landings have more than doubled from the early 2000s to recent years. Despite its growing importance, its life history and population structure are poorly understood, and the current stock status has not been assessed. To better determine its distribution, biology, and long-term changes in abundance and size composition, this study analyzed a fishery-dependent and survey time series from the Azores. M. moro was found on mud and rock bottoms at depths below 300 m. A larger–deeper trend was observed, and females were larger and more abundant than males. The reproductive season took place from August to February. Abundance indices and mean sizes in the catch were marked by changes in fishing fleet operational behavior. M. moro is considered vulnerable to overfishing because it exhibits a long life span, a large size, slow growth, and a low natural mortality.

scholarly journals Coronary artery aneurysms: outcomes following medical, percutaneous interventional and surgical management

Open Heart ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. e001440
Author(s):  
Shameer Khubber ◽  
Rajdeep Chana ◽  
Chandramohan Meenakshisundaram ◽  
Kamal Dhaliwal ◽  
Mohomed Gad ◽  
...  
Keyword(s):  
Coronary Artery ◽  
Surgical Management ◽  
Medical Management ◽  
Cox Regression ◽  
Artery Bypass ◽  
Management Strategies ◽  
Coronary Artery Aneurysms ◽  
Kaplan Meier

BackgroundCoronary artery aneurysms (CAAs) are increasingly diagnosed on coronary angiography; however, controversies persist regarding their optimal management. In the present study, we analysed the long-term outcomes of patients with CAAs following three different management strategies.MethodsWe performed a retrospective review of patient records with documented CAA diagnosis between 2000 and 2005. Patients were divided into three groups: medical management versus percutaneous coronary intervention (PCI) versus coronary artery bypass grafting (CABG). We analysed the rate of major cardiovascular and cerebrovascular events (MACCEs) over a period of 10 years.ResultsWe identified 458 patients with CAAs (mean age 78±10.5 years, 74.5% men) who received medical therapy (N=230) or underwent PCI (N=52) or CABG (N=176). The incidence of CAAs was 0.7% of the total catheterisation reports. The left anterior descending was the most common coronary artery involved (38%). The median follow-up time was 62 months. The total number of MACCE during follow-up was 155 (33.8%); 91 (39.6%) in the medical management group vs 46 (26.1%) in the CABG group vs 18 (34.6%) in the PCI group (p=0.02). Kaplan-Meier survival analysis showed that CABG was associated with better MACCE-free survival (p log-rank=0.03) than medical management. These results were confirmed on univariate Cox regression, but not multivariate regression (OR 0.773 (0.526 to 1.136); p=0.19). Both Kaplan-Meier survival and regression analyses showed that dual antiplatelet therapy (DAPT) and anticoagulation were not associated with significant improvement in MACCE rates.ConclusionOur analysis showed similar long-term MACCE risks in patients with CAA undergoing medical, percutaneous and surgical management. Further, DAPT and anticoagulation were not associated with significant benefits in terms of MACCE rates. These results should be interpreted with caution considering the small size and potential for selection bias and should be confirmed in large, randomised trials.

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