Skeleton weed (Chondrilla juncea) in the Victorian Mallee. 4. Effects of fallowing on wheat yields and weed populations

1971 ◽  
Vol 11 (50) ◽  
pp. 313 ◽  
Author(s):  
GJ Wells
Keyword(s):  
Soil Nitrogen ◽  
Nitrate Nitrogen ◽  
Wheat Yield ◽  
Individual Response ◽  
Phosphorus Fertilizer ◽  
Nitrogen And Phosphorus ◽  
Rainfall Distribution ◽  
Weed Density ◽  
Weed Growth ◽  
The Individual

Experiments to compare the duration of fallows and the substitution of a 2,4-D spray for some fallow cultivations for wheat production on skeleton weed land were conducted in the Victorian Mallee from 1962 to 1966. Generally winter fallows outyielded spring fallows, commenced only two months later, and these in turn gave higher yields than an autumn-cultivated treatment. Compared with autumn cultivation, winter fallowing reduced skeleton weed density by an average of 49 per cent. Substituting a 2,4-D spray for some Gltivations had little effect on wheat yield, but improved the control of skeleton weed. Grain yield was determined primarily by the level of nitrate nitrogen in the surface 15 cm of soil before sowing, and this effect was attributed to the low soil nitrogen status found in skeleton weed situations. Soil moisture was conserved only occasionally, owing to the difficulty of controlling weed growth during the summer coupled with the variable rainfall distribution in the Mallee. Although a nitrogen and phosphorus fertilizer interaction was significant at all sites, neither the individual response nor the interaction was affected by fallow treatment.

Predicting and mitigating weed invasions to restore natural post-fire succession in Mesa Verde National Park, Colorado, USA

2006 ◽  
Vol 15 (2) ◽  
pp. 247 ◽  
Author(s):  
M. Lisa Floyd ◽  
David Hanna ◽  
William H. Romme ◽  
Timothy E. Crews
Keyword(s):  
Soil Nitrogen ◽  
Native Species ◽  
National Park ◽  
Native Plant ◽  
Weed Species ◽  
Nitrogen And Phosphorus ◽  
Weed Invasion ◽  
Weed Density ◽  
Burned Areas ◽  
Mesa Verde

Six large wildfires have burned in Mesa Verde National Park during the last 15 years, and extensive portions of burns were invaded by non-native plant species. The most threatening weed species include Carduus nutans, Cirsium arvense, and Bromus tectorum, and if untreated, they persist at least 13 years. We investigated patterns of weed distribution to identify plant communities most vulnerable to post-fire weed invasion and created a spatially explicit model to predict the most vulnerable sites. At the scale of the entire park, mature piñon–juniper woodlands growing on two soil series were most vulnerable to post-fire weed invasion; mountain shrublands were the least vulnerable. At a finer scale, greater richness of native species was correlated with greater numbers of non-native species, indicating that habitats with high native biodiversity are at the greatest risk of weed invasion. In unburned areas, weed density increased with greater soil nitrogen and phosphorus, and lower salinity. In burned areas weed density correlated with soil nitrogen status and textural class. We also evaluated the effectiveness of a variety of weed mitigation methods; aerial seeding of targeted high-risk areas with native grasses was the most effective treatment tested. We recommend a conservative mitigation plan using natives grass seed on only the most invasible sites.

Competition of Wild Oat in Wheat and Barley

Weed Science ◽  
1968 ◽  
Vol 16 (4) ◽  
pp. 505-508 ◽  
Author(s):  
Allyn R. Bell ◽  
John D. Nalewaja
Keyword(s):  
Triticum Aestivum ◽  
Hordeum Vulgare ◽  
Yield Loss ◽  
Wheat Yield ◽  
Avena Fatua ◽  
Yield Reduction ◽  
Wild Oat ◽  
Phosphorus Fertilizer ◽  
Nitrogen And Phosphorus ◽  
Percent Protein

Wild oat (Avena fatua L.) competition increased the losses in yield of both wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) with increased densities of seedlings. At Fargo in 1965, wild oat densities of 70 and 160 seedlings/sq yd reduced the wheat yield 22.1% and 39.1%, respectively, compared to the wild oat-free check. Similar wild oat densities reduced the barley yield 6.5% and 25.9%, respectively. The addition of nitrogen and phosphorus fertilizer reduced the yield loss caused by wild oat 2 out of 3 years of the experiment. Although a considerable yield reduction occurred in barley and wheat, percent protein and seed size were not influenced noticeably.

Nitrogen and phosphorus requirements of wheat following subterranean clover pasture

1977 ◽  
Vol 28 (6) ◽  
pp. 971 ◽  
Author(s):  
GJ Osborne ◽  
GD Batten ◽  
GD Kohn
Keyword(s):  
Soil Nitrogen ◽  
Nitrogen Fertilizer ◽  
Soil Phosphorus ◽  
Wheat Yield ◽  
Subterranean Clover ◽  
Nitrogen And Phosphorus ◽  
Nitrogen Levels ◽  
Grain Nitrogen ◽  
Available Soil Phosphorus ◽  
Phosphorus Levels

The effects of superphosphate and nitrogen fertilizer on wheat yield, grain nitrogen and phosphorus levels, total soil nitrogen and available soil phosphorus were studied over a 6-year period on plots which had received 718–3343 kg superphosphate ha-1, during a preceding ley pasture-crop period. Wheat yields generally declined with time on all treatments, fertilizer nitrogen reducing the rate of decline. From 125 to 2.50 kg superphosphate ha-1 year-1 was required to maintain maximum wheat yields when nitrogen fertilizer was also applied, but only 125 kg was required in its absence. Grain nitrogen content varied from 1.47 to 2.11% and was not a good indicator of nitrogen fertilizer requirement. Nitrogen removal per crop varied from 27 to 41 kg ha-1 in the presence of added nitrogen and from 21 to 31 kg ha-1 without added nitrogen. Soil nitrogen levels declined at rates varying from 8 to 40 kg ha-1 year-1. Grain phosphorus levels varied from 0.21 to 0.44%. Phosphorus removal in the grain varied from 4 to 8 kg ha-1 per crop. Changes in available soil phosphorus on plots which had previously received 718, 1593, 2468 or 3343 kg superphosphate ha-1 were closely correlated with the rate of superphosphate applied with the crop (r = 0.97, 0.97, 0.93 and 0.80). The amount of superphosphate required to maintain soil phosphorus levels was calculated, and the following conclusions regarding superphosphate use in the pasture-crop rotation in southern New South Wales have been made. Where pastures are not topdressed, the amount of superphosphate needed with each crop varies with the number of years of cropping, the level of soil nitrogen, the number of years of untopdressed pasture relative to the years of crop, and the initial soil phosphorus level.

DEVELOPMENT OF A BARLEY YIELD EQUATION FOR CENTRAL ALBERTA. 1. EFFECTS OF SOIL AND FERTILIZER N AND P

1976 ◽  
Vol 56 (3) ◽  
pp. 233-247 ◽  
Author(s):  
D. K. MCBEATH ◽  
L. A. HEAPY ◽  
J. A. ROBERTSON ◽  
G. R. WEBSTER ◽  
U. M. VON MAYDELL ◽  
...  
Keyword(s):  
Nitrate Nitrogen ◽  
Moisture Stress ◽  
Soil Test ◽  
Nitrogen And Phosphorus ◽  
Pooled Data ◽  
Yield Variation ◽  
Individual Site ◽  
Fertilizer Recommendations ◽  
The Individual ◽  
Stress Term

Equations were derived relating yields of barley, grown on previously cropped land, to inputs of fertilizer nitrogen (NA) and phosphorus (PA) and to soil test values for nitrate nitrogen (NS) and extractable phosphorus (PS). The first model, Y = f (NA, PA), fitted to pooled data of 17 site-years, explained about 23% of yield variations. The second model, Y = f (NA, PA, NS, PS), fitted to the same data, explained 36–38%, depending on depth of sampling. When the optimal nitrogen applications obtained from the latter model were compared to the optimal nitrogen applications obtained from the first model applied to the individual site-years, the 30-cm sampling depth was found to be superior to the 15-cm depth; there was no further improvement by sampling to 61 cm. Our results indicated several ways in which the Alberta Soil Testing Laboratory could improve its fertilizer recommendations, namely: basing nitrogen recommendations on samples taken to 30 cm rather than 15 cm, adjusting recommended nitrogen applications according to level of PS, lowering the levels of phosphorus recommended for various levels of PS, and adjusting the nitrogen and phosphorus recommendations according to prices of fertilizers and barley. Much of the yield variation could not be explained by variations in applied and soil nutrients, indicating that other uncontrolled environmental variables, such as soil moisture and rainfall, should be introduced into the barley yield equations. Part 2 presents the methodology for introducing a "moisture stress" term.

scholarly journals Spectral Pitch Similarity is a Predictor of Perceived Change in Sound- as Well as Note-Based Music

2019 ◽  
Vol 2 ◽  
pp. 205920431984735
Author(s):  
Roger T. Dean ◽  
Andrew J. Milne ◽  
Freya Bailes
Keyword(s):  
Time Series ◽  
Piano Music ◽  
Individual Response ◽  
Discrete Events ◽  
Acoustic Intensity ◽  
Spectral Parameters ◽  
Cross Sectional ◽  
Perceived Change ◽  
Predictive Role ◽  
The Individual

Spectral pitch similarity (SPS) is a measure of the similarity between spectra of any pair of sounds. It has proved powerful in predicting perceived stability and fit of notes and chords in various tonal and microtonal instrumental contexts, that is, with discrete tones whose spectra are harmonic or close to harmonic. Here we assess the possible contribution of SPS to listeners’ continuous perceptions of change in music with fewer discrete events and with noisy or profoundly inharmonic sounds, such as electroacoustic music. Previous studies have shown that time series of perception of change in a range of music can be reasonably represented by time series models, whose predictors comprise autoregression together with series representing acoustic intensity and, usually, the timbral parameter spectral flatness. Here, we study possible roles for SPS in such models of continuous perceptions of change in a range of both instrumental (note-based) and sound-based music (generally containing more noise and fewer discrete events). In the first analysis, perceived change in three pieces of electroacoustic and one of piano music is modeled, to assess the possible contribution of (de-noised) SPS in cooperation with acoustic intensity and spectral flatness series. In the second analysis, a broad range of nine pieces is studied in relation to the wider range of distinctive spectral predictors useful in previous perceptual work, together with intensity and SPS. The second analysis uses cross-sectional (mixed-effects) time series analysis to take advantage of all the individual response series in the dataset, and to assess the possible generality of a predictive role for SPS. SPS proves to be a useful feature, making a predictive contribution distinct from other spectral parameters. Because SPS is a psychoacoustic “bottom up” feature, it may have wide applicability across both the familiar and the unfamiliar in the music to which we are exposed.

Mechanism Analysis and Experimental Research on the Interception of Nitrogen and Phosphorus Pollutants by Gullies in Northern China

2011 ◽  
Vol 250-253 ◽  
pp. 3392-3396
Author(s):  
Yu Jia Song ◽  
Hui Qing Liu
Keyword(s):  
Total Phosphorus ◽  
Nitrate Nitrogen ◽  
Northern China ◽  
Careful Analysis ◽  
Ammonia Nitrogen ◽  
Mechanism Analysis ◽  
Nitrogen And Phosphorus ◽  
Urban Sewage ◽  
Control Section ◽  
Nitrogen Pollutants

The discharge of urban sewage and agricultural non-point source pollutants is the main reason causing eutrophication in gullies in most cities of northern China. Based on a careful analysis on the ecological structure and ecological characteristics of a gully, this article preliminarily studies the interception and degradation mechanisms of nitrogen pollutants by the gully. Meanwhile, to take gullies in Changchun as the object of the study, this article carries out an experiment on the interception effect of nitrogen pollutants by gullies. This experiment respectively establishes a control section in the upper and lower reaches of a gully, and takes water samples four times in each section from May to August to determine total nitrogen, total phosphorus, nitrate nitrogen, ammonia nitrogen and salinity. The result shows: the gully plays some role in the interception of pollutants; total phosphorus accounts for the largest interception in pollutants in the experimented gully section, with the relative interception rate of 27.46%, followed by ammonia nitrogen, with the interception rate of 21.80%, which is the result of the combined effects of aquatic plants, microorganisms and sediment in the gully.

LONG‐TIME RESPONSE PREDICTED BY EXACT ELASTIC RAY THEORY

Geophysics ◽  
1965 ◽  
Vol 30 (3) ◽  
pp. 363-368 ◽  
Author(s):  
T. W. Spencer
Keyword(s):  
Formal Solution ◽  
Intermediate Stage ◽  
Time Limit ◽  
Time Interval ◽  
Individual Response ◽  
Axially Symmetric ◽  
Long Time ◽  
The Difference ◽  
The Individual ◽  
Significant Figures

The formal solution for an axially symmetric radiation field in a multilayered, elastic system can be expanded in an infinite series. Each term in the series is associated with a particular raypath. It is shown that in the long‐time limit the individual response functions produced by a step input in particle velocity are given by polynomials in odd powers of the time. For rays which suffer m reflections, the degree of the polynomials is 2m+1. The total response is obtained by summing all rays which contribute in a specified time interval. When the rays are selected indiscriminately, the difference between the magnitude of the partial sum at an intermediate stage of computation and the magnitude of the correct total sum may be greater than the number of significant figures carried by the computer. A prescription is stated for arranging the rays into groups. Each group response function varies linearly in the long‐time limit and goes to zero when convolved with a physically realizable source function.

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