scholarly journals Rainfall and cotton yields in the Sudan Gezira

1935 ◽  
Vol 118 (809) ◽  
pp. 343-370 ◽  
Keyword(s):  
Field Experiments ◽  
Practical Importance ◽  
Small Samples ◽  
Cultural Methods ◽  
Research Programmes ◽  
Slow Progress ◽  
Highly Correlated ◽  
Cyclic Changes ◽  
Agricultural Areas ◽  
Sudan Gezira

Agricultural meteorology makes slow progress because it is rarely possible to study the correlation of weather and yield for crops grown in normal agricultural rotations over long periods. Both in commercial agriculture and at experiment stations, rotations and cultural methods change sufficiently frequently to destroy the homogeneity of the data, even when records are kept for specific fields or farms. In some of the newer agricultural areas, and especially in those under irrigation, the cropping is simpler, and the need for records and field experiments is more keenly appreciated. Research programmes and practical measures must be determined from experience over only a few decades; but erroneous conclusions may easily be drawn from trends over such short periods, memories of individual years, or simple correlations of yields and single weather variates. In the present paper, modern statistical methods of analysing small samples of data are used to examine the relationships between rainfall and cotton yields under irrigation in the Sudan Gezira for periods up to 23 years. The mean yields from this large and semi-desert area fluctuate violently from year to year in such a way as to suggest the dominance of some climatic factor. It will be shown that the cotton yields are highly correlated with rainfall, and further, that seasonal fluctuations in rainfall, including certain cyclic changes, are sufficient to account for most of the decline in yield on some of the oldest areas. This conclusion has considerable practical importance, because a recent sequence of low yields led some critics (Balls, 1935, Vageler and Alten, 1932) of the scheme to conclude that irrigation without drainage had already produced serious soil deterioration. The significance of some of the rainfall effects established may direct attention to new methods of studying problems of soil fertility and the control of pests.

Effect of nitrogen, phosphorus, and potassium on yield and petiolar nutrient concentration of potato (Solanum tuberosum L.) cvv. Kennebec and Atlantic

1994 ◽  
Vol 34 (6) ◽  
pp. 825 ◽  
Author(s):  
NA Maier ◽  
AP Dahlenburg ◽  
CMJ Williams
Keyword(s):  
Field Experiments ◽  
Solanum Tuberosum L ◽  
Practical Importance ◽  
Total N ◽  
Nitrate N ◽  
N Concentration ◽  
Linear Relationships ◽  
The Difference ◽  
Highly Correlated ◽  
Potato Crops

Data are presented from 3 field experiments that studied the effects of nitrogen (N) up to 360 kg N/ha, phosphorus (P) up to 100 kg P/ha, and potassium (K) up to 480 kg K/ha on tuber yield and the concentration of N, P, and K in petioles of youngest fully expanded leaves (P-YFEL) of potato cvv. Kennebec and Atlantic sampled when the length of the longest tubers was 10-15 mm. Data on the significance of relationships between total N and P, total N and nitrate-N, and chloride and nitrate-N in P-YFEL are also presented. At 1 site, Atlantic yielded 18% higher than Kennebec; at another, it yielded 21% less. Significant K x cv. and N x cv. interactions occurred at some sites. Increasing rates of applied N significantly increased total N concentrations in P-YFEL at all sites and nitrate-N concentrations at sites that were N-deficient. At 1 site, increasing the rate of applied P from nil to 100 kg P/ha significantly increased total N concentration from 2.8 to 3.4%. Total N concentrations in P-YFEL of Atlantic were significantly lower than Kennebec. For total N, there were significant N x K and P x cv. interactions. There was no significant interaction between N, P, and K in their effects on nitrate-N concentration in P-YFEL. At all sites, the application of N and P significantly increased P concentrations in P-YFEL, and mean concentrations were significantly greater in Kennebec than Atlantic. At sites deficient in K, the application of K significantly decreased P concentration. Significant N x cv. and P x cv. interactions occurred at 2 sites. At both K-deficient and non-responsive sites, increasing rates of applied K significantly increased K concentrations in P-YFEL. Differences between cultivars in K concentration were not significant at 2 sites, and although significant at the third, the difference (0.2%) was of little practical importance. At 2 sites, significant N x K and K x P interactions were found. Significant positive linear relationships were found between total N and P concentrations in P-YFEL for both the experimental sites (r = 0.46-0.84) and commercial crops (r = 0.43-0.61). Except at site 1 (r = 0.85), total N and nitrate-N concentrations were not highly correlated. For 1 experimental site and for all the growing regions, there were significant negative linear relationships between nitrate-N and chloride concentrations in P-YFEL (r = -0.38 to -0.83). We suggest that the synergism between total N and P and the negative correlation between nitrate N and chloride are important factors to be considered to ensure reliable interpretation of early-season, petiole plant test data for these nutrients in potato crops; that the critical P and total N concentrations are different for Kennebec and Atlantic; and that when K is not yield-limiting, the main effects and interactions between K and total N, P, or nitrate-N do not confound the use of these nutrients in P-YFEL to assess the P, N, or K status of potato crops.

Alignment of milliarcsecond with arcsecond scale structure in core-dominated radio sources

1986 ◽  
Vol 64 (4) ◽  
pp. 440-444 ◽  
Author(s):  
Raymond Rusk ◽  
Ann C.M. Rusk
Keyword(s):  
Scale Structure ◽  
Small Samples ◽  
Radio Sources ◽  
Angle Distribution ◽  
Long Baseline ◽  
Relativistic Beaming ◽  
Beam Parameters ◽  
Highly Correlated ◽  
Bend Angles ◽  
Larger Sample

Models of compact radio sources as relativistic jets aligned nearly along the line of sight predict large magnifications of intrinsic jet bends due to projection effects. Several authors have examined the distribution of observed bend angles, for small samples of sources, to provide constraints on the relativistic beaming models. In this study, we examine the alignment of Very Long Baseline Interferometry scale structure with arcsecond scale structure for a much larger sample of core-dominated radio sources and compare the distribution of observed misalignment angles with theoretical distributions calculated from models using a range of intrinsic bend angles, ξ, and Lorentz factors, γ. The theoretical distributions produced by simple relativistic beam models are found to be consistent with the data. However, the values of ξ and γ required to fit the data are highly correlated, with equally good fits produced by γ = 5, ξ = 11° and γ = 10, ξ = 5°, for instance. Either ξ or γ must be known independently for an analysis of the misalignment angle distribution to provide a significant constraint on beam parameters.

2014–2015: a view from Greece

2015 ◽  
Vol 61 ◽  
pp. 6-11
Author(s):  
Catherine Morgan
Keyword(s):  
Financial Crisis ◽  
Heritage Management ◽  
Public Communication ◽  
Press Coverage ◽  
Archaeological Research ◽  
New Information ◽  
Research Programmes ◽  
The Face ◽  
Slow Progress

In a year when financial crisis and EU turmoil have gripped Greece and dominated international press coverage, one might be forgiven for assuming that there would be slow progress in archaeological research and heritage management. It has certainly been a tumultuous year, and heartfelt thanks are due to colleagues, especially those in the Archaeological Service, who have gone the extra mile to deliver their own work and to help others in the face of mounting pressures. In 2014 alone, the Central Archaeological Council dealt with 1,477 cases in 42 sittings, and its 2015 target is set to exceed this. Yet as I take stock of what has been achieved in publication, fieldwork, study and public communication, I am struck by the wealth of new information available and in many forms. Individual finds, continuing research programmes and a number of landmark conferences and exhibitions have contributed to real and significant advances in knowledge. There is much to report, and even more to see on the ground for readers inspired (as we hope) to spend time in Greece.

Bromoxynil tolerance during the seedling phase is associated with genetic grain yield improvement in maize

1991 ◽  
Vol 71 (4) ◽  
pp. 1021-1027 ◽  
Author(s):  
M. Tollenaar ◽  
M. Mihajlovic
Keyword(s):  
Zea Mays ◽  
Chlorophyll Fluorescence ◽  
Grain Yield ◽  
Stress Tolerance ◽  
Field Experiments ◽  
Zea Mays L ◽  
Environmental Stresses ◽  
Yield Improvement ◽  
Maize Hybrids ◽  
Highly Correlated

Genetic grain yield improvement of maize (Zea mays L.) in Ontario during the past three decades can be attributed, in part, to increased tolerance to environmental stresses. We have observed a differential response of field-grown old and new hybrids after application of the photosystem II inhibiting herbicide bromoxynil (4-hydroxy-3,5-dibromobenzonitrile). Studies were conducted to test whether tolerance to bromoxynil is associated with stress tolerance and grain yield in maize hybrids representing three decades of yield improvement in Ontario. Experiments were carried out with seedlings of eight maize hybrids grown in pots in controlled-environment growth cabinets and, in one experiment, with seedlings grown in pots outside during the months of July and August at Guelph, Ontario. Bromoxynil was applied to the youngest fully-expanded leaf of plants at the 6- to 8-leaf stage and chlorophyll fluorescence of the treated leaves was measured in the 2- to 24-h period after bomoxynil application. Results showed that the chlorophyll fluorescence ratio Fv/Fm, an indicator of photosynthetic efficiency, declined after bromoxynil application until 4 h after application and, subsequently, recovered slightly during the next 20 h. Large differences in the Fv/Fm ratio were apparent among hybrids in the response to bromoxynil. The Fv/Fm ratio was significantly higher for hybrids released in the 1980s than for hybrids released in the 1970s, and the Fv/Fm ratio of the latter group was significantly higher than that of the four oldest hybrids. Chlorophyll fluorescence ratios Fv/Fm after bromoxynil application in the seedling phase were highly correlated with grain yield of the hybrids in field experiments conducted during 1987 and 1988 (r = 0.91). Results of this study support the contention that maize genotypes that are less sensitive to bromoxynil are less susceptible to environmental stresses. Key words: Zea mays L., stress tolerance, bromoxynil, chlorophyll fluorescence, Fv/Fm ratio, detoxifying agents

THEORY AND PRACTICE OF LOW‐FREQUENCY ELECTROMAGNETIC EXPLORATION

Geophysics ◽  
1948 ◽  
Vol 13 (4) ◽  
pp. 584-594 ◽  
Author(s):  
Haakon M. Evjen
Keyword(s):  
Dielectric Constant ◽  
Field Experiments ◽  
Low Frequency ◽  
Theory And Practice ◽  
Small Samples ◽  
Effective Dielectric Constant ◽  
Field Equations ◽  
First Approximation ◽  
Crystalline Salt ◽  
Simple Potential

Based directly on Maxwell’s Field Equations, the extremely low end of the frequency spectrum may be reduced in first approximation to simple potential theory. The approximation theory is borne out by some field experiments, the results of which are presented. Agreement with the theory, however, requires that the ground have a very large effective dielectric constant. This conclusion is supported by previous observations by a number of independent observers. Thus, the relaxation time has been found to be extremely great, not only in observations directly on the ground, but also in small samples of mud, and the sign of an electric anomaly over a relative insulator, such as crystalline salt or gas and oil, invariably has been found to be negative. Both of these observations can be explained in terms of a very great dielectric constant. The value yielded by the present experimental work is of the order of [Formula: see text].

scholarly journals Quantifying heterogeneous transport of a tracer and a degradable contaminant in the field, under two infiltration rates

2012 ◽  
Vol 9 (4) ◽  
pp. 4827-4868
Author(s):  
D. Schotanus ◽  
M. J. van der Ploeg ◽  
S. E. A. T. M. van der Zee
Keyword(s):  
Field Experiments ◽  
Preferential Flow ◽  
Infiltration Rate ◽  
Soil Heterogeneity ◽  
Early Spring ◽  
Early Summer ◽  
Flow Paths ◽  
Infiltration Rates ◽  
Preferential Flow Paths ◽  
Highly Correlated

Abstract. To examine the persistence of preferential flow paths in a field soil, and to compare the leaching of a degradable contaminant with the leaching of a non-degradable tracer, we did two field experiments, using a multicompartment sampler. The first experiment was done during the snowmelt period in early spring, characterized by high infiltration fluxes from snowmelt. The second experiment was done in early summer with irrigation to mimic homogeneous rainfall. In the second experiment, the soil was warmer and degradation of the degradable contaminant was observed. For both experiments, the highest tracer concentrations were found in the same area of the sampler, but the leached tracer masses of the individual locations were not highly correlated. Thus, the preferential flow paths were stable between seasons. With a lower infiltration rate, in the second experiment, more isolated peaks in the drainage and the leached masses were found than in the first experiment. Therefore it is concluded that the soil heterogeneity is mainly caused by local differences in the soil hydraulic properties, and not by macropores. With higher infiltration rates, the clustering of high and low leaching cells was higher. The leached masses of the degradable contaminant were lower than the leached masses of the non-degradable tracer, but the masses were highly correlated. The first-order degradation rate was 0.02 d−1. The dispersivity varied between 1.9 and 7.1 cm. Soil heterogeneity is the main reason for the heterogeneous water flow and solute transport in this soil. Heterogeneous melting of snow does not influence the heterogeneous flow in the soil much at this scale.

scholarly journals Predicting N Status in Maize with Clip Sensors: Choosing Sensor, Leaf Sampling Point, and Timing

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 3881 ◽  
Author(s):  
Jose Luis Gabriel ◽  
Miguel Quemada ◽  
María Alonso-Ayuso ◽  
Jon I. Lizaso ◽  
Diana Martín-Lammerding
Keyword(s):  
Field Experiments ◽  
N Fertilization ◽  
Fertilizer Efficiency ◽  
Sampling Point ◽  
N Losses ◽  
Sampling Position ◽  
Leaf Sampling ◽  
Key Factor ◽  
Highly Correlated ◽  
N Status

Nitrogen (N) losses from agricultural systems increase air and water pollution, and these losses are highly correlated with the excessive fertilization. An adjusted N fertilization is then a key factor in increasing the N fertilizer efficiency, and leaf clip sensors can help to improve it. This study (combining five different field experiments in Central Spain) tried to identify the ability of the clip sensors in maize N status identification and yield prediction, comparing two different devices (SPAD-502® and Dualex®) and identifying the best protocol for maize leaf sampling. As a result, the study demonstrated that different leaf clip chlorophyll sensors presented similar results, although some differences appeared at larger N concentrations. Complementary polyphenol information (as flavonol) can improve the maize N deficiency prediction. Moreover, valuable information for a proper sampling protocol was obtained with this study. It proved that the sampling position (in the leaf and in the plant) and sampling time were crucial for a better estimation of the maize N status. Proper fertilization recommendations could be achieved based on clip chlorophyll sensor measurements.

Air and soil temperature limitations on photosynthesis in Engelmann spruce during summer

1987 ◽  
Vol 17 (6) ◽  
pp. 527-533 ◽  
Author(s):  
Evan H. DeLucia ◽  
William K. Smith
Keyword(s):  
Soil Temperature ◽  
Field Experiments ◽  
Growth Period ◽  
Extended Period ◽  
Early Summer ◽  
Photosynthetic Rates ◽  
Engelmann Spruce ◽  
Air Temperatures ◽  
Highly Correlated ◽  
Elevational Range

The relative importance of air and soil temperature as potential limitations to photosynthesis during summer was assessed in Engelmann spruce over its natural elevational range in southeastern Wyoming. Low photosynthetic rates measured at constant temperature, irradiance, and vapor pressure deficit were highly correlated with low minimum (night) air and soil temperature, but at different times during the early summer growth period. Substantial and irreversible reductions in photosynthesis occurred after exposure to night air temperatures of −4 to −5 °C that occurred through mid-June. After middle to late June, decreased photosynthetic rates were correlated with low soil temperature. Correlation analyses indicated that subfreezing air temperature followed by an extended period of low soil temperature were the primary limitations to photosynthesis in early summer. Additional laboratory and field experiments corroborate these field observations.

scholarly journals Quantifying heterogeneous transport of a tracer and a degradable contaminant in the field, with snowmelt and irrigation

2012 ◽  
Vol 16 (8) ◽  
pp. 2871-2882 ◽  
Author(s):  
D. Schotanus ◽  
M. J. van der Ploeg ◽  
S. E. A. T. M. van der Zee
Keyword(s):  
Degradation Rate ◽  
Field Experiments ◽  
Preferential Flow ◽  
Infiltration Rate ◽  
Soil Heterogeneity ◽  
Early Summer ◽  
Flow Paths ◽  
First Order ◽  
Preferential Flow Paths ◽  
Highly Correlated

Abstract. To examine the persistence of preferential flow paths in a field soil, and to compare the leaching of a degradable contaminant with the leaching of a tracer, two field experiments were performed using a multi-compartment sampler (MCS). The first experiment was carried out during the snowmelt period in early spring, characterized by high infiltration fluxes from snowmelt. The second experiment was carried out in early summer with irrigation to mimic homogeneous rainfall. During the second experiment, the soil was warmer and degradation of the degradable contaminant was observed. For both experiments, the highest tracer concentrations were found in the same area of the sampler, but the leached tracer masses of the individual locations were not highly correlated. Thus, the preferential flow paths were stable between the two experiments. With a lower infiltration rate, in the second experiment, more isolated peaks in the drainage and the leached masses were found than in the first experiment. Therefore, it is concluded that the soil heterogeneity is mainly caused by local differences in the soil hydraulic properties, and not by macropores. With higher infiltration rates, the high and low leaching cells were more clustered. The leached masses of the degradable contaminant were lower than the leached masses of the tracer, but the masses were highly correlated. The first-order degradation rate and the dispersivity were fitted with CXTFIT; the first-order degradation rate was 0.02 d−1, and the dispersivity varied between 1.9 and 7.1 cm. The persistence of the flow paths during the experiments suggests soil heterogeneity as the driver for heterogeneous flow and solute transport in this soil. At the MCS scale, heterogeneous snowmelt did not seem to have much influence on the flow and solute paths.

scholarly journals Methods of adaptability and stability applied to eucalyptus breeding

2018 ◽  
Vol 53 (1) ◽  
pp. 53-62
Author(s):  
Osmarino Pires dos Santos ◽  
Ivan Ricardo Carvalho ◽  
Maicon Nardino ◽  
Tiago Olivoto ◽  
Alan Junior de Pelegrin ◽  
...  
Keyword(s):  
Factor Analysis ◽  
Field Experiments ◽  
Block Design ◽  
Genetic Breeding ◽  
Breast Height ◽  
Randomized Complete Block Design ◽  
Productive Potential ◽  
The Mean ◽  
Highly Correlated

Abstract: The objective of this work was to evaluate the consistency of the methods of Annicchiarico, Lin & Binns, Wricke, and factor analysis in identifying eucalyptus clones with stability, adaptability, and high productive potential. Eight-four clones, with three years of age, from the genetic breeding program of the company CMPC Celulose Riograndense were used. Three field experiments were carried out in a randomized complete block design, in an 84x3 factorial arragement, with 20 replicates of one plant per plot. The clones were evaluated as to diameter at breast height, plant height, and volume of wood. The methods of Annicchiarico and Lin & Binns are highly correlated with each other, and their use together with the method of Wricke is a sound strategy for the evaluation of eucalyptus clones. The factor analysis identified broadly adaptable clones, and some of them were the same ones identified by the methods of Annicchiarico and Lin & Binns. The use of the mean classification of the clones, along with the factor analysis, is efficient to identify the most adapted, stable, and productive ones among a high number of genotypes.

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