scholarly journals Tillering in Grain Sorghum over a Wide Range of Population Densities: Modelling Dynamics of Tiller Fertility

2002 ◽  
Vol 90 (1) ◽  
pp. 99-110 ◽  
Author(s):  
T. A. LAFARGE ◽  
G. L. HAMMER
Keyword(s):  
Grain Sorghum ◽  
Population Densities ◽  
Wide Range

Evaluation of row spacing and population density effects on grain sorghum over a range of northern Australian environments

1981 ◽  
Vol 21 (109) ◽  
pp. 210 ◽  
Author(s):  
GA Thomas ◽  
RJK Myers ◽  
MA Foale ◽  
AV French ◽  
B Hall ◽  
...  
Keyword(s):  
Population Density ◽  
Full Range ◽  
Moisture Stress ◽  
Grain Sorghum ◽  
Row Spacing ◽  
Root Pruning ◽  
Population Densities ◽  
Planting Dates ◽  
Wide Range ◽  
Growing Conditions

Fifteen experiments were conducted between 1976 and 1978 to determine the response of grain sorghum to row spacing and population density over a range of soil types, planting dates and seasonal conditions. One experiment was at Kununurra, Western Australia, and the rest were in southern and central Queensland. The trials virtually covered the full range of growing conditions likely to be experienced in the sorghum growing area. Narrow and standard single rows (0.33 m to 1.07 m spacings) yielded as well as or better than more widely spaced (1.50 to 4.27 m) single or twin rows (0.33 or 0.36 m apart) at equivalent population densities over a wide range of yield levels. Only at yield levels below 900 kg ha-l was there a trend for 2.00 or 2.13 m twin rows to outyield the 0.33 or 0.36 m single row spacing. Significant yield reductions resulted in a number of trials, at yield levels above 1600 kg ha-l, from the use of wide row spacings. Where there was severe water stress, grain yields were also reduced by high population densities (>150,000 plants ha-l), particularly at the 0.33 or 0.36 m row spacing. There was no evidence that response to row spacing differed between cultivars. In the one experiment where it was studied, root pruning had no effect on grain yield under conditions of ample moisture supply, but yield was reduced by root pruning of wide row sorghum (1.8 m spacing) under conditions of moisture stress.

scholarly journals Assessment of the Potential of Eco-Friendly Nematicides in the Management of Root-Knot Nematodes on French Beans in Kenya

2019 ◽  
Vol 7 (1) ◽  
pp. 62-67
Author(s):  
E. O. Ogumo ◽  
W. M. Muiru ◽  
J. W. Kimenju ◽  
D. M. Mukunya
Keyword(s):  
Reproductive Potential ◽  
Negative Control ◽  
French Bean ◽  
Economic Losses ◽  
Root Knot Nematode ◽  
Population Densities ◽  
Root Knot Nematodes ◽  
French Beans ◽  
Wide Range ◽  
Significant Difference

Root-knot nematodes (RKN) (Meloidogyne spp) are a serious pest causing heavy economic losses in a wide range of agricultural crops. A trial was carried out to evaluate the effectiveness of various eco-friendly nematicides in the management of RKN affecting French bean. The field trial was carried out in two seasons with the following treatments; Rigel-G (salicylic acid), Phyto Protect (Sesame oil extract), Mytech (Paecilomyces lilacinus), Neemraj 0.3% (Azadirachtin), Vydate® (Oxamyl) as a positive control and an untreated control. Various rates; Rigel –G (2.5 ml/l), Phyto Protect (10 l/ha), Mytech (125 g/ha) Neemraj 0.3% (3L/ha) and Vydate® (6 l/ha) of treatments were administered and damage on plants was assessed based on galling indices, crop biomass and yield whereas nematode reproductive potential was assessed based on the J2 counts. There was no significant difference (P ≥ 0.05) in the nematode population densities and galling indices observed among the eco-friendly nematicides and the conventional nematicide (Vydate®). Eco-friendly nematicides had a significant (P ≤ 0.05) reduction of RKN J2 population densities compared to the negative control. The negative control had the highest mean of root-knot nematode densities (240 RKN/200 cc soil) and a galling index of 3.77 while Vydate and Neemraj had the lowest mean density (40 RKN/200 cc soil) in the first season. Similar results were observed in the second season with control having the highest RKN J2 population densities (285 RKN/200 cc soil) and a galling index of 3.89 and Vydate had the lowest (23 RKN/200 cc soil). The results of this study clearly indicate that eco-friendly nematicides can be fully adopted to suppress RKN in French beans as alternatives to conventional nematicides.

Depth distribution of Rotylenchulus reniformis under crops of different host status and after fumigation

Nematology ◽  
2004 ◽  
Vol 6 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Andreas Westphal ◽  
A. Forest Robinson ◽  
Andrew Scott ◽  
Judith Santini
Keyword(s):  
Depth Distribution ◽  
Grain Sorghum ◽  
Cotton Fibre ◽  
Control Population ◽  
Rotylenchulus Reniformis ◽  
Population Densities ◽  
Cotton Crop ◽  
Accurate Predictor ◽  
Host Status ◽  
Field Plots

Abstract Population densities of Rotylenchulus reniformis were investigated in 15 cm horizons from the surface to 120 cm deep in field plots under fallow, grain sorghum (cv. Asgrow 571), and susceptible (cv. DP6880RR) or resistant (cv. HY798) soybean. In 2000, population densities were monitored in non-fumigated plots and in plots fumigated pre-season with 1,3-dichloropropene (1,3-D) at 38 cm depth. Fallow, grain sorghum and resistant soybean reduced the incidence of R. reniformis down to 120 cm in comparison to susceptible soybean. In 2001, population densities were monitored under cotton in these plots and in additional plots that had grown susceptible soybean cv. Vernal or resistant cv. Padre in 2000 and that were fumigated before the 2001 crop with 1,3-D at depths of 0-60, 60-120, or 0-120 cm. In 2000 non-fumigated plots, cotton fibre yields were increased by an average 35% after fallow, grain sorghum or resistant soybean compared to those after susceptible soybean. In the 2000 fumigated plots, cotton fibre yields were increased 38% after grain sorghum and resistant soybean compared to those after susceptible soybean or fallow. In plots cropped previously to susceptible soybean, fumigation at 60-120 cm deep increased cotton fibre yields by 68% compared to the non-fumigated control. Population densities in the 0-120 cm horizon were a more accurate predictor of plant damage than those at 0-30 cm. The value of R. reniformis resistant soybean cultivar-cotton crop sequences was confirmed and the importance of their effects on deep-occurring populations of R. reniformis demonstrated.

The nature and management of the poorer tropical latosols

1979 ◽  
Vol 10 (1) ◽  
pp. 27-32 ◽  
Author(s):  
Anthony Young
Keyword(s):  
Organic Matter ◽  
Rain Forest ◽  
Shifting Cultivation ◽  
Soil Structure ◽  
Fertilizer Application ◽  
Population Densities ◽  
Climatic Zones ◽  
Wide Range ◽  
The Tropics

The latosols, or ‘red and yellow’ soils of the tropics, encompass a wide range of properties and fertility. The poorer types occupy large areas both in the rain forest and in savanna climatic zones. The various systems of shifting cultivation traditionally practised are now inadequate with regard to increasing population densities, and management should be based on fertilizer application at moderate levels together with methods of maintaining organic matter and hence soil structure.

scholarly journals Relative species abundance and population densities of the past; developing multi-species occupancy models for fossil data

2021 ◽  
Author(s):  
Trond Reitan ◽  
Torbjørn Ergon ◽  
Lee Hsiang Liow
Keyword(s):  
Species Abundance ◽  
Biased Sampling ◽  
Occupancy Models ◽  
Geological Time ◽  
Population Densities ◽  
Time Intervals ◽  
Relative Population ◽  
Modelling Framework ◽  
Wide Range ◽  
Species Occupancy

The number of individuals of species within communities varies, but estimating abundance, given incomplete and biased sampling, is challenging. Here, we describe a new occupancy model in a hierarchical Bayesian framework with random effects, where multi-species occupancy and detection are modeled as a means to estimate relative species abundance and relative population densities. The modelling framework is suited for occupancy data for temporal samples of fossil communities with repeated sampling including multiple species with similar preservation potential. We demonstrate our modelling framework using a fossil community of benthic organisms to estimate changing relative species abundance dynamics and relative population densities of focal species in 9 (geological) time-intervals over 2.3 million years. We also explored potential explanatory factors (paleoenvironmental proxies) and temporal autocorrelation that could provide extra information on unsampled time-intervals. The modelling framework is applicable across a wide range of questions on species-level dynamics in (palaeo)ecological community settings.

SOURCES OF COLD TOLERANCE IN GRAIN SORGHUM

1985 ◽  
Vol 65 (2) ◽  
pp. 251-257 ◽  
Author(s):  
SHREE P. SINGH
Keyword(s):  
Sorghum Bicolor ◽  
Cold Tolerance ◽  
Grain Sorghum ◽  
Wide Range ◽  
Early Maturing ◽  
Cold Tolerant ◽  
Soil Temperatures ◽  
Photoperiod Sensitive ◽  
International Testing ◽  
Range Of Variation

The term "cold tolerance" refers to the ability of sorghum (Sorghum bicolor (L.) Moench) genotypes to germinate, grow and produce satisfactory grain yields under conditions of relatively cold (but above-freezing) air and soil temperatures. Sources of cold tolerance and their usefulness in grain sorghum were investigated. Of 380 excessively tall, photoperiod-sensitive, and late-maturing accessions obtained from China, Ethiopia, and Uganda, 39 were cold-tolerant, 157 partially tolerant, and the remainder were susceptible when rated at physiological maturity. Highest levels of cold tolerance were found among accessions from Ethiopia (e.g. Alemaya 70, Jejewegere 935, and Muyra) and Uganda (Mabere, Magune, and Nyundo). Cold tolerance appeared to be a dominant trait. However, in cold-susceptible × cold-tolerant crosses there was a wide range of variation among cold-tolerant genotypes, and the frequency of highly tolerant segregates was less than 10% in the F2, suggesting that several genes controlled the inheritance of the character and that their effects were largely cumulative. A relatively large number of dwarf, photoperiod-insensitive, early-maturing, and cold-tolerant experimental lines were developed. Some of these were very well adapted to the highlands of Honduras, Kenya, and Mexico. In general, they were poorly adapted to high-latitude sites in the northwestern USA, southern Canada and West Germany.Key words: Cold-tolerant sorghum, adaptation, international testing, Sorghum bicolor

scholarly journals Depth Distribution of Rotylenchulus reniformis Under Different Tillage and Crop Sequence Systems

2003 ◽  
Vol 93 (9) ◽  
pp. 1182-1189 ◽  
Author(s):  
A. Westphal ◽  
J. R. Smart
Keyword(s):  
Population Density ◽  
Conventional Tillage ◽  
Grain Sorghum ◽  
Reduced Tillage ◽  
No Tillage ◽  
Rotylenchulus Reniformis ◽  
Population Densities ◽  
Tillage Systems ◽  
Crop Sequence ◽  
Ridge Tillage

The population density of the reniform nematode, Rotylenchulus reniformis, was monitored at depths of 0 to 30, 30 to 60, 60 to 90, and 90 to 120 cm in a tillage and crop sequence trial in south Texas in 2000 and 2001. Main plots were subjected to three different tillage systems: conventional tillage (moldboard plowing and disking), ridge tillage, and no-tillage. Subplots were planted with three different crop sequences: spring cotton and fall corn every year; spring cotton and fall corn in one year, followed by corn for two years; and cotton followed by corn and then grain sorghum, one spring crop per year. The population density of R. reniformis on corn and grain sorghum was low throughout the soil profile. In plots planted with spring cotton and fall corn every year, fewer nematodes were found at depths of 60 to 120 cm in the no-tillage and ridge tillage systems than in the conventional tillage system. Population densities were lower at depths of 0 to 60 cm than at 60 to 120 cm. Soil moisture and cotton root length did not affect nematode population densities in the field. When soil was placed in pots and planted with cotton in the greenhouse, lower population densities developed in soil taken from depths of 0 to 60 cm than in soil from depths of 60 to 120 cm. Final nematode populations were similar in size in soil from the different tillage systems, but reproductive factors were higher in soil from plots with reduced-tillage systems than in soil from plots with conventional tillage. Reduced-tillage practices lowered the risk of increases in R. reniformis populations and reduced population densities following 2 years of non-hosts throughout soil depths, but population densities resurged to the same high levels as in soil planted with cotton every year during one season of cotton.

EFFECTS OF ROW SPACING AND POPULATION DENSITY ON GRAIN SORGHUM PRODUCTION IN SOUTHERN ALBERTA

1976 ◽  
Vol 56 (1) ◽  
pp. 31-37 ◽  
Author(s):  
B. R. HEGDE ◽  
D. J. MAJOR ◽  
D. B. WILSON ◽  
K. K. KROGMAN
Keyword(s):  
Population Density ◽  
Grain Yield ◽  
Yield Components ◽  
Growing Season ◽  
Grain Sorghum ◽  
Row Spacing ◽  
Population Densities ◽  
Southern Alberta ◽  
Sorghum Production ◽  
Narrow Row

Row spacings of 18–72 cm and population densities of 75,000 to 346,000 plants/ha had no consistent effect on grain yield of two sorghum hybrids (Pride X4004 and Pride X4053) because of compensating variations within yield components. Grain yield per panicle increased as row spacing increased but this was offset by a decrease in panicles per plant and panicles per square meter. Grain yield per panicle, panicles per plant, and panicles per square meter decreased as population density increased. The choice of row spacing and population density in field production will, therefore, depend on convenience factors related to crop management. Evapotranspiration for the growing season was 179 mm in 1973 and 204 mm in 1974. Highest water use efficiencies occurred at the low population densities and narrow row spacings. There were differences between the two hybrids. Grain yield of Pride X4004 was greater than that of Pride X4053 because the former produced a greater number of seed-bearing tillers. Grain yield differences in Pride X4004 among the three experiments were due to differences in grain yield per panicle.

Compensation for reduction in seed set due to sorghum midge (Contarinia sorghicola) in midge-susceptible and midge-resistant sorghum (Sorghum bicolor)

1993 ◽  
Vol 33 (2) ◽  
pp. 193 ◽  
Author(s):  
BA Franzmann ◽  
DG Butler
Keyword(s):  
Sorghum Bicolor ◽  
Seed Set ◽  
Grain Sorghum ◽  
Percentage Increase ◽  
Contarinia Sorghicola ◽  
Sorghum Midge ◽  
Damage Compensation ◽  
Wide Range ◽  
The Relationship ◽  
Resistant Genotypes

The relationship between percentage seed set on grain sorghum (Sorghum bicolor) panicles damaged by sorghum midge, Contarinia sorghicola (Coquillett), and percentage compensation (percentage increase in weight) of undamaged seed was examined in 11 experiments covering a wide range of environmental variation and incorporating various sorghum midge susceptible and resistant genotypes. In contrast to previous findings where negative compensation was found after sorghum midge damage, compensation was generally positive, but the slope of the response with respect to seed set changed from positive to negative as seed set increased to >30-50%. Expression of the relationship was similar for susceptible and resistant genotypes. The slope of the relationship for seed sets above the point of maximum compensation was -0.51 for sorghum midge susceptible hybrids, -0.42 for resistant genotypes (various lines and hybrids), and -0.38 for resistant hybrid ATx2755/RTx2767. The pooled slope was -0.45.

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