scholarly journals Monitoring the Spatial Variability of Knapweed (Centaurea diluta Aiton) in Wheat Crops Using Geostatistics and UAV Imagery: Probability Maps for Risk Assessment in Site-Specific Control

Agronomy ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 880
Author(s):  
Montserrat Jurado-Expósito ◽  
Francisca López-Granados ◽  
Francisco Manuel Jiménez-Brenes ◽  
Jorge Torres-Sánchez
Keyword(s):  
Risk Assessment ◽  
Spatial Variability ◽  
Weed Management ◽  
Management Strategies ◽  
Indicator Kriging ◽  
Site Specific ◽  
Weed Density ◽  
Density Mapping ◽  
Probability Maps ◽  
Geostatistical Approach

Assessing the spatial distribution of weeds within a field is a key step to the success of site-specific weed management strategies. Centaurea diluta (knapweed) is an emerging weed that is causing a major agronomic problem in southern and central Spain because of its large size, the difficulty of controlling it, and its high competitive ability. The main objectives of this study were to examine the spatial variability of C. diluta density in two wheat fields by multivariate geostatistical methods using unmanned aerial vehicle (UAV) imagery as secondary information and to delineate potential control zones for site-specific treatments based on occurrence probability maps of weed infestation. The primary variable was obtained by grid weed density field samplings, and the secondary variables were derived from UAV imagery acquired the same day as the weed field surveys. Kriging and cokriging with UAV-derived variables that displayed a strong correlation with weed density were used to compare C. diluta density mapping performance. The accuracy of the predictions was assessed by cross-validation. Cokriging with UAV-derived secondary variables generated more accurate weed density maps with a lower RMSE compare with kriging and cokriging with RVI, NDVI, ExR, and ExR(2) (the best methods for the prediction of knapweed density). Cokriged estimates were used to generate probability maps for risk assessment when implementing site-specific weed control by indicator kriging. This multivariate geostatistical approach enabled the delineation of winter wheat fields into two zones for different prescription treatments according to the C. diluta density and the economic threshold.

scholarly journals Comparative Study of the Effect of Different Weed Management Strategies on Disease Severity and Marketable Yield of Paprika (Capsicum Annuum L.) in the Smallholder Farming Sector of Zimbabwe

2008 ◽  
Vol 48 (1) ◽  
pp. 107-117 ◽  
Author(s):  
Maxwell Handiseni ◽  
Julia Sibiya ◽  
Vincent Ogunlela ◽  
Irene Koomen
Keyword(s):  
Comparative Study ◽  
Capsicum Annuum ◽  
Weed Management ◽  
Leaf Spot ◽  
Management Strategies ◽  
Smallholder Farming ◽  
Marketable Yield ◽  
Weed Density ◽  
Marketable Fruit ◽  
Hand Weeding

Comparative Study of the Effect of Different Weed Management Strategies on Disease Severity and Marketable Yield of Paprika (Capsicum AnnuumL.) in the Smallholder Farming Sector of ZimbabweOn-farm trials were conducted in the Chinyika Resettlement Area of Zimbabwe under dryland conditions to investigate the effects of different weed management methods on disease incidence, severity and paprika (Capsicum annuum) pod yield. The weed control treatments included hand weeding at 2 and 6 weeks after transplanting (WAT); ridge re-moulding at 3,6 and 9 WAT; application 4l/ha Lasso (alachlor) immediately after transplanting, and Ronstar (oxidiazinon) at 2l/ha tank mixed with Lasso at 2l/ha one day before transplanting. The herbicide-water solution was applied at the rate of 200l/ha using a knapsack sprayer. Major diseases identified were bacterial leaf spot (Xanthomonas campestrispv.vesicatoria), cercospora leaf spot (Cercospora unamunoi), grey leaf spot (Stemphylium solani) and powdery mildew (Leveillula taurica) in both seasons. For the 2000/2001 season hand weeding at 2 and 6 WAT and ridge re-moulding at 3, 6 and 9 WAT had the greatest reduction effect on the area under disease progress curve (AUDPC) and the highest marketable fruit yield. In the 2001/2002 season, both herbicide treatments had the same effect as hand weeding and ridge re-moulding on AUDPC and marketable fruit yield. The least weed density was obtained by ridge re-moulding at 3, 6, and 9 WAT in the 2000/2001 season. Weed density was statistically the same across all treatments except the check treatment in 2001/2002 season. Hand weeding operations were significantly (p < 0.05) effective and consequently gave the highest added profits mainly because of their effect on major weeds such asDatura stramonium.

Initial Weed Densities Affect No-Tillage Weed Management with a Rye (Secale cereale) Cover Crop

1997 ◽  
Vol 11 (3) ◽  
pp. 473-477 ◽  
Author(s):  
Inga A. Zasada ◽  
H. Michael Linker ◽  
Harold D. Coble
Keyword(s):  
North Carolina ◽  
Weed Control ◽  
Weed Management ◽  
Cover Crop ◽  
Management Strategies ◽  
No Tillage ◽  
Density Estimates ◽  
Common Lambsquarters ◽  
Weed Density ◽  
Control Effectiveness

The objective of this research was to evaluate the influence of different initial weed densities on weed control effectiveness in no-tillage corn at two locations in North Carolina during 1994 and 1995. Different weed densities were established over a 4-year period (1989–1992) by using various weed management strategies. Resultant density levels were estimated and used to establish high and low weed density plots. Treatments applied were PRE, POST, at-planting, and an untreated control. Weed density estimates were made 37 and 57 DAP. Common lambsquarters at low densities (20 to 40 weeds/m2) was controlled with the cover crop alone, but common lambsquarters at high densities (150 to 170 weeds/m2) and redroot pigweed at any density were not controlled. POST herbicides reduced weed densities as well as the PRE herbicides, regardless of initial weed densities.

scholarly journals Spatial variability of soil fertility in an integrated crop livestock forest system

2017 ◽  
Vol 8 (2) ◽  
pp. 590-593 ◽  
Author(s):  
A. C. C. Bernardi ◽  
G. M. Bettiol ◽  
G. G. Mazzuco ◽  
S. N. Esteves ◽  
P. P. A. Oliveira ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Soil Fertility ◽  
Soil Properties ◽  
Precision Agriculture ◽  
Acid Soil ◽  
Management Strategies ◽  
Fertilizer Application ◽  
Management Tools ◽  
Site Specific ◽  
The Tropics

Knowledge on spatial variability of soil properties is useful for the rational use of inputs, as in the site specific application of lime and fertilizer. Crop-livestock-forest integrated systems (CLFIS) provide a strategy of sustainable agricultural production which integrates annual crops, trees and livestock activities on a same area and in the same season. Since the lime and fertilizer are key factors for the intensification of agricultural systems in acid-soil in the tropics, precision agriculture (PA) is the tool to improve the efficiency of use of these issues. The objective of this research was to map and evaluate the spatial variability of soil properties, liming and fertilizer need of a CLFIS. The field study was carried out in a 30 ha area at Embrapa Pecuária Sudeste in São Carlos, SP, Brazil. Soil samples were collected at 0–0.2 m depth, and each sample represented a paddock. The spatial variability of soil properties and site-specific liming and fertilizer needs were modeled using semi-variograms, the soil fertility information were modeled. Spatial variability soil properties and site specific liming and fertilizer need were modeled by kriging and inverse distance weighting (IDW) techniques. Another approach used was based on lime and fertilizer recommendation considering the paddocks as the minimum management unit. The results showed that geostatistics and GIS were useful tools for revealing soil spatial variability and supporting management strategies. Soil nutrients were used to classify the soil spatial distribution map and design site-specific lime and fertilizer application zones. Spatial analyses of crop needs and requirement can provide management tools for avoiding potential environmental problems, caused by unbalanced nutrient supplies.

Weed Thresholds: The Space Component and Considerations for Herbicide Resistance

1992 ◽  
Vol 6 (1) ◽  
pp. 205-212 ◽  
Author(s):  
Bruce D. Maxwell
Keyword(s):  
Herbicide Resistance ◽  
Weed Management ◽  
Competitive Ability ◽  
Management Strategies ◽  
Agricultural Practices ◽  
Cereal Crops ◽  
Weed Population ◽  
Weed Density ◽  
Population Frequency ◽  
Selection For

As an extension of weed threshold models in which crop losses are based on weed density, an alternative model for grass weeds in cereal crops is proposed that incorporates the theoretical importance of selection for herbicide resistance, initial weed population frequency, and weed seed dispersal. Simulations suggest optimum weed population levels (thresholds) for maintaining genotypes that are susceptible to control practices and which minimize crop yield reductions. Weed population frequency, in combination with dispersal and competitive traits may determine optimum weed management strategies/Model simulations indicate that understanding how agricultural practices select for “weedy” traits (e.g. herbicide resistance, competitive ability, dispersal potential) may be important in determining weed density thresholds.

Separating the effects of crop rotation from weed management on weed density and diversity

Weed Science ◽  
1999 ◽  
Vol 47 (6) ◽  
pp. 729-735 ◽  
Author(s):  
Colleen Doucet ◽  
Susan E. Weaver ◽  
Allan S. Hamill ◽  
Jianhua Zhang
Keyword(s):  
Crop Rotation ◽  
Weed Management ◽  
Management Practices ◽  
Cropping Systems ◽  
Management Strategies ◽  
Integrated Weed Management ◽  
Direct Result ◽  
Weed Density ◽  
Richness Index ◽  
Rotation Study

Crop rotation is thought to reduce weed density and maintain species diversity, thus preventing the domination of a few problem weeds. Because cropping sequence dictates other agricultural management practices, variations in weed populations between cropping systems may be the direct result of crop rotation, the result of different weed management practices associated with crop rotation, or both. Studies that fail to separate the effects of crop rotation from weed management may generate misleading results. A 10-yr crop rotation study was undertaken to study the dynamics of the standing weed vegetation inZea maysL.,Glycine maxL., andTriticum aestivumL. The present paper compared total weed density and diversity between monocultures and rotations under three levels of weed management. Weed management accounted for 37.9% of the variation in total weed density, whereas crop rotation accounted for only 5.5%. Weed density varied between monocultures and rotations in plots where herbicides were applied. The effectiveness of rotations in reducing weed density was dependent upon the crop. Margalef's species richness index (DMG), a measure of diversity, varied among weed management strategies, with 38.4% of the variance attributed to this factor. In the 10th year, when all plots were sown withZ. mays, few cumulative effects of crop rotation were apparent, with two exceptions. In weedy and herbicide-treated plots, weed density was higher on plots cropped withZ. maysthe previous year. Also, under these weed management treatments, including a cereal in the crop rotation reduced weed density. Crop rotation, when used in combination with herbicides, provides additional weed control and is therefore an effective tool in integrated weed management.

scholarly journals GEOSTATISTICAL APPROACH FOR THE ESTIMATION OF SHEAR-HOSTED GOLD DEPOSIT: A CASE STUDY OF THE OBUASI GOLD DEPOSIT, GHANA

2020 ◽  
Vol 5 (2) ◽  
pp. 76-84
Author(s):  
Casmed Charles Amadu ◽  
Gordon Foli ◽  
Bernard Kissi Abrokwa ◽  
Sylvester Akpah
Keyword(s):  
Spatial Variability ◽  
Gold Deposit ◽  
Extreme Values ◽  
Underground Mining ◽  
Parametric Method ◽  
Weighted Average ◽  
Indicator Kriging ◽  
Low Grade ◽  
Geostatistical Methods ◽  
Geostatistical Approach

Underground mining at Obuasi in Ghana has been in operation since 1947. This paper uses geostatistical methods to evaluate gold ore blocks to ensure reliable grades for mining large tonnage and low-grade resources. Historically, the principal ores were low tonnage, high grade and relatively homogeneous quartz stockwork with simple geometry and average bulk grades in the range of 20-30 g/t that were evaluated using conventional polygonal methods and mined by semi-mechanized means. Currently, the ore is a shear-hosted mixed quartz vein and disseminated sulphide type deposit of low grade that is mined using highly mechanized means. The need therefore arises for a re-assessment of the estimation procedures to ensure prolonged and more profitable mining. Both diamond drill (DD) core and stope/cross-cut channel samples were taken from Block 1 at the mine for analyses and re-assessment. A wireframe model was used to constrain the three dimensional (3D) block model of the deposit. Ordinary kriging (OK) and multiple indicator kriging (MIK) geostatistical methods were used to estimate gold grades. Grade distribution is positively skewed with high spatial variability and extreme values while background values are established as <0.6 g/t. The Spatial variability is characterized by fitting models on experimental variograms. The MIK approach mitigates the effects of outliers and establish grades that are consistently lower than the OK and the weighted average method that are widely used at the mine. The MIK method, a non-linear, non-parametric method of local grade estimation are applicable to the deposit architecture. Profoundly, the MIK method is a more reliable approach considering the fact that the MCF based on the estimates at the mine are high despite operational deficiencies on the mine. The results from this study demonstrates usefulness of geostatistics to determine the architecture of Au mineralization at the deposit scale.

Mapping spatial variability of leaf nutrient status of oil palm (Elaeis guineensis Jacq.) plantations in India

2016 ◽  
Vol 67 (1) ◽  
pp. 109 ◽  
Author(s):  
S. K. Behera ◽  
K. Suresh ◽  
K. Ramachandrudu ◽  
K. Manorama ◽  
B. N. Rao
Keyword(s):  
Spatial Variability ◽  
Oil Palm ◽  
Nutrient Management ◽  
Elaeis Guineensis ◽  
Management Strategies ◽  
Nutrient Status ◽  
Nutrient Concentrations ◽  
Site Specific ◽  
Leaf Nutrients ◽  
Elaeis Guineensis Jacq

Spatial variability of leaf nutrients in oil palm (Elaeis guineensis Jacq.) plantations in Goa, Karnataka, Mizoram and Gujarat states of India were examined for implementation of site-specific fertilisation programs. Georeferenced leaf samples were collected randomly for the oil palm plantations. The leaf nutrient concentrations were assessed and analysed statistically and geostatistically. The concentrations of leaf nutrients such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S) and boron (B) in oil palm plantations varied widely at different locations. Leaf P concentration was positively and significantly correlated with S concentration at Goa, Karnataka and Gujarat. Positive and significant correlation between leaf Ca and Mg concentration was recorded at Mizoram and Gujarat. Geostatistical analysis of leaf nutrients showed different distribution patterns at different locations. This study revealed the need to determine spatial variability of nutrient status of oil palm plantations before planning a differential fertiliser program. Therefore, saving of nutrients could be achieved by adopting site-specific nutrient-management strategies.

scholarly journals Growth and Phenology of Vulpia Myuros in Comparison with Apera Spica-Venti, Alopecurus Myosuroides and Lolium Multiflorum in Monoculture and in Winter Wheat

Plants ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1495
Author(s):  
Muhammad Javaid Akhter ◽  
Bo Melander ◽  
Solvejg Kopp Mathiassen ◽  
Rodrigo Labouriau ◽  
Svend Vendelbo Nielsen ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Weed Management ◽  
Lolium Multiflorum ◽  
Management Strategies ◽  
Integrated Weed Management ◽  
Growth Stages ◽  
Neighborhood Design ◽  
Alopecurus Myosuroides ◽  
Winter Cereals ◽  
Arable Weed

Vulpia myuros has become an increasing weed problem in winter cereals in Northern Europe. However, the information about V. myuros and its behavior as an arable weed is limited. Field and greenhouse experiments were conducted in 2017/18 and 2018/19, at the Department of Agroecology in Flakkebjerg, Denmark to investigate the emergence, phenological development and growth characteristics of V. myuros in monoculture and in mixture with winter wheat, in comparison to Apera spica-venti, Alopecurus myosuroides and Lolium multiflorum. V. myuros emerged earlier than A. myosuroides and A. spica-venti but later than L. multiflorum. Significant differences in phenological development were recorded among the species. Overall phenology of V. myuros was more similar to that of L. multiflorum than to A. myosuroides and A. spica-venti. V. myuros started seed shedding earlier than A. spica-venti and L. multiflorum but later than A. myosuroides. V. myuros was more sensitive to winter wheat competition in terms of biomass production and fecundity than the other species. Using a target-neighborhood design, responses of V. myuros and A. spica-venti to the increasing density of winter wheat were quantified. At early growth stages “BBCH 26–29”, V. myuros was suppressed less than A. spica-venti by winter wheat, while opposite responses were seen at later growth stages “BBCH 39–47” and “BBCH 81–90”. No significant differences in fecundity characteristics were observed between the two species in response to increasing winter wheat density. The information on the behavior of V. myuros gathered by the current study can support the development of effective integrated weed management strategies for V. myuros.

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