Simulating the effects of mapping and spraying resolution and threshold level on accuracy of patch spraying decisions and herbicide use based on mapped weed data

2008 ◽  
Vol 58 (3) ◽  
pp. 216-229 ◽  
Author(s):  
Therese With Berge ◽  
Henrik René cederkvist ◽  
Are H. Aastveit ◽  
Haldor Fykse
Keyword(s):  
Threshold Level ◽  
Patch Spraying ◽  
Herbicide Use

scholarly journals Economic Threshold Levels for Signal Grass Control in Sugarcane Cultivars

2016 ◽  
Vol 34 (4) ◽  
pp. 649-656 ◽  
Author(s):  
S.P. TIRONI ◽  
L. GALON ◽  
A.A. SILVA ◽  
M.H.P. BARBOSA ◽  
A.F. SILVA ◽  
...  
Keyword(s):  
Weed Management ◽  
Competitive Ability ◽  
Threshold Level ◽  
Field Conditions ◽  
Economic Threshold ◽  
Brachiaria Brizantha ◽  
Threshold Levels ◽  
Signal Grass ◽  
Herbicide Use

ABSTRACT Weed management in sugarcane fields must be performed rationally, taking into consideration the competitive ability of cultivars and weeds, to allow for reductions in control costs and herbicide use. In this study, an evaluation was made of the interference of populations of Brachiaria brizantha in sugarcane cultivars, with the objective of estimating the economic threshold level of B. brizantha in competition with the cultivars RB72454, RB867515 and SP801816. For this purpose, an experiment was conducted under field conditions, where the cultivars coexisted with different weed densities. Considering the average values of the variables used for calculations, an economic threshold level was achieved with a population of 0.33, 0.46 and 0.66 plants m-2 of B. brizantha for cultivars RB867515, RB72454 and SP801816, respectively.

Weed Decision Threshold as a Key Factor for Herbicide Reductions in Site-Specific Weed Management

2016 ◽  
Vol 30 (4) ◽  
pp. 888-897 ◽  
Author(s):  
Carolina San Martín ◽  
Dionisio Andújar ◽  
Judit Barroso ◽  
Cesar Fernández-Quintanilla ◽  
José Dorado
Keyword(s):  
Spatial Distribution ◽  
Weed Management ◽  
Crop Yields ◽  
Decision Threshold ◽  
Weed Species ◽  
Site Specific ◽  
Patch Spraying ◽  
Key Factor ◽  
Sampling Procedures ◽  
Herbicide Use

The objective of this research was to explore the influence that weed decision threshold (DT; expressed as plants m−2), weed spatial distribution patterns, and spatial resolution of sampling have on potential reduction in herbicide use under site-specific weed management. As a case study, a small plot located in a typical corn field in central Spain was used, constructing very precise distribution maps of the major weeds present. These initial maps were used to generate herbicide prescription maps for each weed species based on different DTs and sampling resolutions. The simulation of herbicide prescription maps consisted of on/off spraying decisions based on information from two different approaches for weed detection: ground-based vs. aerial sensors. In general, simulations based on ground sensors resulted in higher herbicide savings than those based on aerial sensors. The extent of herbicide reductions derived from patch spraying was directly related to the density and the spatial distribution of each weed species. Herbicide savings were potentially high (up to 66%) with relatively sparse patchy weed species (e.g., johnsongrass) but were only moderate (10 to 20%) with abundant and regularly distributed weed species (e.g., velvetleaf). However, DT has proven to be a key factor, with higher DTs resulting in reductions in herbicide use for all the weed species and all sampling procedures and resolutions. Moreover, increasing DT from 6 to 12 plants m−2resulted in additional herbicide savings of up to 50% in the simulations for johnsongrass and up to 28% savings in the simulations for common cocklebur. Nonetheless, since DT determines the accuracy of patch spraying, the consequences of using higher DTs could be leaving areas unsprayed, which could adversely affect crop yields and future weed infestations, including herbicide-resistant weeds. Considering that the relationship between DT and accuracy of herbicide application depends on weed spatial pattern, this work has demonstrated the possibility of using higher DT values in weeds with a clear patchy distribution compared with weeds distributed regularly.

scholarly journals Control period and economic threshold level of glyphosate tolerant weeds in 2.4-D resistant soybean

2021 ◽  
pp. 297-304
Author(s):  
Eduardo Roncatto ◽  
Arthur Arrobas Martins Barroso ◽  
Juliana Calegarim ◽  
Felipe Ridolfo Lucio ◽  
Paulo Fernando Adami
Keyword(s):  
Weed Control ◽  
Weed Management ◽  
Yield Loss ◽  
Control Period ◽  
Threshold Level ◽  
Economic Threshold ◽  
Weed Species ◽  
Randomized Design ◽  
Herbicide Use ◽  
Linear Regressions

Weed densities, species, costs of control, crop value and interference periods should be considered for weed management. With this regard, three experiments were carried out to evaluate weed control periods and weed density in a new soybean cultivar. In ths first trial, control efficacy was measured by visual phytotoxicity of four weed species I. hederifolia, E. heterophylla, Conyza spp. and R. brasiliensis using four different herbicides with two doses each: glyphosate (720 and 1,440 g ea ha-1), 2.4-D (670 and 1,340 g ea ha-1), glufosinate (400 and 600 g ea ha-1) and glyphosate + 2.4-D (410 + 390 and 820 + 780 g ea ha-1). Herbicides were sprayed in an entirely randomized 4x8+1 factorial scheme with six repetitions. In the second experiment, 2,4-D-resistant soybean growth was measured under increasing densities of the same weeds (21 plants m² vs 21, 42, 84, 168 and 336 plants m²). This experiment was conducted under entirely randomized design with 25 treatments with four repetitions. Critical level of damage and economic threshold level of each weed species in soybean were measured using non-linear regressions. In a third experiment, weed with soybean were submitted to increasing periods of control and coexistence (7, 14, 21, 28, 35, 49 and 70 days after soybean emergence, plus two control treatments). Glufosinate and glyphosate+2.4-D (820 + 780 g ea ha-1) showed greater weed control than glyphosate alone (720 g ea ha-1). The yield loss of 0.85, 2.12, 5.71 and 34.24% were found for each weed of E. heterophylla, I. hederifolia, R. brasiliensis and Conyza spp., coexisting with soybean. There was a soybean grain yield loss of 50% in the weedy treatment. Soybean weed management should occur between 18thand 48th days after its emergence. Economic threshold level on soybean yield suggested is below one plant of Conyza spp. and R. brasiliensis per m-². The use of glufosinate and glyphosate+2,4-D provides a greater flexibility of herbicide use for farmers

Maternal DDAVP-induced hyponatremia: Threshold level for fetal urinary diuresis

1998 ◽  
Vol 5 (1) ◽  
pp. 151A-151A
Author(s):  
M NIJLAND ◽  
T ROBERTS ◽  
M CURRAN ◽  
M ROSS
Keyword(s):  
Threshold Level

EVALD – a Pioneer Application for Automated Essay Scoring in Czech

2019 ◽  
Vol 113 (1) ◽  
pp. 9-30
Author(s):  
Kateřina Rysová ◽  
Magdaléna Rysová ◽  
Michal Novák ◽  
Jiří Mírovský ◽  
Eva Hajičová
Keyword(s):  
Czech Republic ◽  
Native Speakers ◽  
Threshold Level ◽  
Automated Essay Scoring ◽  
The Czech Republic ◽  
Linguistic Differences ◽  
Supervised Training ◽  
Language Data ◽  
Overall Performance ◽  
Essay Scoring

Abstract In the paper, we present EVALD applications (Evaluator of Discourse) for automated essay scoring. EVALD is the first tool of this type for Czech. It evaluates texts written by both native and non-native speakers of Czech. We describe first the history and the present in the automatic essay scoring, which is illustrated by examples of systems for other languages, mainly for English. Then we focus on the methodology of creating the EVALD applications and describe datasets used for testing as well as supervised training that EVALD builds on. Furthermore, we analyze in detail a sample of newly acquired language data – texts written by non-native speakers reaching the threshold level of the Czech language acquisition required e.g. for the permanent residence in the Czech Republic – and we focus on linguistic differences between the available text levels. We present the feature set used by EVALD and – based on the analysis – we extend it with new spelling features. Finally, we evaluate the overall performance of various variants of EVALD and provide the analysis of collected results.

The Evolved Security Dynamics of South Asia: Challenges to Pakistan’s Nuclear Threshold

2020 ◽  
Vol 22 (Summer 2020) ◽  
pp. 75-86
Author(s):  
Haris Bilal Malik ◽  
Muhammad Abbas Hassan
Keyword(s):  
South Asia ◽  
Threshold Level ◽  
Security Architecture ◽  
Unresolved Issue ◽  
Muslim Community ◽  
Global Security ◽  
Security Environment ◽  
Military Modernization

The longstanding unresolved issue of Kashmir serves as a nuclear flashpoint between India and Pakistan. Since 2019, the prevalent security environment of the region has dominated the discourse surrounding the regional and global security architecture. India’s policies during the Pulwama-Balakot crisis and the revocation of Kashmir’s constitutional status demonstrate the country’s intentions of dominating the escalation ladder in the region and marginalizing the muslim community of Kashmir. Because of the conventional disparity in South Asia where India is big interms of size, economy and military build-up, Pakistan has been further threatened by India’s aggressive policies and provocative military modernization. Consequently, Pakistan may be compelled to further revisit its nuclear threshold level to overcome India’s aggression.

Farmers Perception in Adoption of Conservation Agriculture Practices in Madhubani District of Bihar, India

2017 ◽  
Vol 4 (04) ◽  
Author(s):  
YUJJWAL KUMAR ◽  
RAMESH CHANDRA BHARATI ◽  
RAVI KANT CHAUBEY ◽  
K. K. RAO ◽  
VED PRAKASH ◽  
...  
Keyword(s):  
Conservation Agriculture ◽  
Decision Processes ◽  
Zero Tillage ◽  
Focus Group Discussions ◽  
Group Discussions ◽  
Male And Female ◽  
Female Farmers ◽  
Direct Seeded ◽  
Herbicide Use ◽  
Bihar State

The study has been conducted in Madhubani district of Bihar state to analyse gender segregated key benefits, advantages, disadvantages, issues and the key decision processes and criteria for conservation agriculture technologiesadoption. Data were collected through focus group discussions involving male and female farmers. Cent per cent farmers expressed saving of labour and reduction in drudgery in Zero Tillage Direct Seeded Rice (ZTDSR). Higher yield through adoption of ZTDSR was revealed by equal percentage (75 %) of male and female farmers. Equal percentage (100 %) of male and female farmers expressed labour saving as one of the most important criteria for adoption of the ZT. Gender segregated data showed almost similar perception related to criteria adoption of ZT technology in rice-wheat system. All the female groups expressed that limited knowledge of herbicide use restricts adoption of ZTDSR. All the female groups were in the view that there is reduction of drudgery through adoption of mechanical paddy transplanter. Preparation of mat type nursery was top most disadvantages for 90 and 70 % male and female groups respectively. Eighty percent farmers groups expressed their opinion that non availability of trained tractor drivers for machine operation limits adoption of ZT machine. Preparation of mat nursery and trained operators for paddy transplanter was major criteria for adoption of mechanical paddy transplanter. There was contradiction in the perception among male and female farmers with respect to yield advantage and associated risk for poor yield due to the adoption of CA technologies.

scholarly journals Monarch butterfly and milkweed declines substantially predate the use of genetically modified crops

2019 ◽  
Vol 116 (8) ◽  
pp. 3006-3011 ◽  
Author(s):  
J. H. Boyle ◽  
H. J. Dalgleish ◽  
J. R. Puzey
Keyword(s):  
Genetically Modified ◽  
Danaus Plexippus ◽  
Genetically Modified Crops ◽  
Monarch Butterfly ◽  
The United States ◽  
Gm Crops ◽  
Herbicide Resistant ◽  
The Past ◽  
Scientific Attention ◽  
Herbicide Use

Monarch butterfly (Danaus plexippus) decline over the past 25 years has received considerable public and scientific attention, in large part because its decline, and that of its milkweed (Asclepias spp.) host plant, have been linked to genetically modified (GM) crops and associated herbicide use. Here, we use museum and herbaria specimens to extend our knowledge of the dynamics of both monarchs and milkweeds in the United States to more than a century, from 1900 to 2016. We show that both monarchs and milkweeds increased during the early 20th century and that recent declines are actually part of a much longer-term decline in both monarchs and milkweed beginning around 1950. Herbicide-resistant crops, therefore, are clearly not the only culprit and, likely, not even the primary culprit: Not only did monarch and milkweed declines begin decades before GM crops were introduced, but other variables, particularly a decline in the number of farms, predict common milkweed trends more strongly over the period studied here.

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