Herbicide Application Decision Support System Research Articles

Site-Specific Weed Management in Cotton Using WebHADSS™

Field trials were established in 2005 and continued in 2006 to evaluate a conventional broadcast herbicide sprayer compared to a variable spray (sensor-activated) weed-sensing sprayer (WSS). The computer-based Herbicide Application Decision Support System (WebHADSS™) was used to determine a portion of the herbicides applied (based on herbicide efficacy and economics). Weed control, herbicide usage, crop yield, and net returns were compared across treatments. The broadcast applications were usually the most effective at controlling weeds. A PPI herbicide did not always improve weed control compared to treatments in which no PPI herbicide was applied. Variable treatments used less herbicide than the broadcast system in both years. Cotton lint yields in broadcast applications were similar to the weed-free check in both years of the study. Variable treatments often provided equivalent net returns (gross yield revenue less weed control cost) to the broadcast treatments. Although herbicide savings were observed in the variable treatments when compared to a broadcast system, a reduction in weed control was observed, indicating the need for future improvements of this system. A site-specific weed management program used in conjunction with WebHADSS™ may have potential in cotton production systems in the Texas Southern High Plains where weed densities are low.

Economics and Effectiveness of Alternative Weed Scouting Methods in Peanut

On-farm trials were conducted in 16 North Carolina peanut fields to obtain estimates of scouting times and quality of herbicide recommendations for different weed scouting methods. The fields were monitored for weed species and population density using four scouting methods: windshield (estimate made from the edge of the field), whole-field (estimate based on walk through the field), range (weed densities rated on 1–5 scale at six locations in the field), and counts (weeds estimated by counting at six locations in the field). The herbicide application decision support system (HADSS) was used to determine theoretical net return over herbicide investment and yield loss ($ and %) for each treatment in each field. Three scouts estimated average weed population densities using each scouting method. These values were entered into HADSS to obtain treatment recommendations. Independently collected count data from all three scouts were combined to determine the optimal treatment in each field and the relative ranking of each available treatment. When using the whole-field method, scouts observed a greater number of weed species than when using the other methods. The windshield, whole-field, and range scouting methods tended to overestimate density slightly at low densities and underestimate density substantially at high densities, compared to the count method. The windshield method required the least amount of time to complete (6 min per field), but also resulted in the greatest average loss. Even for this method, recommendations had theoretical net returns within 10% of the return for the optimal treatment 80% of the time. The count method appears to have less economic risk than the windshield, whole-field, and range scouting methods.

Validation of Weed Competitive Indices for Predicting Peanut Yield Losses in Oklahoma

Weed interference experiments have not been extensively conducted in Oklahoma peanut. Research was conducted in three environments to evaluate usefulness of single-weed density experiments with the use of several weeds to measure their relative competitive abilities with a crop. These data can be used to validate current competitive indices (CIs) used by a model to predict peanut yield loss due to weeds. This model is used by the Herbicide Application Decision Support System (HADSS) and Pesticide Economic and Environmental Tradeoffs (PEET), two decision-support systems (DSSs) available for Oklahoma peanut. Six weeds common in Oklahoma peanut were used: crownbeard, eclipta, ivyleaf morningglory, johnsongrass, Palmer amaranth, and prickly sida plus two others, barnyardgrass and common cocklebur, as benchmark species. Each weed was planted into peanut uniformly at eight weeds/10 m of row. Dry weed biomass accounted for 77 to 90% of variation in in-shell peanut yield loss; however, model parameters only allow for weed number. Yield losses from these experiments were compared to those predicted by the model to test original CI accuracy. Treatment means were compared to the prediction model with the use of protected LSD. Several significant differences were noted, and the CIs for those weed species were adjusted accordingly. Adjusting CIs improved actual yield data goodness of fit to model predictions specific to environment in question, but not necessarily in different environments. The CI changed at Ft. Cobb were eclipta from 1.8 to 4.5 and ivyleaf morningglory from 3.4 to 5.0. CI adjustments at Perkins were common cocklebur from 10.0 to 5.8 and johnsongrass from 3.0 to 4.6. Collecting data for several weed species at uniform density in a crop provides a more time-efficient method for obtaining accurate relative weed interference data; this method is useful in validating or establishing CI lists in areas and/or crops with limited data.

Evaluating the Potential for Site-Specific Herbicide Application in Soybean

Field experiments were conducted on two North Carolina research stations in 1999, 2000, and 2001; on-farm in Lenoir, Wayne, and Wilson counties, NC, in 2002; and on-farm in Port Royal, VA, in 2000, 2001, and 2002 to evaluate possible gains from site-specific herbicide applications at these locations. Fields were scouted for weed populations using custom software on a handheld computer linked to a Global Positioning System. Scouts generated field-specific sampling grids and recorded weed density information for each grid cell. The decision aid HADSS™ (Herbicide Application Decision Support System) was used to estimate expected net return and yield loss remaining after treatment in each sample grid of every field under differing assumptions of weed size and soil moisture conditions, assuming the field was planted with either conventional or glyphosate-resistant (GR) soybean. The optimal whole-field treatment (that treatment with the highest expected net return summed across all grid cells within a field) resulted in average theoretical net returns of $79/ha (U.S. dollars) and $139/ha for conventional and GR soybean, respectively. When the most economical treatment for each grid cell was used in site-specific weed management, theoretical net returns increased by $13/ha (conventional) and $4.50/ha (GR), and expected yield loss after treatment was reduced by 10.5 and 4%, respectively, compared with the whole-field optimal treatment. When the most effective treatment for each grid cell was used in site-specific weed management, theoretical net returns decreased by $18/ha (conventional) and $4/ha (GR), and expected yield loss after treatment was reduced by 27 and 19%, respectively, compared with the whole-field optimal treatment. Site-specific herbicide applications could have reduced the volume of herbicides sprayed by as much as 70% in some situations but increased herbicide amounts in others. On average, the whole-field treatment was optimal in terms of net return for only 35% (conventional) and 57% (GR) of grid cells.

Benefits and Risks of Economic vs. Efficacious Approaches to Weed Management in Corn and Soybean

A 3-yr study was conducted on nine farms across southern Ontario to evaluate the risks and benefits of different approaches to weed management in corn and soybean. Weed control decisions were based on field scouting and recommendations from the Ontario version of HADSS™, the herbicide application decision support system. Treatments were selected to maximize profit (economic threshold approach) or to maximize yield (highest treatment efficacy). Reduced rates of the high efficacy treatment for each field also were included. Weed density before and after treatment, crop yields, weed seed return, and the effect of weed control decisions on weed density 1 yr after treatment were assessed. Crop yield varied among years and farms but was not affected by weed control treatment. Weed control at 28 d after treatment (DAT) was often lower and weed density, biomass, and seed production 70 DAT were often higher with the profit maximization approach compared with the yield maximization approach. However, weed density 1 yr later, after each cooperator had applied a general weed control program, did not vary significantly among the previous year's weed control treatments. Reduced rates of the high efficacy treatments did not lead to increased weed problems the next year, despite lower weed control and increased weed seed production in some years. During the 3 yr of the study, weed control costs with the profit maximization approach were approximately Can$45/ha less than with the yield maximization approach.

Evaluation of Site-Specific Weed Management Implementing the Herbicide Application Decision Support System (HADSS)

A major concern of producers has always been how to reduce the amount of inputs required for crop production while maintaining or improving yields. One area of research addressing this issue is site-specific weed management (SSWM). The objective of this research was to evaluate the possibility of using SSWM herbicide applications to reduce overall production costs when site-specific weed populations are known. Weed populations of three soybean fields (B-East, B-South, B-North), located at the Black Belt Branch Experiment Station, Brooksville, MS, were estimated in 1998 and 1999. Sampling occurred July 8–9, 1998 (8 weeks after planting), and June 30–July 1, 1999 (6 WAP). An established 10 m × 10 m Universal Transmercator (UTM) grid coordinate system was used to divide the fields into 100 m2 cells, with the sample point located in the center of each cell. Optimal herbicide recommendations were obtained for each sample location within each field by subjecting the weed information to the Herbicide Application Decision Support System (HADSS). An average of the weed populations for the entire field was also subjected to HADSS to obtain an optimal recommendation for a broadcast application for comparison purposes. Data from 1998 resulted in 25% and 15% of the field not requiring a herbicide treatment for the B-North and B-South when compared to the whole-field recommendations to receive broadcast treatments. However, B-East received a “no treatment” recommendation for the whole-field analysis. The “no treatment” recommendation was attributed to the sicklepod population exceeding a level deemed economically controllable by HADSS. However, when SSWM recommendations were generated, 49% of the field received “no treatment” recommendation, while 51% resulted in a herbicide application as an economical choice. In 1999, glyphosate-resistant transgenic soybean was used, thereby increasing the POST herbicide treatment options available in HADSS. Herbicide treatment recommendations resulted in 100%, 56%, and 91% of the total area requiring herbicide treatments for B-East, B-North, and B-South, respectively. Comparing the projected net returns for each field can develop a better estimate of the value of SSWM. In 1998, data from the B-East resulted in a projected net return increase of $21.63 ha−1 over that of the broadcast application. Estimated net return increased $5.42 ha−1 at B-North, with simulated SSWM applications over broadcast applications, and $14.67 ha−1 increase at B-South. Net returns for 1999 resulted in only a $0.32 ha−1 increase by using SSWM for B-East, but a $21.00 and $13.56 ha−1 increase for B-North and B-South, respectively. The extra expenses of SSWM, such as sampling and technology costs, are not included in the net returns calculations and, when included, would reduce the difference between SSWM and conventional methods. This research has demonstrated the potential value of SSWM from an economic standpoint; environmental benefits through reductions in herbicide applications are also apparent.

Evaluation and Adaptation of the HADSS®Computer Program in Texas Southern High Plains Cotton

Field experiments were conducted in 1999 and 2000 to evaluate and adapt the Herbicide Application Decision Support System (HADSS®) program for Texas Southern High Plains cotton production. Weed management systems (in glyphosate-resistant, bromoxynil-resistant, and nontransgenic cotton varieties) included trifluralin preplant incorporated (PPI) followed by (fb) HADSS postemergence-topical (POST) recommendations (PPI fb POST HADSS), HADSS recommendations alone (POST HADSS), and Texas Agricultural Experiment Station (TAES) recommendations for the Texas Southern High Plains. In both years, effective season-long weed control was achieved with all weed management systems in the glyphosate-resistant variety, but only the PPI fb POST HADSS and TAES weed management systems controlled Palmer amaranth and devil's-claw in the bromoxynil-resistant and nontransgenic varieties, compared with POST HADSS alone. No differences in cotton lint yield or net returns over weed control costs were observed with weed management systems across variety in 1999; however, in general, the glyphosate-resistant and nontransgenic varieties produced higher yields and net returns than the bromoxynil-resistant variety. In 2000, plots from the TAES weed management system produced higher lint yields than the plots of PPI fb POST HADSS recommendations in the glyphosate- and bromoxynil-resistant varieties, but plots of all management systems yielded similarly in the nontransgenic variety. In 2000, plots from the TAES system produced the highest net returns in the glyphosate- and bromoxynil-resistant varieties. In the nontransgenic variety, the PPI fb POST HADSS and TAES weed management systems produced higher net returns over weed control costs than the POST HADSS system.

HADSS™, Pocket HERB™, and WebHADSS™: Decision Aids for Field Crops1

Row crop weed management decisions can be complex due to the number of available herbicide treatment options, the multispecies nature of weed infestations within fields, and the effect of soil characteristics and soil-moisture conditions on herbicide efficacy. To assist weed managers in evaluating alternative strategies and tactics, three computer programs have been developed for corn, cotton, peanut, and soybean. The programs, called HADSS™ (Herbicide Application Decision Support System), Pocket HERB™, and WebHADSS™, utilize field-specific information to estimate yield loss that may occur if no control methods are used, to eliminate herbicide treatments that are inappropriate for the specified conditions, and to calculate expected yield loss after treatment and expected net return for each available herbicide treatment. Each program has a unique interactive interface that provides recommendations to three distinct kinds of usage: desktop usage (HADSS), internet usage (WebHADSS), and on-site usage (Pocket HERB). Using WeedEd™, an editing program, cooperators in several southern U.S. states have created different versions of HADSS, WebHADSS, and Pocket HERB that are tailored to conditions and weed management systems in their locations.Nomenclature: Corn, Zea mays L.; cotton, Gossypium hirsutum L.; peanut, Arachis hypogea L; soybean, Glycine max L.Additional index words: Bioeconomic models, computer decision aids, decision support systems, weed management.Abbreviations: HADSS, Herbicide Application Decision Support System; PDS, postemergence-directed; POST, postemergence; PPI, preplant-incorporated; PRE, preemergence.

Evaluation of Scouting Methods in Peanut (Arachis hypogaea) Using Theoretical Net Returns from HADSS™1

A perceived limitation to incorporating herbicide application decision support system (HADSS™) into routine peanut weed management decisions is efficient scouting of fields. A total of 52 peanut fields were scouted from 1997 through 2001 in North Carolina to determine the weed density in a 9.3-m2 section for each 0.4-ha grid of the field. These weed populations and their spatial distributions were used to compare theoretical net return (TNR) over herbicide investment for various scouting methods and weed management approaches. HADSS was used to determine the expected net return for each treatment in each 0.4-ha section of every field under differing assumptions of weed size, soil moisture conditions, and pricing structures. The treatment with the highest net return averaged across all 0.4-ha grids was considered to be the optimal whole-field treatment. For all 52 fields, TNR for the best whole-field treatment and for site-specific weed management (applying the most economical recommendation on each 0.4-ha...

Economic evaluation of HADSS™ computer program in North Carolina peanut

Abstract Field studies were conducted at four locations in North Carolina in 1998 and 1999 to evaluate a computer program, Herbicide Application Decision Support System (HADSS™), for weed management in peanut (Arachis hypogaea). Weed management systems included metolachlor or ethalfluralin preplant-incorporated (PPI) used alone or in combination with diclosulam preemergence (PRE) or flumioxazin PRE. These herbicide combinations were used alone, followed by (fb) postemergence (POST) herbicides recommended by HADSS™ or fb a standard POST program of paraquat plus bentazon early postemergence (EPOST) fb acifluorfen plus bentazon POST. The standard POST herbicide system and HADSS™ POST recommendations were also used without soil-applied herbicides. Ethalfluralin PPI alone controlled large crabgrass (Digitaria sanguinalis) better than metolachlor PPI. Combinations of metolachlor or ethalfluralin PPI with either diclosulam or flumioxazin PRE provided equivalent control of all weeds evaluated except yellow nutsed...

Economic evaluation of HADSS™ computer program for weed management in nontransgenic and transgenic cotton

Abstract Field studies were conducted at four locations in North Carolina in 1998 and 1999 to evaluate the use of the Herbicide Application Decision Support System (HADSS™) for weed management in nontransgenic, bromoxynil-resistant, and glyphosate-resistant cotton. Weed management systems included trifluralin preplant incorporated (PPI) plus fluometuron preemergence (PRE) or no soil-applied herbicides. Postemergence (POST) options included bromoxynil, glyphosate, or pyrithiobac early POST (EPOST) followed by (fb) MSMA plus prometryn late postemergence–directed (LAYBY) or herbicide recommendations given by HADSS. Glyphosate-resistant systems provided control equivalent to or better than control provided by bromoxynil-resistant and nontransgenic systems for smooth pigweed, Palmer amaranth, large crabgrass, goosegrass, ivyleaf morningglory, and fall panicum. Trifluralin PPI fb fluometuron PRE fb HADSS POST provided equivalent or higher levels of weed control and yield than trifluralin PPI fb fluometuron PRE ...

Economic comparison of broadcast and site-specific herbicide applications in nontransgenic and glyphosate-tolerantGlycine max

Abstract Weed population estimates were collected from four Glycine max fields during the summers of 1997 and 1998. Seedling weed populations were sampled using a regular coordinate system on a grid either 50 by 50, 30 by 30, or 10 by 10 m. MSU-HERB and Mississippi Herbicide Application Decision Support System (HADSS) (yield loss prediction and herbicide recommendation models for G. max) were used to determine the estimated net gain resulting from simulated herbicide applications at each sample location in each field. When necessary, the appropriate data points from the 10- by 10-m grid were removed to form population data sets on grids 20 by 20, 40 by 40, and 80 by 80 m. The objectives of this research were to compare estimated economic returns of site-specific herbicide management and broadcast herbicide management in nontransgenic and glyphosate-tolerant G. max and to evaluate the effects of various weed sampling intensities on estimated economic returns from site-specific herbicide applications. Site-...

Validation of SpraySafe Manager, an aerial herbicide application decision support system

Spray Safe Manager (SSM) is a computer-based aerial application model, which unlike previous models, has a simple user interface. SSM not only predicts spray deposition but also integrates this data with herbicide-plant dose-response curves. This latter facility allows the operator to predict the size of buffer zone required to avoid damage to sensitive plants outside the spray area and the degree of weed control within the spray block. Validation trials showed that, for a helicopter applied spray, the model tended to overpredict spray deposition on stainless steel plates close to the spray block and underpredict deposition in the region 32-80 m from the centre of the spray release line and on isolated plants. The accuracy of model prediction was greater when the spray was applied using D8-45 nozzles orientated at 90°, than for spray applied using D6 nozzles orientated at 0°. The reasons for this are discussed. The model can also be used to predict possible work rates, hectares sprayed per hour, and potentially as a training tool.

Validation of SpraySafe Manager, an aerial herbicide application decision support system

Validation of SpraySafe Manager, an aerial herbicide application decision support system