Actual Application Rates Research Articles

基于土壤养分检测的变量施肥系统的设计与试验

In order to solve the problems of low correlation between variable fertilizer application system and soil nutrient content detection and insufficient real-time performance, a variable fertilizer application system based on real-time soil nutrient content detection was developed. This paper describes the structure, working principle and design of key components of the soil information acquisition and fertilizer application system. It includes the simulation and analysis of fertilizer application using the discrete element method and the selection of curved blade fertilizer application discs. The system uses STM32F429IGT6 microcontroller and ROS higher-level computer for decision making. The device detects soil nutrients in real time, adjusts the fertilizer motor speed accordingly, and runs autonomously along the planned path. The decision coefficient R^2 between the fertilizer application rate and the speed of the fertilizer application wheel is not less than 0.97, and the relative error between the actual fertilizer application rate and the theoretical fertilizer application rate is up to 5.91%, with the maximum value of the coefficient of variation (CV) of 10.18%. The indoor bench test shows that the relative error between the actual fertilizer application rate and the target fertilizer application rate within a single operating grid is up to 6.2%, with the maximum value of CV being 6.64%. The field test in the orchard showed that the maximum relative error between the actual fertilizer application and the target fertilizer application in a single operation grid was 6.3%, and the maximum value of CV was 12.34%, and the fertilizer application was completed in the operation grid, which demonstrated that the device was able to realize real-time and accurate variable fertilizer application according to the soil nutrient information.

Field Sprayer with Application Rate Control Using Fast Response Proportional Valves under Variable Speed Conditions

In modern agriculture, which is characterised by dynamic field environments, challenges are faced in maintaining consistent application rates due to varying tractor speeds, field conditions, and certain calibration errors. Conventional control systems, which rely on slower valves, have difficulty adapting to these dynamic field conditions. By contrast, the integration of fast-acting proportional valves improves the precision and flexibility of flow rate adjustment during spraying applications. This research focused on evaluating the accuracy of spraying applications under different tractor speed conditions through field experiments and data analysis. This study involves a field sprayer with boom wings divided into right and left sections, where the flow rate of the liquid to each section is controlled by proportional valves with a 3 s full opening and closing time, dependent on speed information. Using a closed-loop control system consisting of a flow meter, proportional valve, and PLC, the valves are controlled by the PLC’s internal PID blocks. Observations reveal that as the tractor speed increases to a certain level, the system effectively adjusts the application rate close to the target value and maintains control against the changing ground speed during all field tests. The study included five different application tests, with target application rates of 100, 150, 200, 250, and 300 L ha−1, with each repeated three times, resulting in a total of 15 field tests at different ground speeds. During these tests, the data were meticulously recorded every second, covering the tractor speed, flow rate, and pressure values for both right and left boom sections, along with regulator pressure, proportional valve opening rates, and application rates. The durations for each application rate were documented alongside instances within specified periods where error boundaries of ±10% were exceeded. During the total test duration of 9734 s, the actual application rate value exceeded error boundaries during only 209 s. Within the application durations, the speed variation intervals ranged from 5.10 to 10.23 km h−1, 4.64 to 9.91 km h−1, 3.68 to 7.89 km h−1, 4.80 to 8.21 km h−1, and from 4.90 to 8.69 km h−1. The absolute percentage mean application errors were recorded as 2.81%, 2.68%, 2.28%, 2.14%, and 2.51% for respective application rates. Furthermore, statistically significant correlations (p < 0.01) were identified among the variables (speed, valve opening rate, flow rate, pressure) in both the right and left boom sections across all application rates.

Active involvement of patients, radiation oncologists, and surgeons in a multidisciplinary team approach: Guiding local therapy in recurrent, metastatic rectal cancer.

Despite the extensive implementation of an organized multidisciplinary team (MDT) approach in cancer treatment, there is little evidence regarding the optimal format of MDT. We aimed to investigate the impact of patient participation in MDT care on the actual application rate of metastasis-directed local therapy. We identified all 1211 patients with locally advanced rectal cancer treated with neoadjuvant radiochemotherapy at a single institution from 2006 to 2018. Practice patterns, tumor burden and OMD state were analyzed in recurrent, metastatic cases. With a median follow-up of 60.7 months, 281 patients developed metastases, and 96 (34.2%), 92 (32.7%), and 93 (33.1%) patients had 1, 2-5, and >5 lesions, respectively. In our study, 27.1% were managed in the MDT clinic that mandated the participation of at least four to five board-certified multidisciplinary experts and patients in decision-making processes, while the rest were managed through diverse MDT approaches such as conferences, tumor board meetings, and discussions conducted via phone calls or email. Management in MDT clinic was significantly associated with more use of radiotherapy (p = 0.003) and more sessions of local therapy (p < 0.001). At the time of MDT clinic, the number of lesions was 1, 2-5, and >5 in 9 (13.6%), 35 (53.1%), and 19 (28.8%) patients, respectively. The most common states were repeat OMD (28.8%) and de novo OMD (27.3%), followed by oligoprogression (15%) and induced OMD (10.6%). Our findings suggest that active involvement of patients and radiation oncologists, and surgeons in MDT care has boosted the probability of using local therapies for various types of OMD throughout the course of the disease.

Farm- and community-level factors underlying the profitability of fertiliser usage for Ethiopian smallholder farmers

ABSTRACT While adoption rates for inorganic fertiliser are relatively high in Ethiopia, application rates are generally considered agronomically suboptimal. Using recent data on Ethiopian smallholder maize producers, we showed that maize response to nitrogen, and the profitability of fertiliser use depended on maize agronomy. The agronomic optimum ranged from 0 to 344 kg/ha with a mean value of 209 kg/ha. The actual nitrogen application rates were only about half the agronomic optimum, on average, and were less than the farm-specific economic optimum on 80% of maize fields. The average economic optimum level was 145 kg N/ha, but when we account for risk aversion, the resulting average optimum level is very close to the average observed usage level of 88 kg N/ha. Addressing risk aversion may help to induce greater levels of fertiliser investments at current prices and yield response rates. Our analysis also suggests that key pathways for increasing the economic returns to smallholder fertiliser investments include: complementing nitrogen inputs with phosphorus inputs and improved varieties, using lower levels of nitrogen under intercropping and manure inputs, enabling farmers to delay output sales beyond the immediate post-harvest period, and lowering the costs of accessing input and output markets.

Assessing the Ecological Need for Prescribed Fire in Michigan Using GIS-Based Multicriteria Decision Analysis: Igniting Fire Gaps

In fire-suppressed landscapes, managers make difficult decisions about devoting limited resources for prescribed fire. Using GIS-based multicriteria decision analysis, we developed a model assessing ecological need for prescribed fire on Michigan’s state-owned lands, ranging from fire-dependent prairies, savannas, barrens, and oak and pine forests to fire-intolerant mesic forests, and including a diversity of wetlands. The model integrates fine-scale field-collected and broad-scale GIS data to identify where prescribed fire needs are greatest. We describe the model’s development and architecture, present results at multiple scales, introduce the concepts of “fire gaps” and “fire sink”, and rate the fire needs of more than 1.8 million hectares into one of six fire needs classes. Statewide, fire needs increase with decreasing latitude. The highest and lowest needs occur in southwestern Michigan and the Upper Peninsula, respectively, but actual fire application rates for these regions are inverted. The model suggests burn rates should be increased 2.2 to 13.4 times to burn all lands with greater than high fire needs. The model identifies regional patterns; highlights specific sites; and illustrates the disparity of fire needs and fire application. The modeling framework is broadly applicable to other geographies and efforts to prioritize stewardship of biodiversity at multiple scales.

Development and Evaluation of a Calibrating System for the Application Rate Control of a Seed-Fertilizer Drill Machine with Fluted Rollers

Seed-fertilizer drill machines with fluted rollers generally utilize a calibrated relationship between the fluted-roller rotation speed and mass flow rate to control the application rate. However, this relationship model gradually deteriorates with operating time and is easily affected by working conditions. To maintain the initial operating accuracy, a self-calibrating system for adjusting the control model parameters was designed. It utilizes the application-rate information and fluted-rollers rotation speed data during the operation process to dynamically establish the calibrated relationship. During the field tests performed 18 times, the self-calibrating system could dynamically re-calibrate the relationship model. After the model parameters were updated, the application rate control system maintained a high accuracy level, though the relative deviation of control parameters was relatively higher. The average relative deviations between actual and theoretical cumulative application rates were 0.97% and 1.22% for seeding and fertilizing, respectively, and the standard deviations were 0.69% and 0.62%. Correspondingly, the average relative deviations of control parameters were 7.29% and 7.86%, and the standard deviations were 1.16% and 3.06%. These results indicate that the proposed method with closed-looped control can maintain high-quality control performance and improve the productivity of the drill machine, which will benefit the agricultural production.

Development and performance evaluation of a control system for variable rate granular fertilizer application

A study was conducted to develop a control system for variable rate application (VRA) of granular fertilizers and evaluate its performance. By the use of a microprocessor, a pneumatic cylinder and a rotary shaft encoder, the manual mechanical fertilizer rate adjustment system of a seed drill (SOLA TRISEM 294/R ESP, Model: 37193 TIPO250) was modified and transformed to a real-time automatic control system. Laboratory based tests were conducted to evaluate the developed system performance in automatically applying the predetermined desired application rates at different ground speeds, which were within the range of 3–12 km h−1. Linear regression and ANOVA tests were among the measures used to assess the accuracy of the developed system. Results of this study revealed that the developed system enabled an efficient automatic setting of the desired fertilizer application rate. The investigated operating speeds showed no significant effects on the performance of the system (P > F = 0.7968). In addition, the system exhibited an overall application rate error (difference between desired and actual application rate) of ±2.6%. The response time of the developed system was found to range between 6 and 11 ms for a change of one kilogram in the application rate.

Performance Assessment of a Variable-Rate Fertilizer Applicator

The objective of this study was to test the performance of a Field-IQ sprayer control system which was interfaced with a John Deere liquid fertilizer applicator. The sprayer control system includes Case IH FM-1000 display integrated with DGPS, Field-IQ spray control with full harness, flowmeter and auto-range valve, and the pump. Tap water was used to simulate the UAN 32% nitrogen fertilizer solution in the test. A total of 120 samples from 8 rows of the applicator in 5 application rates (34, 67, 101, 135, and 168 kg/ha) were collected, and the data were analyzed for application uniformity and application rate accuracy of the system. Results showed the greatest variation from the application rate baseline among the rows was 10.1% and occurred at a swath-end row with the lowest application rate of 34 kg/ha. The rows in the middle section of the swath had the lower variation than the rows at the two swath-ends. The application uniformity increased as the application rate increased. The absolute error of application rate ranged from 1.3% to 6.5% with an average of 3.76%. There was no significant difference between the selected application rate and actual application rate (p &amp;gt; 0.8686).

Moving in the right direction? The role of price subsidies in fertilizer use and maize productivity in Ghana

Despite major maize programs in the last two decades and costly investments in a price subsidy program in Ghana, maize productivity remains very low. Utilizing cross-sectional data on 645 maize plots in Ghana, this paper provides empirical evidence on the responsiveness of maize yield to fertilizer application, profitability of fertilizer use, and how the economics of fertilizer use have changed with the subsidy program. There was a statistically significant maize yield response to increased fertilizer application (i.e. 1-kg of nitrogen leads to a yield increase of 22–26 kg per hectare), higher than those estimated in other countries in Africa. Value-cost ratio shows that maize production with fertilizer is profitable both at market and subsidized prices in different locations and with different farming practices, even after incorporating risk into the estimation and analysis. However, despite subsidized prices and profitable fertilizer use, the actual application rate (at 44 kg/ha of nitrogen on average) is much lower than research institute’s and government recommendation and far off the computed economically “optimal” levels (at 225 kg/ha of nitrogen; where the fertilizer price intersects the value of marginal physical product derived from the yield response model). Results suggest that fertilizer prices do not seem to be the binding constraint in greater fertilizer application and productivity increases in maize; other factors appear to be major bottlenecks to greater fertilizer application and productivity increases including accessibility to modern varieties, mechanization, and hired labor. This result shows the limits to fertilizer subsidy as the focus strategy and suggests a more integrated and holistic approach to encourage greater fertilizer application, productivity and income among maize farmers in Ghana.

Actual versus environmentally recommended fertilizer application rates: Implications for water quality and policy

Excessive application of crop nutrients has been identified as a threat to surface water quality in many jurisdictions. The Western Basin of Lake Erie Collaborative Agreement commits the governments of Michigan, Ohio and Ontario to reduce phosphorus entering the Lake Erie’s western basin by 40% by 2025/2026 from 2008 levels by, among other things, reducing fertilizer use in agriculture. The International Joint Commission (2014) estimates that agriculture accounts for 44% of total phosphorus loadings to Lake Erie. Our study uses a unique micro level data set of 16 farms over 6 years that allows us to examine 397 individual nutrient application choices at the field and farm level. If efforts to reduce excessive application of nutrients are to be successful at aggregate level, they need to be informed by an understanding of how farmers make nutrient application decisions within existing production systems. The study aims to enhance our understanding by determining whether farmers applying nutrients to maximize yields, to maximize net returns or to meet environmental targets, and whether over-application depends on factors such as farm size, crop type, manure use, and type of nutrient. We compare actual nutrient application rates with site specific rates intended to minimize excess nutrient application and we regress nutrient application levels against potential explanatory variables including farm size, crop rotation practices, and application of livestock. The data were collected from farmers in the Gully Creek watershed in Ontario. We found that excess nutrient applications, as a percentage of the total nutrient applications, are much higher for phosphorus than for nitrogen and higher for wheat than for corn. While most of the farmers in the study are not required to comply with provincial nutrient management regulations, many of them apply fertilizer at rates close to that recommended by those regulations and some at rates significantly less. While most farms are applying fertilizer, particularly nitrogen, at rates close to the minimum crop requirements, nevertheless, a few farms apply much more phosphorous than recommended. Policy and research efforts should be directed toward targeting these individuals that appear to be the primary contributor to the nutrient loading issue.

Yield gap analysis and resource footprints of Irish potato production systems in Zimbabwe

Irish potato is the third most important carbohydrate food crop in Zimbabwe after maize and wheat. In 2012, the Government of Zimbabwe declared it a strategic national food security crop. In this study, we examine the country's potential for increasing Irish potato yield and help ease the nation's food security challenges. The magnitude of food production increase on already existing croplands depends on the difference between the current actual yields and the potential yield of the crop in the given agro-ecological environment, also called the yield gap. We used three already well-understood types of yield gap: (1) the gap between actual farmer yields, Ya, and the maximum (potential) yield, Yp, achieved when a crop is grown under conditions of non-limiting water and nutrient supply with biotic stress effectively controlled; (2) the gap between Ya and the water-limited yield, Yw, which is the maximum yield attainable under rainfed systems; and (3) the gap between Ya, and the highest yield, Yh, achieved by the best farmers in an agro-ecological area. A grower survey was conducted on the different potato production systems in the country in order to establish the actual yields and input application rates used in potato production. The actual potato yields were used to calculate efficiencies of natural and synthetic resources use. Potential and water-limited yields, and planting times of potato were established for the different agro-ecological regions using the LINTUL-POTATO model, a model based on interception and utilisation of incoming solar radiation. The mean actual yield observed ranged from 8 to 35% of the potential yield, translating to a yield gap of 65 to 92%, hence there is a huge potential to increase production. Simulated potential water use efficiency based on evapotranspiration range was 19–27gpotato/l against the actual water use efficiency of 2–6gpotato/l based on irrigation and rainfall. The current high fertiliser application rates and low actual yields we report, suggest inefficient fertiliser use in potato production in Zimbabwe. The average actual fungicide and insecticide use efficiencies were 0.7 and 13kgpotato/g active ingredient, respectively, across all production systems. All sampled growers lacked knowledge on integrated pest management, a concept which could possibly improve the biocide use efficiency through lowering biocide application rates while maintaining or even improving yields. Our analysis suggests that there is opportunity to improve water, nutrients and biocides resource use efficiencies and increase potato actual yields in Zimbabwe.

Effects of Poultry Manure Application on Phosphorus in Soil and Tile Drain Water Under a Corn-Soybean Rotation

Long-term application of manure can lead to phosphorus accumulation in the soil and increase the risk of P delivery to tile drainage waters. A long-term study (1998–2009) was conducted on eight tile-drained field plots, ranging in size from 0.19 to 0.47 ha, to investigate the effects of long-term surface application of poultry manure on soil phosphorus dynamics and PO4-P loss in tile drainage in Iowa under a corn-soybean rotation system. The experimental treatments included two poultry manure treatments, applied on an N basis at target rates of 168 kg N ha−1 (PM) and 336 kg N ha−1 (PM2), each with three replications, and one chemical fertilizer treatment of urea ammonium nitrate (UAN) at a rate of 168 kg N ha−1 with two replications. Actual manure application rates and estimated plant available N (PAN) varied annually. Bray1-P methods were used to analyze deep core soil samples at five depths (0–15, 15–30, 30–60, 60–90, and 90–120 cm), which were collected in the spring and fall on the half of each plot planted to corn. Tile drainage samples were collected from each actively draining plot equipped throughout the spring and fall drainage season each year, and PO4-P concentrations were analyzed. The results of this study indicated PM2 and PM resulted in a statistically significant increase in topsoil P at 0–30 cm, with no significant movement of P to deeper soil depths. Although an increase in topsoil P levels was observed with poultry manure application, average annual tile drainage P concentrations were not statistically different throughout the study with average PO4-P concentrations of 0.019 ppm with PM2 application and 0.011 and 0.012 ppm for PM and UAN, respectively. Poultry manure application at agronomical recommended application rates may be an environmentally sound fertilizer option for tile drained fine-loamy, calcareous soils under a corn-soybean rotation. However, surface runoff was not evaluated in this study, and high P levels in topsoil could contribute to elevated PO4-P runoff losses.

Conformance Analysis of Clinical Pathway Using Electronic Health Record Data.

ObjectivesThe objective of this study was to confirm the conformance rate of the actual usage of the clinical pathway (CP) using Electronic Health Record (EHR) log data in a tertiary general university hospital to improve the CP by reflecting real-world care processes.MethodsWe analyzed the application and matching rates of clinicians' orders with predefined CP order sets based on data from 164 inpatients who received appendectomies out of all patients who were hospitalized from August 2013 to June 2014. We collected EHR log data on patient information, medication orders, operation performed, diagnosis, transfer, and CP order sets. The data were statistically analyzed.ResultsThe average value of the actual application rate of the prescribed CP order ranged from 0.75 to 0.89. The application rate decreased when the order date was factored in along with the order code and type. Among CP pre-operation, intra-operation, post-operation, routine, and discharge orders, orders pertaining to operations had higher application rates than other types of orders. Routine orders and discharge orders had lower application rates.ConclusionsThis analysis of the application and matching rates of CP orders suggests that it is possible to improve these rates by updating the existing CP order sets for routine discharge orders to reflect data-driven evidence. This study shows that it is possible to improve the application and matching rates of the CP using EHR log data. However, further research should be performed to analyze the effects of these rates on care outcomes.

Moving in the Right Direction? Maize Productivity and Fertilizer Use and Use Intensity in Ghana

The fertilizer subsidy, reintroduced in Ghana in 2008, seems to have led to increased fertilizer use and use intensity among farmers, but there is limited empirical evidence as to whether this increased fertilizer use has reached the optimal intensity level and has contributed to increased productivity. Using cross-sectional data on 630 maize farmers and 645 maize plots in Ghana, this paper provides empirical evidence on the responsiveness of maize yield to fertilizer use and use intensity and the economics of fertilizer use with or without subsidy. Similar to previous studies in Ghana and Africa south of the Sahara, the results show that there is a statistically significant maize yield response (that is, 1 kilogram of nitrogen leads to a yield increase of 22 kilograms per hectare). Despite subsidized prices, the actual application rate for fertilizer adopters (at 44 kilograms of nitrogen per hectare on average) is far below the optimal level (at 225 kilograms of nitrogen per hectare, where the fertilizer price intersects the value of marginal physical product derived from the yield response model). This result suggests limits to fertilizer subsidy as a strategy to increase fertilizer application, productivity, and income among maize farmers in Ghana. Results suggest that fertilizer prices seem not to be the binding constraint in greater fertilizer application and productivity increases in maize. Other factors, including accessibility to modern seed varieties, mechanization, and hired labor, appear to be major obstacles to greater fertilizer application and productivity increases, and these factors would need to be improved to help increase intensity of fertilizer use in both the northern and southern parts of Ghana. Aside from fertilizer, other factors found to positively contribute to higher yield included modern seed variety use, animal manure, herbicide, and the total number of family labor hours spent working in the maize plot. Plots planted with modern varieties have about a 570-kilogram higher yield per hectare than those planted with traditional varieties, while plots fertilized with animal manure have about a 400-kilogram higher yield and plots with herbicide have about a 170-kilogram higher yield than plots without. Significantly higher yields are obtained when fertilizer application is complemented by these inputs. There is no evidence that certified seeds have a significantly higher yield than recycled or uncertified seeds.

Laboratory Evaluation of a Turn Compensation Control System for a Ground Sprayer

<abstract><title><italic>Abstract. </italic></title> The ability to compensate sprayer nozzle flow across a horizontal boom has the potential to mitigate the problem of inaccurate chemical application rate due to lateral speed differences when sprayers are turning. A laboratory testing platform and procedure were developed and tested with a commercial turn compensation control system for a ground sprayer. Virtual paths consisting of simulated GPS signals representing right and left turns separated by straight segments were simulated with four turning radii (75%, 125%, 250%, and 500%) based on boom width. Actual application rates from 11 nozzles spread across the boom were measured using load cells in real time and were compared with desired application rate. Mean flow rate and coefficient of variation by nozzle position for each segment of the test paths showed a general consistency between the expected application rate and actual application rate for most nozzles at most cases with a small discrepancy for a few nozzles. Application errors were within the accepted ±10% range specified by ASABE. This study contributes to the formation of a test standard for turn compensation control systems calibration in the future.

Effect of different sucrose concentrations on the vase life of different protea cultivars (Protea leucadendron and leucospermum)

Many researchers have recommended carbohydrates supply as a remedy to improve vase life, however the actual application rates are seldom known. An experiment was laid out as a 4 x 4 factorial Structure in a randomized complete block design (RCBD); at Midlands State University Agricultural Laboratory to determine the most effective sucrose concentration in delaying leaf blackening in different protea varieties. Procedures were developed for the pulsing of protea varieties using different sucrose concentrations. Four protea varieties (High Gold, Tango, Scarlett Ribbon, and Safari Sunset) were treated with four different sucrose concentrations (0ppm, 30ppm, 40ppm, 50ppm) with the aim of determining the most effective sucrose concentrations in extension of vase life and delaying leaf blackening. Number of days taken to onset of leaf desiccation and leaf blackening were recorded. The results showed that, there was a significant interaction (p<0.05) on the effect of different sucrose concentrations and protea varieties on vase life. There were significant differences on the effectiveness of different sucrose concentration in extension of vase life of different protea varieties. It was concluded that 40ppm was the most effective sucrose concentration in almost all the varieties and Safari Sunset had the longest vase life of all the varieties.

Wet pavement anti-icing — A physical mechanism

Anti-icing of wet pavements is often explained by the fact that anti-icing chemicals (for example sodium chloride) depress the freezing point of water. It appears however that the required concentration predicted by freezing point depression can be unrealistically high. Recently it has been suggested that anti-icing chemicals weaken the ice that forms when a wet pavement freezes and that it allows traffic itself to destroy the ice. It provides an alternative physical mechanism for anti-icing of wet pavements. This article describes the physical basis of this mechanism and proposes a single parameter (equilibrium brine fraction) to predict if the ice is sufficiently weakened. Existing laboratory and field data are re-analyzed to determine a value for the minimum brine fraction, which is used to calculate the theoretically minimum chemical concentration needed to ensure sufficient tire-pavement friction. Microscopic observations of the freezing process are also given. The results of the analysis provide a conservative estimate of the minimum brine fraction Fb_min=0.4. This brine fraction criterion implies that 60% less salt is needed compared to the concentration predicted by the freezing point depression theory. The predicted theoretical minimum salt concentration should not be confused with actual application rates. Actual application rates have to account for a large number of practical issues like chemical losses during spreading, dilution and temperature drop, uncertainties about weather forecasts, and the cycle time of the plow/salting truck (time).

Influence of Broiler Litter Bulk Density on Metering and Distribution for a Spinner-Disc Spreader

<abstract><title><italic>Abstract.</italic></title> Poultry litter is commonly land applied as an organic fertilizer on crop and pastureland. However, the high variability in physical characteristics of litter, especially moisture content and bulk density, makes it difficult to maintain accurate metering and uniform distribution during application with spinner-disc spreaders. A study was conducted to understand the effect of litter bulk density on conveyor metering and spreading distribution for a spinner-disc, litter spreader. Two sources of broiler litter (termed as A and B) at different moisture contents (32% and 28% w.b., respectively) and bulk densities (416.5 and 480.6 kg/m³, respectively) were acquired and used in this study. Different spreader and rate controller settings (two gate heights: 17.8 and 34.9 cm; four application rates: 1743, 3424, 3486, and 6848 kg/ha; two correct density values: 416.5 and 480.6 kg/m³; and three incorrect density values: 352.4, 416.5, and 544.7 kg/m³) were established as treatments. The spreader rate controller used in this study required litter density as an input variable for managing the discharge rate. Actual and theoretical discharge rates were compared for conveyance data analysis whereas single-pass and standardized distribution patterns were generated and compared using standard pan testing. Results indicated that incorrect density treatments generated high rate errors (>15%) during conveyance tests. Field application rates were also outside the considered acceptable limits, i.e., not within 10% of the target application rate, for both litter types (A and B). For both litter types, the central peak of the single-pass patterns at different density treatments varied with actual application rate (mass flow rate). Standardized patterns at different density treatments for the same litter type were found to be statistically different (p<0.05) at a few transverse positions (between -3.7 and 3.7 m from spreader centerline) across the swath. These results indicated the importance of determining and using the correct density value within a rate controller for accurate application with spinner-disc spreaders.

Calibration of Seal Coat Application Rate Design

Abstract This paper presents seal coat performance evaluations of various emulsion and aggregate application rates using three different evaluation methods: International Roughness Index (IRI), friction test, and visual evaluation. Then, considering the seal coat failure criteria, correction factors for seal coat application equipment are introduced. This study confirms the lack of relevance between seal coat application and IRI values because of the thickness of a seal coat. In addition, friction improvements caused by seal coat applications were confirmed within the range of seal coat rates applied. Overall, IRI, friction, and visual inspection did not reveal distinct differences in seal coat performance in terms of application rates in the testing range. Accordingly, seal coats with rates based on the McLeod method showed acceptable performance. The aggregate application rate should be high enough to protect the seal coat from immediate failure during construction but low enough to avoid unacceptable levels of accumulated fines content. Furthermore, immediate failure occurring locally during construction because of incorrect application rate (e.g., insufficient aggregate rate) can cause total failure of a seal coat road because of a chain reaction. However, discrepancies between designed rates and applied rates were observed in the study even after the seal coat equipment was calibrated prior to operation. The equipment factor for aggregate can compensate for rate discrepancies between the target and actual application rates. It was found that the designed emulsion application rate does not need to be corrected for the emulsion distributor because the emulsion rate discrepancy has an insignificant impact on a seal coat’s performance.

A method to generate and use as-applied surfaces to evaluate variable-rate fertilizer applications

Variable-rate technology (VRT) has been used by farmers in an attempt to better match inputs to local growing conditions. In theory, VRT minimizes over- and under-application of inputs. However, the limitations and errors of this technology have not been well documented. Further, standard methods for quantifying the application accuracy using VRT do not currently exist, limiting practitioners’ knowledge on performance. Therefore, a spatial data model was developed to generate “as-applied” surfaces as a means to evaluate VRT performance of two applicators. The spatial data model uses geographic information system functionality to merge applicator descriptive patterns with a field application file to generate an ‘as-applied’ surface map representing not only the actual deposition of granular fertilizer but more importantly spatial distribution. Field data were collected and used to validate the spatial model. Comparisons between the actual and predicted application rates indicated moderate to good correlations (0.62 < R < 0.88) for two applicators. Longitudinal offset such as for a global positioning system receiver impacted model performance for one applicator but not the other. A comparison of the actual application rates to the prescription maps illustrated the inconsistency of VRT performance to deliver target rates. Both applicators were only within 10 % of the target rates a small percentage of time (<45 %) during field operation. Generated as-applied surface maps highlighted errors associated with VRT along with limitations of the technology within site-specific management (SSM). Thus, as-applied surface maps provide a means to properly evaluate VRT while enhancing researchers’ and practitioners’ abilities to compare and customize SSM approaches.