Evaluating the Profitability of Site‐Specific Farming

Variable rate fertilizer application has the potential to improve fertilizer use efficiency, increase economic returns,and reduce environmental impacts. This study was designed to examine differences in yield and economic returns betweenuniform and variable rate fertilizer applications. During the 1997 and 1998 growing seasons, a variable rate applicator,capable of varying two liquid fertilizers simultaneously, was used to evaluate three fertility strategies: conventional uniformN, uniform N and P, and variable rate N and P. The three treatments were assigned in six blocks within three 14ha grainsorghum fields (two blocks in each field) in a randomized complete block design. Thirtysix soil samples were taken in astaggered systematic grid from each field, and levels of soil nutrients were determined. Application rate maps for the variablerate N and P treatment were generated based on a fixed yield goal and sitespecific soil N and P levels across the experimentalplots, while application rates for the uniform N and P treatment were calculated from the same yield goal and average soilN and P levels for all three fields. Yield monitor data indicated that the variable rate treatment resulted in significantly higheryields than the uniform N and P treatment for both years (400 kg/ha higher in 1997 and 338 kg/ha higher in 1998). Moreover,coefficients of variation of yield monitor data for the variable rate treatment were smaller than those for the two uniform ratetreatments. A simple economic analysis showed that the variable rate treatment had positive relative economic returns overthe uniform N and P treatment ($27/ha in 1997 and $23/ha in 1998). However, if additional costs for soil sampling, equipment,and data analysis associated with variable rate application were considered, these returns would be much lower or evennegative. These results showed that variable rate fertilization can increase yield, reduce yield variability, and improveeconomic returns. More experiments are needed to evaluate the longterm agronomic, economic, and environmental viabilityof variable rate technology in the Rio Grande Valley of south Texas

HighlightsThe influencing factors of the fertilizer dropping time are determined by simulation.The relationship between the influencing factors and the fertilizer dropping time is explored on the VRF applicator.A new method is established to calculate the fertilizer dropping time.Abstract. Lag time is one of the main factors that affect the accuracy of the variable rate fertilizer (VRF) applicator. The key to correcting the impact of the lag time is to determine its influencing factors. This article focuses on the fertilizer dropping time, which is a part of the lag time, and hypothesizes that the rotational speed of the fluted roller, working length of the fluted roller, number of fertilizer particles, and the length of the fertilizer tube may affect the fertilizer dropping time. First, taking advantage of the simple and convenient setting of the working parameters and conditions of the simulation software, different working parameters were set by the EDEM software for simulation, and the simulation results were analyzed to determine that the rotational speed of the fluted roller and the length of the fertilizer tube are the main influencing factors of the fertilizer dropping time. Second, to explore the relationship between the two factors and the fertilizer dropping time in the actual work, experiments were performed on the VRF applicator. The experimental results are analyzed by ANOVA, and the analysis results show that: the correlation coefficient R2 between the rotational speed of the fluted roller and fertilizer dropping time is greater than 0.95, and there is a linear relationship between the factor and fertilizer dropping time; the fertilizer dropping time increases with increasing the length of the fertilizer tube. Finally, the rotation speed-the length of the fertilizer tube-fertilizer dropping time model was established through the multiple regression analysis. With the model, the fertilizer dropping time was accurately calculated according to the rotational speed of the fluted roller and the length of the fertilizer tube. The accuracy of the model is greater than 85%, which helps to calculate the fertilizer dropping time. This study helps to correct the lag distance by sending instructions in advance and improving the accuracy of the VRF applicator. Keywords: Fertilizer dropping time, Fertilizer tube, Rotation speed, VRF.

Input management practices within precision agriculture systems have enabled grain and oilseed producers to apply agricultural inputs variably, facilitating resource, yield, and profit optimization. Despite significant progress in variable rate technologies, research comparing different methodologies and comprehensive guidelines to assist producers in their decision‐making processes is still lacking. This research article aimed to identify and summarize the suggested decision‐making factors for determining variable seed rates and variable fertilizer applications. A systematic review of the literature from the last 2 decades was conducted, summarizing various approaches within precision agriculture related to variable rate applications in canola ( Brassica napus L.), maize ( Zea mays L.), soybean [ Glycine max (L.) Merr.], and wheat ( Triticum aestivum L.). Findings revealed a wide range of decision‐making factors guiding variable rate applications, from site‐specific soil characteristics to complex data‐driven recommendations. Focus crops were maize and soybean in terms of variable seeding rates, while nitrogen was the only fertilizer source discussed. Most articles appeared to address a single specific decision‐making factor, with limited comparisons drawn between different methods. The results underscore the complexity of variable rate decisions, especially in terms of the influence of weather, highlighting the overarching impact that rainfall has on grain and oilseed production in dryland systems. To maximize the effectiveness of variable rate applications across diverse production systems and justify the initial investment in these technologies, it is essential to develop adaptable, context‐specific guidelines for seed and fertilizer management.

The wide scale adoption of site specific management (SSM) and variable rate fertilizer application (VRA) in the next 5 to 10 years portends changes in soil testing and plant analysis. To develop site specific nutrient recommendations, more detailed information about the soil's fertility status will be required which could mean greatly increased samples numbers for soil or plant analysis. Discussions of initial research on the large numbers of samples required to produce quality maps for SSM and VRA among scientists, agricultural industry and producers, however, indicates that this may only be a short phase as the expectation of using remote sensing (RS) to replace or compliment limited soil and plant analysis is already occurring. Soil and plant analysis numbers may increase during the next 5 to 10 years as there is a slow transition to SSM and VRA. During this time, however, there will be research to related RS imagery to soil and crop management problems. After 10 years of this transition, there may be more adoption of RS for primary diagnosis and management with limited soil and plant analysis done from ‘reference’ areas to assure the accuracy of remotely sensed image interpretation.

Abstract. Wild blueberry fields have gentle to severe topography with high proportion of bare spots, and weed patches emphasizing the need for variable rate (VR) fertilization. To evaluate the impact of VR fertilization on subsurface water contamination, two wild blueberry fields were selected in Nova Scotia, Canada. The field boundaries, weeds and bare spots were mapped using real-time kinematics global positioning system. The variation in slope was mapped and management zones i.e. steep slope (Zone-1), moderate slope (Zone-2) and low lying areas (Zone-3) were delineated. Both fields were divided into two halves (VR and uniform). The GPS-guided prescription maps were generated in ArcGIS 9.3 for VR treatment sections. Three fertilization rates 200, 150, and 100 kg ha -1 were applied in Zone-1, Zone-2 and Zone-3, respectively, with a VR fertilizer spreader. The bare spots/weeds were classified as a separate class in the prescription maps and no fertilizer was applied in those areas. For comparison, the uniform fertilizer rate of 200 kg ha -1 used by growers was applied in uniform treatment sections of the selected fields. Subsurface water samples were collected after every heavy rainfall (>20 mm) from 36 suction lysimeters placed in each field with 18 lysimeters in each treatment. The subsurface water samples were analyzed for nitrate nitrogen (NO 3 — N), and ammonium nitrogen (NH 4 + -N) concentrations under VR and uniform fertilization. Leaf samples were collected from both VR and uniform treatments and were analyzed for leaf nutrient concentrations. The results of this study suggested significantly lower NO 3 — N and NH 4 + -N loading from subsurface water samples leaving the root zone in moderate and low lying areas for VR treatment as compared to uniform treatment. The nitrogen, phosphorus, and potassium nutrient levels in leaves were found to be higher than the recommended ranges for uniform treatment as compare to VR treatment suggesting the excess uptake by plants in uniform treatment which may result in more vegetative growth and lower yield. The results indicated that VR fertilization based slope can increase input use efficiency, farm profitability and reduce subsurface water contamination.

Potatoes ( Solanum tuberosum L.) are grown extensively throughout the Pacific northwestern United States as a high value crop in irrigated rotations with other row crops such as wheat ( Triticum aestivum L.) and both field and sweet corn ( Zea mays L.). Center pivots are the predominant irrigation systems. Soil texture ranges from coarse sands to finer textured silt loams and silts and can vary within one field, particularly in fields with hilly topography. Site specific management is being evaluated as an approach to help to optimize inputs (water, seed, agricultural chemicals) to maintain or enhance yield and reduce potential negative environmental impacts from these farming systems. Currently, variable rate fertilizer application technology and harvest yield monitoring equipment are commercially available for potato. Variable rate seeding and variable rate irrigation water application technologies are developed but not fully commercialized and variable rate pesticide application equipment is in development. At the Irrigated Agricultural Research and Extension Center in Prosser, Wash., we have a team of research scientists, interested individuals from local industry, and other key organizations (e.g. local conservation districts) who are working together to evaluate different site specific technologies, improve the ability to use available tools, and to improve decision-making ability by conducting research both on farm and in research plots.

Measuring of fruit tree canopy parameters were required for site-specific management of fruit orchard such as estimation of fruit yield, variable rate application of fertilizer and pesticides precisely on each tree. For riding the effect cased by tractor deviation in driving path between two rows of trees and uneven ground, measuring was designed based on CAN bus, combined robot navigation technology, including AHRS and DGPS-RTK, with the measuring of fruit tree canopy characters, and used C8051F040 micro controller as node ECU. The hardware circuit was introduced in detail, the forming of CAN transmission information frame and software were also analyzed. Experiment with litchi trees in orchard using four ultrasonic sensors showed that system was stable, having highly repeatability (R2=0.9341, RMSE=1.22m3) and accuracy (R2=0.8972, RMSE=1.766m3) of canopy volume measuring.

This review paper synthesizes the current understanding of greenhouse gas (GHG) emissions from field cropping systems. It examines the key factors influencing GHG emissions, including crop type, management practices, and soil conditions. The review highlights the variability in GHG emissions across different cropping systems. Conventional tillage systems generally emit higher levels of carbon dioxide (CO2) and nitrous oxide (N2O) than no-till or reduced tillage systems. Crop rotation, cover cropping, and residue management can significantly reduce GHG emissions by improving soil carbon sequestration and reducing nitrogen fertilizer requirements. The paper also discusses the challenges and opportunities for mitigating GHG emissions in field cropping systems. Precision agriculture techniques, such as variable rate application of fertilizers and water, can optimize crop production while minimizing environmental impacts. Agroforestry systems, which integrate trees and crops, offer the potential for carbon sequestration and reducing N2O emissions. This review provides insights into the latest research on GHG emissions from field cropping systems and identifies areas for further study. It emphasizes the importance of adopting sustainable management practices to reduce GHG emissions and enhance the environmental sustainability of agricultural systems.

Traditional farming practices in eastern Oregon ignore the inherent spatial variability (topography, soils) resulting in inefficient farming and lower net returns. Site‐specific farming (SSF), or farming based on requirements of specific areas in a field, has the potential to improve input use efficiency and farm profits. To implement SSF, however, management zones should be demarcated preferably based on factors that most affect yield. The most common method for demarcating management zones is through intensive grid sampling that can be very expensive. The objective of this study was to find cheaper and quicker ways to demarcate management zones in a field in eastern Oregon. This study evaluated the use of electrical conductivity (EC) and yield maps in demarcating management zones. A 28‐acre field was characterized for depth and nutrients at a 100‐ft grid. Wheat was uniformly seeded throughout the field and harvested at each grid location. Results indicated that the spatial variability of wheat yield was influenced by soil depth. EC data were correlated with both depth and grain yield and can therefore be used to demarcate management zones quicker and cheaper than grid sampling in this field. Information from yield maps was also useful in demarcating management zones for SSF.

In recent years, precision agriculture has received attention from producers, agribusiness, and governmental agencies in an effort to increase profitability and protect the environment. Many aspects of precision agriculture, such as soil fertility, application technology, and economic factors, have received substantial research attention; however, other aspects of precision agriculture have not been well documented. One important issue that warrants increased attention is water quality. Because of precision application technology, variable rate fertilizer application based on within-field heterogeneity has the potential to decrease negative water quality impacts. Therefore, the objective of this paired watershed study was to evaluate the impact of variable rate nitrogen (N) fertilizer application on surface water quality. The variable rate field was divided into management units designated as poor, moderate, and high based on measured yield potential and received 100–160 kg/ha of N fertilizer. A portion of the N application was uniformly applied pre-plant or at planting, and rest was sidedressed at variable rates. The uniform rate field received uniform N application at 135 kg/ha. Surface water runoff and water quality were monitored for each field, and collected samples were analyzed for N and phosphorus (P) constituents. During the 2-year monitoring period with 22 storm sampling events, variable rate N application resulted in few water quality differences compared to uniform rate application, but overall median NO3 + NO2–N concentrations were significantly lower for the variable rate field in the second year of variable rate N application. Overall and event mean NO3 + NO2–N concentrations from the variable rate field tended to be higher, but median concentrations from the uniform rate field tended to be higher.

Development of a sensor-based embedded system for on-the-go variable-rate fertilizer applicator in maize crop

In the U.S. Northern Great Plains, growing seasons are short but extremely productive. Farms and ranches are large, so many of precision agriculture's early adopters reside in the region. Crop yield maps at season's end reveal sizable variations across fields. Farm management relying upon uniform chemical applications is ineffective and wasteful. We provided information about crop and range status in near- real-time, so that in-season decisions could be made to optimize final yields and minimize environmental degradation. We created learning communities, in which information is shared among scientists, farmers, ranchers, and data providers. The new information for agricultural producers was satellite and aerial imagery. Value-added information was derived from ETM+, AVHRR, IKONOS, and MIDOS sensors. The emphasis was on reducing the time between acquisition of data by a satellite and delivery of value-added products to farmers and ranchers. To distribute large spatial data sets in short times to rural users we relied upon satellite transmission (Direct PC). Results include: (1) management zone delineation, (2) variable-rate fertilizer applications, (3) weed detection, (4) irrigation efficiency determination, (5) detection of insect infestation, (6) specification of crop damage due to inadvertent chemical application, and (7) determination of livestock carrying capabilities on rangelands.

Variable rate technology offers a sustainable, efficient, and cost-effective solution for fertilizer application. A study was conducted to design and develop a variable rate fertilizer applicator to detect real-time deficiency of N within the field and apply it per requirement of the crop. The microcontroller system was designed to receive a signal from the N sensor and send a signal to the pulse-width-modulation valve to vary the rotational speed of the hydraulic motor resulting in variation in the rotation of the metering mechanism drive shaft based on the recommended amount of fertilizer. During the field study, three replications were conducted, each of which was divided into four plots. The response time between the N sensing and fertilizer discharging fell within the range of 3.49 to 4.90 s. Fertilizer applied using the developed variable rate applicator indicated that when the fertilizer rate is increased from N1 to N4 (kg ha−1), NDVI increased from 0.56 to 0.78 and drive shaft rotational speed decreased from 20 to 0 rpm in order to apply the fertilizer at a rate of 0.00 instead of 78.36 kg ha−1. Using the developed applicator demonstrates that this technology could reduce environmental impact, making farming more sustainable.

What is lacking in precision farming at present, are more comprehensive and non-destructive methods for obtaining the data needed to prescribe variable treatments. A farmer needs to be informed in order to be efficient, and that includes having the knowledge and information products to forge a viable strategy for farming operations. Current remote sensing (satellite images) sources are too coarse in multispectral spatial resolution and too infrequent in time to allow detailed tracking of phenological stages during the growing season. In this research very detailed and automated on-the-go optical monitoring of the crop is used for detecting and managing zones with different crop yield potential on a seasonal scale. In particular, reflectance properties are used to identify and evaluate optical indicators of the nutritional status of the crop. These indicators should allow site-specific in-seasonal correction of N-application to come to optimal crop yield all over the field. Based on these indicators, site-specific fertilization is done with a variable fertilizer equipped with DGPS. At the end of the season, the crop was harvested with a combine harvester, equipped with precision farming sensors to map final crop yield. In this way final results could be evaluated and analyzed.

The presence of crop residue on the soil surface is important in controlling soil erosion, but residue amounts from lentil (Lens culinaris Medik.) are often insufficient to control soil erosion during subsequent phases of the cereal‐grain legume cropping systems of the U.S. Pacific Northwest. To gain knowledge of residue production by lentil in typical production environments, six lentil cultivars were grown at four slope positions in southeastern Washington over 3 yr. Residue and seed production varied significantly among cultivars and slope positions (P < 0.01). Total residue production ranged from four to 20 times the 290 lb/acre required by conservation standards, however, the amount remaining after sowing of the subsequent winter wheat (Triticum aestivum L.) crop was much less, indicating that large losses occurred during harvesting and tillage operations. On lower slope positions, grain and residue yields were inversely correlated for all cultivars. On upper slope positions, grain yields were nearly constant among cultivars, but ‘Laird’ produced an average of 42% more residue than ‘Brewer’. No single cultivar met yield and residue production criteria across all landscape positions. Growers can improve erosion control by site‐specific sowing of high‐residue cultivars such as Laird. Breeding programs should consider the differences in the upper and lower slope positions for seed and residue production when selecting for cultivars with improved biomass production.Research QuestionSurface residue is a very important factor in preventing erosion on the steep slopes in the Palouse region of the Pacific Northwest. Lentils produce relatively small amounts of residue compared with wheat and other small grains and, in order to maintain sustainable farming systems in the region, this study was undertaken to identify lentil cultivars that produce large amounts of residue across a wide range of slope positions.Literature SummaryThe soils on the rolling hills of the Palouse region of eastern Washington, northern Idaho, and northeastern Oregon are becoming increasingly eroded. Soils on these slopes vary considerably in type and productivity. In general, the upper slope positions are less productive than the lower slope positions due to poorer soil types caused by erosion, leaching of nutrients, and reduced moisture content. Ironically it is the upper slope positions that are in greatest need of residue, however they are the positions that have the lowest potentia1 for residue production. In order to meet regulations regarding minimum surface residue levels set up by the Natural Resource Conservation Service, many fmers have incorporated tillage practices that leave a rough soil surface over the winter while others are eliminating lentil from their rotations altogether. Eliminating lentil from the current rotations could be quite detrimental to the small grain crops, since lentil crops return N to the soil and break up disease cycles. In order to make it more equitable for the farmer, lentil cultivars that produce high levels of residue in the poorer, upper slope positions must be identified.Study DescriptionThis study involved growing six lentil cultivars at the four main slope positions (topslope, backslope, footslope, and toeslope) determining their production potential at each. The experiment was conducted at three different locations over 3 yr (1984, 1985, and 1986). Samples of the mature crop were harvested from a 4 ft segment of the middle two rows in each plot. Total biomass, seed, and residue yields were recorded for each cultivar and harvest index was calculated by dividing seed yield by total biomass yield.Applied QuestionsHow can lentil residues be increased to a sufficient level on the upper slope positions to significantly reduce erosion?This may be accomplished through site specific farming. Farmers would grow high residue producing cultivar on the upper slope positions while growing a cultivar that produced less residue on the lower positions. One caution with thi approach is that the two cultivars have to mature at nearly the same time. Often the crop on the upper positions will mature earlier than those on the lower posi tions due to lower moisture reserves.Can future cultivars be developed to produce adequate levels of residue?Lentil breeding programs should consider using residue production as a selection criteria when developing new cultivars.RecommendationGrowers may consider site specific farming where a cultivar producing large amounts of residue are planted on the upper slope positions while a cultivar producing less residue could be planted on the lower slope positions where smaller amounts are needed.