Variable Rate Fertilizer Research Articles

Improving Soil Available Nutrient Estimation by Integrating Modified WOFOST Model and Time-Series Earth Observations

Information on soil available nutrient (SAN) at key crop growth stages is critical to generate prescription maps for implementing variable rate fertilization (VRF). Our previous study showed that integrating time-series remote sensing (RS) data with the modified World Food Studies (WOFOST) crop model provides a useful approach (preliminary RS-WOFOST-based method) to acquiring information on field SAN; however, the estimation accuracy was low for VRF application. In this paper, three steps were proposed to further improve the SAN estimation accuracy. At the first step, the rapid-nutrient assimilation (RNA) method was used to optimize the crop growth simulation process. Compared with the ensemble Kalman filter (EnKF) method, the RNA method showed an improved performance in estimating soil available nitrogen (N), phosphorus (P), and potassium (K) content [EnKF: $R^{2} = 0.48$ (N), 0.37 (P), 0.15 (K); RNA: $R^{2} = 0.59$ (N), 0.46 (P), and 0.18 (K)]. The improved K estimation at the first step was clearly lower than that of N and P; hence, the K content estimation was further optimized at the second step and the accuracy was improved ( $R^{2} = 0.27$ ) by using the estimated N as an input variable during the K estimation. At the third step, an iteration algorithm was implemented based on the first two steps, and the final $R^{2} = 0.71$ (N), 0.58 (P), 0.49 (K); root-mean-square error = 14.35 (N), 3.70 (P), and 14.87 (K). In general, the optimized approach can overcome the limitations of the preliminary RS-WOFOST-based method and improve the SAN estimation accuracy.

Development and application of the soil moisture routing (SMR) model to identify subfield-scale hydrologic classes in dryland cropping systems using the Budyko framework

Crop yield patterns at the field level in dryland agricultural systems often trace back to the spatial structure of water storage and subsurface flow paths. These lateral flow paths create zones of saturation that promote nutrient loss from runoff and leaching beneath the root zone. Despite its clear importance, a spatially explicit representation of landscape hydrology is frequently missing from site-specific crop and fertilizer management plans. This work uses the grid-based water balance model, SMR (soil moisture routing), to adapt an established method of hydrologic classification, the Budyko framework, for small agricultural watersheds. The model was evaluated with spatially distributed soil moisture data and surface runoff measurements in four annually cropped fields located across the eastern Palouse region of the inland Pacific Northwest. The Budyko framework, modified to include change in root zone water storage and lateral flow, was combined with a separate indicator of yield potential to form a dual-threshold classification scheme for variable-rate fertilizer management that balances agronomic benefit with environmental impact. Each field was divided into zones based on crop yield and nitrogen loss potentials, which link to the hydrologic functioning of the landscape through soil water storage and subsurface redistribution, respectively. Results showed large variability in the annual water balance assessed within individual fields and between fields. The greatest variability was observed in the two eastern-most fields where the wettest zone of each had water supply 172% and 137% that of the dry zone. Depth to a hydraulic restrictive layer and topography were identified as primary landscape controls on the water supply (precipitation plus net lateral flow minus change in water storage) in these fields. Moreover, the steep climate gradient in the region created field-to-field variability in water balance with the ratio of evapotranspiration to precipitation ranging from 91% in the western-most field to approximately 70% in each of the fields to the east. The clearest choice is for growers to apply more fertilizer in areas with high water storage capacity and high crop yield and where fertilizer loss through leaching and runoff is minimal. Less fertilizer should be applied in areas with low water storage capacity that frequently saturate. Areas with high storage capacity and frequent saturation involve a tradeoff between yields and minimizing fertilizer loss that may be best served by splitting fertilizer application to avoid excessive over-winter leaching losses. Even though remote sensing and variable-rate applicators are at the frontiers of precision agriculture, landscape hydrology underlies all dryland crop production and should accordingly be looked to for inspiration in the design of cropping systems.

Soil NPK Variability Mapping for Harumanis Mango Grown in Greenhouse at Perlis, Malaysia

Soil is essential for plant growth. The soil provides support for plant, medium for root growth, and most importantly it offers nutrients for plant uptake. The nutrients variability in soil is vary depending on several factors such as soil type, soil microbes, and soil pH. Therefore, nutrients available in the soil is important to be mapped to investigate the state of nutrient present. In this study, the available content of Nitrogen (N), Phosphorus (P) and Potassium (K) were determined for a high-density planting systems of Harumanis mango plants grown in the greenhouse. Thirty-two soil samples were collected from a greenhouse for analysis of NPK content in top soil. The soil was analyzed using the Kjeldahl method, UV Spectrophotometer and Atomic Absorption Spectroscopy (AAS) for N, P, and K content respectively. These amount of macronutrients were then mapped with respective georeferenced location to produce NPK nutrients maps using standard classification in ArcGIS software. Results have indicated that N, P, and K were ranged between 0.06 - 0.12% (very low), 4 - 648 ppm (low-very high) and 0.02 -1.37 cmol/kg (low-high) accordingly. Overall, it can be concluded, soil in selected greenhouse is poor in N, high in P and moderate in K content. Hence, it is suggested more N and adequate amount of K fertilizer should be supplied to increase the plant's productivity. The produced maps give a new perspective in a farming management concept in term of variable rate fertilizer application for Harumanis mango plants grown in the greenhouse.

Estimating Crop Nutritional Status Using Smart Apps to Support Nitrogen Fertilization. A Case Study on Paddy Rice.

Accurate nitrogen (N) management is crucial for the economic and environmental sustainability of cropping systems. Different methods have been developed to increase the efficiency of N fertilizations. However, their costs and/or low usability have often prevented their adoption in operational contexts. We developed a diagnostic system to support topdressing N fertilization based on the use of smart apps to derive a N nutritional index (NNI; actual/critical plant N content). The system was tested on paddy rice via dedicated field experiments, where the smart apps PocketLAI and PocketN were used to estimate, respectively, critical (from leaf area index) and actual plant N content. Results highlighted the system’s capability to correctly detect the conditions of N stress (NNI < 1) and N surplus (NNI > 1), thereby effectively supporting topdressing fertilizations. A resource-efficient methodology to derive PocketN calibration curves for different varieties—needed to extend the system to new contexts—was also developed and successfully evaluated on 43 widely grown European varieties. The widespread availability of smartphones and the possibility to integrate NNI and remote sensing technologies to derive variable rate fertilization maps generate new opportunities for supporting N management under real farming conditions.

Effects of Variable Rate Nitrogen Application on cv. Barbera Performance: Yield and Grape Composition

This paper follows a first contribution on the long-term effects of variable rate nitrogen application on vegetative growth and leaf nutritional status of a small Barbera vineyard, where three vigor levels classified as low, medium, and high (L, M, H) were identified pretrial from normalized difference vegetation index (NDVI) values determined by remotely sensed imagery (5 megapixel resolution). Variable rate fertilization supplying no N (0 kg/ha; C), standard rate (60 kg/ha; S), and variable rate application (VRA) of 60 or 120 kg/ha to H, M, and L over four consecutive seasons showed that variability among vigor levels was significantly reduced in years three and four, while mean effects related to fertilization strategy were not significant. In this companion paper, L vines were most balanced, suggesting a change in fertilization strategy to no N application in M and H areas, and for maintenance supply in L plots. However, significant vigor level × year interactions indicated that within-vigor variability for total yield and berry weight was considerably reduced, while concomitant seasonal accumulations of sugar and color in 2014 and 2015 were much less variable within dates across vigor levels, suggesting the efficacy of the VRA approach. While the main effects of fertilization supply were mostly non-significant, seasonal accumulation of total soluble solids and anthocyanins in 2014 and 2015 showed that plots receiving 60 kg N/ha had lower within-date values than C (no N), suggesting increasing sensitivity over years. However, the L vines had an almost negligible response to increased N supply, and most observed responses were primarily due to reduced vine capacity.

FARMER PERCEPTIONS OF PRECISION AGRICULTURE TECHNOLOGY BENEFITS

AbstractThe objective of this research was to evaluate producers’ perspectives of four key precision agriculture technologies (variable rate fertilizer application, precision soil sampling, guidance and autosteer, and yield monitoring) in terms of the benefits they provide to their farms (increased yield, reduced production costs, and increased convenience) using a best-worst scaling choice experiment. Results indicate that farmers’ perceptions of the benefits derived from various precision agriculture technologies are heterogeneous. To better understand farmers’ adoption decisions, or lack thereof, it is important to first understand their perceptions of the benefits precision agriculture technologies provide.

Variable-Rate Application on Fertilizer Use in Cotton Production

Precision agriculture technologies are increasingly important in cotton production because input prices continue to rise. Farmers increase input efficiency using precision agriculture technologies by adjusting inputs to match soil fertility and plant nutrition requirements. This research examines the factors affecting changes in fertilizer use following variable-rate fertilizer application in cotton production. Data from a 2009 survey of cotton producers in 12 states of the United States were used in the analysis. Farmers who used precision soil sampling, planted larger cotton area, relied on other farmers for information about PA, grew picker cotton, and had higher household income were more likely to decrease fertilizer application with VRT. Results from this analysis are useful to farmers and policy makers interested in reducing fertilizer use in the face of rising fertilizer prices and growing concerns about the environmental impacts of farming.

Design and experiment of intelligent monitoring system for vegetable fertilizing and sowing

Vegetable production is facing the problems of low resource utilization rate and serious environmental pollution. Vegetable sowing and planting with fertilizer have the characteristics of extensive and low efficiency. An intelligent monitoring system of vegetable fertilization and seeding is designed in this paper. The system uses CAN bus communication protocol to collect sensor signals and PLC to control the execution part. The seeding and fertilization monitoring were carried out by photoelectric sensing technology and piezoelectric thin film technology, respectively. The system is composed of sowing and fertilizing machinery, monitoring system of seed leakage, alarm system of fertilizer blockage, variable-rate fertilization control system and on-board computer. The system uses the GPS module to get the location information of the machine. Combined with the pre-loaded plots map of soil prescription, the target fertilization amount in the current position is determined. Pressure sensor and microcomputer control are used to calculate the current fertilization rate and flow information, and the fertilization rate is adjusted in real time according to the moving speed of the machine. Finally, the detection of miss-seeding, blocking and precision fertilization is realized. The field test results show that the accuracy of monitoring is over 91%. The alarm error of fertilizer blockage is less than 4%. The accuracy of variable fertilization is more than 94%. The whole machine monitoring system can adapt to complex field environment and has better practicability and economy.

Motion analysis and system response of fertilizer feed apparatus for paddy Variable-Rate fertilizer spreader

Precision agriculture and variable-rate technology have gained increasing public interest. To improve the rapid response ability of the control system of a variable-rate fertilization and reduce the errors corresponding to the feed fertilizer system in a centrifugal variable-rate spreader, three devices that could adjust the application rate using different actuators were developed; these involved the gear and rack structure A, electric handspike structure B, and screw slider structure C. Mechanism motion analysis models were established based on vector equations, the response analysis of system delay was performed according to the model of lag fertilization, and subsequently, performance tests were executed to calibrate the lag distance of falling fertilizer, as well as the response time of actuators and the error of feed fertilization flow. The test results indicated that for actuators A, B, and C, the average lag distance of falling fertilization was in the order LA > LC > LB, with the respective values being 3.56, 2.72, and 1.85 m; the corresponding lag correction times were 1.99, 1.74, and 1.48 s, respectively. A positive proportional relation was noted between the application increment and response time of apparatus execution, and TBi > TCi > TAi (i denotes the corresponding feed fertilization flow). Furthermore, the error of fertilization flow first decreased and then increased with the increasing application rate; the extremum appeared between 250g/s and 380g/s, and γBi > γAi > γCi. The feed fertilizer with structure C was optimized and integrated field validation tests, and incorporating the corresponding correction time of lagging response Tlag = 1.74 s into the control system, the mean error of variable-rate fertilization system was determined as 9.67%, and the average lag distance of fertilization was 0.37 m. This indicated that the control system of variable-rate fertilization with correction response time alleviated the problem of lag falling fertilizing, improved the response speed of variable-rate fertilization for rice, and helped achieved better fertilization accuracy.

Wolfberry tree dual-model detection method and orchard target-oriented fertilization system based on photoelectric sensors

Orchard target-oriented fertilizing with on-board sensor technology can improve fertilizer efficiency and reduce environmental pollution. Photoelectric sensors are widely used for object detection because of their low cost and fast response time. This paper presents a Wolfberry tree dual-model detection method and the design of an orchard target-oriented variable-rate fertilization system based on photoelectric sensors. The dual-model detection method includes the Trunk Detection Model (TDM) and Canopy Detection Model (CDM), which can be applied for Wolfberry orchards at the green cluster and mature stages, respectively. A target-oriented fertilization system was designed using the dual-model method, and tested in the lab and Chinese Wolfberry orchard. The laboratory test results showed that the average center offset distances on the condition of detecting trunks, continuous canopies, and discontinuous canopies were 4.1 cm, 9.1 cm and 13.1 cm, respectively. The system could ignore the signals from canes when their diameters were less than 16 mm, and also could determine the gaps within a tree when they were less than 21 cm. The orchard test results showed that the system accomplished target-oriented fertilization 95 times for 92 trees at the mature stage. The results indicated that the dual-model detection method could be used for Wolfberry trees or other trees with similar canopy changes at different growth stages. Keywords: orchard fertilizer, target-oriented fertilization, variable rate fertilization, photoelectric sensor, wolfberry orchard DOI: 10.25165/j.ijabe.20181104.3614 Citation: Yang S, Zhai C Y, Long J, Zhang B, Li H Z. Wolfberry tree dual-model detection method and orchard target-oriented fertilization system based on photoelectric sensors. Int J Agric & Biol Eng, 2018; 11(4): 65-73.

A fixed-amount and variable-rate fertilizer applicator based on pulse width modulation

Fertilizer plays a significant role in increasing crops quality. When fertilizer users use inappropriate fertilization practices in fields, it brings nutrient waste, large investment and residue in soil. The purpose of the present paper is to develop a fixed-amount and variable-rate fertilizer applicator with a vertical spiral conveyor to minimize this risk. As for row replacement, high accurate and uniform application patterns from a reliable fertilizer applicator for precision farming are required. This applicator includes a speed measure unit and a fixed-amount and variable-rate Pulse Width Modulation control system. In order to evaluate our fertilizer applicator, its performance was tested in both laboratory and field. The findings of this study suggest that the applicator with a vertical spiral conveyor and a variable-rate pulse width modulation control system makes fewer errors during application. To guarantee the degree of accuracy of this applicator, the linearity between travel speed and amount of fertilizer is essential. Both of the applicator tests revealed that using the applicator was a positive experience because it can preset expected consumption by operator and always keep amount of fertilizer uniform and accurate while traveling, and it will be widely used in Southwest China.

Precision for Smallholder Farmers: A Small-Scale-Tailored Variable Rate Fertilizer Application Kit

Precision agriculture technology at the hands of smallholder farmers in the developing world is often deemed far-fetched. Low-resource farmers, however, are the most susceptible to negative changes in the environment. Providing these farmers with the right tools to mitigate adversity and to gain greater control of the production process could unlock their potential and support rural communities to meet the increasing global food demand. In this study, a real-time variable rate fertilizer application system was developed and tested as an add-on kit to conventional farm machinery. In the context of low investment costs for smallholder farmers, high user-friendliness and easy installment were the main concerns for the system to be viable. The system used nitrogen (N)-sensors to assess the plant nutrient status on the spot and subsequently adjust the amount of fertilizer deposited according to the plant’s needs. Test bench trials showed that the add-on kit performed well with basic operations, but more precision is required. Variability between N-sensors and metering systems, combined with power fluctuations, created inaccuracies in the resulting application rate. Nevertheless, this work is a stepping stone towards catalyzing the elaboration of more cutting-edge precision solutions to support small-scale farmers to become successful, high producing agro-entrepreneurs.

Nutrient quantification in fresh and dried mixtures of ryegrass and clover leaves using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is an analytical technique that can be used to facilitate variable rate fertilizer application, potentially increasing yield, reducing costs and reducing environmental side effects of nutrient loss. LIBS can give real-time information about macro and micro nutrients with little to no sample preparation. The study reported in this paper investigated whether LIBS can predict nutrient levels of fresh and dried pelletized pasture and what the limitations are. Spectra were acquired in air and under argon. Partial least square regression was used to build models for each macro and micro nutrient. The best results were for potassium, sodium and manganese with root mean square errors of cross-validation of 0.20, 0.029 and 0.0008 wt%, respectively, coefficient of determination of 0.92, 0.93 and 0.90, limits of detection of 0.99, 0.11 and 0.0027 wt%, and precisions of 0.30, 0.042 and 0.0012 wt%. LIBS can be used to assess nutrient levels of fresh pasture. Reducing the shot-to-shot variation will lead to improved calibrations.

Response characteristics and efficiency of variable rate fertilization based on spectral reflectance

The key technical problem of variable rate fertilization system based on spectrum information was precise variable fertilization in certain area according to the acquired spectrum information. Hysteretic fertilizing is a critical problem in most of current fertilizer equipment. Hysteresis model was built and analyzed in this study to improve the system. Fertilizing tests were conducted on different wheat breeds and the results were analyzed. The tests showed that variable rate fertilization had obvious hysteresis phenomenon with the maximum lag distance of 3.82 m, the minimum lag distance of 1.73 m and average of 3.06 m. Hysteresis phenomenon of the variable rate fertilization system was obviously decreased when implanting a correction time of 2.04 s with the maximum lag distance of 0.61 m. Variable effects varied by different wheat breeds. Variable rate fertilization had an advantage of improving spatial differences of Yangmai-23, and the spatial variability of which decreased by 14.23%. In the small test area, the amount of fertilizer in Zhenmai-168 decreased by 2.84 kg, while the amount of which in Yangmai-23 increased by 3.83 kg. Yield of Zhenmai-168 in small area was lower than that in traditional pattern, but the condition of Yangmai-23 was on the contrary. Valuable information for increasing performance of fertilization in variable rate fertilization system was provided in this paper. Keywords: variable rate fertilization, fertilization lag, calibration, fertilization efficiency, winter wheat DOI: 10.25165/j.ijabe.20181106.4086 Citation: Chen M, Yang Z J, Wang X C, Shi Y Y, Zhang Y. Response characteristics and efficiency of variable rate fertilization based on spectral reflectance. Int J Agric & Biol Eng, 2018; 11(6): 152–158.

Optimal Structure Design and Performance Tests of Seed metering Device with Fluted Rollers for Precision Wheat Seeding Machine

In view of drawbacks of the seed metering device with fluted roller, which is widely applied in wheat drill seeding, we provided an optimized design of structure based on basic structures of traditional devices, which usually have the disadvantages of poor adjustability of working parameters, poor working performance with consistency, a relatively higher error of output quantity of sowing, etc.. The main working parameters of the new designed seed metering device, such as opening of fluted roller, and sowing clearance between brush and fluted roller, are accurately adjustable. The main innovation points of the new device are as follow: 1. A new mode of adjusting the opening of fluted rollers by ‘opening adjustment mechanism’ which can effectively solve the problem of poor consistency of opening adjustment. 2. A "7"-shaped brush installation mechanism was designed to accurately locate the brush installation position and accurately adjust the sowing clearance between fluted roller and brush. This design improves the operating accuracy and stability. 3. A combined-type structure of the fluted roller, which is convenient to replace the fluted rollers by hand, which improved the adaptability of the seed metering device. The indoor and in-field performance tests of the designed seed metering device were carried out respectively. 10 seed metering devices were installed on a test platform to run at rotation speed from 2 to 30 r/min during the indoor tests. The average variable coefficient of seeding quantity was 2.3%, the maximum variable coefficient was 3.6%, the standard deviation of variable coefficient was 0.57%. While during the tests in field, 3 levels of target sowing quantity (225kg/hm2,300kg/hm2,375kg/hm2) and 2 levels of vehicle speeds (approximately 2Km/h and 3Km/h respectively ) were set to carry out two-factor cross experiments. 10 seed metering device were installed on a rotary cultivator platform which was driven by a 62.5Kw tractor. The average variable coefficient of seeding quantity was 2.6%, the maximum variable coefficient was 3.8%, the standard deviation of variable coefficient was 0.56%. The test results showed that the performance of the designed seed metering device has high stability and consistency, related research results can be applied to fertilizing in field and provide technical support for the precision seeding and variable rate fertilization, which has a good application prospect in precision agriculture.

Fertilizer sowing simulation of a variable-rate fertilizer applicator based on EDEM

The simulation for a variable fertilization machine could help to show the fertilizing result and provide theoretical guidance in reality machine operation. EDEM (Extended distinct element method) which is a general-purpose software for simulating and analyzing particle system is widely used in simulation experiments of fertilizing machines. In order to optimal design of a variable-rate fertilizer machine. This paper uses EDEM to simulate the spread of three kinds of fertilizers which are potassium chloride, potassium sulfate and urea, commonly used in agriculture, by a centrifugal disc type variable-rate fertilizer applicator. After analysis, the variation coefficients of the lateral homogeneity of the three fertilizers are 43.34%, 26.26% and 39.21%, respectively. The result shows that simulation effect of these three fertilizers is not up to standard, and further research is needed to improve the performance of the fertilizer machine.

Variable Fertilizer Recommendation by Image-based Grass Growth Status

Objective of this research was to recommend variable rate fertilization for sod production fields depending on the site-specific grass growth levels. CCD based images were acquired from three different sod production fields and calibration relationships were obtained between the sensor measurements and grass growth levels. Based on the calibrations, fertilizer recommendation was derived based on the expert experience. For analysis of the spatial variation of growth level and mapping, geostatistical methods such as variogram modeling and Kriging were used. A range of 0.5 to 1, 0.5 to 1.5, and 2 to 4 levels of fertilizers were recommended for the sod production fields with 90%, 70%, and 50% grass growth coverage. This study would contribute greatly to increase fertilizer use efficiency and reduce environmental contamination, if the recommended fertilizers were variably applied.

Fertilization strategy and application model using a centrifugal variable-rate fertilizer spreader

Fertilization strategy and application model using a centrifugal variable-rate fertilizer spreader

Nutrient content monitoring of potato plant based on spectrum device

The nutrient estimation is an important basis for water and fertilizer management in the field. In order to achieve crop nutrient content for variable-rate fertilization, a spectrum device based on the Ocean Optics STS-VIS sensor was developed to measure the spectral reflectance at 350-800 nm. The spectral reflectance data could be measured by optical sensor, data transmission module and the controller. The control software was developed with functions such as acquisition parameters, acquisition control and data management. Before the field application, the calibration experiments were conducted. The correlation was analyzed between the developed device and ASD Field Spec Hand Held 2. The result showed that the average correlation coefficient value was 0.94. It was used to detect the chlorophyll and moisture content of potato plant. The SPAD regression model was established and the determinant coefficient R2 was 0.484, moisture content regression model was established and R2 was 0.735. Results showed that the device has a certain ability to predict chlorophyll content and moisture content of potato leaf.

Numerical simulation of spreading performance and distribution pattern of centrifugal variable-rate fertilizer applicator based on DEM software

Farmers in China have been concerned with the efficiency and utilization rate of fertilizers, because of the rigorous implementation of China’s “dual-reduction” plan, which calls for reducing fertilizer and pesticide usage. This study was aimed to improve the spreading performance and fertilizer distribution uniformity of an independently developed centrifugal variable-rate fertilizer applicator. The spreading performance was evaluated by conducting discrete-element-simulation tests, and the relationship between the variations in the fertilizer particle distribution and the working parameters of the fertilizer spreader was analyzed. The quality of the particles was evaluated using a two-dimensional matrix, and the coefficient of variation of the transverse distribution of the fertilizer particles was determined. The results show that the shape of the distribution varies irregularly with the increase in the vane pitch angle, and the coefficient of variation decreases with the increase in the spreader disc height. Further, when the application flow rate is increased gradually, the coefficient of variation decreases rapidly first but gradually thereafter. In addition, with an increase in the rotational speed of the disc, the distribution gradually changes from a triangular shape to a W shape and ultimately to an M shape. The average coefficient of variation was the lowest (14.39%) for a single-row application flow rate of 300 g/s, a vane pitch angle of 15°, a spreader disc height of 95 cm, and a rotational speed of 600 r/min, with a good spreading uniformity. Field validation tests show that the average coefficient of variation with respect to the effective spreading swath width of the applicator was 16.74%. The relative error was 10.66% with respect to the simulation results, thus validating the simulation model and confirming its accuracy. The results show that the coefficient of variation for the developed variable-rate spreader is reduced, exhibiting a high spreading performance. The results serve as a theoretical basis for farmers for altering their traditional empirical fertilization techniques and should aid design and optimization of centrifugal variable-rate fertilizer applicators.