Variable Fertilizer Application Research Articles

Design and Development of Variable Rate Metering System for Fertilizer Application

A variable rate fertilizer metering mechanism was designed by changing the speed of the feed shaft for use in variable rate fertilizer applicator. A micro-controller unit programmed with a Pulse Width Modulation (PWM) motor driver was used to run the feed shaft for varying speeds. Two types of fluted rollers (straight and helical flute) were used with varying number of flutes having same volume for each fluted roller. No significant difference in discharge rate between helical and straight fluted roller was observed with varying number of flutes (6, 8, 10, and 12). However the discharge rate of SSP fertilizer was significantly higher than that for DAP. Also, significant difference was observed in applied torque and power requirement for straight and helical flute.

Estimation of Sensor-based site specific variable rate fertilizer application for maize (Zea mays L.) crop

Optical spectrometry sensors in crops offer a remarkable technological breakthrough in the field of variable-rate nitrogen fertilization. A field study was conducted during rainy (kharif) season of 2021 at the research farm of the Agricultural Engineering College and Research Institute Tamil Nadu Agricultural University Coimbatore to estimate maize crop nitrogen (N), Normalized Difference Vegetation Index (NDVI) value and chlorophyll content in hybrid maize COH (M) 8. Fertilizers were administered to the plots following the recommendations (250:75:75 kg NPK ha-1) given under Soil Test Crop Response, with a goal yield of 9t ha-1 predicted based on the initial soil available N, P, and K values. The experimental findings revealed a significant impact of nitrogen rate (P<0.001) on the percentage of nitrogen content in the leaves (% N leaf content). Additionally, there was a decrease in maize leaf chlorophyll content index over time, with ranges of 32.96 to 50.57, 28.78 to 41.78, 24.81 to 35.86, 22.12 to 28.54, and 14.34 to 20.56. On the contrary, the NDVI experienced an increase throughout the season, with ranges of 0.32 to 0.49, 0.30 to 0.55, 0.28 to 0.66, 0.46 to 0.88, and 0.56 to 0.84. The study will help foster sustainability within modern intensive farming practices by emphasizing the importance of reducing environmental pollution caused by applying Sensor-based site-specific nitrogen fertilizer for maize crop.

Understanding farmer views of precision agriculture profitability in the U.S. Midwest

Precision Agriculture (PA) technologies are well known to be useful in addressing field heterogeneities and enabling informed site-specific management decisions. While profitability is the foremost factor considered by farmers when making PA adoption decisions, information in this regard is lacking from the farmers' perspective. This paper analyzed 1119 farmer responses from a 2021 survey conducted in four states along the western margins of the U.S. Midwest. Our findings show that while most (around 60%) non-adopters indicate that they are unaware of PA profit change, adopters are likely to rate a major profit increase. About two thirds of adopters rated at least a 5% increase in profitability towards variable rate (VR) fertilizer application (72%), VR seed application (68%), and automatic section control (66%). We modeled farmers' profit change subsequent to PA adoptions. Our regression results demonstrate that the profits from PA usage increase over time and that use of conservation practices likely influences PA profitability in a positive way. As soil quality and weather factors also affect profit ratings, it would be beneficial to compare and demonstrate profitability potential of various PA technologies on a regional basis and tailor the promotion efforts to farmers most likely to benefit from them.

Potential of existing strategies to reduce net anthropogenic inputs of phosphorus to land in the United States

Improving phosphorus (P) management is important for both ecosystem protection and avoiding mineable P scarcity. In order to inform the development of impactful solutions to both of these issues, we assessed the potential of several specific management strategies to reduce demand for new mined P in fertilizers and supplements for livestock, thereby reducing net P inputs to land. The strategies assessed were variable rate fertilizer (VRF) application, improvements to P digestibility for livestock, efficient utilization of manure and wastewater treatment (WWT) P, and elimination of avoidable domestic food waste. The potential of these strategies to reduce net anthropogenic P inputs was assessed at the county level for the coterminous US using the commodity-specific net anthropogenic P and nitrogen inputs (CSNAPNI) model. The largest contributions toward eliminating NAPI in the US can come from efficient manure utilization either at national (30%–50% NAPI reduction) or county-level (21%–30% NAPI reduction). However, widespread adoption of VRF (10%–41% NAPI reduction), and all other strategies considered (5% or greater NAPI reductions each) could make significant contributions. In combinations of strategies that included VRF or P digestibility improvements, negative feedbacks occurred. VRF reduced demand for fertilizer, thereby reducing the potential for efficient manure and WWT P utilization at the county-level. P digestibility improvements in poultry and swine diets reduced the expected production of recoverable manure P by 36%, decreasing the total manure P that could be used to replace mined P fertilizer. However, P digestibility improvements also reduced county-level excess manure P by 25%. Prior studies have focused on quantifying P inputs or the potential of in-situ best management practices to reduce losses to water, but strategies to reduce P inputs are understudied.

Variable rate fertilizer application technology for nutrient management: A review

Variable rate fertilizer application technology for nutrient management: A review

Efficiency analysis and evaluation of centrifugal variable-rate fertilizer spreading based on real-time spectral information on rice

Investigations regarding the use of centrifugal variable-rate fertilizer spreaders and their impact on agriculture production has become increasingly important for determining the effects and economic benefits of precision agriculture variable-rate fertilizer technology applied in the rice-and-wheat rotation areas of the middle and lower reaches of the Yangtze River in China. This study examines a self-developed centrifugal variable-rate fertilizer spreader based on real-time growth information of rice and wheat focusing on rice variety Nanjing 9108 as its research object. Field tests of variable-rate fertilizer application (compound fertilizer) were conducted in the Dongtai rice planting base, Jiangsu Province. Different areas were set up for artificial fertilizer spreading, traditional empirical balanced spreading, and real-time variable-rate spreading. The fertilizer application rates, rice growths, and yields of these fertilizer spreading methods for three consecutive years were compared and analyzed. Furthermore, the operational effectiveness of centrifugal variable-rate spreading was evaluated via partial budget analysis. The experimental results showed that the spreading application rate for the real-time variable-rate fertilization area decreased year by year by approximately 47.64 kg/hm2, whereas the application rate per unit area was reduced by approximately 15.88 %, compared with those for the traditional empirical balanced fertilization area. After the application of topdressing tillering fertilizer, rice growth in the real-time variable-rate fertilization area was better than in the others, whereas the spatial difference in its population structure was the lowest. There were differences in rice yield among the experimental areas: the average yield of the variable-rate fertilization area was 8996.70 kg/hm2, which was 5.93 % higher than that of the traditional empirical balanced fertilization area. According to the operational effectiveness analysis of real-time variable-rate fertilizer application in rice production, its fertilizer cost was only 504.72 RMB/hm2, whereas its yield profit was 17993.40 RMB/hm2. Thus, the fertilizer cost was reduced by 95.28 RMB/hm2, whereas the yield profit was increased by 1007.62 RMB/hm2, compared with those of the traditional empirical balanced fertilizer application. To sum up, this investigation verified that the newly developed centrifugal variable-rate fertilizer spreader, using real-time variable-rate fertilizer, can save on fertilizer and reduce its application, improve the population structure and spatial difference in crop growth, help increase crop yield and degree of balance, and produce economic, ecological, and social benefits. This study can provide a theoretical reference for promoting the pilot application of variable-rate fertilization technology in the rice-and-wheat rotation areas of the middle and lower reaches of the Yangtze River.

Research on Precise Fertilization Method of Rice Tillering Stage Based on UAV Hyperspectral Remote Sensing Prescription Map

Tillering fertilization is an important part of field management in rice production. As the first peak fertilizer requirement period of rice, tillering fertilization directly affects the number of tillers and the growth of rice in the middle and late stages. In order to investigate a method of constructing an accurate fertilizer prescription map in the tillering stage using an unmanned aerial vehicle (UAV) remote sensing nitrogen demand diagnosis and reduce the amount of chemical fertilizer while ensuring the rice yield, this study realized the diagnosis of the rice nitrogen nutrient demand using UAV hyperspectral remote sensing during the tilling stage fertilization window. The results showed that the fertilizer amount was determined using the characteristic waveband and remote sensing. The results showed that five rice hyperspectral variables were extracted in the range of 450–950 nm by the feature band selection and feature extraction for the inversion of rice nitrogen content, and the inversion model of rice nitrogen content constructed by the whale-optimized extreme learning machine (WOA-ELM) was better than that constructed by the whale-optimized extreme learning machine (ELM). The model coefficient of determination was 0.899 and the prescription map variable fertilizer application method based on the nitrogen content inversion results reduced the nitrogen fertilizer by 23.21%. The results of the study can provide data and a model basis for precise variable fertilizer tracking by agricultural drones in the cold rice tillering stage.

Performance Assessment of a Sensor-Based Variable-Rate Real-Time Fertilizer Applicator for Rice Crop

Variable-rate technology (VRT) may reduce input costs, increase crop productivity and quality, and help to protect the environment. The present study was conducted to evaluate the performance of a variable-rate fertilizer applicator for rice (Oryza sativa L.). Three replications were conducted, each of which was divided into four plots. Field performance of the system was assessed at different nitrogen levels (N1 to N4, i.e., 75, 125, 175, 225 kg ha−1), growth stages (tillering, panicle initiation, heading), and heights (40, 60, 80, 100 cm) of the sensor from the crop canopy. Fertilizer rate was at minimum 12.59 kg ha−1 at 10 rpm of drive-shaft rotational speed and at maximum 50.41 kg ha−1 at 40 rpm. The system response time was within the range of 3.53 to 4.93 s, with overall error ranging between 0.83% to 4.92%. Across different growth stages, when fertilizer rate was increased from N1 to N4, NDVI increased from 0.49 to 0.69. Hence, drive-shaft rotational speed is decreased from 25 to 7 rpm to shift the application rate from 30.83 to 9.15 kg ha−1. There was a 45% reduction in total fertilizer rate applied by the system, with respect to the recommended rate.

Single-Neuron PID UAV Variable Fertilizer Application Control System Based on a Weighted Coefficient Learning Correction

Agricultural unmanned aerial vehicles (UAVs), which are a new type of fertilizer application technology, have been rapidly developed internationally. This study combines the agronomic characteristics of rice fertilization with weighted coefficient learning-modified single-neuron adaptive proportional–integral–differential (PID) control technology to study and design an aerial real-time variable fertilizer application control system that is suitable for rice field operations in northern China. The nitrogen deficiency at the target plot is obtained from a map based on a fertilizer prescription map, and the amount of fertilizer is calculated by a variable fertilizer application algorithm. The advantages and disadvantages of the two control algorithms are analyzed by a MATLAB simulation in an indoor test, which is integrated into the spreading system to test the effect of actual spreading. A three-factor, three-level orthogonal test of fertilizer-spreading performance is designed for an outdoor test, and the coefficient of variation of particle distribution Cv (a) as well as the relative error of fertilizer application λ (b) are the evaluation indices. The spreading performance of the spreading system is the best and can effectively achieve accurate variable fertilizer application when the baffle opening is 4%, spreading disc speed is 600 r/min, and flight height is 2 m, with a and b of evaluation indexes of 11.98% and 7.02%, respectively. The control error of the spreading volume is 7.30%, and the monitoring error of the speed measurement module is less than 30 r/min. The results show that the centrifugal variable fertilizer spreader improves the uniformity of fertilizer spreading and the accuracy of fertilizer application, which enhances the spreading performance of the centrifugal variable fertilizer spreader.

Calibration and Testing of Discrete Element Simulation Parameters for Urea Particles

The lack of accurate simulation model parameters in the optimization design process of variable fertilizer application devices has resulted in large errors between simulation and theoretical calculation results, which has restricted the development of variable fertilizer application devices to a certain extent. Additionally, there are few scholars studying urea granules, so many parameters of urea granular fertilizer cannot be directly obtained from the literature. The aim of this study is to calibrate a set of simulation parameters by combining physical and simulation tests. In this study, intrinsic parameters were systematically determined, including the particle size, particle density, elastic modulus, Poisson’s ratio and their static friction coefficients, rolling friction coefficients and restitution coefficients of urea particles. By performing the urea particle stacking test, the static friction coefficient between urea particles was calibrated to 0.27, and the rolling friction coefficient between particles was 0.11. To check the reliability of the calibration parameters, the simulation and physical tests of the repose angle and bulk density of urea particles were compared, and the results show that the relative error of repose angles and bulk density of urea particles was 0.78% and 1.19%, respectively. Through the simulation of the mechanical variable fertilizer discharger and the comparison test of the benchtop fertilizer discharging performance, the maximum relative error between the simulation and physical test fertilizer discharge is 3.69% when the working length of the outer sheave is 25 mm; the maximum relative error between the simulation and physical test fertilizer discharge is 3.39% when the working length is 35 mm; the maximum relative error between the simulation and physical test fertilizer discharge is 6.86% when the working length is 45 mm; the maximum relative error between the simulation and physical test fertilizer discharge is 4.95% when the working length is 55 mm. The maximum relative error between the simulated and physical test fertilizer discharge was 6.86% at 45 mm opening and 4.95% at 55 mm opening, and the results show that the urea particle calibration parameters are reliable. The results of this study can provide a theoretical reference for the optimization design and simulation study of variable fertilizer application devices.

Feasibility of variable rate application of diammonium phosphate fertilizer to wheat crop under center pivot irrigation system

A study was conducted, on a 30 ha wheat field under a solar energy powered center pivot irrigation system in a commercial farm located 400 km north of Khartoum, Sudan, to evaluate the feasibility of variable rate fertilizer application of Diammonium Phosphate (DAP) on wheat crop based on variable soil phosphorus content. Soil phosphorus content was divided into three categories (low: 3.75 to 4.50 ppm, medium: 4.51 to 5.25 ppm and high: 5.26 to 6.00 ppm) and a GIS soil phosphorus content map of the experimental field was generated. Three variable application rates (200 kg ha−1, 160 kg ha−1 and 120 kg ha−1) of granular DAP fertilizer were determined to fit the low, medium and high soil phosphorus contents, respectively. The the DAP fertilizer rate of 200 kg ha−1 was the rate practiced for wheat production in the experimental farm.The normalized Difference Vegetation Index (NDVI), measured at different wheat growth stages using sentinel-2 satellite images, and wheat grain yield were used to evaluate the response of wheat crop to the variable DAP fertilizer application rates. Excluding the tillering stage, the results showed significant differences in the NDVI values among different soil phosphorus levels and DAP fertilizer application rates at other growth stages, including stem elongation, grain filling and maturity stages. Moreover, wheat yield results showed significant differences among different soil phosphorus contents (P > F = 0.0001) and DAP fertilizer application rates (P > F = 0.0457). On the average, the highest yield of 2.449 t ha−1 was recorded in the field areas treated with the high DAP fertilizer application rate (200 kg ha−1), where the second highest yield of 2.441 t ha−1 was observed in field areas under the medium DAP fertilizer application rate (160 kg ha−1); however, no significant differences between these two yield values. Based on these results, the total savings of the DAP fertilizer was estimated to be 792 kg (equivalent to 475.2 $) in the experimental field (30 ha), only when the medium DAP fertilizer rate (160 kg ha−1) was used in the medium and high soil phosphorus zones, saving 15.84 $ ha−1 without affecting production.

Investigation of the Influencing Factors of Fertilizer Dropping Time for a Variable-rate Fertilizer Applicator

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.

РАЗРАБОТКА ЦЕНТРОБЕЖНОГО РАБОЧЕГО ОРГАНА РАЗБРАСЫВАТЕЛЯ МИНЕРАЛЬНЫХ УДОБРЕНИЙ

In variable-rate application of solid mineral fertilizers (SMF), working units of centrifugal fertilizer distributors can regulate precisely the application rate and evenly distribute pellets over the fi eld. To determine the most rational parameters and modes of a solid fertilizer distributor, infl uencing the fl ight path of pellets and the uniformity of their distribution over the fi eld, the authors carried out theoretical and experimental research of a centrifugal disc of a solid fertilizer distributor equipped with a rotary acceleration chamber and a set of exchangeable U-shaped blades. The authors describe the infl uence of the blade length on the trajectory and the fl ight distance of the fertilizer pellets as well as the infl uence of the rotation of the dispersal chamber outlet window on the fertilizer distribution pattern. The experiment on determining aerodynamic properties of the nitroammonium phosphate pellets (60:60:60) was carried out using the developed laboratory bench of the solid fertilizer distributor. The experiment allowed determining the physical parameters of pellets infl uencing the range and trajectory of their fl ight - the winglet ratio and the critical speed. It was found that the rotation displacement of the dispersal chamber outlet window of the spreading disc leads to the displacement of the intensive coverage zone in the direction of the window rotation. This makes it possible to regulate the intensity and has a direct impact on the distribution zone of solid mineral fertilizers. The paper justifi es the most rational design of the spreading disc. The research proved that the greatest uniformity of solid mineral fertilizer spreading is observed when using a disk with eight paired coaxially located blades with a length of 300, 250, 200, and 100 mm.

Precision Agricultural Technologies for enhancing crop productivity: A way forward to Sri Lankan Agriculture

Precision agriculture (PA) is an information-based production technology that manages spatial and temporal variability within a farming system to optimize its productivity and profitability while ensuring the sustainability of land resources. Today, several sophisticated technologies such as robotics, wireless sensor networks (WSN), aerial images, a global positioning system (GPS), global navigation satellite system (GNSS), smart mobile devices, internet of things (IoT), variable rate application (VRA), weather modelling, radio-frequency identification (RFI) are greeted with PA at a global scale. An exponentially increasing trend in adoption can be seen in developed countries such as the USA, Canada, Australia, and European countries, but to a limited extent in some developing countries. The degree of adoption of PA varies on economic, social, and geographic factors such as the scale of production, input cost, and features of the technology. Developing economies like Sri Lanka, where small-scale food crop agriculture is dominating, have the potential to benefit from precision agricultural technologies (PATs) to a greater extent. Relatively low-cost but effective PATs that would fit well with small-farm production units are emerging globally. Providing small farming units with the correct tools and greater control of the production process would support such farming communities, unlocking their potential and meeting the ever-increasing national and global food demand. Land laser levelling, real-time variable-rate fertilizer and pesticide application, mechanical harvesting and low-cost IoT-based crop management systems for protected agriculture are the most promising PATs that have great potential in Sri Lanka. This review presents a global overview of PA technologies for enhancing food crop production and their benefits, the adoption of PA technologies by different countries and the constraints, and the role of PA in Sri Lankan Agriculture, past and present. Finally, the synthesis and way forward.

Energy Efficiency of Variable Rate Fertilizer Application in Coffee Production in Brazil

Coffee is a crop of great relevance in socioeconomic terms for Brazilian agribusiness, which is the world’s largest producer in cultivated areas. The implementation of precision agriculture in the coffee culture has provided countless benefits to its development, which over the years has been cultivated in the same area. However, there is a lack of studies that address the impact of the application of variable-rates inputs in soil on the energy efficiency and sustainability of these systems. This study aimed to analyze how variable-rate fertilization influences energy efficiency in coffee growing. A production area subjected to variable and fixed rates of fertilizer in alternating rows was evaluated. Geo-referenced yield data was collected to assess yield response for fixed and variable rate applications. The energy assessment was combined with the Geographic Information System (GIS) to determine site-specific energy indicators. To determine the energy flow, only NPK fertilizer applications were considered as inputs and the yield as output. The results obtained indicated that the variable rate fertilizer application has a small difference, indicating greater energy efficiency concerning the applied fertilizer and coffee production per crop season. It was observed in the 06/07 crop, the incorporated energy was 10.7 MJ kg−1 for VR and 10.2 MJ kg−1 for UR and for the 07/08 crop it was 30.7 MJ kg−1 for VR and 34.9 MJ kg−1 for UR. The energy balance was more efficient at variable rates, as it provided fertilizer savings without compromising yield. However, the difference between the embodied energy per mass of coffee produced was very small compared to the fixed rate.

Design and Development of a Variable Rate Applicator for Real-Time Application of Fertilizer

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.

Comparative Appraisal of Three Low-Cost GPS Speed Sensors with Different Data Update Frequencies

Low-cost GPS (Global Positioning System) speed sensors have been available to quantify vehicle speed on different platforms including agricultural tractors in precision agriculture applications such as yield monitoring, variable rate fertilizer and pesticide applications. One of the advances in low-cost GPS receivers is the higher data update frequencies. However, we found no studies on the accuracy of low-cost GPS speed sensors with different update frequencies, especially under variable speed conditions. Thus, this work investigated the effect of the update frequency on the accuracy of low-cost GPS speed sensors under both constant and varying speed conditions. Three GPS speed sensors with update frequencies of 1 Hz, 5 Hz and 7 Hz (GPS1Hz, GPS5Hz and GPS7Hz) were simultaneously tested under the same conditions. A total of 144 tests were conducted on three different days and at three different times of each day with four speed levels and four repetitions. The percent errors were found to be up to 2.3%, 1.8% and 1.4% at constant speeds; up to −47%, −16% and −12% at the increasing speeds and 24%, 6% and 5% at the decreasing speeds, depending on the acceleration and deceleration levels, for GPS1Hz, GPS5Hz and GPS7Hz, respectively. The differences among the error values of the GPS speed sensors were found to be statistically significant (p < 0.05). The GPS speed sensors with higher update frequencies (5 and 7 Hz) provided higher accuracy compared to the one with lower frequency (1 Hz), particularly in the case of higher acceleration conditions. In sum, low-cost GPS speed sensors with higher update frequencies should be used for better accuracy, especially in variable speed conditions.

Identifying hotspots and representative monitoring locations of field scale N2O emissions from agricultural soils: A time stability analysis

Greenhouse gas sampling from agricultural fields is laborious and time-consuming. Soil and topographical heterogeneity cause spatiotemporal variations, making nitrous oxide (N2O) estimation and management a challenge. Identification of representative monitoring locations, hotspots, and coldspots could facilitate the mitigation of agricultural N2O emissions. The objective of this study was to identify and characterize representative monitoring locations, hotspots, and coldspots of N2O emissions in agricultural fields (Baggs farm; BF and Research North farm; RN) in Cambridge, Ontario, Canada, under humid continental climate. Soil in both fields was classified as Orthic Melanic Brunisol, with some areas categorized as Gleyed Brunisolic Gray Brown Luvisol and Orthic Humic Gleysol. In total, 28 sampling points were selected following conditional Latin hypercube design using topographical parameters (digital elevation, slope, topographical wetness index, and Pennock landform classification). Gas samples were collected over a two-year crop rotation with corn (2019) and soybean (2020). Additional sampling was conducted at BF at spring thaw (2020). Time stability analysis using mean relative difference (MRD) and standard deviation of mean relative difference (SDRD) was performed to test the hypothesis that “simultaneous analysis of spatiotemporal variations in N2O emissions could help to identify and characterize representative monitoring locations, hotspots, coldspots and areas with few hot and cold moments. Most of the hotspots were located at shoulder positions, coldspots, and cold moments at backslope, and representative monitoring points were located at leveled positions or localized depressions. Time stability analysis coupled with multivariate groping analysis supported our hypothesis and helped successfully identify hotspots, coldspots, and representative locations based on landform classification with few exceptions. However, inclusion of additional topographical (curvature, contributing area, aspect) and morphological parameters (texture, thickness of soil horizon, depth to bedrock, and water table) are suggested for consideration in future research to manage variable-rate fertilizer application and mitigate N2O hotspots at landscape level.

On-The-Go Variable Rate Fertilizer Application Method for Rice Through Classification of Crop Nitrogen Nutrition Index (NNI)

The standard practice among rice farmers in Malaysia is to apply fertilizer using a single application rate for the whole field. However, fertility conditions vary across the field. The excess use of fertilizer leads to increased input cost and can be damaging to the environment. The focus of this research was to develop a method to apply fertilizer on-the-go while sensing the crop nutrient status of rice plants. A machine learning approach was used to develop a crop nitrogen status prediction model. The model used spectral data from an active canopy reflectance sensor and several vegetation indices as inputs. The model was then incorporated into an on-the-go variable rate fertilizer application system. System performance was then evaluated in the field. The results from this work showed that the model had and accuracy of 83% in classifying the nitrogen status of the rice plants. The results also showed that our method was able to save up to 20% fertilizer use while maintaining yield. These findings are important for large estate farmers who are looking to increase productivity and efficiency.

GPS and Sensor Based Technologies in Variable Rate Fertilizer Application

With an average consumption of 165.8 kg per hectare, India stands as the third-largest producer and consumer of fertilizer in the world. Farmers practice traditional methods to apply fertilizers uniformly throughout the field. This uniform and constant rate application of fertilizer is inefficient and mostly leads to over-fertilizing certain areas and at the same time, under-fertilizing others, not meeting the actual nutrient demand. Variable-rate fertilizer application (VRFA) is the process of applying various rates of crop nutrients by synchronizing existing machinery with mechatronics according to the variability within any agricultural field. One such effort are to be made to develop VRFA systems to meet the soil and plant needs. A variable rate fertilizer application (VRFA) system based on a digital map was developed in Kharagpur and achieved an appreciable target application rate at selected grid points (Chandel et al., 2016). The system was effective, accurate and showed quick response to target application rates with a negligible time lag. The coefficient of variation at all the outlets was in the range of 11.7–15.0 percent. The system was able to meet the target fertilizer application rate with a variation of up to 15 percent for a grid resolution of 8×8 m. Another VRFA system was developed for controlling the amount of fertilizer that works by measuring the NDVI of crops using an optical sensor (Zhang et al. 2014). This type of VRFA system does not use prescription maps but relies on sensors to provide real-time crop detection. The coefficient of variation was ranging from 0.35 to 2.67 percent and elapsed a response time of less than 0.875 s. The system helps in maintaining desired application rate by making real-time adjustments with on-the-go monitoring. It is revealed that the use of VRFA system helped to improve input use efficiency and decrease the negative effect on the environment. Thus, it is a promising technology through which the performance of a unit area could be tracked, mapped and analyzed. Also, the farmer will be able to know the exact production of each part of the field.