Variable Rate Fertilizer Research Articles

Variable rate fertilizer application technology for nutrient management: A review

Variable rate fertilizer application technology for nutrient management: A review

Short-term Response of Greenhouse Gas Emissions from Precision Fertilization on Barley

Precision fertilization is a promising mitigation strategy to reduce environmental impacts of N-fertilization, but the effective benefits of variable-rate fertilization have not yet been fully demonstrated. We evaluated the short-term response (23 days) of GHGs emissions following variable-rate fertilization on barley. Yields, biomass (grains + straw) and different N-use indicators (N uptake, grain protein concentration, recovery efficiency, physiological efficiency, partial factor productivity of applied nutrient, agronomic efficiency and N surplus) were compared. Four N fertilization treatments were performed: (i) conventional– 150 kg ha−1; (ii) variable with granular fertilizer; (iii) variable with foliar liquid supplement; (iv) no fertilization. According to proximal sensing analysis (Greenseeker Handheld) and crop needs, both variable-rate treatments accounted for 35 kg N ha−1. Cumulative GHGs emissions were not significantly different, leading to the conclusion that the sensor-based N application might not be a GHGs mitigation strategy in current experimental conditions. Results showed that both site-specific fertilizations ensured the maintenance of high yields with a significant N rate reduction (approximately by 75%) and a N use improvement. Variable-rate N fertilization, due to similar yields (~6 tons ha−1) than conventional fertilization and higher protein content in foliar treatment (14%), confirms its effectiveness to manage N during the later phases of growing season.

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.

A new approach for variable rate fertilization based on direct read of soil map image

Aim of study: To develop a methodology for variable rate (VR) fertilization with less complexity in practice for variable rate fertilization. Area of study: Northwest of Iran. Materials and methods: A software was developed to read a soil map image pixel-by-pixel to provide the required information to tailor the fertilizer rate, regardless of which software was used for map generation. A total of 78 soil samples were collected and analyzed for soil potassium, and the results were used to generate an actual map including zones ranging from 70 to 190 kg/ha. The application rates were evaluated based on 50 deposition pans and compared with those calculated from the actual map. Based on the lag time in fertilization, three applied maps were also generated. Main results: The correlation coefficients found between the application rates computed based on the original soil samples and posted the locations of the sample points on the applied maps were 0.95, 0.95, and 0.94, over the ravel speeds of 6, 7, and 8 km/h, respectively. The results showed there is a correlation coefficient of 0.96 with an RMSE of 1.88 kg/ha, where the application rates computed from deposition pans compared with the corresponding location on the actual map. All applied maps were identical to the actual map. The results showed that the VR fertilization based on a direct read of a map image operated as expected. Research highlights: Fertilizer application was based on the direct read of map image. This study highlights also the need of new approaches in programing for simplicity of precision agriculture.

Fertilization Control System Research in Orchard Based on the PSO-BP-PID Control Algorithm

In order to improve the precision of the variable-rate fertilization system in orchards, this paper conducted a simulation by MATLAB and experimental research based on a variable-rate fertilization experiment platform. The variable-rate fertilization experimental platform was mainly composed of a power supply, DC motors, a PPC-15A1 on-board computer that contains a PCI8932 PC-DAQ, speed sensors, fertilizer dischargers, and a NAV60 module that can receive Beidou Navigation Satellite System positioning data. According to the fertilizer application mechanism of an external grooved wheel fertilizer applicator, the control system model of the variable-rate fertilization driven by the DC motor for orchards was established. A BP neural network adaptive PID controller based on particle swarm optimization (PSO) was proposed to improve the control precision of the system. The step response simulation results by MATLAB show that the overshoot of the BP-PID controller optimized by the PSO algorithm (PSO-BP-PID) is 12.7%, and the adjustment time is 0.557 s. The variable-rate fertilization experiments were conducted, in which the control system was tested by using the PSO-BP-PID controller. The variable fertilizer seeder control system of the Chinese national standard was adopted to evaluate the performance indexes of the system, such as the range of fertilizer amount adjustment, the response time of fertilizer amount adjustment, and the control precision of fertilizer amount. In the variable rate fertilization experiments, the average fertilization errors, respectively, are 1.16% and 1.07%, under the conditions of changing the target fertilization amount and the vehicle speed. The test results are consistent with the simulation results, and the variable-rate fertilization performance parameters are improved.

Study on Prediction Model of Soil Nutrient Content Based on Optimized BP Neural Network Model

ABSTRACT Soil nutrient content is an important index to determine the amount of fertilizer. Traditional soil nutrient content is obtained by manual sampling, which greatly increases the cost of agricultural production input. In order to solve this problem, this paper studies the relationship between soil nutrients, fertilizer amount, yield and the next year’s soil nutrients, and establishes an optimized BP neural network model to realize the prediction of soil nutrient content. Aiming at the problem that the traditional BP neural network model will affect the prediction accuracy due to the different weights and thresholds, the Grey Wolf algorithm with reverse learning mechanism is introduced to obtain the optimal solution of BP neural network weights and thresholds. The soil nutrient content data collected in chenjiadian village, Nongan County, Jilin Province for five consecutive years were used to test the model. The data of the first four years were used as the training set and the data of the fifth year as the test set. The prediction results of BP neural network model, Grey Wolf algorithm optimized BP neural network model and Grey Wolf algorithm optimized BP neural network model with reverse learning mechanism were compared The prediction accuracy of BP neural network model optimized by Grey Wolf algorithm with reverse learning mechanism reached 88.7%, which was better than the first two models. It can provide basis for the fertilization decision of variable rate fertilization in the next year, so as to reduce the input of labor cost.

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.

Predictive zoning of pest and disease infestations in rice field based on UAV aerial imagery

Bacterial leaf blight (BLB), bacterial panicle blight (BPB), and stem borer (SB) are serious infestations to the rice crop. Detection is the first essential step for effective management. The objective of the study is to provide a fast and accurate tool in detecting the infestation damages through Unmanned Aerial Vehicle (UAV) aerial imagery. System of Rice Intensification (SRI) was implemented and a UAV equipped with a digital multispectral camera was used to capture image of 20 rice plots that were treated with two types of fertilizers (organic and inorganic) in two different treatment rates namely; uniform rate and variable rate. Ground truths of infestation were observed and collected. Geospatial interpolation (kriging), linear regression analysis, and Soil Plant Analysis Development (SPAD) value models were carried out to predict the zones and level of infestation damages in the rice field. Maps showing areas with high, medium, and low counts of infestation damages were prepared using spatial analysis. The results of the relationship indicate that there were a strong correlation and high R2 between SPAD values obtained through the UAV method and infestation counts during the growth stages of 60 Days After Transplanting (DAT), 80 DAT, and 100 DAT. The findings show that the high severity of infestation happened in the plot that used a high amount of fertilizer compared to the plot that supplied with variable rate fertilizer. Infestation maps produced from the UAV aerial image would be an effective tool in detecting the pest and disease in the rice field.

Calibration of Physical Characteristic Parameters of Granular Fungal Fertilizer Based on Discrete Element Method

Based on a combination of physical and simulation experiments, a set of basic physical characteristic parameters and contact parameters suitable for granular fungal fertilizers were calibrated, which up to now have received little attention. The physical morphological characteristic parameters (overall dimension, 1000 grain weight, density, and moisture content), mechanical characteristic parameters (Poisson’s ratio, elastic modulus, and shear modulus), and contact parameters (static friction coefficient, rolling friction coefficient and recovery coefficient) of particles were measured through physical experiments. The parameters were screened for significance using the Plackett–Burman test. The results showed that the impact recovery coefficient, static friction coefficient, and rolling friction coefficient for the granular fungal fertilizer particles had a significant effect on the repose angle. The best range for the three parameters was determined using the steepest climbing test. The second-order regression model was optimized using the Box–Behnken design test. The relative error between the simulated repose angle (21.74°) and the physical test repose angle (21.84°) was small (0.50%). These optimal parameters obtained by calibration can provide a basis for the simulation analysis and parameter optimization of variable-rate fertilization systems.

Soil Electrical Conductivity and Satellite-Derived Vegetation Indices for Evaluation of Phosphorus, Potassium and Magnesium Content, pH, and Delineation of Within-Field Management Zones

The optimization of soil sampling is very important in precision agriculture. The main aim of this study was to evaluate the relationships between selected spectral indices (NDWI—normalized difference water index and NDVI—normalized difference vegetation index) and apparent soil electrical conductivity (EC) with soil nutrient content (phosphorus, potassium, and magnesium) and pH. Moreover, the usefulness of these variables for the delineation of within-field management zones was assessed. The study was conducted in 2021 in central Poland at three maize fields with a total area approximately 100 ha. The analyses were performed based on 47 management zones, which were used for soil sampling. Significant positive correlations were observed between the NDVI for the bare soil and all the studied nutrient contents in the soil and pH. A very strong positive correlation was observed between the soil EC and the potassium content and a moderate correlation was found with the magnesium content. A multiple-regression analysis proved that the soil nutrient content, especially potassium and phosphorus, was strongly related to the EC and NDVI. The novelty of this study is that it proves the relationships between soil and the crop attributes, EC and NDVI, which can be measured at field scale relatively simply, and the crucial soil nutrients, phosphorus and potassium. This allows the results to be used for optimized variable-rate fertilization.

Tool for the Establishment of Agro-Management Zones Using GIS Techniques for Precision Farming in Egypt

Agro-management zones recently became the backbone of modern agriculture. Delineating management zones for Variable-Rate Fertilization (VRF) can provide important ecological benefits and better sustainability of the new Egyptian farming projects. This article aims to represent an approach for delineating management zones using Spatial Multicriteria Evaluation (SMCE) within irrigated peanut pivot situated at the eastern Nile Delta, Egypt. The results indicated that soil data, such as soil texture, soil type, the elevation of the landscape, and slope, allow for sampling the study area into similar classes and in smaller units, along with a crop productivity map. The effects of the variability in soil characteristics within the field on Peanut yields are predicted by the soil suitability model. In addition, final management zones map a varied amount of nutrients that could be added to different pivot zones. In conclusion, mapping soil units with a sufficient number of field observations within each class provided an acceptable accuracy, and a good spatial distribution of the suitability classification was achieved. Hence, agro-management zones are essentially needed for policymakers in a specific field in order to furnish an evaluation about the transformations at a territorial scale and for studying the strategies to realize environmental sustainability and to reduce the territorial impacts.

Analysis on Chlorophyll Diagnosis of Wheat Leaves Based on Digital Image Processing and Feature Selection

Crop nutrition measurement is of great significance in agricultural practice, especially in variable rate fertilization. The chlorophyll content, an important indicator of nitrogen nutrition in crops, largely depends on crop growth and development, photosynthesis, and crop yield, and plays an important role in the monitoring of crop growth. This paper tries to detect the chlorophyll content of wheat quickly, using the digital image processing technology. Specifically, a feature selection method was developed based on wrapper and light gradient boosting machine (LGBM), and combined with logistic regression (LR) to predict the chlorophyll content of wheat. The results show that: the optimal model is the combination between the 17 image evaluation indices screened by LGBM and the LR prediction model; the optimal results were coefficient of determination (R2) of 0.728, and root mean square error (RMSE) of 4.979. The optimal model can predict the chlorophyll content of wheat accurately based on digital images in field prototype.

Control System of Liquid Fertilizer Variable-Rate Fertilization Based on Beetle Antennae Search Algorithm

In order to solve the problems of low precision of variable-rate fertilization and uneven fertilization flow of field liquid fertilizer applicator, a control system of variable-rate fertilization of liquid fertilizer based on beetle antennae search algorithm was proposed. First of all, this study established a mathematical model for the variable-rate fertilization control system of liquid fertilizer. Then, according to the control requirements, the search algorithm is used to optimize the three parameters of Proportion Integration Differentiation (PID). Finally, the response time and overshoot of the system are analyzed by software simulation, and the PID control based on beetle antennae search algorithm is compared and analyzed with fuzzy PID control and traditional PID control. The control effect of the control system is verified by a bench test. The results show that the actual response time of the variable-rate fertilization control system based on the beetle antennae search algorithm can reach 2 s, and the average relative error can reach 1.27%. Therefore, the control system of this study can achieve a better control effect, and the control method of this study provides a feasible scheme for the study of variable-rate fertilization.

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.

Use of Sentinel-2 Satellite for Spatially Variable Rate Fertiliser Management in a Sicilian Vineyard

Satellites can be used for producing maps of within-field crop and soil parameters and, consequentially, spatially variable rate crop input application maps. The plant vegetative vigour index (i.e., Normalised Difference Vegetation Index—NDVI) and the leaf water content index (i.e., Normalised Difference Water Index—NDWI) maps were used to study—through both time and space—the phenological phases of two plots, with Syrah and Nero d’Avola grapevine varieties, in a Sicilian vineyard farm, located in Naro (Agrigento, Sicily, Italy). The aim of this work is to produce spatially variable rate nitrogen fertiliser maps to be applied in the two vineyard plots under study as well as to understand when they should be fertilised or not according to their target crop yields. The average plant vegetative vigour and leaf water content of both the plots showed a high temporal and spatial variability during all phenological phases and, according to these results, the optimal fertilisation time should have been 12 April 2021. In fact, this crop operation is aimed at supporting the vegetative activity but must be performed when the soil water and, therefore, the plant leaf water content are high. Therefore, spatially variable rate fertilisation should have been performed around 12 April 2021 in both plots, using previous NDVI maps and taking into consideration two management zones. This work demonstrates the usefulness of remote sensing data as Decision Support Systems (DSS) for nitrogen fertilisation in order to reduce the production cost, environmental impact and climate footprints per kg of produced grapes, according to the European Green Deal challenges.

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.

Economic impacts of variable rate nitrogen fertilization: Input saving and yield increase in cereals

Abstract The purpose of this study is to discuss the economic impacts stemming from variable-rate (VR) nitrogen fertilization, one of the main precision agriculture practices. Economic impacts are related to reduced nitrogen use and increased crop yields thanks to a better distribution of inputs, net from possible spatial and temporal uncertainty. This paper reviews N=31 case studies (in 29 articles) that compared the performance of VR nitrogen applications versus uniform treatments. The comparisons covered nitrogen fertilization for cereal crops, in particular wheat and maize, for different years and in different countries. Findings highlight relevant changes in amounts of nitrogen applied, with the evidence of higher nitrogen efficiency resulting in reduced operating costs, while changes in crop yields are less evident: VR applications and uniform applications substantially reach the same production level, and higher nitrogen use efficiencies are achievable without significantly compromising yields. Overall, net economic impacts are in favour of VR fertilization. This work can raise farmers’ and other stakeholders’ knowledge of the actual economic impacts stemming from the adoption of VR fertilization and helps policymakers to understand the economic impact of precision agriculture and the need to foster sustainability-based policies.

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.

NPK dynamics with differential mineral fertilization in off-line mode

The efficiency of mineral fertilizers depends upon various factors, one of which is fertilization method. In heterogeneous condition of fields of nutrient content, the benefits of variable rate fertilization will increase, cause as much fertilizer will be applied to each section of the field as is necessary specifically on this section to obtain the planned yield. Experimental results have revealed the following features: variable rate fertilizer of nitrogen to reduce the variability of the nitrate nitrogen content in the tillering phase of spring wheat to 36% relative to the content before sowing, variable rate fertilizer of phosphorus and potassium to reduce variability of labile phosphorus and potassium in soil to the phase of wheat harvesting by 11 and 21%. The fertilization of one rate is less effective. This method leads to a decrease in the variability of nitrate nitrogen to 48%, labile phosphorus by 10%, by variability of labile potassium increases by 17% in the same time. Yield of spring wheat was 4.36-4.46 t / ha with a protein content of 14.03-14.57%, wet gluten 33.0-35.0%, glassiness 87-88%, weight of 1000 grain 36.1-36.3 g were applied with variable rate fertilizers in off-line mode.

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.