1. Introduction
Potato (
Solanum tuberosum L.) is the most important non-cereal crop in the world, playing a crucial role in global food security as the crop that produces the highest nutrient content per unit area of cultivated land [
1]. In Canada, potatoes are the largest vegetable crop, particularly important in Atlantic Canada where it represents 36 to 40% of total production [
2]. Improving nutrient management is essential for the sustainability of potato production systems as the excessive use and inadequate application timing of inputs often leads to substantial losses, such as nitrogen leaching into groundwater, resulting in environmental risks and financial waste [
3].
Precision agriculture (PA) offers promising solutions to these challenges. Defined as a management approach that integrates temporal, spatial, and plant-specific data with decision-support tools, PA aims to optimize resource use efficiency, productivity, profitability, and sustainability [
4]. Since the early 1990s, PA has gained global attention for its ability to improve crop yields while minimizing input use by accounting for within-field variability [
5,
6]. One of the principal approaches used in precision agriculture is the delineation of management zones (MZs), several discrete, homogeneous areas within the field [
7] that have different agricultural potential, such as fertility, water-use efficiency, and yield [
8]. These zones can respond differently to inputs, and, consequently, require specific input management to ensure better input placement.
The delineation process uses spatially variable information linked to crop or soil properties in the field. The acquisition of this information is typically obtained through an intensive soil sampling program [
9,
10,
11] including the use of proximal sensors [
5,
12]. Acquiring this highly effective data requires considerable time and specialized equipment, which is often inaccessible to most growers, thereby hindering the widespread adoption of this technique. In response to these challenges, remote sensing approaches have gained significant attention in recent years. Among them, optical satellite images have emerged as a promising solution for addressing data accessibility issues in PA. This technology enables the mapping of large areas at relatively low investment costs [
13].
In potato production research, the delineation of MZs relied on proximal sensors such as the Geonics EM38 [
14] and the VERIS 3100 models [
12], which generate detailed georeferenced data to estimate indirect soil properties like apparent electrical conductivity (ECa). These measurements are used to characterize within-field variability [
5,
12,
14]. ECa has been widely adopted due to its relative temporal stability [
14] and shows strong relationships with several soil characteristics [
15]. Recent studies have applied data fusion approaches combining soil ECa with complementary datasets such as topography, yield maps, and satellite imagery to enhance spatial variability characterization and improve the MZ delineation [
16,
17].
One popular technique is the application of vegetation indices (VIs). VIs highlight spectral features in images, allowing for the analysis of crop phenotypic traits by combining reflectance information from multiple image bands [
18]. The Normalized Difference Vegetation Index (NDVI) is the most extensively studied index in agricultural applications [
19], as it is closely correlated with biomass production, yield, and vegetative health. Additionally, NDVI should provide insights into the yield of potato crops by assessing on the functionality of detected leaves, essential for capturing light and carbon dioxide (CO
2), the key components for the growth of storage organs, such as tubers [
20], most NDVI studies focus on nutrient management and yield prediction, including yield prediction models, for cereals such as wheat [
20], rice [
21] and corn [
22]. They demonstrate that VIs can be effectively used in the MZ delineation process, providing complementary data in productivity maps [
13]. In the case of tuber crops like potatoes, as they accumulate most of their biomass underground, VIs such as NDVI, primarily detects above-ground traits, may have limited accuracy, potentially leading to mismatches in yield data and affecting crop characterization for PA. Recent studies have also investigated the adjustment of soil-related parameters in vegetation indices to mitigate saturation effects and improve the estimation of canopy biophysical variables, such as leaf area index, from multi-sensor satellite time series [
23]. Despite these limitations, some studies have used NDVI for yield predictions [
20,
24,
25] for MZ delineation in potato [
16]. However, research on satellite-based vegetation indices for this MZ delineation remains scarce.
The aggregation of VI time series in addition to the merger of multiple sources of satellite data improve the delineation process by accounting for crop and yield dynamics [
26]. For example, Řezník et al. [
27] used the Enhanced Vegetation Index (EVI) time series derived from Landsat 8 and Sentinel-2 multispectral satellite to identify yield productivity zones for cereals, their study showed strong correlations between yield zones and actual productivity, demonstrating the potential of these zones for long-term yield forecasting and decision-making.
One of the techniques used to optimize VI time series analyses is image composition, primarily employed to enhance change detection at regional scales [
28], this technique reduces the high-volume data required for time series analyses while conserving the essential information needed to identify characteristics in the field. Some also use metrics derived from composite vegetation index images as a robust alternative to reduce the noise in the classification process. For example, Maxwell and Sylvester [
29] used the maximum and standard deviation of the NDVI temporal composite derived from Landsat imagery for the classification of ever-cropped land. Lanucara et al. [
30] integrated composite VIs, including NDVI and SAVI2 (modified soil-adjusted vegetation index), climate data, soil and crop properties for MZ delineation at a regional level in a web-based spatial decision support system.
To our knowledge, no studies have yet applied a multi-source, multi-year NDVI composite approach for the delineating MZs in potato production, nor extended this analysis beyond individual field scales. This gap highlights the need for approaches that integrate temporal and spatial crop information over multiple seasons and fields to more effectively capture the variability associated with agricultural potential. Indeed, larger scales may enhance the delineation process by incorporating the inter-field variance, a factor not considered in the traditional field-level MZ approach. We hypothesize that crop development will adequately represent the key factors that affect agricultural potential (AP)—productivity per unit area per unit time [
31], such as meteorological conditions, soil physicochemical characteristics, and agricultural management practices (e.g., fertilization). Therefore, VIs derived from optical satellite imagery offer an effective method for capturing AP variation within a given field and therefore delineating MZs, due to the connection between vegetation’s spectral properties and its biochemical and biophysical attributes [
32]. Consequently, time series analysis of the vegetation indices in a field could effectively capture crop temporal dynamics at a regional level and provide a stronger delineation approach by considering factors not evaluated by traditional methods like soil sampling and proximal sensing.
The objective of this study is to develop a methodology for delineating MZs based on the concept of AP for commercial potato fields using a multisource diachronic analysis of optical satellite images. An eight-year (2015–2023) NDVI time series of Sentinel-2 and Landsat 8 images were used across 17 fields, and the delineation results were validated using potato tuber yield data and the soil physicochemical properties obtained from soil sampling.
4. Discussion
4.1. NDVI Derived Metrics Are a Valuable Proxy of Agricultural Potential as Evidenced by Correlations to Yield and Soil Properties
Higher tuber yields tended to occur in areas showing more vigorous and consistent crop development, as indicated by higher mean and lower temporal variability of NDVI MVC-derived metrics (
Table 2). Although these correlations are weak, they suggest that NDVI metrics may serve as useful, though indirect, indicators of crop performance over time. Notably, the positive correlation with NDVI MVC skewness metric—interpreted here as a tendency toward left-skewed distributions—suggests that areas exhibiting earlier and more sustained vegetative growth tend to yield higher production.
The temporal patterns in NDVI MVC-derived metrics also provide insights into the stability of crop development. Zones with NDVI MVC skewness values near zero and lower NDVI MVC standard deviation metric values indicate more uniform and stable vegetative dynamics, reflecting favorable growing conditions that are likely influenced by a combination of nutrient availability, soil texture, and environmental factors.
The sensitivity of NDVI-based temporal metrics to underlying soil nutrient conditions was reflected in statistically significant, though modest, correlations with total N, total C, K, and Mg. These patterns indicate that NDVI MVC metrics capture general trends in soil fertility rather than precise quantitative relationships. In particular, high levels of total N and total C—recognized as key determinants of potato productivity [
14,
48,
49]—likely support sustained canopy development and reduce temporal NDVI variability. In addition, the correlation between higher NDVI MVC mean metric values and higher total N content further suggests a link between vegetation vigor and nitrogen availability. This aligns with previous studies that emphasize the role of N as the most yield-determining macronutrient in potato production [
41,
50,
51,
52]. Total C trends followed those of total N, which is expected due to their shared origin in organic matter. Higher total C may indicate greater soil organic matter (SOM), a key factor in enhancing soil fertility through improved water-holding capacity, nitrogen mineralization, and aggregate stability [
15]. Furthermore, the measured ranges for total N and total C closely matched values reported for potato fields in New Brunswick by Perron et al. [
12], reinforcing the validity of the observations.
The pH remained remarkably stable, both within and across the AP MZs, corroborating earlier findings that pH generally exhibits low spatial variability due to its logarithmic nature [
53,
54]. While the observed pH values (5.8–5.9) are slightly below the optimal range for potato growth [
55], their consistency may still provide a suitable environment for crop development. Finally, while statistically significant, the observed differences in clay and sand content across zones were not agronomically relevant, as all areas exhibited comparable textures within the loamy class. This texture is widely recognized as optimal for potato cultivation due to its favorable balance between drainage capacity and nutrient retention [
56]. However, prior studies have noted that even small variations in clay content can impact water retention and drainage efficiency [
12], which could subtly influence crop performance. Nevertheless, the observed relationship with sand content underscores the role of soil texture in shaping vegetation dynamics.
The observed yield trends aligned well with the MZ delineation, particularly in distinguishing high- from lower-yielding zones. Indeed, despite the lack of statistical significance, the intermediate AP MZ consistently exhibited higher average tuber yield than the low AP zone suggesting that the methodology was still capable of capturing most of the spatial and temporal yield variability in the studied fields. Given that the validation grid (50 m) exceeded the semivariogram range (36 m) (
Table 4), the samples can be considered spatially independent, thereby supporting the validity of the statistical comparisons used for validation (Tukey/Kruskal–Wallis test). Notably, the field adjacent to Field Z demonstrated a strong spatial relationship with a subsection that differentiates between two-year and three-year crop rotations (FOF CA communication,
Figure 3). Even though certain years included rotation crops instead of potatoes, the significant correlations between the AP MZs and tuber yield highlights the robustness of the methodology.
These results suggest that the NDVI-based temporal composite method is a potentially reliable tool for delineating MZs, as the NDVI MVC metrics captured key aspects of the underlying spatial variability and agricultural potential, even when the composite incorporated multiple crops in certain years, demonstrating its ability to reflect both short-term variability and longer-term patterns in crop performance. This approach enables data integration across years and crop types which may provide resilience against seasonal fluctuations (year to year variation) and may offer a practical solution for data-limited situations. Overall, the three delineated zones show a strong alignment with the yield patterns, supporting the practical utility of this simplified approach, that is, the use of NDVI MVC metrics as a valuable proxy of AP for identifying spatial zones of agronomic significance within a field.
4.2. Methodological Limitations and Areas of Improvement
A key limitation of this study is the use of only one year of potato tuber yield data for validation. Multi-year yield data, encompassing multiple crop types would have provided a more robust basis for evaluating the temporal stability and agronomic relevance of the delineated AP zones. Access to long-term, high-quality yield data remains a challenge as yield maps are often affected by errors related to field machinery operations, such as irregular combine harvester paths [
57,
58] and this issue is further exacerbated in the case of yield time series as highlighted by previous studies [
59,
60,
61]. Also, the inclusion of rotational crops in NDVI composites likely introduced additional noise, partially explaining the moderate correlations observed between NDVI MVC metrics and yield or soil properties.
Temporal and crop rotation effects may have further influenced the correspondence between MZs and yield. Inter-annual climatic variability—including precipitation, temperature, and growing season length—can alter vegetation dynamics and NDVI signals. Similarly, rotational crops with differing canopy structures and rooting systems can modify soil properties and vegetation responses, potentially shifting the spatial boundaries of MZs over time. While the use of multi-year NDVI composites was used to integrate these effects and improve the characterization of agricultural potential patterns, temporal alignment between remote sensing imagery and yield observations remains critical for improving the robustness of management zone delineation.
Spatial resolution and smoothing also introduce limitations. The MZs were delineated at a 10 m resolution, while yield maps were generated at 1 m, leading to a loss of spatial detail and generalized intermediate values. The smoothing applied to create agronomically homogeneous zones further reduces sensitivity to small-scale variability. In addition, the methodology showed limited ability to capture differences, especially between the intermediate and low AP MZs for most soil properties may reflect the intrinsic limitations of the delineation approach in capturing subtle soil property gradients or the relatively homogeneous nature of these zones. Also, the lack of significant slope variation suggests that the spatial resolution and smoothing applied in the methodology may limit its sensitivity to topographic features. This may limit the methodology’s ability to capture such as water runoff and redistribution, which are influenced by terrain [
62,
63].
At the field level, discrepancies were observed. In Field Y, the intermediate AP MZ did not correspond to local yield patterns, likely due to resolution mismatches. In Field X, no statistically significant differences were detected among zones, even when accounting for in-field variability, and the low AP MZ occasionally corresponded to intermediate yields. This mismatch may be partly explained by residual effects from rotation crops, localized nutrient redistribution, or unaccounted for management practices influencing crop growth. Another contributing factor is that the classification was based on a broader dataset which included fields beyond those evaluated in the yield analysis. This wider spatial scope may have reduced the representativeness of the MZs for specific field-level conditions, making the yield maps less reflective of local variability across the study area. Finally, the constraint to three AP MZs may limit the resolution of spatial variability; using more classes (e.g., five zones) could improve precision.
Despite these limitations, the three delineated zones aligned well with yield patterns, and significant correlations between AP MZs and tuber yield (r ≥ 0.25, p ≤ 0.05) highlight the robustness of the methodology. NDVI MVC metrics partially capture much of the underlying spatial variability and agricultural potential patterns, even under multi-year, multi-crop scenarios. Notably, distinct patterns were detected in the main physicochemical properties, suggesting that further research is needed to determine the optimal conditions and temporal evaluation window for improving zone separation. Such refinements would enhance the methodology’s capacity to identify zones where vegetation develops most favorably and consistently, even under multi-crop scenarios such as crop rotation.
4.3. Practical Implications of the Methodology
The AP MZs identified in this study have strong practical value for precision and regenerative potato production. By integrating multi-year NDVI MVC metrics, producers can identify areas of high and low productivity potential and adjust management accordingly. High AP zones, showing stable vegetation and higher total N and C, can be managed with lower input intensities and focused nutrient monitoring. Intermediate AP zones benefit from adaptive management, such as variable-rate fertilization and targeted irrigation, while low AP zones—linked to weaker vegetation and greater variability—require soil structure improvement and organic matter restoration through practices like cover cropping. Ultimately, linking AP zones to regenerative practices can enhance sustainability outcomes.
Although the NDVI-based delineation enables spatially targeted management and optimized resource use, its implementation requires data processing and coding skills beyond most commercial farms. This is where McCain Foods and similar businesses play a crucial role, centralizing the processing of satellite data and generating ready-to-use AP maps for growers. By embedding this methodology into grower-facing digital solutions, McCain can translate complex geospatial analyses into actionable field recommendations that support variable-rate inputs, irrigation planning, and soil health improvement. The approach would also support seasonal decision-making: early-season NDVI for stand establishment, mid-season for nitrogen and irrigation adjustments, and post-harvest for assessing residue and cover crop performance.
Overall, this methodology offers a scalable, cost-effective, and science-based decision-support framework that bridges satellite monitoring with farm management. By leveraging McCain’s technical capacity and grower network, it can transform complex remote-sensing outputs into practical, regionally tailored guidance that improves both profitability and environmental performance in potato production.
5. Conclusions
This study presented a methodology utilizing NDVI composite time series as a tool for delineating AP MZs in potato production systems using multiple sources of satellite data. Despite tuber-yield-limiting factors and the lack of crop differentiation, the methodology successfully identified trends in key physicochemical soil properties associated with potato fertility, such as total C and total N. Additionally, the methodology detected spatial trends in tuber yield with moderate accuracy, though performance varied across fields especially at in-field scale.
These findings address a key research gap: the development of a scalable, cost-effective approach for assessing spatial patterns of agricultural potential without reliance on extensive soil sampling. By leveraging multitemporal, multi-source, and multi-field-scale satellite-derived vegetation indices, the methodology proposed a practical alternative to traditional, sampling-intensive approaches, enabling the MZ delineation in a more accessible and efficient manner.
Moreover, the method provides valuable tools for spatially assessing agricultural potential and supporting data-driven decision making in crop management. Further research into VI-composite-based approaches is highly encouraged, particularly to evaluate the effects of crop variability, the influence of delineation variables, and the temporal and spatial limitations of the methodology.