Nitrate Pollution of Water Bodies from Agricultural Sources: The Role of Training in Enhancing Awareness and Knowledge in Andalusia

Abstract

Nitrate pollution from agricultural activities is a major cause of surface and groundwater degradation across Europe. In Andalusia, southern Spain, approximately 26% of the regional territory is affected by this type of contamination. To mitigate and prevent nitrate pollution, a regulatory framework has been implemented, establishing specific restrictions and recommendations for agricultural practices and nitrogen fertilization management in designated areas. However, the effectiveness of these measures is often constrained by limited awareness of the issue, insufficient understanding of existing regulations, and a general lack of training in nitrogen fertilization management among farmers. To address these challenges, a specialized training program on crop fertilization was developed for agricultural professionals. This initiative aimed to raise awareness of the environmental impacts of nitrate pollution, disseminate information about relevant legislation, and strengthen technical knowledge related to nitrogen fertilization planning and management, thereby enhancing on-farm decision-making. This study analysed the impact of this training activity on the level of awareness and knowledge regarding nitrate-related issues in Andalusia.

1. Introduction

In Andalusia (southern Spain), agriculture plays a key economic, social, and environmental role, leading national production in both olive oil and horticultural crops. Furthermore, agriculture remains the main source of employment in nearly half of the region’s municipalities [1]. However, the intensification of the agricultural systems aimed at increasing yields and market competitiveness has generated complex new agro-environmental challenges [2].

Diffuse nitrate pollution derived from agricultural practices is one of the principal causes of surface and groundwater degradation across Europe. This has serious implications in human health since high nitrate levels in water can lead to methemoglobinemia, particularly in infants, and has been linked to an increased risk of certain cancers. From an environmental perspective, excess nitrates contribute to eutrophication in aquatic ecosystems, leading to algal blooms that deplete oxygen levels, harming aquatic life and disrupting biodiversity. Moreover, this contamination also affects soil health, reducing microbial diversity and impacting crop production [2,3]. To address and prevent these issues, the European Council adopted Directive 91/676/ECC in 1991 [3], which requires Member States to identify water bodies affected by nitrate contamination—those with nitrate concentrations exceeding 50 mg L⁻¹—and to designate Nitrate Vulnerable Zones (NVZs). Member States must also implement Action Programs in these NVZs, establishing specific restrictions and recommendations for agricultural practices.

In Spain, regional governments (Autonomous Communities) are responsible for implementing these measures, as they hold authority over both agricultural and environmental matters. In Andalusia, the first designation of vulnerable zones occurred in 1998, identifying 13 zones based on municipal boundaries. A major revision in 2008 expanded this number to 22, using GIS-based delineation instead of municipal limits. Subsequently, two additional zones were incorporated and one expanded in 2009. In 2019, monitoring studies identified new affected waters, including both interregional and intraregional water bodies. Currently, a total of 35 NVZs have been designated [4,5], covering an area of 22,376 km². Given the total regional area of 87,260 km², approximately 26% of Andalusia’s territory is now classified as vulnerable (Figure 1). Moreover, both the number and extent of NVZs are expected to continue increasing following the implementation of Spanish Royal Decree RD 47/2022 [6], which establishes stricter standards than the current regional regulation [7]. This new legislation lowers the thresholds for identifying affected water bodies to nitrate concentrations exceeding 25 mg L⁻¹ in surface water and 37.5 mg L⁻¹ in groundwater, compared with the previous uniform European threshold of 50 mg L⁻¹ [3].

The risk of nitrogen (N) losses in intensive irrigated farming systems is particularly high, primarily due to nitrate leaching, gaseous emissions, and the accumulation of residual mineral N in soils after harvest. In the latter case, leaching may occur during rainy periods between successive cropping cycles [8]. In addition to their environmental impact, N losses also have significant economic consequences for farmers, especially considering the rising cost of fertilizers following the war in Ukraine [9].

To reduce N losses and optimize irrigation and fertilization management, several decision-support systems (DSS) have been developed, such as the VegSyst-DSS for horticultural crops [10,11], CropManage for horticultural and field crops [12], and Reutivar app for olive groves [13]. However, despite scientific and technological advances, a recent study in Andalusia [14] found that 55% of farmers determine fertilizer timing and rates based on personal experience, while only 17% consider the crop’s actual nutrient requirements. These findings suggest that achieving optimal nitrogen management—balancing productivity with minimal environmental impact—requires effective knowledge transfer and the promotion of available decision-making tools.

Agricultural training, along with broader environmental and technical knowledge, plays a key role in the transition toward more sustainable farming systems [15,16,17]. Specialized training has been shown to improve crop management decisions, enhancing both productivity and profitability in a sustainable manner [18]. Based on this, our hypothesis is that specialized training in nitrogen fertilization management can substantially improve farmers’ and advisors’ awareness of nitrate pollution risks, their understanding of regulatory frameworks, and their technical capacity to implement sustainable fertilization practices. Such improvements are expected to contribute to the mitigation of nitrate contamination in agricultural areas.

Accordingly, the specific objectives of this study were to: (i) assess the impact of specialized training on awareness, regulatory knowledge, and technical competencies related to sustainable fertilization practices in Andalusia; (ii) identify the key information, skills, and decision-support tools required by farmers and advisors to adjust nitrogen fertilization to crop needs and make evidence-based management decisions; and (iii) analyze the main barriers hindering access to information and tools that enable efficient nitrogen management, as well as to identify the public policy measures that stakeholders consider essential for improving nitrogen governance in agriculture.

The insights obtained from this research aim to guide the design of training programs and experimental initiatives and to inform governance strategies that promote more sustainable nitrogen management in the agricultural sector.

2. Materials and Methods

The research was conducted across all eight provinces of Andalusia. The study involved administering a face-to-face survey during June and July of 2022 and 2023 to participants attending specialized training courses on fertilizer management organized by IFAPA all across the region. Thus, this research relied on convenience sampling, with participant selection based on availability and ease of access [19].

The questionnaire included both open-ended questions—primarily aimed at gathering information on the respondents’ profiles—and closed-ended questions. The response options for the closed-ended questions were developed based on findings from previous studies [14,20]. Prior to data collection, a pilot test was conducted to ensure that the questions were clearly understood and could be answered without difficulty.

The final questionnaire (Table S1, Supplementary Material) was structured into five sections as follows:

• Respondent profile information (age, gender, professional background, and prior training) (open-ended responses).
• Opinions on the realistic possibilities of adjusting and reducing nitrogen fertilizer use (both open- and closed-ended responses).
• Opinions on the use of different decision-support tools (closed-ended responses).
• Perceptions of the role of public administration in improving nitrogen management (closed-ended responses).
• Self-assessment of knowledge improvement regarding nitrate pollution issues, existing regulations, and fertilization planning management for different crops (closed-ended responses).

The questionnaire was originally written in Spanish to facilitate comprehension and minimize interpretation bias that could result from translation into English.

A total of 257 valid surveys were collected: 134 in 2022 and 123 in 2023. Figure 2 shows the distribution of participants across Andalusian provinces. Data were analyzed using univariate descriptive statistics with the software Statistix 9 (version 9.1, Analytical Software, Tallahassee, FL, USA).

3. Results

3.1. Profile of Survey Respondents

The age of participants ranged from 20 to 64 years, with a mean age of 39. Overall, 58.4% were men and 41.6% were women. The most common profiles correspond to agricultural advisors (51.6%), followed by farmers (22.3%) and other professionals (26.1%), including agricultural workers (36.1%) and university graduates (34.4%) from agriculture-related fields. In total, 58.8% of respondents reported having received previous specialized training in fertilization management, mainly through technical courses and/or university education.

3.2. Opinions on Fertilization Management

More than 95% of participants believe that nitrogen fertilizer doses could be reduced, with most (55.1%) estimating a potential reduction of around 20–30%. A negative correlation between the farmer’s age and the perceived potential for fertilizer reduction was observed in only one of the eight Andalusian provinces. Specifically, in Seville province, there was a significant negative correlation between potential fertilizer reduction (Y) and farmer’s age (X) (Y = 43.5 − 0.5X, R² = 0.25, p < 0.01). Regarding the information considered essential to adjust nitrogen fertilization according to crop needs, both farmers and local advisors identified soil analysis as the most important factor (94%), followed by estimates of crop yield and nitrogen uptake (85%) and nitrogen supplied through irrigation water (Figure 3). No significant differences were observed between the responses of farmers and advisors.

During the training, participants were introduced to a series of DSS for fertilization planning, including crop nutrient status monitoring sensors and mobile applications (APPs) available for different crops and production systems (Figure 4). When asked about the main limitations hindering improved fertilization management, participants indicated the need for specific training on the use of these tools (58%), lack of awareness of their existence (57%), and the need for technical support to learn how to use and interpret the outputs of these tools (37%). The latter limitation was particularly frequent among farmers (Figure 5).

3.3. Opinions on Potential Measures to Improve Nitrogen Management in Agriculture

Among the measures proposed to improve nitrogen management in agriculture, nearly 90% of all participants emphasized the need for more specialized training in this area. Local advisors highlighted the importance of additional demonstration trials and enhanced communication with public authorities, while farmers stressed the need for stronger technical advisory services (Figure 6).

It is worth noting that the Regional Order of 23 October 2020 mandates the inclusion of a fertilization record sheet in the field logbook for areas designated as vulnerable to nitrate pollution. More than 90% of local advisors and 86% of farmers considered this measure useful. However, 20% of advisors and 24% of farmers report difficulties in completing these records.

3.4. Evaluation of the Training Received

Training participants were asked to rate, on a scale from 1 (none) to 5 (a lot), the extent to which their knowledge improved following participation in the specialized fertilization management course (Figure 7). The majority of respondents reported a significant or substantial improvement in their level of awareness (83.7%), knowledge of the regulations (91.4%), and training in the calculation and management of nitrogen fertilization (85.2%).

4. Discussion

Nitrogen is an essential element for agricultural production, but its excessive application is one of the main causes of contamination in both surface and groundwater bodies. Properly adjusting N fertilizer inputs to crop needs—avoiding losses and optimizing use—requires a basic understanding of irrigation and fertilization [21,22,23]. Moreover, awareness of the regulatory limits governing fertilization is crucial to ensure compliance and environmental protection. A study conducted in the valley of Granada province area (Vega de Granada, southern Spain) during 2010–2011 revealed that 74% of surveyed farmers were unaware of nitrate pollution regulations, and only 3% knew the maximum N limits for their crops established by law [5,24]. Among these farmers, just 10% had performed soil analyses and only 3% had conducted water analyses. The authors concluded that greater efforts from public authorities were needed to disseminate information on obligations and best practices for irrigation and fertilization management in Nitrate Vulnerable Zones (NVZs) such as the Vega de Granada [24]. A decade later, an exploratory study on irrigation and fertilization management in Andalusian agriculture [14] found that more than 70% of surveyed farmers-regardless of their awareness of nitrate regulations-still lacked a systematic methodology for N fertilization management. Despite the legal requirement to account for N contributions from soil and irrigation water when calculating fertilizer doses [7], only 18% of farmers had conducted soil analyses and 41% had analyzed irrigation water during the previous three years. By contrast, in our study, more than 90% of farmers and advisors recognized the importance of conducting soil analyses to properly adjust N fertilizer rates to crop needs.

The present research analyzes the effect of specialized training—delivered through the course “Sustainable Nitrogen Management in Agriculture”—on participants’ knowledge and awareness of nitrate-related issues in Andalusia. The training was voluntary, and participants aimed to enhance their understanding of N fertilization management, a crucial step for mitigating risks to both public health and the environment. At the end of the training, more than 84% of participants reported a substantial improvement in their awareness, suggesting that targeted capacity-building initiatives can effectively contribute to improved management of nitrate pollution and to progress toward a more sustainable agricultural model. Similar results have been reported in other contexts, where training significantly enhanced environmental awareness and decision-making among agricultural professionals [25,26,27].

Recent studies have also linked farmers’ perceptions of nitrate pollution to farm characteristics [28]. For instance, only 16% of farmers with extensive crops and organic N fertilization perceived nitrate pollution as a problem, compared to 60% of those managing intensive horticultural systems with mineral fertilizers. In our study, although the sampling approach was non-probabilistic, convenience-based, and voluntary-thus precluding formal statistical inferences-we explored one potential relationship: between farmer’s age and perceived N fertilizer reduction potential. A significant negative correlation was found in Seville province, suggesting that older farmers, particularly in this region dominated by extensive herbaceous crops, may be more resistant to changing fertilization practices. No such correlation was observed in the remaining Andalusian provinces. This result should be interpreted cautiously, as more robust, stratified, and probabilistic sampling designs would be necessary to confirm such trends and to develop adaptive training programs tailored to different farmer profiles.

According to both farmers and advisors, the main barriers to improved fertilization management are the lack of specific training and the limited awareness of available technological tools. These barriers could be effectively addressed through targeted outreach activities that promote the use of decision-support systems, which are increasingly valuable in the context of precision and digital agriculture [29]. Furthermore, nearly 90% of participants emphasized the need for additional specialized training to enhance nitrogen management and support evidence-based decision-making in agriculture—an outcome consistent with previous findings demonstrating that education and advisory support can significantly reduce nitrate pollution risks [30]. Despite more than half of participants having received prior specialized training, the majority reported notable improvements in their awareness, understanding of regulations, and ability to calculate and manage N fertilization after completing the course.

Finally, it is noteworthy that over 95% of participants, including both farmers and advisors, believe that nitrogen fertilizer doses could be reduced. This finding reinforces the importance of integrating farmers into policy design processes, ensuring that long-term adaptation strategies are co-developed to balance compliance with agri-environmental policies and the achievement of sustainable farm incomes [25].

5. Conclusions, Implications, Limitations and Future Perspectives

This study highlights the crucial role of specialized technical and environmental training in improving nitrogen fertilization management within the agricultural sector of Andalusia. The surveyed farmers and advisors identified the lack of training and limited awareness of available information and tools as the main barriers to achieving more efficient and sustainable fertilization practices. More than 80% of participants reported significant improvements in their awareness of nitrate pollution, understanding of regulations, and capacity to calculate fertilization needs after receiving training. These results underscore that well-designed training programs can lead to informed decision-making and behavioral change among farmers and advisors, contributing to both environmental protection and agricultural competitiveness.

The evidence demonstrates that professional training is an effective, low-cost, and high-impact instrument to promote more sustainable nitrogen management and mitigate nitrate contamination in agricultural areas. Improved fertilizer efficiency also generates economic co-benefits by reducing production costs and nutrient losses, thereby enhancing farm profitability, resilience, and environmental performance. These outcomes align with the objectives of the Nitrates Directive (91/676/EEC), the European Green Deal, and the Farm to Fork Strategy, reinforcing the relevance of training as a key governance tool to achieve sustainable agriculture in Andalusia.

From a policy perspective, several strategic actions emerge from the findings of this study. First, technical training on nitrogen management should be integrated within the environmental conditionality of the Common Agricultural Policy (CAP), either as an eligible agro-environmental measure or as a prerequisite for accessing specific subsidies. Furthermore, permanent advisory and training programs should be established in Nitrate Vulnerable Zones (NVZs), coordinated by regional administrations and supported by research centers and professional associations. The promotion and integration of digital Decision Support Systems (DSS) into both training modules and farm advisory systems can further strengthen decision-making capacity.

To monitor progress and ensure accountability, it is essential to link educational indicators—such as the number of trained farmers or the adoption rate of good practices—with environmental indicators, including water quality data in NVZs. Awareness campaigns involving cooperatives, irrigation communities, and farmers’ associations can help connect sustainable practices with product quality, territorial value, and market differentiation. Additionally, voluntary certification schemes, such as a “Responsible Nitrogen Management Farm” label, could provide recognition and incentives for producers adopting best practices.

Nevertheless, this study has some limitations that should be acknowledged. As an exploratory, perception-based analysis, the results may overrepresent participants with higher levels of environmental awareness, given that sampling was based on non-probabilistic nature and voluntary participation in training activities. The lack of field-based nitrate data prevented a direct linkage between perceived knowledge improvements and actual environmental outcomes. Moreover, the short-term evaluation captures immediate learning effects but not the persistence of behavioral changes over time. Finally, while the survey covered all eight Andalusian provinces, local differences in cropping systems, irrigation methods, and governance frameworks may influence the generalization of results.

Future research should aim to address these limitations through longitudinal studies that assess how training influences long-term fertilization practices and nitrate pollution trends. Integrating socio-economic and biophysical data—such as nitrate concentrations, soil characteristics, and training participation records—into spatially explicit models could enhance the evaluation of policy effectiveness. Economic and environmental assessments of different training and advisory approaches, based on cost–benefit or optimization models, would also provide valuable insights for public decision-making. In future research, stratified and representative sampling by province, region, crop, and management system will allow more robust correlation and multivariate analyses to identify relationships among variables (e.g., training needs, farmer profiles, age, type of crop, level of nitrate contamination, etc.). These analyses will help design more targeted and effective training and policy interventions.

In the domain of education and knowledge transfer, digital and blended-learning modules on sustainable nitrogen management should be developed to complement face-to-face courses, enabling continuous learning. Interactive pedagogical tools—such as digital guides, mobile applications, or simulation platforms—can enhance farmers’ and advisors’ capacity to manage nitrogen efficiently and integrate fertilization with irrigation practices. The pedagogical effectiveness of such approaches should be assessed through learning outcomes and adoption indicators.

Finally, from a governance perspective, comparative analyses across Mediterranean regions—including Spain, Italy, Greece, Portugal, and France—would be useful to identify shared challenges and successful models of agricultural training systems. Promoting transnational and Interreg projects focused on agricultural education, decision-support tools, and environmental monitoring in NVZs could foster regional cooperation and innovation. Establishing multi-actor platforms involving research institutions, policymakers, and producer organizations in Andalusia would further strengthen nitrogen governance and accelerate the adoption of sustainable fertilization practices in the region.