Nitrogen (N) is a key input to food production. Nearly half of N fertilizer input is not used by crops and is lost into the environment via emission of gases or by polluting water bodies. It is essential to achieve production levels, which enable global food security, without compromising environmental security. The N pollution level expected by 2050 is projected to be 150% higher than in 2010, with the agricultural sector accounting for 60% of this increase. In this paper, we review the status of the pollution from N fertilizers worldwide and make recommendations to address the situation. The analysis reviews the relationship between N fertilizer use, N use efficiency, no-point pollution, the role of farmer management practices, and policy approaches to address diffuse pollution caused by N fertilization. Several studies show a lack of information as one of the main hurdles to achieve changes in habits. The objective of this study is to highlight the gravity of the current global non-point pollution as well as the need for a communication effort to make farmers aware of the relationship between their activity and N pollution and, therefore, the importance of their fertilizer management practices.

This paper explores the impacts of water pricing as a demand management policy, at a regional level (or basin-sector). To this aim, a hydro-economic model for the Guadalquivir River basin (southern Spain) is proposed here. This basin constitutes a perfect example of a Mediterranean basin subject to frequent and long drought periods, where challenges related to water scarcity are increasing, leading to social conflicts among water users. Moreover, this basin is characterised by a closure state meaning that all available water resources are already allocated among users. In this context, water pricing policy may act as an effective tool to reduce water demand by encouraging changes of behaviour in water users. In particular, those who perform irrigation practices in the agricultural sector. This paper focuses on the irrigation sector since it is the main water user in the basin (87%). Additionally, alternative water-availability scenarios have been used to test the effect of water pricing under drought conditions. The hydro-economic model presented here has been sectorized into four basin sectors with common characteristics (hydro and economic). This enables the analysis of alternative price scenarios in the agricultural sector, in terms of water used, crop patterns and gross margin. Results show that water pricing policy should consider the regional characteristics at the basin-sector scale to gain effectiveness and equity at the river basin scale. Moreover, it has been found that both water availability and the crop pattern at the basin-sector scale have an effect on the reduction of water used (and therefore in gross margin.

This research explores the dynamic interplay of water, energy, and carbon in Axarquia, Spain (1990–2030), focusing on the escalating water deficit and rising emissions. It seeks to comprehend the impact of subtropical crop expansion on regional resources. A comprehensive methodology integrates data on water demand, alternative sources and energy-intensive processes. Key methods include assessing the influence of subtropical crops on water requirements by calculating the FAO 56 crop coefficient (Kc), the total annual energy (GWh) as a consequence of the volume of water demanded, identifying the predominant water sources and quantifying CO₂ emissions by calculating the carbon footprint balance, providing a holistic view of regional resource dynamics. The methodology developed here can be adapted to basins elsewhere and can be a useful tool to help the design of water management policies in basins where the balance of the Water, Food, Energy nexus is of particular interest. The study reveals a substantial 30% surge in water demand due to exponential growth in subtropical crops. Additionally, energy-intensive processes linked to alternative water sources contribute to a projected surge in emissions (2022–2030), indicating significant regional challenges. Axarquia faces imminent challenges with a widening water deficit and escalating emissions. However, the region emerges as a vital carbon sink, evidenced by the net carbon balance. With 176,413 tCO₂eq sequestered by cultivated plant mass, the study underscores the potential for environmental improvement and climate change mitigation in the region.

Farmers in the developed world tend to over-apply fertilizer, and we explore a model for decision-making under uncertainty in yields. This article proposes an agro-economic model for farmer decision-making based on subjective expected yield and crop response to fertilization. The model explores subjective yield probability distributions that are both better suited to subjective crop yields than the previously proposed probability distribution and is easier to extract from farmers. The model allows the analysis of the impact of changes in fertilizer price and variance of expected yields. The model result is consistent with observed farmer behavior based on the rule of “fertilizing for the good years” that appears, according to our model, as rational and consistent with expected profit maximization under yield uncertainty since the cost of over-application is lower than that of the opportunity cost of under-application. The goal of increasing the efficiency of nitrogen use requires both technical innovation and an expansion of the knowledge on the socioeconomic factors underlying excessive crop fertilization that must be improved both to meet future food demands and to prevent environmental degradation and climate change.