Renewables
Ayat-Allah Bouramdane
Ayat-Allah Bouramdane
·Posted in Renewables
Sat, Apr 11

Under the panels and under the sun: when agrivoltaics reinvents fertilization between the Mediterranean and Australia

Agrivoltaics, which combines agricultural production and solar energy generation on the same land area, is emerging as a key strategy to simultaneously address the challenges of food security, energy transition, and soil sustainability. In this context, optimizing fertilizer use becomes a central lever, as nitrogen inputs—although essential for crop productivity—are also responsible for major environmental impacts such as nitrous oxide (N₂O) emissions, groundwater pollution, and ecosystem degradation. Agrivoltaic systems significantly alter crop microclimatic conditions (partial shading, reduced evapotranspiration, lower water stress), which directly influences fertilizer efficiency. However, these effects are not universal and vary greatly between Mediterranean and Australian climates, which represent two contrasting yet highly relevant agroclimatic contexts for studying these interactions.

In Mediterranean regions, characterized by hot summers, highly variable rainfall, and frequent drought episodes, agrivoltaic systems have shown a strong stabilizing effect on agricultural production and water use. Recent studies indicate that partial shading from photovoltaic panels reduces crop water stress and significantly improves water-use and nitrogen-use efficiency, particularly in arid and semi-arid areas such as the Iberian Peninsula. Indeed, crops grown under agrivoltaics exhibit better nitrogen use efficiency (NUE), as reduced evapotranspiration limits losses through volatilization and leaching. In this context, fertilizers can be applied more precisely and efficiently: moderate inputs are often sufficient to maintain or even increase productivity. For example, simulations in Mediterranean systems show that some C3 crops can sustain high yields even with a significant reduction in nitrogen inputs, while also reducing Nâ‚‚O emissions. However, excessive reduction in fertilizers can lead to a critical threshold beyond which productivity declines, especially in areas where light becomes the main limiting factor under the panels.

In contrast, Australian climates display greater diversity, ranging from the arid zones of inland Australia to the temperate regions of the southeast. In highly sunny and arid areas, agrivoltaics play a role similar to that observed in the Mediterranean, reducing water stress and improving crop resilience. However, in some temperate or already well-irrigated regions, shading can become a limiting factor for photosynthesis, thereby reducing the positive response of crops to fertilizers. Under these conditions, applied nitrogen may be less efficiently converted into biomass, leading to lower input efficiency. For instance, in Australian cereal systems, high fertilization under agrivoltaics may not result in proportional yield increases if light availability becomes insufficient. This creates an imbalance between nutrient supply and the plant’s photosynthetic capacity, highlighting the need for precise calibration of fertilizer doses based on shading levels and crop type.

The comparison between the two regions highlights a fundamental difference in how fertilizers interact with agrivoltaic systems. In the Mediterranean basin, agrivoltaics tend to simultaneously improve water and nitrogen efficiency, enabling a potential reduction in inputs without compromising yields, especially under high water stress conditions. In Australia, by contrast, the benefits are more heterogeneous and strongly depend on the trade-off between available light and water limitation. This implies that fertilizer optimization cannot be uniform; it must be tailored to the specific configuration of the agrivoltaic system, panel density, and local climatic conditions.

A key aspect of this optimization lies in the existence of critical fertilization thresholds. In both contexts, studies show that agrivoltaic systems can enhance productivity up to a certain level of nitrogen input reduction, but beyond these thresholds, yields decline rapidly. In Mediterranean regions, these thresholds are higher in arid areas, where water is the primary limiting factor, whereas in Australia they vary more depending on light availability and crop type. For example, C4 crops, which are more efficient under high light conditions, are generally more sensitive to excessive shading under panels, reducing their responsiveness to fertilizers.

From a broader perspective, optimizing fertilizer use in agrivoltaic systems fits within the water–energy–food–climate nexus. Solar panels not only affect energy production but also modify biophysical flows at the soil level, thereby influencing nutrient dynamics. By reducing evaporation and stabilizing microclimatic conditions, they can limit nitrogen losses and improve the sustainability of agricultural systems. However, such optimization requires an integrated approach combining agroclimatic modeling, nutrient flow monitoring, and local adaptation of farming practices.

In conclusion, agrivoltaic systems offer significant potential for optimizing fertilizer use, but this potential is highly dependent on climatic context. In Mediterranean regions, they support effective input reduction while maintaining yields by alleviating water stress. In Australia, they require more refined and dynamic management, where the balance between light, water, and nutrients becomes the determining factor. The future challenge will therefore be to develop optimization models capable of simultaneously integrating climatic, agronomic, and energy variables in order to maximize the sustainability of agricultural systems in environments increasingly constrained by climate change.

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