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Nitrogen (N) is one of the most limiting nutrients for cereal production, especially in wheat, which is one of the main crops cultivated globally. To achieve high yields, wheat requires a certain amount of nitrogen (N), as N deficiency can lead to a decrease in yield and thus reduce income for farmers. In contrast, excessive applications of N fertilizer can be detrimental to both terrestrial and aquatic environments. To optimize N fertilizer applications in wheat, a three-year field experiment was conducted to evaluate the impact of different N fertilization strategies on various N-related physiological and agronomic traits. Moreover, to optimize N utilization efficiency while maintaining crop productivity, a mixture of five winter wheat varieties was used to mitigate the possible impact of environmental constraints. These strategies were based on a simultaneous increase in N fertilization and N fertilizer fractionation at key stages of plant development in a soil conservation agriculture (SCA) system in which legumes were grown prior to the cultivation of the main crop. In this SCA system, we observed that 200 kgN·ha−1 was optimal for both N use efficiency (NUE) and aerial and grain biomass production. Moreover, we found that at this level of N fertilization, of the application strategies, a 40%/40%/20% split application at full tillering, at the first node, and at booting, respectively, appeared to be the best option for the highest plant productivity.

Arbuscular mycorrhizal fungi (AMF) play major roles in nutrient acquisition by crops and are key actors of agroecosystems productivity. However, agricultural practices can have deleterious effects on plant–fungi symbiosis establishment in soils, thus inhibiting its potential benefits on plant growth and development. Therefore, we have studied the impact of different soil management techniques, including conventional moldboard ploughing and no-till under an optimal nitrogen (N) fertilization regime and in the absence of N fertilization, on AMF spore density and soil chemical, physical, and biological indicators in the top 20 cm of the soil horizon. A field experiment conducted over six years revealed that AMF spore density was significantly lower under conventional tillage (CT) combined with intensive synthetic N fertilization. Under no-till (NT) conditions, the density of AMF spore was at least two-fold higher, even under intensive N fertilization conditions. We also observed that there were positive correlations between spore density, soil dehydrogenase enzyme activity, and soil penetration resistance and negative correlations with soil phosphorus and mineral N contents. Therefore, soil dehydrogenase activity and soil penetration resistance can be considered as good indicators of soil quality in agrosystems. Furthermore, the high nitrate content of ploughed soils appears to be detrimental both for the dehydrogenase enzyme activity and the production of AMF spores. It can be concluded that no-till, by preventing soil from structural and chemical disturbances, is a farming system that preserves the entire fungal life cycle and as such the production of viable spores of AMF, even under intensive N fertilization.

Arbuscular mycorrhizal fungi (AMF) play a major role in the uptake of nutrients by agricultural plants. Nevertheless, some agricultural practices can interrupt fungal-plant signaling and thus impede the establishment of the mycorrhizal symbiosis. A field experiment performed over a 5-year period demonstrated that both the absence of tillage and of nitrogen (N) fertilization improved AMF colonization of wheat roots. Moreover, under no-till conditions, N uptake and aboveground biomass production did not vary significantly between N-fertilized and N-unfertilized plots. In contrast, both N uptake and above ground biomass were much lower when N fertilizer was not added during conventional tillage. This finding strongly suggests that for wheat, no-till farming is a sustainable agricultural system that allows a gradual reduction in N fertilizer use by promoting AMF functionality and at the same time increasing N uptake.