Nitrogen

Optimizing nitrogen fertilization and planting date is essential for improving forage maize productivity under semi-arid conditions. This study evaluated the effects of nitrogen application rates and planting dates on growth, forage yield, and quality of maize (Zea mays L.) in Upper Egypt. A two-year field experiment (2024–2025) was conducted at the Experimental Farm of Assiut University using a strip-plot design arranged in a randomized complete block design with three replications. Four planting dates (15 April, 15 May, 15 June, and 15 July) were assigned horizontally, while three nitrogen rates (167, 238, and 309 kg N ha⁻¹) were applied vertically. Growth traits, fresh and dry forage yield, dry matter percentage, crude protein content, and protein yield were recorded at 60 days after sowing. Results showed that planting date, nitrogen rate, and their interaction significantly affected most measured traits in both seasons. Sowing in mid-May consistently produced the highest plant height, chlorophyll content, fresh and dry forage yield, and protein yield. Increasing nitrogen application enhanced biomass production and forage quality, with the highest values generally recorded at 309 kg N ha⁻¹. The strongest yield response to nitrogen occurred when maize was sown at the optimal planting date, indicating that nitrogen utilization was closely linked to favorable environmental conditions. Phenotypic correlation and multivariate analyses revealed strong associations among vegetative growth traits and forage yield, with a single dominant factor explaining more than 91% of the variation in yield-related traits across seasons. Overall, the results demonstrate that synchronizing planting date with appropriate nitrogen fertilization is critical for maximizing maize forage yield and quality under semi-arid conditions. Mid-May sowing combined with adequate nitrogen supply represents an effective management strategy for forage maize production in Upper Egypt, while further research is needed to optimize nitrogen-use efficiency and long-term sustainability.

In recent years, dietary changes towards reducing animal-based proteins was recognized as a nitrogen pollution-mitigating strategy. This is because producing animal protein generates higher nitrogen emissions compared to its plant-based alternatives. In Japan, there is a switch towards an animal-based diet, potentially leading to degraded water quality. While national-scale studies are common, watershed-level scale dietary changes are not researched, even though nitrogen pollution is often localized. This study aims to evaluate whether dietary and feed self-sufficiency changes can reduce nitrogen load and improve water quality in the Kasumigaura watershed. Firstly, nitrogen load was quantified and spatially distributed. Then, the estimated nitrogen concentration was compared with observed data. Finally, the impact of dietary and feed self-sufficiency changes on nitrogen load and water quality was assessed. Results estimated that nitrogen loading for year 2020 was 4403 tons/N/year, correlating with previous research. Results further showed that switch from livestock to legume protein would significantly improve water quality, up to 0.27 mg N/L. On the other hand, increasing feed self-sufficiency would negatively affect the water quality, up to 0.32 mg N/L. The results emphasize the importance of dietary patterns in mitigating nitrogen pollution. This method can be generalized on other watersheds.

Mineral fertilization is crucial for maximizing wheat yield, ensuring optimal nitrogen and phosphorus supply according to plant development, pedoclimatic conditions, and previous crops, with a balanced N:P ratio being decisive for productivity. This study, conducted at ARDS Turda during 2020/2021–2024/2025, evaluated the long-term effects of nitrogen and phosphorus fertilization on the yield, grain protein content, and foliar disease incidence of winter wheat grown after maize and soybean. The experimental design was polyfactory, in randomized blocks, including 25 variants and 6 repetitions, according to the uninterrupted protocol used since 1967, winter wheat being cultivated after maize for grain and soybean. Phosphorus (0–160 kg P₂O₅ ha⁻¹) was applied in autumn, while nitrogen (0–160 kg N ha⁻¹ after maize and 0–120 kg N ha⁻¹ after soybean) was split 50% in autumn and 50% in spring. Results indicate that wheat yield is strongly influenced by nitrogen–phosphorus interactions and climatic conditions, with nitrogen increasing yield by 450–2700 kg·ha⁻¹ and maximum yields of 7600–7828 kg·ha⁻¹ achieved at N₁₂₀ with higher phosphorus rates. Grain protein content (14.96%) was high at N₁₂₀ dose, while foliar disease incidence and severity were low at minimal fertilization and rose with intensified mineral nutrition.