Interactions of soil micronutrients and sulphur with nitrogen and their effect on nitrogen cycling, losses and use efficiency in winter wheat in a range of northern European soils

Conventional agriculture can disrupt soil nutrient balance, exhausting certain nutrients, such as Mn, Zn, Cu and S, while applying excess nutrients, such as N, which can escape into the wider environment. Efficient N use in wheat is critical for sustainable crop production and environmental protection while maintaining high yields. Many nutrient interactions with N are poorly understood, particularly in relation to N use efficiency (NUE) and N cycling across diverse soils. The relative abundance of nutrients and other soil characteristics can profoundly affect the uptake and, ultimately, the loss of other nutrients from cropping systems. This PhD research assessed the impact of S, Zn, Cu, and Mn applications on NUE and N dynamics in wheat systems through controlled environment and field-based trials. A comprehensive literature review establishes the context for this research and outlines the current state of knowledge on Cu, Mn, S, and Zn fer[lisa[on with a par[cular focus on their interac[ons with N. A pot trial across 5 contrasting soils evaluated wheat response to S, Zn, Cu, and Mn applications at 0 and 300 kg N ha-1. Results indicated a small and inconsistent effect of these nutrients on crop yield parameters and highlighted the importance of organic matter for soil fertility. A fully factorial field trial was implemented to construct N response curves under different Zn, Cu and S treatments. S+Cu appeared to interact synergistically with N; this effect was influenced by N application rate and water availability. In a lysimeter study, N leaching was measured under Mn or S applications with different rates of N. Mn and S did not affect N leaching. Most leaching occurred in autumn and winter, during periods of low plant growth and was increased by erratic rainfall in combination with reduced crop yield. Overall, N application was associated with greater crop yields and an increase in N leaching pollution. This research demonstrates a range of nutrient interactions across a variety of environments and highlights the situational specificity of nutrient uptake relationships.