Dynamic change and accumulation of grain macronutrient (N, P and K) concentrations in winter wheat under different drip fertigation regimes

Understanding the grain macronutrient uptake requirements with increased grain yield is essential to optimize the irrigation and fertilizer management for high-yield and high-quality wheat production to meet the increasing future food demand. A three-season control experiment was conducted on drip-fertigated winter wheat to investigate the dynamic changes in concentrations of nitrogen (N), phosphorus (P) and potassium (K) under varying water and fertilizer supply regimes. The results showed that the grain N concentration firstly decreased and then increased during grain filling. Specifically, it firstly increased and then decreased with the increase in fertilization rate, while it firstly decreased and then increased with increasing irrigation rate. The average of grain P concentration decreased with the increase in irrigation and fertilization rates. The grain K concentration showed a slow decline trend at the initial grain-filling stage until reaching a stable value at the mid-filling stage, and it increased with the increase in fertilization rate. Grain NPK uptake at maturity increased with increasing fertilization rate under normal irrigation, while the mild water deficit was found to promote grain NPK uptake. Grain yield and grain N concentration exhibited a positive relationship, and both irrigation and fertilization had significant effects on grain yield and NPK uptake. The grain protein content and N:P ratio were mainly affected by fertilization. The mild water deficit and appropriate fertilization rate improved the grain NPK uptake and production of winter wheat with higher grain protein content, which was conducive to the development of water- and fertilizer-saving agriculture.