Wheat mineral nutrient uptake, harvest indices, and grain density from a regional perspective

Research is lacking on wheat (Triticum aestivum L.) mineral nutrient uptake at broad scales, accounting for environmental variation, which is needed to effectively manage and model nutrient dynamics of wheat cropping systems. Therefore, our primary research objectives were to (1) provide analysis and estimation tools characterizing wheat nutrient (N, P, K, Mg, Ca, S, Mn, Fe, Zn, Cu) uptake in grain and the whole crop at farm and regional scales and (2) evaluate nutrient harvest indices (NutHIs)—nutrients deposited in grain relative to total aboveground uptake—as an indicator of crop nutrient relations/economies. There were clear linear relationships between grain yield and nutrient uptakes in grain and the whole crop. Functions describing the nature and error of these relationships are presented, along with more flexible estimation approaches. Median NutHIs approximated averages synthesized from recent studies and generally exceeded those from older studies, consistent with evidence that NutHIs have increased with wheat improvement. The NutHIs, except ZnHI, were generally positively associated with grain harvest index and not related to yield. Given that grain mineral density, an indicator of nutritional value, has declined over time, making ongoing progress in simultaneously improving grain yield and mineral density may depend on selection for increased crop nutrient uptake and partitioning to grain. This study also provided corroborative evidence that the modern wheat classes do not differ in grain mineral density. In summary, this research provides valuable data and tools useful for sustainable nutrient management and provides insights into the nutrient economy and nutritional value of modern wheat.