U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


Document Type


Date of this Version



Precision Agric (2012) 13:276–284; DOI 10.1007/s11119-012-9258-5


A recent paper in Precision Agriculture concluded that algorithms to calculate in-season fertilizer nitrogen (N) recommendations need to include yield and fertilizer response considerations because grain yield and yield response index are independent of each other. The authors used maximum and zero N yields from selected long-term wheat and maize studies to support their conclusion. Yields from plots receiving intermediate N rates in the maize study indicated a probable dependence between grain yield and yield response index, which is contrary to the authors’ conclusions. Data from a more recent, long-term irrigated maize study on a similar soil type were used to illustrate that grain yield and yield response index are definitely dependent on each other and further that the in-season sensor-based sufficiency index is highly correlated with relative yield. The implication is that a yield component, as such, does not necessarily need to be included in development of an in-season N recommendation algorithm.