“…This is a routine test for many vegetable and fruit crops. Measurement of sap NO 3 can guide N fertilization of annual cereal grasses used for forage (Delgado & Follett, 1998; Ismail & Withers, 1984; Westcott, Cash, Jacobson, Carlson, & Welty, 1998; Zhang, Redmon, Fuhrman, & Springer, 1999); annual cereal grasses and maize used for grain (Palenski Brown & Kemp, 1989; Cornforth, 1980; Hoel, 1999; Jia et al., 2004; Justes, Meynard, Mary, & Plenet, 1997; Papastylianou, 1989; Shou, Jia, Cui, Chen, & Zhang, 2007; Thompson et al., 2004; Wang et al., 2020; Withers, 1982; Zhang et al., 1999); and for perennial or short‐lived grasses used for forage (Lyons, Hawley, & Jeffrey, 1992; Reddiex, Rowarth, & Searle, 1997; Viana et al., 2014). The most common routine use of fresh sap NO 3 measurements in grasses, however, is to prevent NO 3 poisoning in livestock consuming the herbage and not as a guide to optimize yields.…”