“…However, multiple linear regression analysis is limited to describing linear relationships between crop parameters and site variables, and the results may be misleading when these relationships are not linear (Kitchen, Drummond, Lund, Sudduth, & Buchleiter, 2003;Liu, Goering, & Tian, 2001). Several non-linear, nonparametric techniques have been applied in such situations, including project pursuit regression (PPR) (Drummond, Sudduth, Joshi, Birrell, & Kitchen, 2003), state-space analysis (Wendroth, Kuhn, Jurschik, & Nielsen, 1997), classification and regression tree (CART) (Stewart et al 2002), boundary line analysis (Kitchen et al 1999) and artificial neural network (ANN) analysis Kitchen et al 2003).…”