Technical ArticlePredicting Soil Phosphorus Fertilizer Rate Using Hierarchical Segmented Regression ModelsShuai, Xiufu1; Yost, Russell S.2; Smyth, T. Jot3Author Information 1Water Resources Research Center, University of Hawaii at Manoa, Honolulu, HI 96822. Dr. Russell S. Yost is corresponding author. E-mail: firstname.lastname@example.org 23190 Maile Way, Room 102, Department of Tropical Plant and Soil Sciences, University of Hawaii at Manoa, Honolulu, HI. 3Soil Science Department, North Carolina State University, Raleigh, NC. Received November 18, 2010. Accepted for publication March 10, 2011. Soil Science: June 2011 - Volume 176 - Issue 6 - p 303-306 doi: 10.1097/SS.0b013e318219db24 Buy Metrics Abstract Predicting soil phosphorus (P) needs and P fertilizer requirements is important for plant nutrition and reducing environmental risk. The P requirement (PR) can be calculated from three components: the current status of soil P (P0), soil P buffer coefficient (PBC), and the soil P critical level (PCL). The PBC and PCL can be predicted from soil clay content using linear-plateau models. The PR, PBC, and PCL form a hierarchical model because PR depends on PBC and PCL, which, in turn, depend on soil clay content. The objective of this study is to estimate the parameters in this hierarchical model to ensure reasonable performance and behavior of PR in a large range of soil clay contents. Results showed that the linear-plateau model described the change of PBC with soil clay content in the range of 39 to 760 g kg−1. This model also described the change of PCL with soil clay content in the range of 80 to 760 g kg−1 for six crops, including cotton, cowpea, maize, peanut, soybean, and wheat. The obtained PR showed irregular behavior of PR within soil clay content range from 288 to 357 g kg−1 when PBC and PCL were independently predicted from soil clay. When the join points in the linear-plateau models of PBC and PCL were set to be equal, the irregular change of PR with soil clay content disappeared. The hierarchically modeled system predicts a decrease in PR with increasing current status of soil P and a curve-plateau trend with soil clay content. © 2011 Lippincott Williams & Wilkins, Inc.