3.4.6 Soil P prediction
The relationship between the observed and predicted P for calibration revealed MARS to predict the P with acceptable prediction accuracy (R2c=0.80; MBEc=-1.12; RMSEc=10.75; RPDc=1.80 and rank=1.00). These predictions were classified as good. The prediction accuracy for the validation using PLSR was observed as non-reliable with R2p=0.33; MBEp=-3.41; RMSEp=19.09; RPDp=0.89. The best overall rank of 2.25 was recorded for the PLSR (Figure 4f). Xu et al.(2018) reported comparably better prediction accuracy based on SVMR and BPNN model for total phosphorus (TP) with R2=0.35-0.81. Similarly, Udelhoven et al. , (2003), Cozzolino et al. , (2013), Hu (2013) and Schirrmannet al. (2013) also reported possibilities of P prediction using spectroscopy through multivariate modeling.