Table 6. Principal components analysis under different nitrogen fertilizer management strategies.

Statistical parameters	PC1	PC2
Eigen value	16.9	3.6
% of Variance	80.4	17.0
Cumulative variance (%)	80.4	97.4
Factor loading	Eigen vectors
Grain yield	0.230	0.169
Total biomass	0.241	−0.037
Harvest index	−0.120	0.453
Grain nitrogen (N) uptake	0.205	0.276
Total N uptake	0.240	0.041
Grain phosphorus (P) uptake	0.212	0.252
Total P uptake	0.242	0.051
Grain potassium (K) uptake	0.223	0.191
Total K uptake	0.240	−0.067
N harvest index	−0.211	0.230
P harvest index	−0.173	0.360
K harvest index	−0.099	0.476
N agronomic efficiency	0.230	0.169
P agronomic efficiency	0.236	0.030
K agronomic efficiency	0.238	−0.004
N recovery efficiency	0.240	0.041
P recovery efficiency	0.230	−0.060
K recovery efficiency	0.237	−0.093
Cost of cultivation	0.202	0.290
Net return	0.242	−0.036
Benefit to cost ratio	0.219	−0.209