Cropping Systems: Applications, Management and Impact

44 Liliana Suñer and Juan Galantini

Table 1. Eigenvalues of principal components including all variables

analyzed in the system under study

Lambda Value % Cumulative %

1 3.19 0.43 0.43

2 2.98 0.25 0.68

3 1.46 0.12 0.8

4 1 0.08 0.89

5 0.68 0.06 0.94

Table 2. Eigenvectors of the parameters analyzed for the first two

principal components

Variables CP1 CP2
rP 0.10 0.06
rN 0.01 - 0.02
gr P 0.33 0.04
dm P 0.34 0.10
Ygr 0.40 0.03
dmY 0,40 0.13
Pe - 0.16 0.33
Po 0.05 - 0.45
Pi - 0.23 0.49
wue 0.34 0.17
rcc 0.31 0.21
Po/Po+Pi 0.19 - 0.49
rP, phosphorus rate; rN, nitrogen rate; Pi, inorganic phosphorus; Po, organic
phosphorus; Pe extractable phosphorus; dmY, dry matter yield; grY, grain yield,
dmP, dry matter phosphorus, grP, phosphorus grain; wue, water use efficiency;
rcc, rain crop cycle.

This suggests that available phosphorus in the soil solution is not the only
important, but also the other P-forms, and most especially the equilibrium
between organic P-forms and total P. Fernández et al. (2005) have
demonstrated the important role of microorganisms in cycling nutrients,
particularly P. The content of SOM may thus be related to P-availability
because of the role of P as a food source for microorganisms, not because of
the content of P in SOM (Needleman et al., 1999). The results show that P-