Regression

Coefficients

Pr > F

Linear

0.2051

<0.0001

Quadratic

0.2258

<0.0001

Cross product

0.0016

0.5608

Total model

0.4324

<0.0001

Parameters

Coefficients

Pr > |t|

Constants

1.5141

<0.0001

P

0.0522

<0.0001

Ca

0.0086

0.0007

Mg

0.0060

0.0268

P × P

−0.0005

<0.0001

P × Ca

−0.00001

0.4696

P × Mg

−0.00002

0.2568

Ca × Ca

−0.0001

0.0012

Ca × Mg

0.00001

0.6300

Mg × Mg

−0.00007

0.0121

P × Ca × Mg

4.63 × 10⁻⁸

0.8953

Critical values

Factor

Critical doses (kg/ha)

Optimal doses (kg/ha)

RDG (t/ha)

P

48.49

41

Ca

40.23

37

3.06

Mg

33.07

29