  We study the non-linear realization of supersymmetry. We classify all lower
dimensional operators, describing effective interactions of the Goldstino with
Standard Model fields. Besides a universal coupling to the energy momentum
tensor of dimension eight, there are additional model dependent operators whose
strength is not determined by non-linear supersymmetry, within the effective
field theory. Their dimensionality can be lower than eight, starting with
dimension six, leading in general to dominant effects at low energies. We
compute their coefficients in string models with D-branes at angles. We find
that the Goldstino decay constant is given by the total brane tension, while
the various dimensionless couplings are independent from the values of the
intersection angles.
