A self-propelled irrigation machine including an elongated main boom pivoted at one end to a center pivot and supported on a plurality of self-propelled, non-steerable drive units. A check valve formed with an elastically compressible hollow cylindrical insertion body is inserted in the tubular part, which is configured as a receiving part and comprises a fluid passage and a contact region serving as a valve seat, the insertion body at the end thereof opposite the contact region of the fluid passage carrying a sealing element. The invention also comprises means for positioning the pressure chamber and adjusting its location along the lumen. The dispersion vehicle is a polar dispersion vehicle having a boiling point within a range from 150\xb0 C. Also provided herein are vectors and host cells comprising those nucleic acid sequences, chimeric polypeptide molecules comprising the polypeptides of the present invention fused to heterologous polypeptide sequences, antibodies which bind to the polypeptides of the present invention and to methods for producing the polypeptides of the present invention.