I have just studied the issue of Crop circles in some detail and this is my report that might shed some light as to why I personally believe some of our "UNIVERSAL SPACE SHIPS" are indeed "responsible for some" but not all of these manifestations of CRAZY WALLABIES THAT GET SLEEPY FROM POPPY SEEDS!
After all Opium is a "tranquilizer" as anyone knows that has tried opium before which I have not, so that you do not call me an "AMBASSADOR ON DOPE" like William Jefferson Clinton, who stated he "tried Weed" but did not inhale!
For one we thought it was "impractical" to transport Wallabiess on space ships just to "prove we do not exist" and leave no traces in the natural environment, when we "come and go" as we indeed please sometimes with in a "FLASH" as has been reported in some cases of "crop circle creation"!
Needless to state we can "put ourselves under Universal Cloak" kind of like the Masons do when they "put on their 14th degree rings" which they claim has the "power of higher magic" and also "makes them invisible" or so they think at least!
We also like to "leave some traces" to get people's hope up that they are not alone in this world or UNIVERSE better stated and thereby we "confirm that hope" by "irradiating some of the soil" if the crop is still young, the radiation tends to affect the seeds negatively meaning their "seedlings" created from those areas prove to be stunted in their growth, but if it is
during the final phase just before the harvest then seedlings obtaned from those crop circles do tend to grow up to twice or 3 times faster and the nodes are wider spaced than on regular crops, now I cannot claim, this is either a "beneficial" or "detrimental mutation" due to irradiation, therefore I can only warn people not to get "HIGH ON CROPS" that have been irradiated, for while there are "researches" on this topic on our home world, I am not currently up on it, so I merely suggest you take proper precautions, for the "final judgment" on "improved crops" by mankind is not yet in, so to invest in crops that have been "mutated by aliens" that could be a "very dangerous undertaking", and if anything goes wrong, no doubt we would be blamed in the process, therefore I am not willing to vouchsafe for the safety of that procedure!