I agree with the others, he is abusing the situation. How are the other guys getting paid? Are they being strung out as well? or his he paying them on time? Are they also people he would could consider a friend? or are they just employees?
As a business owner, there are times that funds get tight, and there is a set order in which you pay your bills, bassed on importance. First paid is always your EMMPLOYEES, then come vendors, banks, taxes based on importance and who will cut you off first. Then if you have funds left owner you pay your self. Also there is no reason you should be regularly paying for anything for the business. On occasion my guys may need to grab something that they can't get from a nearby vendor who I have a credit line with, such as if they need to run into homedepot. For this, each truck has an envelope with $100 in the glovebox. If the guys need to grab something more expensive, and the only option is for them to grab it right then, then I will give them cash or a check that afternoon, the next day at the latest.
If I was in your shoes I would start looking for another job, one with a reputable company. If you are a good irrigation tech then you should be able to find work. Once you find a new job, let him know if you do not receive full pay plus re-imbursement you will go to the state.
Why do people not respect us as they do other tradesmen? Because every Tom, Dick, and Harry doesn't think he can be a plumber or electrician!