There is something about walking into a business and the staff has on matching uniforms. Not sure the psychology behind it, but I typically view the business as being more professional.
I am sure you can name an impressive place with a uniformed look and appearance. Have you ever considered the impact uniforms could have on your farm? Most farms consider uniforms and immediately think, "cost." Should they be thinking "profits?"
There are several positives for uniforms. It adds advertising for your business. Your employees are walking billboards representing your business in the field, at the local diner, the hardware store, etc. Your name will be more present in the community. More presence results in more conversations. More conversations lead to more opportunities.
Along with advertising, matching attire supports a professional image and appearance. It is a statement about your company to others that you are a progressive, stable and prideful organization.
It also has a large impact internally with your team and their performance. It promotes team unity and confidence amongst the staff. There have been several studies and articles stating a uniform approach at work can augment positive attitudes.
As for implementing a uniform policy, consider several factors such as who will pay for them, who will handle replacements and what type of material makes sense for your team. Would you use a uniform company or simply have t-shirts with logos?
You can legally require an employee to pay for their own uniforms as long as the deduction does not put them below minimum wage requirements. However, I would be careful making them pay in full as it may have a negative effect on employee morale. I recommend the employer cover at least a portion of the cost.
Extend the company clothing beyond your employees. An excavating company I use gives out sweatshirts. I wear this garment all the time and have become a walking billboard for them without even working there. Several individuals have come up to me to chat about them. Regardless the topic, it spurred people to talk about their company. And that can be a good thing – shouldn't people be talking about your operation?