There can be many reasons for the range of prices for essentially the same product, including what you mentioned- big brand names. If the guaranteed analysis is 10-10-10, the nutrient sources may be somewhat different but you are getting the same amount of N-P-K in the same chemical form with similar release rates. We are not aware of any "slow-release" formulations of 10-10-10 fertilizer.

So it would make sense to buy the least expensive. The environmental harms- use of fossil fuels in manufacturing, mining of rock phosphate, etc.- will probably not vary much between synthetic fertilizers.

You can read more about fertilizing for gardens and vegetables on our web pages: 

• https://extension.umd.edu/resource/garden-fertilizer-basics/
• https://extension.umd.edu/resource/fertilizing-vegetables/

If you can start your own compost to use in the garden or supplement what you need to purchase, that would cut costs and you would know what it contains. It would also help reduce household waste (thus reducing fossil fuels from sanitation vehicles etc.) and nutrient recycling on your property. You can read about how to start a pile on our 'How to make compost at home' page. If you don't have the ability or space to have a pile in your yard, you can look into any local compost pick-up programs that may have an upfront cost but benefit from the finished compost. There is also the option of a worm bin! 

Let us know if you have any further questions. 

Emily