Interestingly, home gardeners use 3 times as much fertilizers than farmers -- more is NOT better!

Joel C. Reid, Mesa Verde Resources:

What to Do

We know that nitrogen inputs are important in crop and turf production, however we suggest that nitrogen inputs be managed much, much more carefully and recommend the use of humates to restore soil carbon in its most active form. Applications of humates will not only increase soil carbon levels, but will improve water retention, drainage, soil tilth and nutrient retention. Humates also provide a healthy substrate for beneficial soil microbes.

Research has shown that soils with less than 3% organic matter can lose 15% to 40% of N in a growing season. Anchoring nitrogen in the soil is part of the important job of soil carbon/humus, as N binds readily with carbon-based acids such as humic and fulvic. This reduces the need for heavy, expensive inputs of N fertilizers. Moreover, the stimulation of symbiotic and free-living nitrogen-fixing bacteria by humic substances adds to availability of N from the atmosphere, supplying, in many cases, up to 75% of a crop’s needs.

By applying humates to soils where synthetic N and other fertilizers are used, we can restore soil carbon levels, balance the ratio of carbon to nitrogen and break the vicious cycle we have created in most conventional production soils. Humates are a direct input of soil organic matter, providing the most important aspect of a healthy, productive soil.

I just purchased humic acid for the first time this spring and I still have a lot to learn about fertilizing and amending our desert soils for vegetables and fruit trees.  Recently we got nitrogen fixing microbes, mycorrhizae and minerals.  And of course I've done a ton of reading -- my head is spinning.   So much fascinating info, I'll have to elaborate in new posts.