Here are a couple subjects I found that are seldom discussed in articles and forums. I think they can impact your success growing hops.
Poor subsoil conditions. Have you done a compaction/perk test? Take a shovel or a post hole digger and walk your site. Dig or auger a series of holes a minimum of 2 feet deep across the site. Check for orange iron banding in the soil which could indicate a seasonally high water table. Do the holes fill up with water? If they do, you may have to install drain tile or sockpipe. Also, note any "hardpan" - soil layers that are so compacted that roots can't penetrate. (If you have difficulty digging through the soil, imagine a plant trying to put a root down into it.) Hardpan is really common in agricultural land that has been field-cropped with tractors for many years.
Crops like corn, wheat, and soybeans are relatively shallow-rooted and grow fine in the top 10 to 12 inches of soil. Tillage equipment used to grow these crops creates a compaction zone 12 to 18 inches below the soil surface. Hops can easily root to depths of 3 feet or more. Subsoil compaction can halve your potential yields per acre. If you find these conditions, I highly recommend finding a local farmer who has subsoil tillage equipment capable of going at least 24 to 30 inches deep and going across your site in two directions. Do this before you set up your trellis system and plant. It is pretty tough to do afterwards.
Prior herbicide applications to your site. Do you know what chemicals were applied to your site? Has Atrazine, dicamba, 2,4-D or any generic version of these ever been applied? These herbicides are very persistent and slow to break down. Atrazine, in particular, has a half-life of over 25 years. It simply leaches and moves deeper into the soil strata. It takes 3 to 5 years just to leach out of the top 6 inches of topsoil. (Now it is starting to show up in well water.) If you have a site with past applications of these herbicides, you can expect damage to the Hop plants ranging from slight yield reductions to outright death. The hop plants may start out fine, but when their root system reaches the contaminated zone expect trouble. Unfortunately, there is not much you can do, other than select a new clean site. You can have your subsoil sampled and tested prior to planting, to be certain. A possible visual clue is to check out any trees growing around the perimeter of the site. If they appear sickly with dead branches and distorted or stunted growth be aware their deeper roots are probably picking up the residual herbicides.
In short, it pays to investigate these things before you start . . . Thanks for reading and hope this helps your hop growing.
Lynn, the head hop grower at Great Lakes Hops has over 30 years of experience in the horticultural field. Browse the blog articles here to find useful growing information for humulus lupulus, based on personal experience and observations at Great Lakes Hops.