How Does Soil Become Depleted?

Can anyone recommend some good articles online about how modern farming methods (using pesticides and heavy fertilizer applications) deplete the soil of nutrients? I'm especially interested in 2,4-D (herbicide) and how it impacts the soil, etc.

I tried to garden in an area farmers had farmed last year, and it was a nightmare. I'm organic. And then I learned they'd used this 2,4-D stuff (after initially having been told they were merely using soap and dish detergent to kill the weeds!) and wonder if that's why it took my sunflower seeds 5 weeks to germinate and I had such low germination rates of seeds, etc. My transplants stunted. Watermelons, pumpkins, cantaloupes, and strawberries all stunted and then turned to dust and blew away. Only radishes, peas, and lettuce did well.

Could the bugs have been driven out of the field with the 2,4-D and into my organic patch and that is why my seeds mostly didn't germinate-- they were eaten?

And the stuff I grew in hot horse manure did well, too.
Online

There may have been enough residual herbicide to inhibit germination and growth of your plants.

Hi Clare

First you have to understand that the soil is (or was) alive. Microorganisms live there. They are an essential part of "the soil". Strictly looking at nutrients, or compaction, etc will not give you a complete picture of the overall soil health.

Basically every single thing that is done in modern agribusiness is damaging to the soil. The only reason why it is able to produce anything at all is because it has massive amounts of external energy input applied, in the form of fertilizers.

In your case of a land rehabilitation - Which is admirable THANK YOU FOR DOING THIS! - You'll want to jump start the life in the soil itself. There are many approaches to this, and it may (or may not) simply take care of itself over time naturally.

I would suggest a nitrogen fixing cover crop that would turn itself into mulch. And, any mulch you can import will help immensely.

Where are you in the world?

As far as resources, there is a great chapter on soil health in the "Edible Forest Gardens" book. Here is a link. This is a great resource to have around and covers a broad range of permaculture related topics.

Thanks for the responses. I am in Salt Lake City, Utah.

Some in another group have suggested that perhaps the soil was just too dry for the seeds to germinate?

The plants the farmers grew last summer were left there all winter. I wondered whether that might have caused pathogens to be present in the soil that were not killed off during our extremely mild winter? The crops left in the ground over the winter were tomatoes and hot peppers.

Clare Scifi wrote:Thanks for the responses. I am in Salt Lake City, Utah.

Some in another group have suggested that perhaps the soil was just too dry for the seeds to germinate?

The plants the farmers grew last summer were left there all winter. I wondered whether that might have caused pathogens to be present in the soil that were not killed off during our extremely mild winter? The crops left in the ground over the winter were tomatoes and hot peppers.

Your germination problems could be caused by many things. Dryness or bugs eating the seedlings are certainly a possibility. If the area has been cropped conventionally, you may also have high levels of saline in your soil (which can be determined by a soil test.)

2,4D has a short half-life (10 days), so you probably do not have soil contamination from that preventing germination. The crops left on the ground may have helped spread blight if you have it, but it would be a problem specific to solanaceous crops. They probably did you a favor by leaving some organic material out there in the soil. And if they were growing tomatoes and peppers, they weren't spraying them with 2,4D because it would have killed them. However, there are other herbicides that are persistent in the soil which they may have used that you don't know about.

I suggest doing a bioassay with the soil in pots inside in controlled conditions. Some instructions and information here:
http://ipm.illinois.edu/pubs/iapmh/15chapter.pdf

But as Ed mentioned, it may simply be that the soil is "dead." I would include fresh compost tea as part of your remediation plan to reintroduce microorganisms, and all the organic matter you can get. If the worms and other soil macrocritters don't come in a year or two, you have want to import some native worms, at least.

herbicides definitely reduce soil microbial content skewing it towards fungi. Residue can inhibit germination of dicots for as much as 3 years (toxicological study I did in university years ago), monocots are far less susceptible. Enhancing organic content speeds soil recovery especially application of rotted manure, so long as they aren't sterilized. Drought can also inhibit germination and growth but the same addition of organics will enhance water retention so you can't lose.

A cover crop, as mentioned earlier, is probably a solid place to start. Making the transition from conventional can take a bit of time, and growing a grass/brassica/legume mix can be a good way to ease into the transition. Any organic matter that can be applied will help, apply and then plant.

Grazing your cover crop, and whatever weeds sprout, is an excellent way to help the transition process (as long as the nitrate levels in the soil are acceptable). Grazing will additionally add a nice manure/urine spread. Cattle are essentially fermentation tanks on 4 legs, and can be utilized as a wonderful tool to achieve your goals (sheep and goats will too...I prefer working with sheep in small areas and cattle on larger ground, but goats are awesome as well). A ruminant passes 85% of the nutrition through it's gut, photosynthesis can make up the rest along with healthy soil life. If you really want to get into it....run poultry too, as they help to balance the nutrient content. Geese are good grazers too, and can be used in small areas if you don't want to mess with larger stock.

If you have livestock, put them into a paddock (size depends on your land and desired stocking rate) and feed them hay while they graze. It will provide the livestock extra nutrition, and any waste will not be wasted but rather turned into fertility and water holding capacity. This is a great way to avoid hauling manure/compost as well.