How necessary is bacterial inoculation for legumes

Hello all,

I am planting legumes in my wood chip mulch-gardens with the obvious intention of getting nitrogen fixation in the mix.  I did go out and buy a little package of the black, dusty inoculation for the peas I planted, dumped all the powder and all the peas into a little plastic bag, shook them up and went out and planted.  In retrospect, I realize I should have moistened the peas to get more of the inoculant to stick to the peas, but I am pretty sure that there are lots of bacteria on those peas in the ground.  When I was done planting over 300 peas I emptied the remainder of the inoculation onto the garden bed just to get the bacteria into my gardening medium.

But back to my original question, are there nitrogen fixing bacteria in the soil naturally?  Instinct tells me that these bacteria are all around us and that legumes just make associations with these microbes.  Further, instinct tells me that by adding inoculation to the seeds (peas in this case) we are sort of super-charging an already existing relationship and that repeated plantings of legumes would only take advantage of the increased bacteria left from previous crops.

So my basic assumptions lead me to the question of whether the inoculation is even necessary in the first place.  Good to be certain, but would planting repeated crops of legumes create their own flushes of nitrogen fixing bacteria even without adding them to the soil in the first place.  I understand that there may be cases where a person may have incredibly sterile, barren soil (perhaps by adding too many chemicals in the first place), but I would think that bacteria, fungi, and virtually all other microbes are pretty mobile and will make their way to the legume roots one way or another.

Another thought for those who are making wood chip mulch gardens and especially those using mushroom compost in their beds--would it not be best to add the bacterial inoculation at the time of spreading the fungal spawn, just to get the bacteria into the "soil" in advance so that when planting a legume the micro biota areready to go?  

These questions seem reasonable and logical to me, but I do not in fact have any direct knowledge or specific information pertaining and I am basing my questions on assumptions that soil microbes are fairly widespread.  If anyone has any information or knowledge either supporting or contrary to my assumptions, I would love to know your thoughts.

Thanks in advance,

Eric

If you are in a rural place, or know the weeds in your yard, are there other types of legumes/clovers growing?   They don't all use the exact same type, but they are an indication that pod production/seed production is happening because they are finding it in the soil.

Organic soil, rich in multiple sources of composting material, ought to have enough inoculant for all types.  I haven't used inoculant in years and haven't had any problems with legumes.  I encourage clovers and vetch to grow until they reseed and die back.  If I need to plant where the clover is growing, I just yank out a chunk and plant among it.    I've got knee-high clover in the rows between orchard trees that produces a lot of seeds to spread around elsewhere.   Big patches of vetch also encourage ladybugs and other beneficials.

In a new garden I would place my bets on several inches of good, rich compost to create the right environment.

Cristo, thanks for the reply,

Well, you fairly well described my gardening location and setup.  I do live in a rural area, and the bed had been pasture since time immemorial before it was a garden.  I have grown many types of crops on the bed before converting it to a wood-chip based garden about 2 years ago.  Now it has two year old wood chips about 1' thick that have been thoroughly inoculated with wine cap mushroom spawn which are not showing any mushrooms as of yet, but are rapidly breaking down the wood chips which was the main reason I spread the spawn in the first place.  If the inoculant was not there before, after planting the peas (which are coming up now) I spread the extra inoculant around the bed after planting the peas.  There are some leguminous weeds growing so by your measure and my instincts, I would have to think that the bacteria are already there.

Thanks a lot for your input,

Eric

Eric, sorry for the brevity this is busy spring season!

If you have vetch growing anywhere around there, you will have the correct rhyzobium for peas on your place. Clover is a different species, and I believe some other legumes are a third. There are several different species used, but honestly, I haven't ever inoculated except for areas that were forest and were cleared, if there was no understory vegetation. I throw whole plants in the compost at the end of the year, and there seem to be nodules on everything.

However....This is the first year I have planted the big wood chip bed, and I threw some winterpeas in there last winter, which should have the same rhyzobium as peas. Most of the winterpeas did not do well, so it appears there were not available bacteria in the chips. So it may be necessary to inoculate either with commercial or some pureed nodules when starting out.

TJ,

Any reply is better than no reply, so thanks for the input.  It will be interesting to see how things go. The peas are technically inoculated by now, though as they were dry, they maybe don't have as much inoculation as they could.  I just don't know if this even matters as I am pretty sure that even if there is a little bacteria on the peas at planting it will grow and multiply as the peas grow.  And I put the rest of the inoculate in the bed anyways.  So far the little pear look nice and healthy, but then they just poked their heads up in the last day or so.  

Thanks again for the reply,

Eric

Eric, there are well over 2,000 different Rhizobium species and most (as far as we currently know) have symbiotic relations with one or up to four different species of plants.

Within a single family such as peas, you might need as many as 20 different Rhizobium to cover all the different species and subspecies of edible peas.

If the plant is in the ground and doesn't appear to be thriving, then a watering (or dusting) of the roots with one of the commercial Rhizobium packets should take care of that issue.
The alternative is to plant the same things in the same places two years in a row, bacteria seem to be able to detect where their companion plants are growing, if you have a good mycelium population those bacteria can hear the call of the plant roots and they will find their way to the new home.

Redhawk