My former field manager added wood ash to the fields as a soil amendment. I am researching online but I figured people in this forum could give me another perspective on this. any info or resources will help. The farm is certified organic.
My much better half's employers out of town have clay that tends towards the acidic due in part to nearby native conifers. They also heat with wood. They use their wood ash to bring their soil pH up, as D. Logan mentioned.
Wood ash appears to be only a third as effective as lime at liming the soil, so three times as much wood ash may be required to achieve the same effect. However, it is noted that commercially available wood ash is less nutritionally significant as that from woodstoves at home. In any case, determining the pH of individual batches can easily be done in a rough manner with any variety of litmus-based kit. That pH can be compared with the standard for lime in application calculations, and a precise measurement can be achieved at need.
It may take three times as much material to do the same job as lime, but if it's accumulated over time, and can be had for free, and potentially worth carbon credits, or at least not cause carbon deficit by avoiding use of lime, there's enough going for it that it makes overwhelming sense to do, if your soil tends towards the acidic and you heat with wood, or if wood ash is a common industrial byproduct locally.
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The minerals others have mentioned are dependent upon; 1. species of tree the ashes came from, 2.what minerals were available to the growing tree, 3.how long the ashes were stored prior to spread on the soil.
Wood ashes are; 1. soil conditioner, 2.pH adjusting for a limited time, 3. source of minerals, 4.can help new ions of minerals form for use by plants as a nutrient.
Benefits of incorporating wood ashes into soil start with all the above benefits and then there is the beginnings of "terra preta", ashes are one of the primary components of terra preta and the ashes are being found to be a huge portion of what allows terra preta to be self forming. There is a special symbiosis between the organisms of the microbiome of good soils and the ionic exchanges wood ash brings to the party. It can also be instrumental in fungi being able to create concretions in the soil sub surface which is a very big deal if you want to grow food producing plants. If there happens to be any little bits of charred wood lingering in those ashes, all the better for the microbiome and your soil profile.