Compost spreaders are working in almond orchards in this area. The addition of composted organic matter – often composted yard waste — to soil should generally benefit soil physical and chemical properties. However, it isn’t a source of short-term plant available nitrogen. Research by UC Davis specialists Tim Hartz and Jeff Mitchell has shown that composted yard waste, when mixed with sand and held under constant, optimum moisture and temperature (the optimum conditions for mineralization of organic nitrogen) produces a very little plant available nitrogen (2% of total nitrogen in the compost) in the short run (12-24 weeks). When compost is broadcast on the soil surface and not incorporated, plant available nitrogen should be even less. Dr. Hartz did conclude that manures and composts had value in long-term soil building in vegetable crop production, where those materials are incorporated into the soil. [Untreated/uncomposted manure use in almonds is a food quality risk and not supported by the almond industry.]
Why bring up compost use? Growers are willing to pay for it and seem happy with the results. Here’s why. If California agriculture ends up in a regulatory situation where nutrient budgets are required of growers, it should be recognized that the short term nitrogen benefits from composted yard waste are almost non-existent and the long term benefits are unknown.
Previous entries on compost applications can be found here and here.
GBowman
November 30, 2012I wish there was more research regarding the benefits of compost in almond production and whether or not it can substitute conventional fertilizer if used over a period of time. In speaking with different people in the compost industry it appears they are reluctant to fund research as they seem to have no problem selling compost. I am intrigued with the idea of substituting compost for conventional fertizers such as potassium and phosphorus as you not only gain the nutrient value but also a whole host of microbial benefits. However, I know that the release of P and K can take multiple years to become available and I would think that early on a compost program would have to overlap with a conventional program to see that the trees nutrient demands are met. I wish the compost industry would fund some of this type of research but for now I’ll just play around with it a little myself!
David Doll
November 30, 2012Thanks for the comment. We are in the works of developing a project to review the long term benefits of compost applications. This is a very complicated issue, so there are many aspects that we are trying to cover. Most of our data is based upon annual crop work by Dr. Tim Hartz (UC Davis). What he has shown is that most nutrients are more readily available than we use to think. It is no longer the assumption of 33% in year one, 33% in year two, 33% in year three, but rather more like 90%, 8%, 2% over that same three year period. I reviewed his research in a previous entry, and would encourage you to view it to address the questions of potassium and phosphorous availability. Both of these nutrients (as well as nitrogen) do become available to the plant within the year of the compost application — much more quickly than we traditionally thought.
JJ.
February 6, 2015Has any work been done with humic acid?
David Doll
February 7, 2015JJ,
No, not within almonds or other tree nuts. Sorry that isnt much help,
David
Sara S
August 22, 2015Is it ok to put compost down before planting? Don’t want too much N but need something on very sandy soils, I think.
David Doll
August 22, 2015Sara,
Yes, it should be fine. We have applied relatively high rates of compost pre-plant and then incorporated the material into the berms. Within our rootstock trial, we applied 5 tons per acre to the berm (about 10 tons/treated acre), imediately disced in, pulled berms and planted about 2 months later. The amount to apply should vary depending on the type of compost, the amount of nitrogen, and the amount of salt. Keep in mind that too much may damage newly planted trees especially if it is too concentrated within the rootzone (Our’s was mostly OM, with minimal nitrogen). The risk can be reduced by incorporating the material a few months prior to planting.
David
Alec Earle
October 13, 2018It has been 6 years since this article was posted. Are there any updates to the benefits of compost application for almond orchards. We have 3rd leaf trees and have applied compost each year. We’re getting ready to do it again. If spreading compost provides no benefit, we’ll be happy to spend our $$$ on something else. Thank you. Alec
David Doll
November 3, 2018Alec,
The results of compost applications have been mixed. Vivian Lopez, my former SRA, did confirm that compost applications help improve water infiltration. We did not see any positive impacts on yield. A larger, and much more complex study by Sat Darshan and colleagues have found increases in soil organic matter with continual applications of compost. This, however, has not led to an increase in yield improvements within the multiple testing sites. It is thought that these positive aspects will have a long term benefit on orchard growth and yield.
Also, it does appear that nutrients within the compost do make their way into the tree – particularly potassium,, phosphorous, etc. Amounts vary by the source, and analysis should be conducted prior to application. The value of nitrogen from the compost, however, appears to be a bit more limited. Some uptake occurs, but not at the levels in which it is applied within the compost. In other words, if 100 lbs of nitrogen were applied by compost, the tree response doesn’t match what would be expected for that rate. This effect may be due to tie up of the nitrogen by the microbes within the soil, but it could also be lost from the system due to conversion into nitrous oxide. We still need to determine this aspect.
In saying all of that – it is bit of a grab bag of results. Is it worth the expense – that is for the operation to decide. If looking to improve soil organic matter, there are other ways that may provide a greater benefit – including cover crops. Fertilizers can be used to supply nutrients and soil amendments can be used to maintain infiltration. I believe there is a benefit to compost, but high priced compost may not make economic sense – especially when I hear compost budgets of $250+/acre (after spreading).
David