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Deep Mulch Mineral Balancing

feelgoodfarms
Tue, 19 Mar 2019 16:02:17 GMT

Hey guys, this is the soil test from our government compost facility.http://www.ewswa.org/wp-content/uploads/2018/07/Compost-Test-Results-2018-Row-C17.pdf As you can see the ph is 7.9! Apparently this is because of the high sodium content. I was planning on dumping 4" of this on my sandy loam soil without tilling it in. Does anyone think a ph this high will affect my production? Im growing mostly brassicas, lettuce, beets, spinach. But mostly brassica roots and leaves. I think I will probably have to amend to fix the ph right? Does anyone have any experience with lowering the ph? I want to avoid tilling so Id be mixing it all with strirrup. Maybe I should just put 1" down since my sandy loam has great texture already? Thanks everyone, im going to my county research station to test my native soil to see what is up.

David Blanchard
Thu, 21 Mar 2019 10:19:51 GMT

Here's how a nutrient management calculation looks to me for a 4" application of this compost. I'm doing this on a per-acre basis because that's how most crop nutrient requirements are given. 1 acre = 43560 square feet, and 4" = 0.33 feet, so a 4" application is 43560 X 0.33 = 14375 cubic feet applied per acre. Because this is an application by volume, and the compost test results are a percent by weight, we need a way to relate weight to volume. This is what bulk density does: it tells us how much a given volume of compost weighs. The analysis gives the bulk density of this compost as 448 kg per cubic meter. Converting to U.S. units, the conversion factor for kg/cubic meter to pounds/cubic foot is 0.062 (you can look this up online). So 448 X 0.062 = 27.8 lbs/cubic foot. If we apply 14375 cubic feet/acre, that will weigh 14375 X 27.8 = 399625 lbs. The analysis gives the nitrogen content of this compost as 1.6%. So our 4" application will provide 399625 X 0.016 = 6394 lbs. of N/acre. THAT IS A LOT OF N! Of course, not all of this N is immediately plant-available. The analysis shows that this compost is well matured, so a reasonable estimate would be that 15% of the N will be available to plants in the first year. So 6394 X 0.15 = 959 lbs. N available in year 1. To put this in context, you can grow a 200 bushel/acre corn crop on 200 lbs/acre of N. Most vegetable crops require 100 to 120 lbs/acre N, with only really heavy feeders like storage cabbage or potatoes requiring 200 lbs. So with a 4" application you would be applying 5 to 10 times as much N as your crops could use. And that compost will keep on releasing 10 to 15% of the remaining N each year until it has all been mineralized. And that's the problem. Plant-available N is very mobile in the environment, so if your plants don't take it up a significant portion will end up in either ground or surface water, where it has now become a pollutant. Excessive N (and P) from agriculture is the main reason why Lake Erie turns green in the summer and there is a huge dead zone at the mouth of the Mississippi River. As far as the pH is goes, it's normal for composts to have an alkaline pH, and this isn't usually a problem in the short term. Long term heavy use of compost can raise the soil pH to the 7.5 range, which is a problem because of reduced availability of P and some trace elements. If you're planning to direct seed into this compost, the high EC of 2 ms/cm ("soluble salts" in this analysis) is more of a concern. With potting mixes we try to keep the EC below 1 ms/cm because anything higher can inhibit germination.

feelgoodfarms
Sat, 23 Mar 2019 23:14:31 GMT

Wow thank you so much for typing this out for me. I learned a whole lot I didnt know and this will change things for me. I will be applying much less compost and saving alot of money too. I am concerned about the salts, im not sure there is anything I can do about that except make my own compost. I cant afford a tiller so I need to mulch the soil with compost. Thank you so much you are one of a kind.

feelgoodfarms
Sat, 23 Mar 2019 23:15:09 GMT

Did you study agronomy?

feelgoodfarms
Sat, 23 Mar 2019 23:17:46 GMT

It is only the mineralized 15%, I have to keep in the range of what plants need? Is the 85% non-available N also a concern for leaching?

David Blanchard
Sun, 24 Mar 2019 12:44:53 GMT

I studied soil science way back in the 1970s, but never finished the degree because the attitude toward organic agriculture at at universities was so hostile.

David Blanchard
Sun, 24 Mar 2019 13:00:44 GMT

I later studied ecology and managed to finish that degree. What I learned there has been really useful in my 40 year farming career! Getting back to the nitrogen question, it is the 15% that's plant-available that's subject to leaching. However, consider that a deep layer of compost will be subject to erosion in a heavy rainfall if your land has any slope, just like bare soil would be. That could be a route for excess N to end up in surface water. It's my opinion that leaving a large amount of compost on the soil surface is an environmentally risky proposition. A deep layer of material with a high concentration of nutrients lying on the soil surface is something that you just don't find in healthy natural ecosystems!

feelgoodfarms
Sun, 24 Mar 2019 14:15:06 GMT

That is a good point, I never thought about compost in this way before. Thanks David. You should be on the podcast, you must have alot of useful knowledge for beginning farmers. :) I appreciate it.

stonehousemarketfarm
Fri, 29 Mar 2019 03:25:17 GMT

So, David, this is going to sound pretentious and I really don't mean it to be. You're obviously quite knowledgeable and could teach us a thing or two. Which is why I have a few honest questions regarding no-till. You are on a no-till forum, after all... What's you're take on no/low-till? If you're presumably not continually stratifying your amendments/minerals via tillage, what do you propose? There's an awful lot about annual vegetable farming that isn't "natural" though we can do the best we can to mitigate some of the unnatural effects, erosion.runoff included. Do you incorporate no/low-till in your own farming? What are the approaches/best practices you use? We, personally, use a deep compost mulch system on our farm. In short, we cover our amendments with a layer of low nutrient value compost and have begun mulching the pathways with ramial wood chips primarily to prevent bed erosion (2-3% grade) from the beds into the surrounding field. We also have a catchment pond we monitor for any runoff. The extent of our tillage is a broadfork and tilther, except when crea ting beds for the first time, which we use a power harrow for the initial amendment/compost incorporation. We've found broadforking/harrowing a new bed (on clay soil) drastically reduces erosion. All of that to say, how can we make deep mulching better? What do you propose? I know it's all very context specific, but do you have any insights or experiences that could help us improve the deep compost mulch approach? Maybe integrating complete coverage of the beds as often as possible with living material or straw? Hard mulching the perimeters of garden spaces? Thank you for your input on the forum, by the way! We really do enjoy your posts.

buddingmoonfarm
Fri, 29 Mar 2019 14:35:34 GMT

I was intrigued the first time I encountered deep compost mulch. The veggies produced were huge, looked amazing, and sized up so quickly (the excess production easily justified the cost for the farmer I was working with). But, then I tasted the product. It was extremely bland. For this reason, I do not use deep compost, just a thin (1”) layer every 3 yrs. in my rotation, and instead use cover crops and rock dust for fertility. I have no clue what the analysis of that compost was where I first tasted the results. Perhaps a more balanced product would have not affected flavor.

stonehousemarketfarm
Fri, 29 Mar 2019 15:24:43 GMT

I don’t disagree, but would hesitate to say the previous step didn’t contribute to the later success. I, too, have noticed subsequent crops doing better than previous ones for the same reason. A shit ton of compost alone seems a little simple and inconsiderate to me, as well. I use a deep mulch for weed suppression and a quick shot of OM along with some mineralization to begin with, then will amend as the tests read out over time. I think where the nuance of some of these conversations is lost is most people assume we’re—generally—adding 50 tons/acre on a repeated continual basis, whereas it’s just step one.

David Blanchard
Sat, 30 Mar 2019 16:27:17 GMT

OK, lots of good discussion going on here! My replies to the above questions asked and points made may come in the form of several short posts, because I'm absolutely swamped with greenhouse work right now. First, I want to make clear that I would never presume to tell anyone how they should or shouldn't farm. The points I have made about the deep compost mulch system were made in the spirit of ensuring that everyone using the system is thinking it all the way through, including being aware of how much plant nutrients they're adding to their farm, how this relates to the nutrient needs of their plants, and what the effects on the surrounding ecosystem will be. My experience has been that organic farmers are sometimes pretty casual about nutrient management, thinking that nitrate and phosphate pollution of water arises only from chemical fertilizer use, and therefore needn't be a concern for organic folks. But actually, once nutrients in compost or other organic amendments have been mineralized, the nitrate and phosphate ions released are identical to those originating in chemical fertilizer, and are just as much of a problem if they escape the farmers' fields and enter the broader environment. Moving on to the point that farming isn't natural, no argument there. I do think, though, that healthy natural ecosystems provide a useful model for how healthy agroecosystems might look and function. Here are two characteristics of natural (non-desert) ecosystems that I think are worth considering: 1) Bare soil is almost nonexistent, and 2) Nutrient cycling is very tight, with negligible losses of plant nutrients to groundwater, surface water, or to the atmosphere.

David Blanchard
Sat, 30 Mar 2019 18:40:02 GMT

Now here's some information that Jackson requested on how we do things on our own farm. It's a two person operation, my wife Cindy and myself, certified organic, mostly vegetables with a few beef cattle (100% grassfed) and 120 laying hens (intensively pastured during the grazing season). We are full-time farmers and this is our sole source of income. We've been in business for ourselves for 40 years, and spent 10 years before that working on other people's farms. Over the years we've marketed in most ways possible: on-farm sales, farmers' markets, CSA, and wholesale, but now retail everything through a single year-round farmers' market. We are there 51 weeks a year, gross around $115,000, net around $50,000. For the first 20 years of our career we were dairy farmers, grew a lot of corn, and no-tilled rye into the corn residue after harvest with a Great Plains 8' drill for a winter cover crop. It was really impressive how that drill could produce a dense stand of rye working through a 3" layer of corn residue. After we switched to vegetable production our cropping was don e in 4' wide permanent beds with 2' sod paths between them, laid out across our 3 to 6 percent slopes. Our 45 HP tractor straddles the beds so there is no wheel traffic in the production area. We use a 3 pt. hitch flail mower on crop residue and cover crops, and a spading machine run shallow and at low RPM when tillage is needed. We use a lot of mulch, both cover crop residue and hay, to avoid bare soil whenever we can. Many transplanted crops are planted by hand right through the mulch without tillage, and then for things like carrots that require a seedbed we use the spader. Five years ago we believed that the organic no-till carrot would never happen. That may be about to change. Getting back to that no-till grain drill, we have often wished we could use such a machine on our vegetable beds, but the available ones were just too wide. Now, however, there are at least two manufacturers building full-blown no-till drills, 3 pt. hitch mounted, that are only 4' wide - perfect for our system. We have one of these ordered and are expecting delivery soon. We'll use it for all of our cover crops, and are going to try tweaking the seed meters so we can use it for carrots and beets as well. The crop sequence will look like this: winter rye seeded in September 2018, terminated by flail mowing in late May 2019, buckwheat no-tilled into the rye residue, terminated by mowing in early July 2019, carrots no-tilled into the combined rye/buckwheat mulch. We'll let everyone know how this works out! We don't call ourselves no-till farmers because we do use some tillage. We are working toward minimizing tillage and maximizing soil cover in every way we can think of. Our goal for winter is to have zero bare soil, with living cover crops wherever possible, or hay mulch on beds where the cash crop finished too late to get a stand of rye (early October in our location in Nova Scotia, Canada).

David Blanchard
Sat, 30 Mar 2019 21:33:02 GMT

And finally, how to improve the deep compost system? I think it comes down to 1) Know what's in the compost nutrient-wise by having it tested; 2) Know what your crop will require nutrient-wise; 3) Apply the appropriate amount of compost to avoid drastic over-application of nutrients. For a high-testing compost like the one described at the beginning of this thread (1.6% N), this is going to be more like a 1/4" to 1/2" layer rather than the 4" proposed. If this means not a deep enough compost layer for weed suppression, either source a lower nutrient compost, or add a nutrient-poor supplemental mulch like aged leaves or rained-on hay on top of the compost to get the weed control you need. Also be aware of possible erosion and counter it through layout of beds across the slope, and permanent sod or other runoff-stopping breaks (like wood chips) either between each bed or at least every few beds. For a useful guide to nutrient planning and management in organic syste ms, check out this free download from NRCS: file:///C:/Users/Acer/Downloads/Nutrient-Management-in-Organic-Systems-Western-States-Implementation-Guide.pdf

huerta_tarruco
Tue, 02 Apr 2019 21:48:11 GMT

What about the theory that deep compost itself is so strong in retaining water that even mineralised excess nutrients won't be leaching. I seem to recall something like this in an article about singing frogs farm ages ago. That their runoff and ground water tests showed no N leaching whereas their compost application rates suggested major over fertilizing. It's good to be prudent with nutrient application but there might be things that work differently in no till as compared to conventional ag soils. My gut tells me there should be quite some buffering capacity in a rich, living, OM full soil that makes it so that heavy compost applications don't translate to environmental problems as they would on dead soils... Might be some studies out there too.

David Blanchard
Thu, 04 Apr 2019 10:10:59 GMT

While it's true that some composts have good water retention qualities, in a heavy rainfall event any compost layer will eventually become saturated and start to lose water. Here are a couple of studies which can be accessed for free and which looked at nutrient leaching from compost mulch layers: https://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=7212&content=PDF https://www.sciencedirect.com/science/article/pii/S2095633916300454 Both studies were done in rainfall simulators to make it possible to collect the runoff water so it could be analyzed for nutrient content, and both looked at several different types of compost. The interesting points to me are: 1)The large variability between different composts in the amount of nutrient leaching; 2) The fact that some composts leached high amounts of both N and P. As for the idea that healthy soils have more capacity to retain nutrients than degraded soils, that is undoubtedly true. But is also true that all soils have a finite capacity for nutrient retention, and if that capacity is exceeded they will leak nutrients into the surrounding environment. And for those who are inclined to dismiss nutrient management concerns, consider the study "A Safe Operating Space for Humanity", which can be accessed free here: https://s3.amazonaws.com/academia.edu.documents/36531028/7_ROCKSTROM_A_safe_operating_space_for_humanity1.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1554375278&Signature=4jMmPiv7ULMdC22184nlmuO6AdE%3D&response-content-disposition=inline%3B%20filename%3DFEATURE_A_safe_operating_space_for_human.pdf. Many people who are concerned with sustainability consider this to be one of the most important studies published in recent years. The authors selected what they considered to be the nine most significant ways in which humanity is fucking up Planet Earth, and tried to assess the boundaries for each beyond which we should not go. Two of the nine were directly related to nutrient management in agriculture: excessive loading of phosphorus and reactive nitrogen into the biosphere. We have already far exceeded the safe limit for nitrogen, and are close on phosphorus.

Dawson Mehalko
Sat, 13 Apr 2019 19:13:29 GMT

Absolutely killer thread here guys. Thank you for sharing. I fully believe that the best farmers are in and of themselves scientists and this kind of thread helps demonstrate that very well.