"Closed Loop" Farms?

@Hal 7853 wrote:

I have recently been thinking a lot about how it is possible for farms to export products (to the public that eats them) and still be sustainable as a closed loop (without outside inputs to replace the nutrients lost in the “exported” foods). Does a well designed farm system actually create “new” nutrients/fertility that allow it to export “old” nutrients/fertility in foods that it sells? I just don’t understand how it could be possible to export foods without, however slowly, reducing the store of nutrients on farm unless some of those nutrients are replaced with outside fertility sources.

I would really like to better understand the idea of “closed loop” farms that still sell products to be consumed by people off the farm. Does anyone have thoughts about this issue?

I would guess it has to do somewhat with what crop you are producing; grain or hay versus produce or an animal crop of some sort. I suspect the nutrient drag on soil is much heavier with the former two versus the latter two. Is it possible to “create” nutrients? I don’t know the answer to that; does the use of legumes qualify? Perhaps we are just recycling existing nutrients to some degree. It would seem that if soil fertility were built to its theoretical maximum, any type of crop that leaves the property takes the fertility down from that point. In that sense, the answer is “No” … you must import nutrients of some sort.

I do know that there are soil scientists that say that if you sell hay off of your property you are doing exactly what you suggest, slowly reducing your soil fertility. Seems logical that this would apply to other crops as well. The degree to which you are doing this would vary with a number of factors, however. Maybe the slash that you leave to rot in the woodlot, the manure that animal agriculture produces, and the hay that you buy in to feed those animals offsets that which is lost to production.

Seems to me that we had this discussion in a soil science class I took in college, it has just been too many years ago to remember the conclusion that we reached. 😉

Sustainability is a nice word and a represents a noble goal but I view at as somewhat a simplistic concept when applied as it often is applied to agriculture. As has been mentioned what you are trying to take from the land is the major factor as to whether you can do this sustainably. Trying to grow monoculture corn or exporting hay are examples of programs which would be hard to sustain without outside inputs.
What are we trying to sustain? A soil that is in prime condition and fertility or one that is run down and in need of many improvements? Soil minerals can be sustained by letting the PH drop thus tying many of them up in the soil. Organic matter can be sustained by green manuring, liberal manure applications and timely cutting plants to waste and sustainable cropping can be achieved by fallowing ground and reducing production which can sometimes be counterproductive as to financial sustainability.
The natural system does have the capacity to resupply the soils and plant needs. For instance nitrogen fixed by legumes or from lightning in rain storms. Leached minerals re-brought to the surface by deep rooted plant communities, soil particle charges that make some minerals available to plants, cropping systems that encourage the recycling of root systems into organic and inorganic components which growing plants then can utilize. The sun working on leaf surfaces to draw mineral laden water into plant roots and other actions of solar photosynthesis.
Some soils have been cropped continuously for centuries with little or no outside soil additives. Stories about Chinese farmers comes to mind but this is an example of low input intensive agriculture relying on much human labor to be successful. My own farm which we bought over 30 years back is in much better condition than when we bought it. We have added lime and some trace minerals and we import hay because of the number of animals we keep but even without these helps I think the cropping system and livestock manures are the most significant reasons for this change.
Sustainability comes down to soils which vary tremendously, are very complex and can be a significant management challenge. That is why I think the concept of sustainability is good but the devil is in the details. My view is we work with these variables the best we can and try not to ask more from the system than it can come up with on it’s own while balancing the need to remain financially viable with respect to production volume. And to not feel guilty importing some limestone and other soil minerals which in their natural states are not sustaining much of anything.
And lets not forget the most important sustainability need and that is the human race. People need food, good nutritious food to live and have healthy lives. We farmers need to be wise in producing this food to meet the needs of the folks we feed and at the same time protect the soil for future generations to reuse for the same purposes. Sustainability is a big part of that challenge but not the only part.

I think it’s a very good question. How well you maintain fertility depends hugely on the nature of your practices.

Generally any kind of tillage (disturbance) involves a greater or lesser degree of soil and nutrient loss. The nutrients you can replenish in this particular disturbed area by moving fertility around on your farm, such as composting manure from overwintered livestock and spreading it on this cropped field. Sooner or later you will run out of phosphorous though, or something else–later if you are careful.

It is also generally understood that permanent pasture, managed for grazing, produces a substantial surplus of fertility. This is what makes everything possible. You can have a field of mixed grasses, graze it, then remove the mass of flesh and bone that has resulted from this grazing and ship it off-farm. Plus, take a substantial portion of that animal’s manure and apply it to a different area where you are doing more damage to the soil than you are on your pasture, such as your garden or a grain crop.

The effect of repeated grazing on the grasses, the presence of legumes in the grass mix, and the permanent sod cover allow you to do better than break even by grazing well. You can build and enrich your soil through the action of the sod. Some contend that you can do insanely better and cover your fenceposts with new soil–I don’t know about that, but you can ship steers off your grazing land in a temperate clime year after year and increase fertility as you do so.

This kind of gets into a whole meta-level of caloric and/or carbon accounting, which to me is intriguing but also mathematically daunting. I suppose one rule of thumb would be to ship out as little carbon as you can–better to sell $50 worth of beef than $50 worth of hay. If you grow grain, don’t sell the straw (I’ve been very tempted by this one…). It is all about trying to keep expectations reasonable and working with the limited surplus of fertility a well-managed closed loop will yield to you in time.

I read a book that described agriculture as question posed by the farmer to nature. Maybe in 15 or 20 years you get an answer.

@goodcompanion 7879 wrote:

You can use legumes to fix nitrogen from the atmosphere. It’s also of course found in animal wastes. Easily lost and easily replaced, with the help of friendly carbon to keep it stable in organic compounds. In that sense you can lose it and create it all the time, once you get the knack of it.

If I remember my soil science, P and K are both much harder to replace once lost. Other than mining them (phosphates and potash) I think both can be derived from oceanic sources, such as kelp.

That is in line with what I recall of the subject. I did read recently where you can get a bump in your soil K by burning off grasses and weeds that are standing dead (winter kill, etc). Not sure though if the total K available would be any more than if you turned those same plant materials under, or composted them and applied to the soil. I would think you would still just be recycling what is already there.

@jenjudkins 7908 wrote:

Well, I’m not sure those ‘farms’ are being totally up front about how they function. If you buy feed for your animals from off the farm, whether it be hay of grain or supplements and use their manure for compost, you are adding nutrients.

I agree. I would imagine that any farm touting itself as a closed loop farm would not buy in hay or feed but would be self-sufficient in those primary foodstuffs. I myself aspire to be a closed-loop farmer in that regard. However I have never known anyone to refuse to buy minerals for their animals on principle, or lime for that matter.

How about a whole different way of looking at this question. Is a farm a net producer of energy or a consumer of it? Electricity, gasoline, hay, and grain can all be quantified in calories, or btus, or whatever unit we can agree on. Back in medieval europe, farming yielded a slight profit (in energy) which supported all those ladies making tapestries and all those knights clobbering each other with lances. Slight being maybe 5 % energy returned over energy invested (EROIE, an oil industry acronym). The highest EROIE ever documented in agriculture is wet rice farming, something like 25% EROIE, once the system is set up. In other words if China had one billion people growing rice entirely by hand, without any imported energy of any kind, the resulting rice would be enough to support those farmers and 250 million others. Medieval europe supported just five non-farmers for each farmer, which is pretty much what the culture looked like then.

I find that a really thought-provoking way of looking at farm planning and operations. But I don’t have the scientific chops to really break down everything on my farm to inflow and outflow of calories. I wish more people did, then grunts in the field like me would have some clue about whether we can make it in a real energy economy. Without this elaborate accounting to tell you whether you are or are not doing a good job, one just has to work with what economy we have (a ludicrous one), go with your gut, and react to changes in the world as they occur.

Hi Howie,

I agree that without returning materials and nutrients to our farms we are really mining it. Just some of us have more to mine (better soil) than others so it just takes longer to “play out” if you don’t replenish.

As far as lime goes, how do you apply the lime on your farm? Do you use a spreader of some sort or have it applied? Also, do you just but it in bulk (by the ton)? Out here in ID the fertilizer plants don’t carry lime because the big wheat farms in our area don’t use it (although their soil pH’s are in the mid 5’s) and on top of that no one has lime spreaders. I thought about using my drop spreader that is used for spreading granulated fertilizer but I hear lime will just pack down in it and not “flow”. Same with the “spin spreaders”. What do you think?