Ten years ago we were still trying to stop water erosion after nearly 20 years of actively working the problem, and soil health was a general term without specifics. Today, we have stopped ~95% of erosion by water, and have an idea on how to stop another ~4%, --I'm leaving ~1% as uncontrollable at this point. We are now hearing more of a consensus of what Soil Health means, --it turns out to be multi-faceted. For us, Soil Health breaks down too four basic elements, --1) maintain surface residue, 2) minimize soil disturbance, 3) diversify crops, 4) keep a live root growing as long as possible during the year. Working to maximize these four elements will hopefully remove soil erosion, build soil structure, feed the biota, build SOM that will result in improved soil health.
WHERE ARE WE TODAY:
The pic on the left: --2006 WW seeded on CF following SB. We were using a high disturbance hoe drill, and you can see a lot of exposed soil. Along with WW we were inadvertently planting weed seed that existed as well. With the exposed soil and impressions left by the hoe, the field was vulnerable to soil erosion going into winter.
The pic on the left: --2015 WW seeded on SP stubble. We have progressed from high disturbance no-till to ultra-low disturbance(ULD) no-till through the use of the stripper header and the CrossSlot drill. We have enough residue on the ground that you see no dirt. In our environment with high summer temperatures, freezing winter temperatures, and most of our moisture coming during the winter(~15"), it's important to conserve as much of our rainfall as possible by increasing percolation and moderating our near surface soil temperatures. The ULD system does this better than any other system out there. The system also reduces erosion from the common forces of wind, water and tillage to near zero.
More detail on the four basic elements mentioned above:
--RESIDUE: The need to maintain 100%+ surface cover (a good gauge is that if you see dirt you need more residue). Unfortunately our most vulnerable ground still has some dirt exposed. Residue protects the soil surface from the destructive forces of the raindrop which helps prevent surface sealing, and slows water movement. Surface residue moderates soil temperature. In the summer we have measured ≥20 degrees cooler temperatures under the residue compared to bare soil. This is a definite moisture saver. It slows the replacement rate of the boundary layer (the 100% humidity zone at the soil surface). In the winter, soils remain 2-4 degrees warmer than bare soil. When we do our spring seeding, seed zone temperature lags about three days behind bare cultivated soil. We find that insignificant when compared to the benefits.
--TILLAGE: We have decreased soil surface disturbance to the absolute minimum. This maximizes residue retention, and maximizes channeling from worm activity, and decayed root structure, which continue to build over time. Those channels help reduce the time our soils stay in a water saturated (anaerobic) state, and that in turn, reduces the buildup of various pathogens, and conditions that negatively impact our cash crops.
---Another benefit from maximizing residue retention and minimizing soil disturbance is less weed pressure. Minimum soil disturbance combined with heavy residue leaves a very hostile environment for any cultivar to get a start. If you enlarge the pic at the left you can clearly see that disturbed ground, even if it is only a wheel track encourages weed growth. The undisturbed areas do have some growing cultivars, but the number is significantly less and tend to be spots with the least or no residue. Also, maximizing residue retention and minimizing soil disturbance makes for faster water percolation into the lower soil profile. This drys the soil surface faster reducing compaction from heavy equipment during early spring seeding.
--CROP DIVERSITY: We have started to stretch our cropping system to include winter wheat, spring wheat, spring barley, billy beans,mustard, canola, winter and spring peas. The rotation is dynamic (meaning no particular crop following a particular crop). More crops may be added to the mix in the future like soybeans, sunflower, millet, and sorghum. Crop diversity along with a dynamic rotation is being used to address weed and disease issues as they become evident. A mono-culture crop promotes certain weed types, --downy brome in winter wheat is an example. Crop diversity allows us to use herbicides with different modes of action. This will lengthen the useful life of the chemistry available to us by lengthening out the time when weed species develop resistance to a specific herbicide. Keep in mind that we haven't had a herbicide with a new "mode of action" marketed for 30 years, and there is none currently in the pipeline. Crop diversity helps improve soil health through the root exudes. The more variety of cultivars we can get into the rotation the better for the soil biota as well.
--LIVING ROOTS: The biggest challenge for us will be lengthening the time we keep living roots in the soil during the year. Research is showing this to be a major factor in feeding soil biota and increasing SOM. Currently we use CF in front of our WW. In our arid environment that has to change to make a positive increase in SOM. Currently we are bumbling along, doing a variety of things that are not well understood or coordinated. Last spring we attempted to establish a ~30ac perma-cover with White Dutch Clover. That has failed, but we will try again this fall. We do have a ~70ac field that we have replaced CF with green fallow (GF). This spring we will be seeding the GF which will include lentils, forage peas, forage oats, and radish and dutch white clover. This is the second rotation of GF on this field. Unlike the past we plan to terminate the CC at the high N production cycle instead of letting the cover continue through maturity. How we terminate is yet to be decided. This fall (2018) we will seed this field to WW.--Soil Biota: In 2015 we took soil samples of the 70ac field and sent them to Earthfort Labs in Corvallis, OR. We plan to retake those tests in 2020 for comparison. The early tests (more detailed in an earlier post) showed we were very high in bacteria, very low in fungi, flagellates, ameba, and beneficial nematodes. Fortunately we were also low in ciliates, and harmful nematodes. The low fungi count along with the high bacteria count is the natural occurrence from a history of raising only grass cultivars, which are bacteria dominate. I'm reading where healthy soils have a Fungi/Bacteria ration ~1/1 which requires raising higher secession plants. We are no where near that ratio. There is no history of higher cessation plants like brassicas or pulses, that support fungi on that ground. The Earthfort report summary stated that the biota needed food. We have to figure out whether we can buildup the fungi numbers from the remanent we have or whether we need to add inoculant of fungi and support them with higher cessation plants. Also, can we successfully feed the biota with biological amendments, --there are several available from a variety of sources. Currently we are riding a train that is accelerating down the track in the use of commercial inputs. The only hope to reverse this trend is to increase our knowledge of what makes a healthy soil, and apply that knowledge. There is evidence that this can be done. How do WE do it in our specific climate/environment is the question.
