Crop rotations for weed management? At first glance, it doesn’t seem possible. We know, however that in our previous videos, Dr. Anderson showed us how (1) no-till reduces weed prevalence and (2) how he verified this idea experimentally. In this third video, Dr. Anderson discusses why rotating cool season crops into our warm season rotations are so beneficial to weed control. Dr. Anderson demonstrates how through the synergistic effects of no-till combined with diverse rotations, one can reduce weed pressure by a factor of eight before the first drop of herbicide is used. We recommend you view the first two videos (“Fate of the Weed Seed in Conventional and No-Till Soil” and “Seedling Emergence in Conventional and No-Till Fields” with Dr. Anderson.
In our previous video, Dr. Randy Anderson walked us through the various fates of the weed seed in conventional and no-till fields. In this video, the theory comes alive as he discusses the results of a three year study he did in comparing conventional and no-till weed seedling emergence.
In a world where technology offers a quick fix to our weed problems, but inevitably leaves us with unintended consequences, the USDA Agricultural Research Service (ARS), Brookings, SD, Dr. Randy Anderson offers an approach to weed science that says “wait a minute”, what are we doing? In our systems to encourage or reduce weed proliferation before we consider which herbicide to use? To begin to grapple with this question, we have to understand the fate of the weed seed. Dr. Anderson considers weed seed when on the surface of the soil and when buried. Join us in this, the first of three discussions as Dr. Anderson shows us how we can use natural systems to reduce weed populations and save on herbicides.
As Dr. Anderson says, “A key point is when you leave the weed seeds on the soil surface you enhance these fates [predation, environmental exposure, natural death]. In other words, predation is much greater if insects can reach the seeds – if they are buried in the soil, the insects do not process the soil looking for weed seeds so therefore tillage actually protects seeds. Almost all studies with weeds seeds have shown that when you bury them in soil the weed seeds live longer and survive longer.”
We introduce the idea of weeds, and touch on how the production agricultural model views weeds. As the first in the Merit or Myth series on weeds, we’d like to introduce an alternative way of viewing weeds namely, to understand their ecological role as the “scabs” or “ambulance workers” of the land. The natural job of a weed is to cover disturbed soils and through tillage and monocultures, we create ideal environments for weeds. With the ecological way of thinking of weeds and by using a systems approach to our farming systems we can, according to Dr. Dwayne Beck, outsmart them. Rather than wage a full-on chemical warfare with weeds (and do everything the same) we can use natural systems to perform a little ecological ju-jitsu on weeds and not only reduce their populations but save on herbicide costs. Take a peek at this 2 minute video that sets us up for a three part series with the ARS’s (Brookings, SD) Dr. Randy Anderson.
While research showing that tillage actually reduces infiltration into the soil, and that cover crops actually enhance infiltration is proven, the refrain of “it won’t work here” is nevertheless often heard when it comes to applying soil health principles. This is not unique to South Dakota, soil health, nor to farming, but this phenomenon is common. In Merit or Myth’s final video on soil water movement, we are giving a perspective from three producers, one from way East River, one from the center of the state and one from way West River. Our point is: these principles work across landscapes and indeed across the state of South Dakota. As Doug Sieck says in the video, “we need to stop making excuses for why it won’t work here” and rather say “how can we make it work here”?
This spring (2017) SDSU Extension’s Anthony Bly and farmer, or shall we say “citizen scientist,” Al Miron got together to look at the influence of tillage, cover crops and manure on infiltration in a number of fields in Minnehaha County, SD. They compared soils in two long term (9 year) no-till fields, two conventionally tilled fields that had not been tilled for a year and one field that was deep tilled in the fall and then again tilled with a field cultivator in the spring. Al and Anthony did 4 repetitions at each site and came up with some interesting results as concerns the effect of cover crops and tillage. The “aha” moment experienced by the grower who loaned the team some tilled land to do the study on is important as his paradigm was “more tillage = less infiltration”. As this farmer saw the results, especially of the 5th (double-tilled) field, he was sold on the idea pretty quickly!
Dr. Tom Schumacher, SDSU, (Retired) walks us through the experimental setup he used with large rainfall simulators, the type developed for the Universal Soil Loss Equation (USLE), on three different tillage systems. The data Dr. Tom discusses is based on experimental runs conducted four years after this land was taken out of CRP and then continuously treated under three different farming systems: moldboard plow, a chisel plow and no-till. With the use of TDR probes that sense moisture at 10 cm (4inches) and 40 cm (16 inches). In this video, Dr. Tom discusses how much quicker water infiltrates into the no-till system and explains why that is. The chisel plw treatment discussed at the end is somewhat in between the no-till and moldboard plow treatments – notice the chisel plow surface still gets saturated and water has a tough time getting into the soil profile at 16” showing a 50-minute delay.
Dr. Tom Schumacher, Retired, SDSU, walks us through the experimental setup he used with large rainfall simulators, the type developed for the Universal Soil Loss Equation (USLE), on three different farming systems to evaluate soil infiltration. The data Dr. Tom discusses is based on experimental runs conducted four years after this land was taken out of CRP and then continuously treated with a moldboard plow, a chisel plow and no-till. With the use of TDR probes that sense moisture at 10 cm (4inches) and 40 cm (16 inches), Dr. Tom shows what happens to soil moisture at 4 and 16 inches in the moldboard plow treatment and what the runoff consequences are and he briefly compares them to the other two treatments. In the next video we will continue as Dr. Tom walks us through the no-till and chisel plow treatments.
While soils are made up of solid materials (sand, silt, clay and organic materials), Dr. Tom Schumacher, SDSU (retired) shows us how important soil structure or soil architecture is for soil hydrologic function, i.e., making water infiltrate and keeping water for the next crop. Natural soils have an architecture that includes a diversity of interconnected macropores, mesopores and micropores, when soil architecture is destroyed by tillage this is equivalent to a wrecking ball to a building, so while all of the components of the building/soil remain, it no longer functions as it was originally designed. Dr. Dwayne Beck finishes off the video by emphasizing that in natural systems, TILLAGE IS A CATASTROPHIC EVENT!. While in nature, we do see catastrophic events from time to time, tillage once or twice a year is catastrophic and will serve to continually degrade the very resource the farmer depends on.
From a purely technical standpoint, Dr. Tom adds the following: “I was working on something that required a quantitative look at pore sizes and I noticed that I took liberties with my pore classification terminology used in the video. The point that I wanted to make is still valid that pores of different sizes are important for different functions. However I do not want to get you in trouble with “pore size taxonomists”. There are several classification systems for mesopores and micropores. To make a point I used my own classification tht does not match the commonly used Luxmore, 1981 classification of greater than 1 mm (1000 um) macropores; 10-1000 um mesopores; less than 10 um micorpores. Pores greater than 1 mm drain quickly, pores between 1000 um and 30 um drain more slowly but are usually empty at field capacity (around 3 days after being saturated), pores between either 30 and 10 um (depending on if sand or clay) and 3 um hold water that is easily available to crops, pores between 3 and 0.6 um hold water that is less available to the crop slowing growth, pores 0.6 to o.3 um hold water that is more difficult for plants likely resulting in stress, pores 0.3 to 0.2 um hold water that is difficult for crops to extract and will likely result in significant wilting but recovery at night under low transpiration., pores less than 0.2 um in diameter hold water unavailable to most crops, they wilt and do not recover. As you can see I oversimplified the terminology to make a point, and you may wish to clarify.”
In this video, we recap the last 11 videos on our Merit or Myth Series that deal with residue and tillage. We sum up the information provided by our farmers and researchers, from West River to East River of South Dakota. As we consider the statement: “Farming without tillage and with surface residue is not only possible, it works!” we have to ask “Merit or Myth?”. It’s up to the viewer to decide.