Soil QualityShould you be concerned? Dr. Joel Gruver WIU Agriculture firstname.lastname@example.org
Of approximately 40 trials that we have conducted over the past three years, in no instance was more than 1.2 lbs of N per bushel of grain needed to optimize productivity, and in most cases,considerably less was required. Averaged over locations and years, our economic optimum N rates averaged slightly less than 1.0 lbs per bushel (with a range of almost none to 1.2 lbs). Somewhat surprising were the relatively high yields produced without any supplemental N (generally >>100 bushels per acre), and the fact that the highest optimum N rates were typically associated with the lowest-yielding environments. http://agronomyday.cropsci.illinois.edu/2001/tours/nitrogen-need/index.html
Relationship between corn yield and most profitable N rate (72 site years)Only 13 out of 72 site-years in IL required more than 1 lb of N per bushel 1 : 1 line too high 82% of the time
Relationship between corn yieldand most profitable N rate (72 site years) too high 96% of the time 1.2 : 1 line
Where does the N come from that enters a corn crop ?N uptake (lbs/a) Magdoff and Weil (2003)
A well-fertilized the N come fromobtains Where does corn crop typically that more enters a corn crop ? SOM than half of its N fromN uptake (lbs/a) Less N tie-up ! Why more N uptake? Magdoff and Weil (2003)
What happens to fertilizer N ? 100 90 80 ? Measured after harvest http://agronomyday.cropsci.uiuc.edu/2001/tours/n-fate/index.html
What happens to fertilizer N ? 100 So how were the scientists able to Leaching, 90 80 track the fate of fertilizer N? They used fertilizer spiked with N15! ? denitrification, volatilization… Measured after harvest http://agronomyday.cropsci.uiuc.edu/2001/tours/n-fate/index.html
How much of Illinois was originallyIllinois once wascovered by forest ? covered by tall grass prairie ? covered by a complex mix ofprairie and forest Prairiedominated the Old growthflat expanses forest in Forestdominated the hilly land
Soil texture does not normally change with management. USDA 12 Textural textural triangle classes http://www.oneplan.org/Images/soilMst/SoilTriangle.gif
What are these crazy people doing ?Location:Laurenburg, NCDate: 1961 Unsuccessfullyattempting to create deep Midwest like soils in the Southeastern US
Nov/Dec 2011 issue of J of Soil and Water Conservation
Are you familiar with the concept of tillage erosion?
Soil Changes After Sixty Years of Land Use in IowaJessica Veenstra, Iowa State University, 1126 Agronomy Hall, Iowa State University, Ames, IA 50010 Soils form slowly, thus on human time scales, soil is essentially a non-renewable resource. Therefore in order to maintain and manage our limited soil resources sustainably, we must try to document, monitor and understand human induced changes in soil properties. By comparingcurrent soil properties to an archived database of soil properties, this study assesses some of the changes that have occurred over the last 60 years, and attempts to link those changes to natural and human induced processes. This study was conducted across Iowa where the primary land use has been row crop agriculture and pasture. We looked at changes in A horizon depth, color, texture, structure, organic carbon content and pH. Hill top and backslope landscape positions have been significantly degraded. Catchment areas have deeper topsoil.
Keeping soil in place is only the beginning of soilconservation. Soil also has to function well. It must hold nutrients and pesticides in place and keep them out of surface water. Soil must deliver nutrients and water to plants as they need them. Soil should minimize the effects of floods and droughts. By addressing conservation issues from the perspective of soil quality instead of erosion, the focus is on enhancing the soil as opposed to managing for tolerable degradation.
Have you observed the impact of management on your farm?
Soils from sites mapped as the same soil type but rated as high and low quality by farmers did not differ significantly with respect to standard soil test parameters (P, K, Ca, Mg, pH). In contrast, most of the higher rated soils had higher levels of OM, better structure and more biological activity.
SQ tests in the tool box Soil Respiration Test - indicates the soils biological activity. Infiltration Test - measures the soils ability to take in water. Bulk Density Test - measures the soils compaction or pore space.Electrical Conductivity (EC) Test - measures the salt concentration in the soil. pH Test - measures the soils acidity or alkalinity Soil Nitrate Test - measures the soils nitrate levels Aggregate Stability Test - measures the amount of water stable aggregates. Slake Test - estimates the stability of soil fragments in water Earthworm Test - measures the number of earthworms in the soil Water Quality Tests estimates salinity and nitrate/nitrite levels in water
Soil Quality is Not an End in Itself The ultimate purpose of researching and assessing soil quality is not to achieve highaggregate stability, biological activity, or someother soil property. The purpose is to protect and improve long-term agriculturalproductivity, water quality, and habitats of all organisms including people.
The effects of degraded soil quality are far reaching!
20 years of25 years of bluegrass sod corn with followed by 5moldboard years of corn with tillage moldboard tillage
After adding water Water stable aggregates 25 yrs of Only 20 yrs of bluegrass, then 5 0.4% conventional corn yrs in OM difference conventional corn
How do these soils differ ?? manure cover crops crop residues crop residues Also less than 1% difference in OM20 years of similar tillage and total organic input but different types of organic inputs Rodale Institute Farming Systems Trial
Contrasting stands of corn in the NC 9 tillage systems experiment > 3%OM < 1%OM Continuous Fall plow/ No-till spring disk
Physical changes are happening… Long term sod crop fieldSame soil type – very different water holding capacity
But this much divergence is rare…. unless severe erosion has occurred
Artificial drainage has greatly increased the number of days when soils in the Upper Midwest are suitable for field operations but has also contributed Pollution of to environmentalwater resources problems Loss of SOM
"But with the removal of water through furrows, ditches, and tiles, and the aeration of the soil by cultivation, what the pioneers did in effect was to fan the former simmering fires of acidification and preservation into a blaze of bacterial oxidation and more complete combustion. The combustion of the accumulated organic matter began to take place at a rate far greater than its annualaccumulation. Along with the increased rate of destruction of the supply accumulated from the past, the removal ofcrops lessened the chance for annual additions. The age-old process was reversed and the supply of organic matter in the soil began to decrease instead of accumulating." William Albrecht – 1938 Yearbook of Agriculture
5-10% OM ~50% ancient OM~30% slowly decomposable OM ~20% active OM
2-5% OM ~75% ancient OM~20% slowly decomposable OM ~5% active OM
Long term no-till Intensive tillage Clearly more OM Does this profile contain more SOM?Ontario Ministry of Ag and Food
It is widely believed that soil disturbance by tillage was a primary cause of thehistorical loss of soil organic carbon (SOC) in North America, and that substantialSOC sequestration can be accomplished by changing from conventional plowing to less intensive methods known as conservation tillage. This is based onexperiments where changes in carbon storage have been estimated through soil sampling of tillage trials. However, sampling protocol may have biased the results. In essentially all cases where conservation tillage was found to sequester C, soils were only sampled to a depth of 1 foot or less…
Many studies were only sampled ~6” deep!Very few tillage studies have been sampled deeper than 1’
Effect of tillage on microbial activity + SOMCTNT Soil respiration in CT system Havlin et al. (1999)
Effect of tillage on microbial activity + SOM Which tillage system has more microbial activity ?CT Soil respiration in NT systemNT Havlin et al. (1999)
Effect of tillage on microbial activity + SOM Which tillage system has more microbial activity when plants can use the CO2?CT Soil respiration in NT systemNT Havlin et al. (1999)
Ecological Applications 2009The quantity of belowground organicN fertilizationbest predictor of Increases in decay rates with inputs was the offset gains long-term soil C storage. the soil in such ain these systems,C in carbon inputs to This indicates that, way that soil in comparison with increased N-fertilizer additions, selection of crops/cover crops with high root productionof a more effective sequestration was minimal in 78% is the systems management practice for increasing soil CN additions. studied, despite up to 48 years of sequestration.
Ecological Applications 2009Increases in decay rates with N fertilization offset gains in carbon inputs to the soil in such a way that soil C sequestration was minimal in 78% of the systems studied, despite up to 48 years of N additions.
Broadbalk continuous wheat experiment Data modelled by RothC-26.3 (solid lines) 100 Organic C in soil (t C ha-1) Farmyard manure annually 80Soil C (tons/ha) 60 Why has the NPK program resulted in so little increase in SOM? 40 NPK 20 unfertilized Unmanured 0 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 2020 Year
Why does the system with the highest residue productionhave the lowest OM content?