Research Coordinator: Dr. Akim Omokanye
Research Technician: Dr. Lekshmi Sreekumar
From: Peace Country Beef & Forage Association 2016 Annual Report
The PCBFA has been actively involved in the facilitation and delivery of the ASB Environmental Program for Big Lakes County, Clear Hills County, MD of Fairview, MD of Peace, MD of Spirit River, Saddle Hills County and Birch Hills County. For the last ASB Environmental Program (2014-2016), which involved on-farm soil nutrient budgeting and mapping, PCBFA identified 6 livestock and cropping operations across the Peace Country for the project. Baseline and subsequent yearly data on water and soil were collected from these sites from 2014 - 2016. The goal is to decrease water body/source and riparian area contamination in the Peace Country by creating awareness of nutrients, nutrient distribution, collection and management on farm from wintering sites to pastures and crop land. This report presents a summary of our findings.
For this project, we worked with the producers listed in Table 1. The production systems examined are also shown in Table 1. Soil particle size analysis carried out in 2014 showed that the soil texture of the sites used was mostly silt clay (Table 2).
For each site, 5-25 acres were used for the studies. Baseline data collection was done in 2014. Baseline and subsequent data collection (2015 & 2016) for each project site (or selected production system) involved:
1. Soil nutrients & nutrient leaching in 0 to 24 inches soil depths
2. Soil temperature and Water infiltration in 0 to 6 inches soil depth
3. Soil compaction reading with a digital penetrometer in 0 to 6 inches soil depth
4. Water sampling from on site dugout for water quality issues
Soil sampling - for both bale grazing and bale processing, soil sampling was done within the areas where bales have been previously fed. Soil sample frequency ranged from taking 2 to 3 samples in 0.5 acre units of the field.
Both soil & water samples were submitted to Exova Edmonton for analyses using standard laboratory procedures. Water samples were also analyzed by Exova for water quality using stand laboratory methods provided by the American Public Health Association Standard Methods for the Examination of Water.
Results and Interpretation
Soil organic matter (SOM)
The SOM was consistently higher at the 0-6” depth at the winter feeding site than other sites examined (Figure 1). Swath grazing site was second in SOM at 0-6” depth, followed by grain-corn grazing site. In this study, both pasture and bale grazing sites had similar SOM at the 0-6” over the course of the project.
In some cases, SOM increased slightly at a particular depth over the study period (2014-2016). This pattern was more obvious with winter feeding, grain production (canola-wheat-canola rotation) and canola-corn silage production sites particularly at the 0-6” depth (Figure 1). The canola-corn silage production (Site 6) field had a dramatic increase in SOM at 0-6” from 2014 to 2016 compared to other sites. The canola-corn silage production (Site 6) had manure applied to the field in 2015 after the corn was silaged, and this was thought to be responsible for the sharp increase over a short period.
Overall, increases in SOM from 2014 to 2016 came from 3 sites/productions systems in the following order: Bale grazing & Pasture (each with 2.2% SOM) > Winter feeding site (1.9% SOM). The changes with other systems or sites were far less or inconsistent.
There are many advantages to increasing or maintaining a high level of SOM. These are reduced bulk density, increased aggregate stability, resistance to soil compaction, enhanced fertility, reduced nutrient leaching, resistance to soil erosion, increased biological activity and reduction of greenhouse gases by soil C sequestration. In most agricultural soils, organic matter is in-creased by leaving residue on the soil surface, rotating crops with pasture or perennials, incorporating cover crops into the cropping rotation, or by adding organic residues such as animal manure.
It is very important for producers to know that even for every fraction of SOM built, there will be more water holding capacity. Research studies have shown that every 2% SOM will hold 32,000 gallons of water (or 21% of a 5.5 inch rain). Every 5% SOM will hold 80,000 gallons (or 53% of a 5.5 inch rain) and every 8% SOM will hold 128,000 gallons of water (or 85% of a 5.5 inch rain).
Soil Infiltration rate
Soil infiltration is the ability of soil to allow the intake of water into and through the soil profile.
The mean infiltration rate (2014 - 2016) was highest for the grain production (canola-wheat-canola rotation) site (4.06 inches/hour) (Figure 2). The winter site came second (1.74 inches/hour), followed by swath grazing (1.25 inches/hour) and then bale grazing (0.52 inches/hour). The pasture site had the lowest infiltration rate (0.05 inches/hour).
The compacted soil layers in pasture might have contributed to the poor water infiltration rate at the pasture site (see compaction below).
Going by the standard permeability classification system, grain production (canola –wheat rotation), with the highest infiltration rate, had moderately rapid infiltration.
Soil compaction occurs when soil particles and aggregates are forced together so as to reduce the pore space for air and water. Readings of 400-500 PSI indicate potential soil compaction. The winter site showed the most compacted soil out of the 6 sites examined (Figure 3). On the other hand, the least compacted soil was with the grain production site (canola—wheat—canola rotation), followed by bale grazing. For each site, compaction was least at 1” and then compaction increased gradually, in most cases, with increasing depths.
Soil Mineral Nitrogen (SMN)
Nitrogen is available (soluble N) to plants as either ammonium or nitrate and comprises only 2-3% of the total soil N. Both ammonium and nitrate are called the mineral N fraction.
Overall, the bale grazing site had the most SMN, followed by the winter site (Figure 4). Surprisingly, the pasture site had lower SMN than other sites. In most cases, SMN was higher at 0-6” depth than other depths. Both bale grazing and swath grazing showed potential for SMN leaching through soil depth over the years, as SMN seemed to be higher at 18-24” depth in 2016 than 2014. The higher SMN at 0-6” for site 6 (canola-corn silage) was due to the manure applied in the fall of 2015.
From 2014 to 2016, soil P appeared to be highest at 0-6” and then it decreased with increasing soil depth (Figure 5). At the 0-6” depth, the winter site had the highest mean soil P (109 lbs P/acre), followed by the canola – corn silage production site (93 lbs P/acre), bale grazing (77 lbs P/acre) and then pasture (64 lbs P/acre).
The highest level of soil K was observed in the subsurface soil depth (18-24”) for the second year in the canola-wheat rotation production site (1404 K lbs/acre) (Figure 6). In the winter site the soil K level remained constant for the surface soil depth (0-6”). Also, there is a constant decrease in the soil K level for the subsurface soil depth (6-12 - 18-24”) for the winter site from 2014 to 2015. For bale grazing site, in the second and third year the soil K level remain constant in the surface soil (0-6”) and subsurface soil depths (6-12”, 12-18” and 18-24”). In the pasture, the highest K level was observed in the surface soil (1068 K lbs/acre) in the third year (2016) and there is a constant decrease in the level of soil K in the subsurface soil from 2014 to 2016.
The soil nutrients (N, P & K) and health indicators (infiltration rate and compaction) from 2014 to 2016 examined here have been most improved by bale grazing. The grain production system, which involved canola -wheat - canola rotation and no-till systems appeared to have the least compacted soil than other systems as well as the highest infiltration rate than other systems or sites.