Small-plot Study. All five pipelines were supplied with water from settling ponds. The KCl stock solution was injected using an injection wand inserted through vertical air-vent pipes at the pipeline inlets. When the pivots were turned on to start flow through the pipeline, a dosing pump was used to inject the KCl stock solution. Individual pivots were turned off when the KCl-treated water reached the pivots. When the last pivot was turned off, the injection was stopped and the pipeline inlet closed. The KCl-treated water was held in the pipelines for about 24 to 48 h. After the hold period, the pivots were turned on and the pipeline inlet open and the KCl-treated water was purged from the pipelines and applied to the fields. The area within each field that received the KCl-treated water was recorded. Rain gauges were placed in the field to determine how much KCl-treated water was applied. The pivots were operated until untreated water reached the pivots. Water samples were collected at the pivots, and in-field measurements were carried out using electrical conductivity (EC) to determine when the KCl-treated water had reach each pivot during the injection phase and when untreated water had reach each pivot during the purging phase. Water samples were also analyzed in the laboratory following each pipeline trial to confirm K+ concentrations. Surface soil samples (0–2.5 cm and 0–15 cm layers) were collected in ten locations before and after the KCl-treated water was applied to the fields. Samples were air-dried, ground (<2 mm), and analyzed for extractable K+, extractable Cl-, and EC. There was only one opportunity to collect crop samples. Alfalfa samples were collected at Site 3, Pipeline B (Figure 1) on June 29, 2017, 8 d after the KCl-treated water was applied to the field. Two transects of 10 sampling points were located in the field: one transect where KCl-treated water was not applied (i.e., control), and the other transect where KCl-treated water was applied (i.e., treatment). At each sampling point, a 0.25-m2 area was harvested by hand removing all plant material above ground. The samples were placed into perforated paper bags and dried at 35oC. The plant samples were analyzed for the content of total K, nitrogen (N), phosphorus (P), sulphur (S), calcium (Ca), magnesium (Mg), zinc (Zn), boron (B), copper (Cu), iron (Fe), and manganese (Mn).
Small-plot Study. Site. The site for this 2-yr study was a circular field, about 100 m in diameter, with a single-span center pivot irrigation system at the Alberta Irrigation Technology Centre near Lethbridge. The field was divided into 12, pie-shaped plots, and the plots were grouped into four quadrants, with three plots per quadrant. The quadrants were designated as Replicates A, B, C, and D. The three plots within each replicate were randomly assigned one of three treatments: 0, 100, or 500 mg L-1 K+ (0T, 100T, 500T, respectively) concentration in irrigation water. A sub-plot (3 by 3 m) was located near the outer edge and in the center of each main plot. Soil and crop samples were collected from these subplots. Crop. The site was seeded to barley (Hordeum vulgare L. var. Amisk) in 2016 and 2017. Routine agronomic practices were used in terms of seeding, fertilizing, weed control, irrigation scheduling, and harvesting. Crop samples were collected at the silage or green-feed stage (about 65% moisture) on July 26, 2017. At each subplot, a 0.25-m2 area was harvested by hand, and all of the above ground material was placed in a bag. These samples were used to determine dry- matter yield. A second, smaller sample was collected for plant tissue analysis. All samples were placed in a drying room at 35oC for 2 d. The 0.25-m2 samples were weighed after drying. The plant tissue samples were analyzed for the content of total K, N, P, S, Ca, Mg, Zn, B, Cu, Fe, and Mn. Crop samples were not collected in 2016 because of the late application of the treatments. Treatment Applications. Treatments were applied using a fertigation unit (Xxxxxx Xxx A Series Metering Pump model MRAIIX0002) connected to the center pivot. The fertigation unit was turned on to inject the appropriate rate of stock solution for the 100T and 500T plots. The 0T plots received regular irrigation water, during which the fertigation unit was turned off. The treatments were applied two times late in the 2016 growing season and once after the crop was harvested. In 2017, the 500T only received untreated irrigation water. Based on the initial pipeline trial in 2016 (i.e., Pipeline A), it was reasoned that such a high application rate of KCl is unrealistic. Plus, applying only untreated irrigation water provided an opportunity to assess the effects on the elevated EC, K+, and Cl- levels observed in 2016. The 100T were applied three times in 2017 before the crop was harvested at the green-feed stage. The concentration of K...
