NORTHERN SOIL AMENDMENT FIELD TRIAL:
YEAR 5
Prepared by:
Matthew Ball, Agrologist
Brad Barton, Research Technician
Krystal Isbister, Research Technican
October 2014
NORTHERN SOIL AMENDMENT FIELD TRIAL:
YEAR 5
Yukon Department of Energy, Mines and Resources
Agriculture Branch
©2014 Yukon Department of Energy, Mines and Resources
Copies available from:
Yukon Department of Energy, Mines and Resources
Agriculture Branch
Box 2703, Whitehorse, Yukon Y1A 2C6
Phone (867) 667-5838, Fax (867) 393-6222
Email:
Also available online at ww.emr.gov.yk.ca
Northern Soil Amendment Field Trial: Year 5
Location: Government of Yukon Research Farm
Initiated: 2010
Funding: Government of Yukon and Canada-Yukon Growing Forward Program
Partner: City of Whitehorse
Objective:
In partnership with the City of Whitehorse, the Agriculture Branch initiated a long term trial at the Yukon government Research Farm in 2010 to test the effectiveness of soil amendments in northern soils.
Introduction:
A soil amendment is a material added to the soil to improve its properties. Common soil amendments include fertilizers, manures and compost. Deciding which amendments to use is always a challenge as farmers must consider the transportation and application of products, the availability of local products, and the increasing cost of fertilizer and shipping. The four major amendments being studied are synthetic fertilizer (NPK), organic fertilizer (ORG), city compost (COM), and city compost with lime (C&L). In 2011, biochar was added in combination with each of the other four treatments and plots with humic acid were added in 2012. Different vegetables are grown in rotation each year starting with beets in 2010, carrots in 2011, kale in 2012, and snap peas in 2013. The rotation was restarted in 2014 with beets being seeded across all plots.
Site Description
The Yukon Government Research Farm is located in the Gunnar Nilsson and Mickey Lammers Research Forest located at the junction of the Yukon and Takhini River valleys. The research site is two hectares surrounded by lodgepole pine (Pinus contorta) and embedded in soils that are typical of those encountered at many farms in the southwest region of Yukon. The forest provides shelter from winds, but consequently creates a frost pocket. The soil, landscape and climatic properties of the site are typical of the farms in this region of Yukon. The area was cleared of willow (Salix sp.), aspen (Populus tremuloides), white spruce (Picea glauca), lodgepole pine, soapberry (Sheperdia canadensis), and bearberry (Arctostaphylos uva-ursi) in 1987, and has been worked intensively for a variety of research projects since. The soil texture is silty loam to fine loamy sand and moderately well to well drained. The pH is 7.0 with organic matter levels around 2%.
Materials and Methods:
The long term trial is set up at the Research Farm in the southwest corner of the irrigated field. This section was left fallow for a number of years prior to the trial to help establish soil homogeneity. The plots were permanently delineated and mapped in 2010 to ensure amendments would be kept consistent over time (see Figure 1).
Figure 1: Layout for soil amendment trial in the southwest corner of the YG Research Farm
The compost and fertilizer was added in early June and beets seeded on May 29thwith a four-row Jang precision seeder calibrated for 1” spacing between seeds and 6.5” between rows. The amendment amounts are listed below in Table 1.
Table 1: Amendment Schedule
Amendment / 2010 / 2011 / 2012 / 2013 / 2014Synthetic Fertilizer (NPK) / 100 Kg/ha N
20 Kg/ha P
50 Kg/ha K / 100 Kg/ha N
20 Kg/ha P
50 Kg/ha K / 100 Kg/ha N
20 Kg/ha P
50 Kg/ha K / 0 Kg/ha N
45 Kg/ha P
125 Kg/ha K / 100 Kg/ha N
20 Kg/ha P
Kg/ha K
Organic Fertilizer (ORG) / 100 Kg/ha N
20 Kg/ha P
50 Kg/ha K / 100 Kg/ha N
20 Kg/ha P
50 Kg/ha K / 100 Kg/ha N
20 Kg/ha P
50 Kg/ha K / 0 Kg/ha N
45 Kg/ha P
125 Kg/ha K / 100 Kg/ha N
20 Kg/ha P
50 Kg/ha K
Compost (COM) / 45 t/ha / 40 t/ha / 35 t/ha / 40 t/ha / 45 t/ha
Compost and Lime (C&L) / 45 t/ha + 6.7 t/ha lime / 40 t/ha / 35 t/ha / 40 t/ha / 45 t/ha
Biochar / 0 t/ha / 10 t/ha / 10 t/ha / 0 t/ha / 0 t/ha
Humic Acid / 0 t/ha / 0 t/ha / 0.44 t/ha / 0.44 t/ha / 0 t/ha
A low pressure centre pivot system was used to irrigate the plots with 150 mm of water applied over the summer and an additional 234 mm of precipitation fell between May 1st and September 16that the Research Farm. Weeding on site was by hand rogueing in mid to late July.
Beets were harvested on September 16th by Whitehorse high school students as part of the Yukon Envirothon ( Students collected four samples of beets per plot from 1 x 1 m sampling squares. Beets were washed, patted dry and topped before weighing. Individual weights were recorded and each sample kept separately. Discrepancies in sample size were standardized by measuring the total length of four samples and proportionally correcting values. Because the students washed and handled the beets very gently, all samples were able to be donated to the Whitehorse Food Bank after the data was recorded.
Results and Discussion:
Research Farm Beet Yields in 2014
To determine harvestable yields, all beets with a weight of less than 20 g were removed prior to analysis. Before calculating average yields of each plot, samples within major amendment plots (NPK, ORG, C&L, COM) were analyzed for variance due to secondary amendments (biochar, humic acid). Only the ORG plots showed significant differences and all samples for NPK, COM and C&L were grouped together to calculate average counts, individual weights, and yields (see Table 2.).
Table 2. Harvestable Beets 2014 (>20 g): Average Counts, Weights, Yield and Fertilizer Cost
Major Amendment / Average Count/ m2 / Average Beet Weight (g) / Average Yield (t/ha) / Cost of Fertilizer per HectareCOM / 35.1 / 74.5 / 26.1 / $1550/year
C&L / 32.7 / 75.1 / 24.4 / $1550/year + one time $6700/ha for lime
NPK / 29.5 / 114.5 / 33.3 / $420/year
ORG / 36.2 / 87.4 / 31.6 / $2300/year
The average count data is interesting when compared to average weights. There is a slight negative correlation between count and size, but the variation in seeding and thinning was not enough to drastically affect average yields. For example, COM plots had an average count of 35.1 plants per m2and ORG had 36.2. Average weights of ORG beets, however, were 87.4 g compared to 74.5 g for COM beets and thus count did not play a major role in beet weight. Fewer beets in NPK plots may be caused by earlier growth and more thorough thinning during the summer or simply variation in seeding rate.
Synthetic and organic fertilizers yielded about 25% more thancompost and compost/lime plots. Differences in yield between ORG and NPK beets were within the range of sampling error, as were differences between COM and C&L. It appears that the current application rate of compost is still not adequate to produce comparable yields to fertilizer and will be increased for the 2015 season. The costs of the different amendments in Table 2 appear dramatic, however, fertilizer costs are only a small percentage of the potential earnings from a hectare of market garden production.
Biochar was first incorporated into the trial as a secondary amendment in 2011 and to date no clear trends have emerged. In 2014, the only statistically significant difference (p<0.05) was seen between biochar and a standard treatment was in the ORG plots. The plots with organic fertilizer and biochar yieled a higher count of larger beets. This increase in productivity has not occurred in any other year and will be monitored in 2015 to determine whether this becomes a consistent trend or if other factors were involved.
Humic acid was added to the trial as a secondary amendment in 2012. It is a naturally occurring component of soil that is formed by the microbial decomposition of organic matter and can also be made commercially available by extracting it from mineral deposits similar to coal. No significant differences were found in yield within the COM, C&L, ORG or NPK plots when humic acid was added. Local gardeners in the Whitehorse area, however, have reported vegetable yield improvements with the addition of humic acid. Humic acid will continue to be studied in 2015’s soil amendment trial and trends may become more apparent over the long term.
Comparison of 2010 and 2014 Beet Yields
Initial comparison of soil fertility between the years is most valid between NPK plots. As 2010 was the first year of the trial, compost and organic fertilizer plots had not had the years required to improve overall soil health whereas synthetic fertilizer nutrients are available much sooner after application. This does not, however, account for the more than double yield of beets in 2014 compared to 2010 within the NPK plots (see Table 3).
Table 3. Total Beet (>5 g) Yield Comparison 2010 vs. 2014Treatment / Average Yield (t/ha) 2010 / Average Yield (t/ha) 2014 / Average Weight/ Beet (g) 2010 / Average Weight/ Beet (g) 2014
COM / 8.1 / 27.4 / 24.2 / 59.4
C&L / 8.1 / 25.4 / 22.4 / 63.0
NPK / 15.9 / 34.9 / 40.1 / 108.9
ORG / 3.9 / 30.2 / 15.7 / 86.0
Before the amendments trial was implemented in 2010, the southwest field had been fallow for approximately four seasons. More importantly, the Jang precision seeder had not yet been purchased and the seeding rate was significantly higher and more variable in 2010. These two factors are most likely the cause of the lower yields in 2010. Though the weather summaries shows comparable overall growing conditions, 2010 had a killing frost at the end of June (-2.2°C) and four minor frosts in July. Beets are a cool hardy vegetable, but such events do affect growth.
Conclusion:
The organic fertilizer plots produced comparable yields to the synthetic fertilizer plots for the third year in a row as expected (see Figure 2 on next page). The compost and compost/lime plots maintained yields of approximately 20% less than synthetic fertilizer plots. The application rate was increased in year and it appears it needs to be increased even further the match fertilizer yields.
Figure 2: A comparison of each crop yield against the yield from plots treated with synthetic fertilizer (NPK). For example, in the first year the COM treatment produced half the yield (50%) of the NPK treatment.
In future years, the yield of the compost treatments is expected to increase and eventually be equal to the synthetic and organic treatments. The soil amendment trial at the Research Farm will continue in 2015, further exploring the use of biochar and humic acid as well as the main amendments: compost, compost with lime, synthetic and organic fertilizer.
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