Agronomist Notes

I caught up with colleagues at last week’s Syngenta consultant update to review the 2010 fungicide, insecticide and herbicide trials. It looks like Syngenta will be introducing a new cereal seed treatment with a different fungicide group in 2012.

This week we’ll be finalizing plans for our controlled traffic research project and looking for funding to go ahead with our high yield 180 bu/ac barley field trials. At this point in time, crop rotations are planned, herbicides, fertilizer and seed are bought, just the thousand kernel weights left to calculate and we’re good to go for 2011.  

This week we’ll be looking at the use of EM38 sensors to build soil zone maps. I’ve seen some impressive maps coming from EM derived base maps that I’d like to share. Next, I’ve included a recent study comparing yield and maturity inside wheel ruts verses outside to show how little the freeze thaw cycle and cultivation repairs compaction. I’ve included my latest interview with Shaun Haney at Crop Production week in Saskatoon talking about controlled traffic. Last, I’ll briefly talk about pushing plant densities in barley this year with an example from a grower producing top notch malt barley yields with heavy plant densities. We’ll finish with fundamental and technical grain market news.

Agronomy

Using electromagnetic EM38 readings to produce soil zone maps

Producing zone maps for variable rate applications can be done numerous ways. Over the last few years we’ve looked at NDVI, elevation, yield, Veris and EM38 maps to help develop the base map from which we determine high yielding to low yielding areas. After reviewing some of the most successful practices of precision ag specialists from Australia to Canada, many use EM38 readings to produce zone maps. 

The EM38 is a sensor that measures electrical conductivity in the soil and was originally used to measure soluble salts and soil moisture. Research soon found a strong correlation between EC values and soil texture so it became a tool to map soil zones. It can also be used to estimate topsoil depth or depth of clay, herbicide degradation and crop productivity.

There are a few characteristics of EM to note:

• EM value has no direct effect on crop growth.
• EM relates to soil properties that are agronomically important.
• With adequate soil testing (ground truthing) the EM map can be used as a “surrogate” soil type map.
• Patterns of EM remain stable over time.

To produce an accurate EM map, most consultants advise you to run 50-foot transects across the field if you’re capturing elevation data at the same time. If not producing an elevation map, you can run transects up to 100ft apart. Travelling speed depends on the field finish but many consultants will run between 20 and 40 km/hr.  EM data is logged every 15ft which would give the average quarter section approximately 12,000 measurements. Soil that is excessively wet or excessively dry can skew results.     

To give you an example of the accuracy EM maps can provide I have a few maps to show you. First, let’s review the zone soil test results to ground truth the EM readings with CEC values. The CEC or Cation Exchange Capacity gives an indication of soil texture, productivity potential and reflects the soils ability to hold nutrients. It is well known that sandy soil has a low CEC value and therefore cannot hold nutrients very well. Compare that to a clay soil which has a high CEC value and it has a tremendous potential to hold on to nutrients.

Table 1: Zone Soil Test Results from EM

CEC Value and Soil Texture
0-8 = Sand
8-12 = Loamy Sand
13-20 = Sandy Silt Loam
21-28 = Loam
29-40 = Clay loam
>40 = Clay

If you look at the Zone Soil Test data in Table 1 you’ll see how the CEC values increase from a low in Zone 1 of 11.9 to a high of 47.3 in Zone 7. The soil texture moves from a loamy sand to a sandy silt loam and all the way up to a clay soil in the highest yielding area in zone 7. There are five soil types in this field and each one holds moisture and nutrients differently and therefore has a different productive capacity. Bottom line, the soil tests confirm what the EM map picked up on differences in soil texture. 

The three maps you see here from left to right are the soil test zone map, the EM map and a yield map from the same field that correlates to the soil test data shown above. I realize the yield map only follows the EM map slightly but don’t forget we can’t assume that they’ve dialed in the perfect agronomy to match the productive potential of each zone. I’m saying don’t throw the baby out with the bath water when you see a yield map that doesn’t quite fit the zone map. When the base map has been developed, the zones confirmed with soil tests, it’s then up to the farmer and agronomist to see what the upper yield potential of each zone. That’s a work in progress, especially when you only get one shot at it each year.  

The cost of EM mapping in Alberta ranges from $6.50 to $10.00 an acre depending on who is doing the mapping and who owns the data. The lower end price is for those purchasing a large volume of acres and the savings from economies of scale are passed on. There are similar EC mapping units called like Veris Technology which I don’t have data on but the going rate on Veris mapping is roughly $7.00 to $10.00 acre. The cost of an EM-38MK2 is about $17,000 and the Veris unit runs about the same cost. That doesn’t include the vehicle, the GPS source and the labour.

In the end, I like that the EM38 produces a soil texture map which directly relates to nutrient and water holding capacity. Other maps like NDVI change from year to year and elevation maps don’t always follow productive capacity. If you can produce a base map of soil texture and ground truth it with soil testing like you’ve seen here, you can start to focus in on what limiting factors are reducing production on your farm.  

I’d like to thank Colin Bergstrom of Seven Islands Agriculture based in St. Albert, AB for sharing his data with me. All the maps and soil test data are examples from one of his clients that he services north of Edmonton. Colin is one of the leading precision ag consultants in the province with a strong background in variable rate technology.  SL

For more information on EM mapping contact:
Colin Bergstrom P.Ag, CCA
Precision Agriculture Consultant
Seven Islands Agriculture Inc. 
P: 780-651-1723
M: 780-886-7173

Source: http://www.growercentral.com/UPLOADS/PDFS/understanding%20a%20soil%20analysis.pdf
EM-38MK2: http://www.fugroinstruments.com/pdf/Fugro_EM38-Mk2.pdf

My latest interview at Crop Production Week talking about CTF

If you’d like to hear more about my thoughts about controlled traffic, its relevance to Western Canadian agriculture and the precision applications that naturally flow out of CTF, have a look at this interview with Shaun Haney from RealAgriculture.com.

http://www.youtube.com/watch?v=QAvQeHYEpPk&feature=player_embedded

Study finds 17% yield loss in wheel ruts from harvest traffic

I came across a recent study done by the University of Minnesota looking at the effects of wheel ruts on corn growth and yield caused by combine traffic. Researcher Jodi DeJong-Hughes performed a GPS analysis on seven pairs of ruts and neighbouring non-rutted areas in four fields near Clarkfield, Minnesota in 2010. This area is well known for its multiple freeze thaw cycles, wet autumns and temperatures dipping to the mid -20’s Celsius and lower during winter.

To begin, the combine ruts in the observation areas were repaired in the fall of 2009 with a chisel plow and followed by cultivation in the spring. One field was disked in the fall followed by cultivation in the spring. In the spring of 2010, the observation areas were flagged and tracked throughout the season. The areas were hand harvested and final population, grain moisture and corn yield were determined. Here are the results:

• The plant population was not statistically different between rutted and non-rutted areas.
• The non-rutted corn was 8.5 inches taller and was one growth stage ahead of the rutted corn (V10.4 versus V9.1).
• Final plant population and grain moisture were not affected by the rutted soil.
• Yield was decreased 28 bushels an acre (159 versus 131) where the field had been rutted.
• The rutted areas had a 17-percent yield decrease that was fairly consistent across the seven sites.
• There was the same number of ears gathered (same population), but the differences in ear length, diameter and kernel fill were easy to see.

I find it interesting to note that even with a fall and spring working with a chisel plow and cultivator plus a freeze-thaw cycle, wheel track damage was still not alleviated. The myth that freeze-thaw cycles remove compaction needs to be challenged and it goes to show that cultivation doesn’t fix the damage caused by wheel ruts, it simply masks it. SL

Source: http://www.agprofessional.com/cornrc.php?id=1308080&page=5

Pushing plant densities in barley

I’m working on a project that’s seeking funding for a high yield trial looking at the potential to produce 180 bu/ac barley, a target reached 20 years ago in Alberta. We’ve already started preliminary discussions about the type of agronomy that will be necessary to produce 180 bushel yields on each farm. The subject of optimum plant densities was tossed around and I thought I’d share some of the best practices from some of the top barley growers in the province.

When targeting optimum plant stand densities you have to take a few things into consideration. First, you need to consider within row plant spacing ensuring each seed has equal access to moisture, nutrients and sunlight. Next, you must provide the right balance of nutrition to support a high plant density. Third, you must keep your plants healthy in order for them to reach their full potential.   

The optimum plant stand density in barley will vary depending on your row spacing and opener width. For example, in a high moisture area like Olds, AB long time malt grower Gordon Ellis will target 32 plants per ft2 in his AC Metcalfe malt barley. His 4 inch paired row opener on 10 inch spacing can support a high plant density without stacking seeds on top of each other. To give you an example of optimal in-row spacing compared to suboptimal in-row seed placement, see the example below:

Gordon: 10"/row ÷ 12"/ft/row = 0.83 x 32 plants/ft2 ÷ 12"ft/row ÷ (2 x 1” rows) = 1.1 seeds per inch 
Too narrow: 12"/row ÷ 12"/ft/row = 1 x 32 plants/ft2 ÷ 12"ft/row ÷ ¾” opener = 3.55 seeds per inch

If you look at this example, Gordon’s opener and row spacing allows for 1.1 seeds per inch of row where the narrow opener on 12” spacing packs over three times as many seeds into the same 1 inch of row. The wide row and narrow opener example would not allow each plant to access to water, sunlight and nutrients equally and create a highly competitive environment between plants. Some of the biggest wheat and barley crops in the world all have one thing in common, low within row plant competition.

The goal with high plant densities is to produce as many main stems as possible instead of inefficient tillers with low kernel number and kernel weight, the main drivers of yield. Gordon has achieved 90% plump malt barley consistently using high plant densities where 160 to 180 lbs/ac of AC Metcalfe seed is not uncommon, especially when he’s targeting 32 plants per ft2. These plant densities have allowed Gordon to achieve field averages up to 120 bu/ac with Ac Metcalfe and his yield monitor indicates that some areas are hitting 160 bu/ac. So, he’s got room for improvement! 

Next, you must ensure a balanced crop nutrition program to reduce the risk of lodging. With high plant densities, lodging can be a concern if nutrition isn’t matched to support the crop. For example, we know that barley responds well to potassium even on high potassium soils and will help reduce lodging. I have growers using upwards of 30 lbs/K/ac on high potassium soils and lodging has subsequently dropped since we increased K fertility. The next two nutrients which should not be in short supply are copper and boron, which both provide benefits to straw strength and standability. I won’t point out the obvious with excessive nitrogen applications and its effect on lodging.

Last, the key to keeping your plants healthy at a high plant density is a strong fungicide program. Both Tilt, Stratego and even Proline work well to provide protection against diseases like scald and net blotch. There have been many examples where a fungicide application made the difference between a standing crop and a lodged crop. The plants must be kept healthy through to the end of the season, which in some years might mean a second fungicide application.

So the key to managing high plant densities in barley is to minimize in-row competition, provide proper nutrition to support high plant densities and be sure to keep the crop healthy. I believe we’ve only begun to understand how high we can push plant densities in barley, even in the drier areas of Western Canada, It’s great to hear success stories like Gordon’s who manages to keep heavy crops standing and pull off malt quality barley. Seeding rates between 160 and 180lb sound ridiculous. I’d say it’s awesome, keep pushing. SL