April 24, 2014

Agronomist Notes

Hello Reader

I’ve finished up the last of my spring soil sampling and it looks like we are in good shape to begin seeding next week. Soil temperatures are hovering around 4C and we’re sitting around 60% stored soil moisture capacity in the top 24 inches. Some areas in the west will take another 10 days before the ground is firm enough to support machinery.

Urea is in short supply with prices hovering around $750 a tonne, MAP at $800 a tonne and AMS at $500 a tonne. Supply is limited at most retail outlets.

In this week’s issue, we’ll look at an inter-row, mini-strip till concept and compare it to undisturbed stubble. Then I’ll share a revolutionary new concept in nutrient application called vertical rate technology. Last, we’ll look at the effects of tall stubble versus short stubble on soil temperatures and address some misconceptions out there. We’ll finish with technical grain market news.

Have a great week.

Photo: A client heads out to do some snow massaging to help drifts melt faster so seeding can begin. S. Larocque

Agronomy

Strip till on narrow rows shows promise

There has been a renewed interest in two pass seeding systems to help manage residue and increase soil temperatures in the spring. Heavy residue and cold soil temperatures have negative impacts on emergence, crop vigor and tillering in cereals and oilseeds. Research in the US has shown strip tillage to warm soil and maintain stored soil moisture equal to zero-till and more so than pure cultivation. See here. Allen Jones, of Airdrie, AB took the concept of strip till in wide rows and brought it down to narrow rows through inter-row banding NH3.

The row spacing on Allen’s air drill and NH3 cultivator are both 12 inches wide. He uses a Trimble RTK system and nudges the GPS to line up between the rows. He banded NH3 to a depth of 5 inches to help break up compaction and reduce potential nitrogen losses. The picture you see here shows the undisturbed stubble above and the inter-row banded on the bottom.

I took soil moisture and temperature measurements between the inter-row banded stubble and the undisturbed stubble to compare the differences. Are we achieving the desired result of managing residue and warming soil? Let’s review my observations below.

Undisturbed stubble
50% soil moisture content in the top 6 inches
Soil temperature was 4C in the top 2 inches
90% residue cover
8-inch tall stubble

Inter-row NH3 banded stubble
80% soil moisture content in the top 6 inches
Soil temperature was 2C in the top 6 inches
30% residue cover
8-inch tall stubble

The inter-row banded stubble did see a 60% reduction in surface residue, which is what we were aiming for. The benefit of the inter-row system is leaving the 8-inch tall stubble intact to reduce surface wind and evaporation, while leaving a black strip between the rows. Oddly enough, the soil temperature was actually 2C cooler in the banded side versus the undisturbed side which is opposite of what we were trying to achieve. The recent snowfall melted quickly and may have ran into the 5-inch deep furrows, quickly cooling the soil.

The banded stubble actually stored 30% more moisture in the top 6 inches than the undisturbed stubble. The temporary aeration may in fact increase stored soil moisture versus drying it out which is the opposite of what most people would expect. In a dry winter with little snow melt inter-row banding could cause a drier seedbed. That wasn’t the case this spring.

In the end, the strip till experiment created a loaded soil moisture profile in the top 6 inches and reduced surface residue by 60% but only inside the furrows where seed will be planted. The soil will warm up quickly after one more pass at seeding, more so than the undisturbed soil. The standing stubble has kept the soil intact and will help reduce reosion and evaporation by slowing surface wind speed.

The biggest perceived risk with an inter-row banding system is drying out the soil, thus leaving a dry seedbed. However that hasn’t happened in Allen’s field. I’ll keep you updated on the crop’s progress; it could be a real winner. SL

Combining variable rate with vertical rate

A Soil Use Efficiency Model

After 17 years of soil testing, I am constantly reminded how variable our soils are both horizontally and vertically across each field. In our soils, we often see a thick layer of organic matter in the top two inches, followed by a layer below that is denser, has less organic matter and a higher pH. Move deeper you’ll start to find a change in soil texture, bulk density, clay percentage, nutrient values and pH. The discussion about how we manage that variability has moved from variable rate to vertical rate technology. Vertical rate is really the incorporation of accurate and appropriate soil information (to soil horizon) in farmed soils. The soil horizons can be as different as layers on a cake. Vertical rate is a term coined by Injekta Field Systems to define the field assessment needed when assessing soil condition and soil structural stability. Vertical and variable rate assessment should be inseparable partners.

Beyond Agronomy has been working closely with Injekta Field Systems from Adelaide, AUS to optimize the "Vertical Rate" strategies used with a new technology built by Peter Burgess of Liquid Systems in Australia. Peter has designed a four-stream (six streams are possible) liquid delivery system that allows you to variable rate nutrients vertically. This system allows the proper nutrient package to be placed in the seed row and then a separate one below based on individual soil and nutrient constraints across the field. Vertical rate will be the entry point for established soil science to enter precision agriculture and move diagnosis systems into a far more effective and productive range.

To give you an example, we often have a very dense layer of organic matter in the top 2 inches where we place our seed. The level of organic matter in this layer can be upward of 10-15% rather than the 4-5% we measure when taking a 0-6-inch deep soil sample. A dense layer of organic matter can lead to a reduction in copper and manganese availability in the seed row. Below the seed row, we may have a dense layer of soil where compaction begins or higher calcium carbonate levels occur, which can tie up phosphorus and zinc. A vertical rate nutrient and soil conditioner program can be used to address those issues and optimize the nutrient support package at each horizonal depth.

The photo you see here is a four stream Liquid Systems design mounted on to a John Deere disk drill. The top liquid line applies fungicide or inoculants in furrow. The second line applies nutrients like phosphorus, potassium and micronutrients like copper, manganese and zinc. The next two lines are used to apply liquid nitrogen and sulphur down one stream below the furrow and a soil conditioner like Infiltrax, which is used to flocculate soil and improve soil porosity below the furrow down another stream. There is also a granular fertilizer starter program used in combination with this liquid system to compliment the liquids and reduce costs. Most liquid delivery units complement a sound granular program.

I think we’ve always known conceptually that soils differ at specific depths in the soil profile. For now, we’re trying to address micronutrient deficiencies in the furrow by applying them as a seed dressing, which doesn’t allow you to apply enough to support the crop. Across the landscape, you could begin to increase zinc on eroded hilltops or copper and manganese in low areas with high organic matter content, all with GPS guided sectional shutoff (no overlap). The possibilities to improve nutrient support in the furrow and below the furrow are endless. What I would like you to start thinking about is how we can use this technology to manage our crop nutrition strategies differently. It is a game changer in agriculture that will develop capacity very quickly. SL

Taking stalk of tall and short stubble

I get a lot of questions about the effects of leaving tall stubble. When possible, we leave wheat stubble 16 inches tall and barley stubble as tall as possible, which is usually around 10 inches tall. Most people cringe at the thought of leaving tall stubble because of the risk it creates with plugging during seeding. With RTK guidance, an offset hitch and CTF, we have no trouble seeding into tall stubble and have for four years. The reason we do goes back to the research done by Herb Cutforth et al 2001 which found increasing yield in wheat, canola and lentils with increasing stubble height. See here for graphs showing yield increases.

As you can see in the graphs, as you move from (6-inch) stubble to 45cm (17 inches) stubble, yields increase in wheat, lentils and canola. With canola, the 45cm tall stubble increased yield by 200 kg/ha or 3.5 bu/ac over the 15cm tall stubble. At today’s canola prices that increase in stubble height generated a $35.00 per acre increase in revenue. They concluded that tall stubble height reduced evapotranspiration and increased solar reflectance, which translated to yield increases in wheat, lentils and canola.

The question that is normally asked is whether the tall stubble shades the ground and reduces soil temperatures, an undesired effect in our cool climate. I went out on the weekend and compared the soil temperatures between no standing stubble versus 16-inch tall stubble. This winter we had a seismic crew come through and plow down a few tramlines, flattening the stubble. This left me a check with no stubble compared to tall stubble in wheat. I was happy to see there was no difference in soil temperature between tall and flattened stubble. They both sat at 4 degrees Celsius.

Leaving tall stubble increases yield, harvest efficiency, fuel consumption, reduces residue load on surface, improves germination, emergence, and crop vigour and doesn’t require expensive technology. There is a misconception that soils will stay cooler from the shading caused by tall stubble. From my experience, it looks like there is little to know difference. Also, as the spring progresses, I would think having all your residue chopped and piled on the ground will keep you soil cooler and increase frost risk more so than taller stubble. With a potentially cooler spring ahead of us, I’ll be sure to let you know how this long term experiment goes. SL

Beyond Agronomy Apps

Tank Mix & Rainfastness Guide

This tank mix app, built for Western Canadian farmers, answers the everyday questions about herbicide rainfastness and the proper order to tank mix herbicides.

Apple or Android

Seeding Rate Calculator

An app designed to help you calculate how much seed is needed to produce a desired plant population when calibrating your seeder.

Apple or Android

Air Cart Maximizer

The air cart maximizer quickly calculates the maximum number of acres per fill based the size of each compartment in your air cart and the desired fertilizer and seeding rates. The app indicates which compartments should be dedicated to seed or fertilizer and how much product to deliver out of each to achieve the greatest number of acres per fill every time.

Apple or Android