Agronomist Notes
It was crunch time this week as I crafted my keynote presentation for FarmTech on Wednesday. I’m really looking forward to presenting some agronomy topics that are a little left of centre, mainly for the conversations afterwards!
In this newsletter, we’re going to look at managing calcium and magnesium levels to help improve soil structure and crop emergence. We’ve made a few changes on our farm this way and I’ll share the results we’ve seen. Next, we’ll look at building yield in wheat by maximizing grain fill. We’ll finish with fundamental and technical grain market news. Have a great week. SL
Agronomy
Understanding the effects of Ca/Mg ratios on soil structure
The use of calcium and magnesium ratios and their relevance on crop yield has been argued for decades. In some theories, optimum crop yields can be achieved at a number of different Ca/Mg ratios. That’s not my shtick but what interests me is managing Ca/Mg ratios to help improve soil structure. Ideally, you want calcium levels up around 60-70% and magnesium levels down to 10-15% on base saturation level. That’s where you’ll find a great aerated structure where crusting is not an issue.
Soils that are high in magnesium tend to be sticky when wet, compact easily, have fewer pour spaces, less oxygen and usually crust over after drying out. Any gumbo farmers out there? I’m one of them and know the challenges high magnesium soils create. In some areas of our farm, the magnesium content is about 36% on a base saturation level. Because high Mg soils compact easily, the packer wheels on our Concord air drill make a nice cement layer over the seed. With pneumatic tires, we’re able to drop the tire pressure to 8 psi to reduce the compaction but we know we’re still getting big losses. Seeds germinate and then twist, coil and bend sideways to get around the compacted roof, usually to no avail. We typically lose 25% of the wheat we plant because it never has a chance to emerge. This is a major issue, never mind canola.
In the winter of 2008, we applied a gypsum/compost blend that was high in calcium at a rate of 4 T/ac and up to 7 T/ac in some areas. The goal was to improve emergence by kicking magnesium off the clay particles and replacing it with calcium. Calcium tends to break apart tightly bound clay particles, improving aeration and drainage. The 7 T/ac rate worked really well as we applied it to areas with the highest magnesium levels. Its effect on the soil profile was shallow; in fact, it only improved the soil tilth in the top two inches- just perfect for the excellent emergence we wanted and got. In 2010 I’ll be applying 2 T/ac on the worst of the high magnesium areas, about 30 acres. Now, does managing calcium and magnesium make dollars and cents? Here’s how I’ve penciled it out.
Steve’s quick math
A 2 T/ac application of straight gypsum sulphate would cost roughly $45.00/ac applied on our farm. My math suggests we could generate a possible $2.00 to $4.50/ac through improved germination and emergence by reducing our seeding rates and seed treatment. That’s a 10 to 15-year return on investment and completely out of the question.
Where you could justify the cost of the gypsum is in the sulphur content you receive. A one-time application of 2 T/ac gypsum contains 15% sulphur and 22% calcium. That would supply 660 lbs/ac of sulphur, enough to sustain your sulphur needs for at least 7 to 10 years. At a current cost of $0.33/lb for sulphur, it’s worth $218.00/ac. Provided you don’t farm a sandy beach at risk of leaching sulphate below the root zone, that investment in sulphur may offset the cost of the gypsum application and you get the bonus of improved soil structure, drainage and crop emergence. Food for thought. SL
Maximize grain fill to build wheat yield
One of the most overlooked areas in cereal production is the grain filling process. The grain filling process occurs from flowering to maturity and takes roughly 6 to 7 weeks. Carbohydrates generated in the leaves, stems and heads build the yield. Unfortunately, it’s during this time that nutrient deficiencies start to occur, compaction starts to rear its ugly head, diseases set in and leaves begin to die pre-maturely. We’re leaving a lot of money on the table if we don’t change this scenerio. Here’s why.
The number of main stems, tiller, heads and head size is set at the three to five leaf stage. It’s the pollination that occurs during flowering that determines the number of kernels that will develop on head. The overall yield potential could be 100 bu/ac but won’t be realized until the carbohydrates produced in the leaves, stems and heads during photosynthesis begin to move into the developing kernels. If leaf tissues begin to die prematurely, yield is directly impacted because photosynthetic capacity has decreased. To further my point, a breakdown of each plant part and its contribution to grain fill is as follows: flag and penultimate leaf 65%, heads 20%, third and fourth leaf 10%, stems 5%.
Natural leaf senescence during grain fill begins at the leaf tip downward. The hormone ethylene starts to increase which begins the breakdown of chlorophyll and, consequently, photosynthesis stops. It’s very rare to see our crops die or senesce naturally. Typically, I see the third and fourth leaf covered in leaf blotch diseases (tan spot, septoria), like in this photo, and areas of dead leaf tissue smattered throughout all the leaves and stems.
I haven’t pin pointed the problems yet but I suspect we’re losing a good portion of grain filling potential in the third and fourth leaves as well as the stems. That leaves a margin of yield loss potential up to 15%, which is quite significant. We could be losing 4 to 7 bu/ac from pre-mature leaf senescence in wheat. It’s time to start paying closer attention to the yield robbing factors during grain fill and do everything we economically can to keep those leaves green and healthy all season long.
Reference: http://www.fwi.co.uk/academy/article/110121/flag-leaf-treatment-in-wheat.html
Market News
Technical Analysis
Canola: March Futures. The long and short term trends are down. Look for a possible rally here.
HRS Wheat: March Futures. Short and long term trends are down.
Corn: March Futures. The short and long term trends have turned down. Further lows are possible.
Soybeans: March Futures. Short and long term trends are down. Look for possible rally here.
Canadian Dollar: March Futures. Long and short term trends are down.
US Dollar Index: March Futures. Long and short term trends are up.
Crude Oil: February futures. Short term is down. Long term trend is up.
