Improved agronomy | How to increase yields for the world’s wheat crops
Good science and a little water go a long way toward understanding wheat yields.
“It seems like it should be a mystery, how this little seed can know when it is the right time to launch into producing a great big plant, and with nothing more than what is packed into that little, tiny package and some water, get to be a seedling, inches high,” said Markus Braaten, an agronomist from Kalispell, Montana, who heads agronomy extension work for Agri-Trend in the United States.
“But it’s not. It’s science. Every seed has all of the necessary nutrients to do it, or it should have.”
Braaten, who provides agronomy services to a mix of irrigated and dryland grain production covering 50,000 acres, said plants’ main concern is getting to reproduction.
“Our job as farmers is to maximize that system. We could spend a lot of time talking about the role of boron in a plant, but we need to fix all the big stuff first,” he told Agritrend’s 2013 Farm Forum Event in Saskatoon last week.
“When we think of yield potential, target yield, we have to think of what is economically possible, versus what is theoretical. Two hundred and thirty-two bushels spring wheat in New Zealand is the world record. We might not be talking a goal that high, but 100 bu. per acre is not out of reach.”
Numbers of spikes per acre, florets per plant and kernels per spikelet deliver yield, and agronomists calculate that higher yields from spring wheat are possible, as long as the necessary supports are in place to deliver plant health at the right times and to the right numbers of plants per acre.
Braaten said the bigger problems holding back yields relate more to ideal plant populations and fertility as it pertains to the major nutrients.
Montana farmers planting winter wheat earlier this fall saw variations in seed populations of 10,000 to 18,000 seeds per pound.
“When you are measuring your seeding rate in bushels per acre, you aren’t doing the one thing that matters the most: figuring out how many plants you will have in the field (by flowering time),” he said.
For example, wheat with a seed size that yields 10,000 seeds per lb. and seeded at a rate of 131 lb. per acre will result in 30 seeds per sq. foot. A 12,000 count per lb. will reach that same goal at 109 lb., while 16,000 seeds will take only 82 lb. At 18,000 seeds per lb., the same 30 seeds per sq. foot will be reached with just 73 lb. of wheat seed.
While the larger seeds tend to produce healthier young plants that will do better, seedling survival can also be influenced by seed treatment and careful planting regimes.
“You need to plan for the ideal number of plants to produce your target yield. Spring wheat is going to be higher than winter wheat when it comes to an ideal plant population,” Braaten said.
“More plants equals more photosynthesis. We often short our potential by not getting our plant populations high enough. Percent germination, seed size and mortality all play into growing big wheat yields. Seed based on a target plant population — if you seed a bushel and a half per acre, how many plants is that? If you don’t know, spend the time to figure that out.”
Once the number of plants is known, a fertility plan can be established with reasonable expectations of reaching a yield goal, provided the crop receives the necessary moisture.
He said 25 to 30 plants per foot are ideal in dryland production and 30 to 35 for irrigation systems.
Braaten said an ideal wheat crop on the U.S. Plains and western Canada requires 135 frost free days, timely rain in May, June and mid-July, soil pH near 6.5, no days hotter than 29 C, no days hotter than 26 C with a strong wind, few weeds and phosphorus soil tests of at least 22 parts per million and potassium of 250 p.p.m.
“OK, we won’t get all of those, so we had better manage what we can,” he said.
Manitoba agronomist Geza Racz said projecting what a crop needs for its major nutrients is critical to maximizing yields.
“Planning for nitrogen removal by the crop you want to grow gives you an idea of what you will need to provide to reach that targeted yield,” he said.
Braaten said the 2013 season was a good example of nitrogen use.
“You haul the same amount of nitrogen to the elevator in the winter. When you have higher protein in your seed, you haul it in fewer loads. This year, producers had higher yields and found they had lower protein,” he said.
“Overall, we get paid by the pound, with a bonus for protein.”
Research at the U.S. Department of Agriculture has shown that the amount of calcium, magnesium, potassium, phosphorus, iron, copper, zinc and selenium contained in harvested American wheat between 1963 and 2003 fell by 10 to 20 percent in most cases. The amount of selenium fell by 50 percent.
“So farmers and breeders have been focusing mainly on wheat yields, not what is inside the grain,” he said.
When it comes to wheat seeking nutrients in the soil, he said the crop only uses two percent of the dirt in any given year.
“So think about where you are locating your immobile nutrients. The phosphorus, copper, iron, manganese and zinc: they have to be where that wheat plant will find them,” he said.
Corn research in the U.S. is starting to focus on banding immobile nutrients in the seed row, but the strategy could also work for wheat and canola crops, say researchers at the University of Illinois.
“As we start to get to higher yields in wheat, we are going to need to examine new ways to deliver nutrients. There will need to be some banding and strategies such as seed placed ESN to deliver N when the plant needs it, without damaging plant populations,” he said.
“I expect that in my lifetime we will have average wheat yields of 200 bushels per acre. We will need to find ways to deliver 400 to 500 lb. of nitrogen to that crop. There will need to be some strategies for getting balanced nutrition in place.”
Soil types are tougher to control. For most producers it is a matter of living with what they have.
“Low pH will limit what is available in terms of yield potential, but knowing the fields and knowing where to invest and where not to will create the overall profitability needed to farm the better land well,” he said.
“A pH drop from 6.8 to five will cut yields by a quarter. So knowing what you are working with is critical to successfully managing the crop,” said Braaten.
He said the crop will need to access 23 inches of moisture to reach the 100 bu. average yield.
“It is easier in irrigation, but wheat is a very good scavenger and will go very deep into the soil’s profile to find what it needs,” he said.