Features Agronomy Cereals
Breaking the Guinness world record for wheat yield: 232 bu/ac

Now this is intensive farming. Chris Dennison of Oamaru, New Zealand, set a Guinness world record for wheat yield in 2003 at 15.015 t/ha (223 bu/ac), since surpassed by another Kiwi farmer, Michael Solari, with 15.636 t/ha (232.64 bu/ac) on March 8, 2010 at Otama, Gore.

What can Canadian farmers take away from their approach to wheat production? Attention to detail, optimum stand establishment, frequent crop scouting, managed crop rotations, a long, cool, growing season and a prescriptive approach to managing the wheat canopy. “How high can we go? This year (2010) we saw 21 t/ha (312 bu/ac) on our yield monitor. That makes me wonder if I am under-managing some of the land,” says Chris Dennison, who spoke at the Advanced Agronomy Conference in Leduc, Alberta, in late fall of 2010. 

Dennison farms literally on the edge of the Pacific Ocean at 45 degrees, south latitude; roughly similar to the same northern latitude as Portland, Oregon, Minneapolis, Minnesota, and Ottawa. His land is a heavy silt loam with 10 inches of black topsoil over a tight iron pan that impedes drainage. Under that iron pan is a deep gravel bed.

Soil pH is a concern and Dennison aims for a pH of 6. If the pH drops below 5.8, he puts on lime at one tonne per acre every five to six years, usually prior to a pea crop. Recently, Dennison considered a change to his liming practice, moving to an annual application of one-quarter tonne every year, because his high urea nitrogen (N) use can cause a decrease in pH.

Winters are wet and can cause flood problems on the land, and annual rainfall is 22 inches per year, although it falls sporadically. Dennison’s land is on an exposed, windy plain and typically has an eastern summer breeze that dries out the land. Summers are traditionally dry, making irrigation critical for grain farming. Snow is rare, hail occurs occasionally, and the farm receives a high number of sunshine hours. Summer temperatures rarely exceed 33 degrees C.

Crop rotations
Dennison has a rotation that is based on a barley-canola-wheat rotation with an additional break crop aimed at reducing disease problems. He has tried peas, beans, borage, cabbage, carrots, coriander and phacelia (an herb). Ryegrass for seed is also commonly grown in the rotation. The break crop is necessary to control take-all disease, a seedling blight that can devastate a wheat crop. Dennison has seen wheat yields drop from 9.0 to 6.0 t/ha (133.8 to 89.2 bu/ac) because of take-all. “We are short on profitable break crops. We can make money on wheat, but the break crops are not profitable. So we have tried a lot of different crops and found it is best just to grow the crops we are good at instead of chasing the exotic ones,” explains Dennison.

Stand establishment
Dennison grows winter wheat with seeding starting as early as April, during New Zealand’s autumn season. The earliest seeding dates provide the highest yields, with performance declining for seeding dates after May 1. He seeds English feed wheat varieties Einstein, Oakley and Equinox. English varieties were only allowed into New Zealand in 1999. “The English varieties resulted in a step change in production. We found that if they performed well there, they performed well for us, and much better than the few New Zealand varieties we had available.”

The crop is sown on six-inch row spacing, with a targeted plant population of 125 plants per square metre (13 plants per square foot). Depending on the variety, the seeding rate ranges from 62 to 90 pounds per acre. The seed is treated with a basic fungicide seed treatment and Gaucho, a systemic insecticide that helps control barley yellow dwarf virus. 
Depending on the preceding crop, the land may have been plowed, cultivated with a tyne cultivator/soil crumbler/roller, or double disced. Super phosphate fertilizer (nine percent) are broadcast-applied at a rate of 890 lbs per acre prior to seeding to supply 80 lbs per acre phosphate (P) and 98 pounds of sulphur (S). Dennison is aiming to build his P fertility, to an Olsen-P soil test level of 30 to 35 lbs so his P fertilizer rate is roughly  double what the crop removes from the soil. The P fertilizer is double disced into the soil prior to seeding.

Seeding is done with a Great Plains drill equipped with disc openers. A leading disc cuts a slot for a double disc opener where seed is placed. Because all fertilizer is either applied pre-seed or post-emergent in the spring, no fertilizer is applied with the seed. Spraying tramlines are set up during seeding by blocking off two seedrows to match the sprayer track width.

Spring fertility program
The fertility program is developed based on crop nutrient removal. With the exception of P, Dennison aims to replace crop removal of nitrogen (N) potassium (K) and sulphur (S) with fertilizer. He soil tests canola, pea and ryegrass stubble to a depth of two feet to assess fertility. In the years he does not soil test, he assumes there is no residual N in the system and fertilizes accordingly. 

Potash (KCl) is mixed with N and applied in the spring at rate of 45 lbs of K per acre. For trace elements, magnesium levels have been dropping in the soils, so magnesium-coated urea is used to correct deficiencies. Boron is standard practice on canola and copper has been an issue, and is applied to manage deficiencies. 

His 15-tonne (133.8-bushel) wheat crop requires approximately 27 to 30 kg of N per tonne of wheat, or about 450 kg per hectare (400 lbs per acre). Dennison applies N in three applications at a rate of 195 lbs per acre of urea (90 lbs of actual N per acre). If the crop stand is thin, he will apply the first application to stimulate tillering, generally around Growth Stage (GS) 31. If the stand has heavy tillering, he will hold off applying that rate for a week or so to better manage the plant stand. The aim is to have an open canopy with a leaf canopy index of five to six.

Dennison explains that managing the crop canopy with nitrogen applications is critical to high yielding crops. “The crops can look pale in the spring, the thinking used to be that early was good, but if you fertilize too early, that sets up the crop with too thick of a canopy. When you hold off on N application at this stage, there can be pretty mangy wheat crops, but if the soil N is good, we have found that it is best to hold off.”

He follows up with a second application at flag leaf and the third at early head emergence.

The record-breaking wheat crop requires a fully watered soil profile throughout the growing season. Total water required is 500 millimetres (20 inches) combined with rainfall and irrigation from April during fall seeding through to harvest in February or March. To achieve 500 millimetres, Dennison irrigates three to four times at a rate of 40 millimetres each time. His water use efficiency is about 30 kg of grain per millimetre of water.

Fungicides and growth regulators
Dennison uses four applications of fungicides to manage disease. The first application of epoxiconazole (at 120 ml per acre) goes on when the third leaf has emerged. The second and third applications are a tank mix of 120 ml per acre of epoxiconazole and 150 ml per acre of Amistar (azoxystrobin; similar to Quadris) at the flag leaf and head emergence stages. The last application is at the ear wash stage with 100 ml per acre of Amistar. He says protecting the top three leaves and head are critical to building high yield. “We find the strobilurins (Amistar) have a greening effect and delays maturity. We find there is a 3.7 bu/ac yield increase for every day that maturity is delayed. The final strobilurin application allows us to utilize the long, cool growing season.”

The growth regulator, chlormequat, is applied at GS 30, around early stem elongation, at a rate of 400 to 600 millilitres per acre, at a cost of $2.40 (Cdn) per acre. Depending on variety and crop canopy, a second growth regulator, Terpel (mepiquat chloride), is applied at the flag leaf stage. This application can knock off six to eight inches in height from the crop.

Harvest
Combining starts when the crop reaches 17 percent moisture. Dennison dries more than two-thirds of his crop because of the damp winds blowing in off the ocean at harvest. Despite the growth regulators, his straw volume is often so large that he must either bale the straw for sale, or burn it. “You can’t pick out a record wheat crop from the road. The difference between a 180 and 230 bushel per acre wheat crop can’t be picked out. You have to harvest it.”

November 30, 1999  By Bruce Barker