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Ontario Grain Farmer Magazine

Winter Wheat Nutrient Uptake, Partitioning and Removal

Principal Investigator: Peter Johnson

Research Institution: Middlesex Soil and Crop Improvement Association (MSCIA)

Timeline: September 2018 – December 2022

Objectives:

  • To determine nutrient uptake and partitioning of wheat, across genotypes and different classes, at various growth stages under both high and low nitrogen (yield) environments. This information will be summarized into a series of nutrient uptake curves by growth stage. Nutrient dynamics and nitrogen use efficiency will be determined, and management opportunities identified.
  • To develop a wheat extension publication with nutrient uptake curves, nutrient dynamics, and suggested management options to maximize yield and minimize environmental impact.
  • To publish a peer reviewed paper in an appropriate scientific journal.

Impacts:

  • By understanding the nutrient uptake timings and needs of high yield wheat, growers will be able to fine tune fertility applications to support high yields.
  • Determination of nitrogen dynamics will identify opportunities for improved nitrogen use efficiency, by either reducing nitrogen rate applied, or supporting higher yields, or both, all of which reduce the environmental impact of applied nitrogen.

Scientific Summary:

Nutrient uptake and partitioning efforts in corn and soybean have shown significant changes in nutrient uptake with new varieties and high yields, emphasizing nitrogen timing (corn) and the importance of phosphorus uptake through grain fill (corn and soybean). Exponential increase of nitrogen uptake appears to be required for high yields: Vyn et. al., showed that tissue nitrogen contents increased 8-fold in 300 bushel/acre corn compared to 150 bu/acre corn. These findings have helped to identify improved fertilizer management strategies in both crops. Similar opportunities exist in wheat but have not been investigated. Wheat production and genetics have changed significantly over the past decades. 2016 brought a new yield record to Ontario (96.7 bu/ac), with 2017 the second highest yield ever (89.6 bu/ac, Agricorp data). Yield trendlines have shown consistent increase of 1.05 bushel/acre/year.

Physiological changes in the wheat plant to support higher yield most likely have altered nutrient uptake patterns. These new or potentially altered uptake patterns have not been investigated for wheat, nor for high yield wheat. Previous wheat nutrient uptake studies have been in low yield environments (Kansas, Montana, Saskatchewan) on hard red wheat, either winter or spring.

This project investigated the nutrient uptake and partitioning of winter wheat in Ontario across classes of wheat and under high and low management input systems. Four locations were planted in each of 3 production years. A range of environments was experienced, from incredibly harsh winter conditions (2019) to extremely high yields (2021). Tissue samples were collected at 5 different growth stages, across replications and treatments, and analyzed for 13 different nutrients (i.e., nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), sulphur (S), sodium (Na), iron (Fe), aluminum (Al), manganese (Mn), copper (Cu), boron (B) and zinc (Zn)). Plant parts were separated at later growth stages, and analyzed separately, to look at nutrient partitioning within the crop. Data were analyzed to look at differences between crop classes and management levels. Management opportunities based on nutrient uptake information were developed to aid growers in making better management decisions around fertilization of the winter wheat crop.

Results

The results of this project have the potential to greatly improve grower understanding of nutrient demands of the Ontario winter wheat crop, what nutrient demand actually is, and when application has the greatest potential of success.

N, S, K, Ca, and Na showed rapid uptake during the early growth stages, with at least 70% of total uptake occurring by flag leaf stage. From flag leaf until milk stage, greater than 40% of total Mg, B, Mn, Cu, and Al occurred, making the grain fill period the most significant uptake period for these nutrients. P and Zn had the most consistent uptake, with at least 10%, to a high of 25% of total uptake occurring between each growth stage measured in this project. P and Zn also had the highest percentage of total uptake after the milk stage, with 22% of total uptake occurring during late grain fill.

P and Zn also had the removal of some of the total uptake, with over 90% of total uptake found in the head at maturity. N (83%) and Cu (75%) also had a relatively high percentage of total uptake in the head at maturity. Nutrients with the lowest removal out of the total uptake were K (27%), Ca (20%), Na (45%) and B (33%). All of these nutrients reached maximum uptake prior to maturity and data suggest that leaching from the plant began prior to physiological maturity. Total K and Ca peaked at anthesis and total nutrient levels at maturity were significantly lower than the levels reached at anthesis. Total K in the plant at maturity dropped 40% and Na declined 5% from the maximum uptake reached at anthesis. B and Ca reached maximum uptake at the milk stage and were down 24% for B and 20% for Ca at maturity. Removal of these nutrients remained low compared to total uptake, with 47% of K, 27% of Ca, 50% of Na, and 44% of B contained in the head at maturity.

From flag leaf to milk stage, stem biomass approximately doubles and remains relatively constant. P, K, Na, Zn, Cu and Al repeat this relationship, with almost double the nutrient levels in the stem versus the leaves up to milk stage. The leaves have slightly higher concentration levels, but higher stem biomass rules the day. N, S, Mg, and Mn all have elevated concentration in the leaves, resulting in about a 50/50 split of total uptake stored in the stem and leaves up until the milk stage. Ca, B, and Fe all have substantially higher concentrations in the leaves with 70% for Ca, and 60% for B and Fe, of total uptake stored in the leaves.

There was very little difference in nutrient concentration between the fungicide treatments for each individual N rate. Nitrogen was the exception, as N content in the leaf at maturity was higher in the no fungicide treatments for both the high and low N rates. Plant concentrations of all other nutrients were very similar, and any slight increase in nutrient uptake was due to increased plant biomass. Conversely, high N and low N treatments showed differences across most nutrients. P, Mg, and Fe nutrient uptake correlated with total plant biomass. N, S, K, Ca, Na, Zn and B all had slightly higher plant concentrations in the high N rate treatments. Mn and Al had slightly higher plant concentrations in the low N treatments.

The high N treatments had both a higher rate of uptake, and higher total uptake for all nutrients. Most of the increased nutrient uptake corresponded to an increase in biomass accumulation. S was the exception, where increased N concentration resulted in increased S concentration. N and K had the highest daily rate of uptake (2.7 lbs N/acre/day, 3.7 lbs K/acre/day) and highest total uptake (143 lbs N/acre, 132 lbs K/acre) in the high N rate with fungicide treatment. B and Cu had the lowest total uptake of 13.2 and 20.6 g/acre.

There was very little difference between varieties in nutrient uptake and partitioning but there were a few exceptions. HRW varieties, especially Gallus, showed higher N concentrations in the head, but lower grain yields balanced the higher N concentrations such that the proportion of total N uptake removed was equal across varieties, at about 83%. The HRW and again especially Gallus also had lower Mn concentration in the leaves and stem through all stages of growth, but the concentration in the grain was similar to the other varieties. There was a very slight difference in Al concentration between varieties with 25R40 having significantly lower Al concentration in the head while the HRW varieties had higher Al concentrations in all parts of the plant.

Boron is a nutrient that has recently been suggested as being deficient and needing to be applied. The actual total plant uptake of boron (micronutrient) is only 13 grams per acre. While soils may be deficient, the application of 2 pounds (908 grams) of boron (standard suggestion) per acre would be sufficient to supply the crop needs for 70 years. While plants may benefit from an application once or twice, repeated applications are highly unlikely to be of value. Boron uptake peaks early in grain fill, and no further uptake occurs after early grain fill. This indicates that application would be best made at the beginning of stem elongation, if any response is to be attained. With the cost of boron application at $30 plus at a 2-pound application rate, this information will save growers tremendous input costs by understanding that one application should do for a number of years, unless leaching is severe.

Magnesium (secondary nutrient) is another nutrient currently under investigation as benefitting from application in fertilizers. Total Mg uptake is ~13 pounds/acre. Uptake is minimal until stem elongation. This suggests that spring application of Mg may be more beneficial than fall application. Total removal in the grain is about 8 pounds/acre. This indicates that applications of 6 pounds/acre (standard recommendation) will not maintain soil levels of magnesium over time, and on fields with very low magnesium, application rates may need to be increased.

Nitrogen (macronutrient) uptake is most rapid through the stem elongation stage, and by anthesis fully 83% of total nitrogen uptake has occurred. This leaves only 17% of the nitrogen to be taken up through the grain fill stage, a significantly different outcome than in corn, where 37% of nitrogen uptake occurs through grain fill. This information will inform growers that the key nitrogen application needs to be made at the beginning of stem elongation, and the second application should not be left much beyond flag leaf stage if yield gain is the target.

Phosphorus demand is consistent throughout the growth of the wheat crop. This supports the need for solid base fertility for high yield wheat.

External Funding Partners:

This project is funded by the Canadian Agricultural Partnership, a five-year investment by Canada’s federal, provincial, and territorial governments.

Project Related Publications:

None.