Phosphorus Nutrition of Canola

Outline: P Nutrition of Canola Photo courtesy of Canola Council of Canada What are the nutrient requirements of canola throughout the season? Why is P needed early in the season? Why is placing P near the seed important? How can I be sure P supplies are adequate? What are some good strategies for managing P?

NASS; Statistics Canada What Have the Trends Been in Canola Yield?

What Is the Role of P in Plants? Photosynthesis and respiration Energy transfer and storage (ATP) Cell division and enlargement Transfer of heredity traits Seed formation

What are the nutrient requirements of canola throughout the season? Photo courtesy of Canola Council of Canada

Primary orthophosphate ion: H 2 PO 4 - (pH < 7.0) Secondary orthophosphate ion: HPO 4 = (pH > 7.0) The form most common is a function of soil pH – both equally present at neutral pH Plants Take Up P As: Solution P

Johnston et al., 1999 P 2 O 5 & S N K2OK2O 39 bu/A canola leaf elongation full flower end of flower 50% podded full pod harvest Growth stage Nutrient uptake, lb/A How Much N, P, K, and S Does Canola Take Up

How Are Nutrients Distributed in Canola at Harvest? Crop removal 0.7 – 0.9 lb P 2 O 5 /bu 39 bu/A Canola N P2O5P2O5 K2OK2OS Nutrient content, lb/A SeedStraw

Seed P and Early Season Canola Growth Seed P concentration can play a major role in early plant growth Seed P has been found to support canola growth for about 7 days After that period the seedling requires an external P source, either from soil or fertilizer to optimize growth Photo courtesy of Canola Council of Canada Brassica napus Brassica rapa

Canola Plant P Acquisition Strategies Canola has been shown to release organic acids from its roots, acidifying the rhizosphere, and increasing soil P availability Canola produces longer root hairs than many plants, increasing the soil volume from which it can absorb P In addition, canola root hair length and density increases as P supply decreases, further helping to access soil P Photo courtesy of Neil Harker

P Deficient Canola - Symptoms?

What Role Does Fertilizer P Play in Canola Growth?

What Happens to Fertilizer P After I Apply It? Absorbed by crop in year 1: –10 to 30 % of applied P –Highest on low P soils Labile P (future years): –70 to 90% of applied P –Future supply –Metastable Ca-phosphates and adsorbed P Solution PLabile PNon-labile P

Response of Canola and Wheat to Fertilizer P Strong and Soper, % 153% 145% 128% 106% Dry matter yield, g/pot Firdale - CK Firdale - Fert Lakeland - CK Lakeland - Fert Tops Roots

Proportion of Fertilizer P Taken Up by Canola Karla and Soper, % 51% 53% 48% 46% 41% RosetteBoltingFirst flower Harvest P uptake, mg/pot Soil P Fert P

Impact of Fertilizer P Placement Photo courtesy of Roley Rumbold

Why is band placement of P near the seed important?

The primary cause of low short-term uptake of P fertilizer is: The inability of P to move to absorbing roots Solution: Roots adapt and respond through increased development when they encounter sources of soil and fertilizer P Plant root Higher P concentration Diffusion Lower P concentration

Plant Root Growth in P Band Reaction Zone Strong and Soper, 1974 In this pot study, the proportion of plant roots found in a simulated fertilizer band in the soil is shown All plants displayed the ability to proliferate root growth in the P fertilizer band area Canola was by far the crop which showed the greatest root response to the fertilizer P zone in this non- calcareous P deficient soil Percent of roots in P band CanolaWheatFlax Check P band

Spring broadcast, 40 lb P 2 O 5 /A Seed-placed, 20 lb P 2 O 5 /A Agrium P Placement Can Influence Crop Response

Effect of Seed Row P (as MAP) on Canola Emergence and Yield Nyborg and Hennig, % seed bed utilization 8 bu/A 10 bu/A 20 bu/A 17 bu/A 21 bu/A lb P 2 O 5 /A Plant emergence, plants/m 2 Seed row1 in. below row P 2 O 5 placement

What Role Does P Placement Play in Canola Yield? Little difference was recorded between seed row and banded P when N was banded The split of P between 1/3 seed row and 2/3 band shows a minor advantage, and is attributed to those sites with cold soils at seeding Western Co-operative Fertilizers Ltd. 75 lb N/A + 25 lb P 2 O 5 /A Check N+Bcst P N+Band P N+Seed P N+2/3 band P, 1/3 Seed P Canola yield, bu/A

What Is the Role of P in Balancing Canola Nutrition? Photo courtesy Neil Harker

Lafond, 2003 Nitrogen x Phosphorus Interactions 100% 106% 144% 90 N 30 P 2 O 5 90 N + 30 P 2 O 5 Fertilizer applied, lb/A Canola yield, bu/A

Hybrid Canola Response to N and P Rates Karamanos, Unpublished data P 2 O 5 lb/A N rate, lb/A Canola yield, bu/A

Does P Fertilizer Form Influence Crop Response? Fixen, 1989; Leikam, 1990 Research evaluating crop response to MAP, DAP and APP has found that all sources give equal crop response In addition, no agronomic differences have been found between dry and liquid sources The only exception is rock phosphate which provides limited crop response due to low P solubility

Related Impact of P Nutrition in Canola Photo courtesy of Canola Council of Canada Phosphorus fertilization can lead to earlier maturity of canola – a major factor improving yield and quality in short- season environments

How can I be sure P supplies are adequate? Photos courtesy of the USDA NRCS

What Information Does a P Soil Test Provide? An index of the amount of plant-available P in the soil This index must be calibrated to yield response: –Examine responses to P additions at various soil test levels –Conduct studies across a wide range of soil test levels and environmental conditions

Nyborg, 1975 How Is A Soil Test Calibrated to Yield Response? 25 0 to 6 ppm P 13 to 19 ppm P PO applied, lb/A Canola yield increase, bu/A

Example of P Soil Test Calibration Data McKenzie et al., 1995 Calibration curve indicates which soil test levels tend to limit yields Data based on P responses observed across several sites and years

Critical Soil Test P Level The results of this calibration data set from Alberta show a critical level of 20 to 25 ppm (40 to 50 lb/A) P This is the level of soil test P above which only maintenance (starter/removal) application would be required McKenzie et al., 1995

What Are the Best Uses for Soil Test P Information? —Estimating average probabilities of crop response —Examining changes in levels over time —Estimating average relative yield response —Estimating a specific probability of response for a given site and year —Estimating a specific relative yield response at a given site and year Good Fair Poor

What are some good strategies for managing P? Photos courtesy of the USDA NRCS

Approaches to P Fertilization Sufficiency approach: Apply P to maximize net returns to fertilization in the year of application –Strategy: fertilize only when there is a good chance that a profitable yield response will be realized –Soil test levels kept in lower, responsive ranges –Normally adopted on land leased for short periods of time or when cash flow is limited Relative yield, % Soil test P level

Approaches to P Fertilization Build and maintenance approach: Remove P as a yield-limiting variable –Strategy: apply extra P (more than expected crop removal) to build soil tests to levels that are not yield-limiting –Soil test levels kept in higher, non-responsive ranges –Normally adopted on owned land or land leased for longer periods of time Relative yield, % Soil test P level

Summary - P Nutrition of Canola P nutrition is critical to reaching the attainable yield potential of canola Canola responds to P deficiencies by changing its root development, forming more root hairs Canola will concentrate its roots in the area of P fertilizer bands, increasing fertilizer recovery P nutrition must be part of a management strategy that considers the importance of other nutrients Land ownership/rental and cash flow have a large impact on the approaches taken to managing soil fertility

Ref: International Plant Nutrition Institute (IPNI) 655 Engineering Drive, Suite 110 Norcross, GA Phone: ; Fax: