Starter Fertilizers with Canola – Too Much of a Good Thing?

Seed-placed phosphorus (P) fertilizer is one of the most efficient means of applying phosphorus, often with better results than broadcast application. Starter fertilizers work very nicely with cereals and corn, aiding stand establishment and boosting yields. In winter wheat, starter fertilizer MAP has shown up to an 8 bu/ac yield advantage in Soil & Crop trials. 

Canola Less Responsive

Canola, on the other hand, is less responsive to seed-placed fertilizer. In the first 30 days of wheat plant's life it uses fifteen pounds per acre of phosphorus. Corn uses four pounds per acre in the first 25 days. Canola uses 3 lbs in the first 35 days (5-leaf stage). Seed phosphorus content is enough to support canola seedling growth for about 7 days. After that time the seedling requires an external phosphorus source from the soil or fertilizer. Canola is recognized as a better scavenger of soil nutrients than many crops. Not only does canola produce longer root hairs, it releases organic acids that help it extract nutrients from the soil. 

More Sensitive to Burning

Canola is also much more sensitive to seed-placed fertilizer than corn or cereals. Corn, wheat and spring cereals are monocotyledons plants. This means the seed sends out the shoot and root from the ends of the seed, and the seed remains basically intact. The seed coat protects the plant as it emerges. Canola and soybeans are dicotyledons. As the canola plant emerges, the two halves of the seed split apart. Fertilizer can burn the tender heart of the plant that is no longer protected by the seed coat. 

Research

A recent University of Saskatchewan study confirmed the higher sensitivity of canola to starter fertilizer (Figure 1). There were no significant differences in canola emergence at rates up to 20 kg/ha of phosphorus, applied as MAP (11-52-0), but at 30 kg/ha canola emergence was reduced to 83%. 

Figure 1. Effect of seed row phosphorus (MAP) on canola emergence

Figure 2. Effect of seed row P on canola and spring wheat plant uptake

Adapted from Crop Tolerance & Response to Seed-row Fertilizer, University of Saskatchewan, 2005.

Link to data equivalent charts

Plant phosphorus uptake in the first 4 weeks of growth increased in response to seed-placed P as expected, as did overall growth (Figure 2). Spring wheat was much more responsive to seed applied phosphorus in plant uptake than canola. There is some evidence to suggest that on low testing phosphorus soils, canola does benefit in early growth and yield from starter phosphorus.

OMAFRA Recommendations

The OMAFRA recommended rate for spring canola is a maximum 20 kg/ha (18 lb/ac) phosphate fertilizer be drilled with the seed as superphosphate or monoammonium phosphate (MAP). Nitrogen, except as MAP and potash, should not be applied with the seed. Table 1 compares the maximum safe rate of a couple of fertilizer types placed with the seed for canola and spring grain. Seed placed fertilizer injury is less likely to occur in a year with good soil moisture.

¹ For information on maximum safe rate of nutrients on spring cereals or other crops refer to OMAFRA Agronomy Guide 811 (pg 47), Soil Fertility Handbook (pg 171), or on the Omafra website.

Related Links:

• OMAFRA Agronomy Guide - Maximum Safe Rates of Nutrients

| Top of Page |