Fertilizers for Winter Wheat

T.E. Bates, Land Resource Science, Ontario Agricultural College

Fertilizer requirements for wheat in Ontario can best be estimated by using a soil test along with information on past management factors such as legume sod plowed down and manure applied. To provide dependable fertilizer recommendations each field should be tested at least once every third year.

Winter wheat is quite responsive to nitrogen and phosphate and while it does require potash it appears to be less responsive to this nutrient than most crops. Where phosphate fertilizer is required for wheat, on the basis of soil tests, it is best drilled with the seed and may be accompanied by small amounts of nitrogen and potash. Because of the greater chance of dry soil conditions at the time of seeding, winter wheat is more susceptible to fertilizer toxicity and resulting poor germination than spring-seeded cereals. Not more than 15 kg nitrogen or 30 kg of nitrogen + potash per hectare, and neither urea nor diammonium phosphate, should be drilled with the seed. If more potash is required than is safe to drill with the seed of winter wheat it should be broadcast and worked in before seeding.

Most of the nitrogen for winter wheat should be applied broadcast in April (Tables 1 & 2). Work of C.K. Stevenson at Ridgetown and of W.l. Finlay at Harrow shows ammonium nitrate and urea to be equally effective for broadcast applications in April. Where winter wheat is not preceded by a legume sod and is not manured it requires approximately 90 kg of nitrogen per hectare (Tables 2 & 3). The data of Stevenson (Table 3) were obtained with Fredrick and Yorkstar varieties and no difference in nitrogen requirement was found between the two. Where wheat is grown immediately after a 50% legume (alfalfa, clover or trefoil) sod no nitrogen is required. Where wheat is manured, nitrogen requirements should be adjusted using figures provided in Ontario Ministry of Agriculture and Food Field Crop Recommendations, publication 296.

Table 1 : Time of application of 34 kg Nitrogen/ha on winter wheat on Brookston Clay 1975 - 1976

	Nov.	Dec.	Jan.	March	April	May	No nitrogen
Time of application	13	18	29	9	7	11
Yield t/ha	3,54	3,70	3,53	4,12	4,42	4,01	3,29

Table 2 : Time of Nitrogen application on winter wheat - 8 trials in S. Ontario 1959 - 1962

Nitrogen rate Kg/ha	Time of nitrogen application late fall (after Nov.15) grain yield t/ha	Time of nitrogen application early spring (before April 20) grain yield t/ha
0	2,62	2,62
11	2,84	2,88
22	2,84	3,00
44	3,01	3,37
88	3,45	3,44

Table 3 : Nitrogen rates on winter wheat - average 8 trials on Brookston Clay 1974 - 1976

Nitrogen rate grain yield t/ha

3,49

3,85

4,17

4,27

112

4,23

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