Sulfur deficiency in canola

There has been a lot of discussion among agronomists and farmers about S deficiency in crops - especially canola. The photo shown here is a leaf from a canola crop grown in the Bealiba district of western Victoria. The paddock was mixed lighter soil types, and the symptoms were seen on the sandier parts.
The paddock received no ammonium sulfate or gypsum. The crop is running up and so it is probably too late to apply this season to get good recovery from the S stress, and with low confidence of additional rainfall and so a fair to good seasonal finish, S strategies will roll into the following season.
A deep soil S test will be of value to assist with refining the future strategies.

Some dot points about S and canola:

• S is mobile (like N) in the profile

S can be leached in lighter soils and in wetter years - depending where it ends up (ie how far down the profile), this can

• S can be mineralised from OM like N, Humus N:S ~8:1 (Kirkby et al.)

50 kg mineralised N = 6 kg mineralised S

• S needs to be where the plant can get it –

Root zone – control release rates to avoid leaching

• In synchrony with plant demand – ability to recover from nutrient stress

Table below shows the effect of timing and rate of S supplements from a field trial reported by P. Hocking et al. (1996) on a very low S soil (a "red brown earth" in New South Wales).
Rate was pretty important (40 always better than 10)
Late low applications were ineffective (10 at sowing versus 10 at SE).

S applied Kg/ha	Sowing	5-6 Leaf	Buds Visible	Stem Elongation
10	1.73	1.62	1.56	1.41	LSD 0.43
40	2.15	2.26	2.11	2.19

Thanks to Matt Sparke for sending in the photograph.