Farmer Focus: Questioning the value of variable rate fertiliser applications to rape crops

Over the last five months the farm rain gauge has measured a total of 720mm. This compares with an average for those months over the previous 14 years of 405mm. However, the same period over the winter of 2000-01 yielded an amazing 835mm so in fact it was even wetter.

We have a healthy flow of water through the cellar of my house, we narrowly saved a barn let for storage from being flooded by laying some emergency earthworks, and spring field work is much delayed with a splattering of temporary ponds having appeared. But, of course, this is nothing compared with other parts of the country and I count myself lucky. Even nearby on the Weald many fields are underwater.

Despite the rain I am more relaxed this spring than last with much bigger, healthier looking crops not crying out for rapid nitrogen applications and only about a quarter of the drilling to do compared with what we faced a year ago.

Applying NIAB TAG’s latest OSR nitrogen equation in conjunction with masses of green area index measurement pictures produced an N recommendation nearly 100kg/ha less than I was planning to apply. I’ll probably end up somewhere in between and might try some variable rate applications, the value of which I still haven’t made my mind up about.

There has been a lot of talk of rust and pre-T0 fungicide applications, but so far my “not too susceptible” varieties do not seem to warrant this approach. However, I remain cautious given that a couple of years ago my planning was for increased droughts.

I shall also be keeping a careful watch on my latest companion crop in OSR experiment; at the moment it doesn’t look like the vetch and clovers will compete and require the added expense of Galera (clopyralid + picloram), but we shall see. The cost of these companion seed mixes in the UK is still too high for me to adopt this approach across the board and I may well continue next year by copying one of my neighbours and using straight vetch.

See also: More from all our Arable Farmer Focus writers

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