Crops are less variable than other years due to relatively infrequent pigeon grazing damage. Most canopies are between GAI 1.5 and GAI 2.5. The more canopy you have currently, the less spring-applied N you need to generate the optimum GAI 3.5. And less spring nitrogen is a saving.

You need to get 50kg N/ha of nitrogen in the plant to generate a GAI of 1. But because uptake efficiency is only about 60%, you need to apply 80-85kg N/ha to get the 50kg into the plant. So a crop with GAI 2.5 will need 80-85kg N/ha now while a GAI of 1.5 will need 150-160kg N/ha. Applied N can by reduced by what you consider to be your level of soil N.

Application of N is a priority as rape is creating canopy and yield potential in early growth. Hunger would take from potential yield now but excessive canopy can hit yield.

Sulphur is important for rape so your fertiliser should supply at least 25-30kg S/ha. Sulphur may be less critical where organic manures have been applied over a number of years. Boron is also important. And don’t forget adequate P and K and also the necessity to have optimum pH.

Read more

Tillage management: weather and ground conditions

Tillage management: winter barley