Farmers are facing tough choices this spring with many autumn planted crops coming out of the winter stunted with poor root systems, says Mark Tucker, Head of Agronomy at Yara UK. Farmers will be desperate to apply early N to encourage backward crops, but it is important they make the right decisions based upon the right information to make the most of what is already turning out to be a tough season
Recent soil analysis carried out by Yara across six sites has shown that over 70% of the nitrogen measured in October last year has leached away leaving an average of 31KgN/ha compared to 109Kg/ha just four months previously.
Tot Min N
Total Min N
On backward crops the problem is more difficult. The efficiency of uptake of N by a plant can vary from 10-80% which means that for every Kg N the crop requires it needs 1.25 to10kg available in the soil. Therefore small stunted plants with a small root ball are going to need access to a significant quantity of N to provide the boost required to develop biomass growth. However how much to apply?
In trials we conducted in 2004 we were interested to see the effects of early N on tillering of winter wheat and its subsequent effects on yield, says Mr Tucker. From the results we can conclude that too much early N creates a huge energy hungry canopy with a 250% increase in the number of shoots per m. This did not translate into higher yields. There is therefore a balance to be had and we calculate the early N rate to be somewhere between 70 and 100kg N/ha.
For these backward crops I would change the three split ratio to 40:40:20, advises Mr Tucker, reflecting not only the low soil N availability but also the poor root system. There may well be an argument this season to consider splitting the application into four providing a greater focus on filling the ear and individual grains rather ear density.
If there is any season where precision farming comes into its own then this has to be it with such variability across farms and indeed across fields. Any tool that will help management decisions to optimise what we have got has to be of value. With no easy measure of root biomass, then the crop itself is still