The form and timing of nitrogen treatments can often be a challenge. We don’t want to apply N if it leads to too much vegetative growth, and we don’t want to apply it too early as cool soil temperatures and low root activity can mean that most of the applied N is lost.
Nitrogen form and losses
Nitrate N is the most plant available source. Urea is a low cost form of N, however, it is often a false economy applying urea as losses can be high.
All nitrogen applied to the soil can suffer from losses such as denitrification, volatilisation and leaching depending on soil type, climatic conditions and N form.
Urea undergoes conversion into ammonium and then into nitrate when it is applied to the soil. Nitrate nitrogen is taken quickly into the plant and is converted back into amine then into proteins as food. The downside of pure nitrate nitrogen is that it can elevate N levels too quickly and lead to an over vegetative tree with longer internodes. This can sometimes detract from setting and filling the fruit.
The nitrogen dilemma
Growers are faced with the dilemma of what N source to use and when to apply it.
Research in the early 1980s showed that ammonium N, in combination with calcium, did not volatilize as quickly as when no calcium was present. The calcium inclusion eliminated root zone shortage of calcium caused by the ammonium N.
Compromise
It seems that however you apply nitrogen, there will be a tendency for the plant to receive mainly the nitrate form of N. It therefore makes sense to attempt to balance this with the application of some non-nitrate N. The best form of non-nitrate N includes calcium and an inhibitor to slow conversion in the soil.
A nitrogen tool from Stoller
The Stoller Group developed a product range using N in the amine form, with calcium and an inhibitor to keep N in the amine form for longer.
This encourages the plant to take in a higher ratio of non-nitrate nitrogen. This amine nitrogen appears to promote root growth and leads to a more balanced tree with less toppy growth.
Stoller’s N-Hib range (most in liquid form) are applied through the irrigation system.
BudFeed Plus is a dormant treatment incorporating N-Hib for application to the bark and woody tissue prior to budburst. When applied this way the N (in amine NH2 form) is ready for use by the tree when spring growth commences.
Using N-Hib type nitrogen delivers the N in a form ready to be made into amino acids and utilised by the tree.
Stoller Australia has a number of unique N-Hib nitrogen sources including: •N-Hib 12 and N-Hib 23 (Liquid N soil fertilisers with calcium and magnesium) •RootFeed (root enhancing N liquid with calcium and magnesium) •BudFeed Plus (Dormant applied woody tissue nutrient with nitrogen, calcium and magnesium).
Phone 1800 337 845 e-mail
See this article in Tree Fruit August 2013
