Unlocking a crops potential

Article taken from National Farmer magazine

Improving efficiency of nitrogen fertiliser

In the presence of adequate oxygen, warm temperatures and some moisture, any nitrogen supplied as a commercial fertiliser is ultimately transformed in the soil to a nitrate form of nitrogen (or at least a significant fraction of that supplied).

Ammonium-N is converted to a nitrate-N through a biochemical process (known as nitrification) that requires two forms of soil bacteria.  The first bacterium Nitrosomonas converts ammonium-N to nitrate-N.  The second bacterium Nitrobacter converts nitrate-N to nitrate-N.  During the process of nitrification, significant amounts of nitrogen can be lost from the rooting zone.  First of all as nitrous oxide, on of the most potent greenhouse gasses associated with agriculture and secondly through leaching when converted into nitrate form, as nitrate-N is negatively charged and therefore unable to bind to soil colloids and organic matter.  Not only are these losses of key environmental concern, but they are also a waste of one of our single greatest variable inputs, nitrogen fertiliser.

Nitrifaction inhibitors slow the process of ammonium converting into nitrate.  This is an advantage because plants can use nitrogen in both the nitrate (NO3-) and ammonium (NH4+) for growth.  As ammonium-N is positively charged, it is less prone to leaching through the soil.
Nitrification inhibitors therefore keep nitrogen available in the root zone for longer, optimising yield and reducing the potential for nitrate leaching losses and nitrous oxide gas emissions.  N Lock, a micro-encapsulated formulation, acts as a nitrogen stabiliser to help with N management and N efficiency.  N-lock contains nitrapyrin which inhibits Nitrosomonas spp, bacteria slowing down the process of nitrification, therefore keeping applied N in the preferred ammonium form for longer. 

Whilst a plant can take up nitrogen in both ammonium and nitrate forms, nitrate requires more energy than ammonium to be converted to into usable forms and therefore nitrate has a higher metabolic cost to the plant and is a less efficient form of nitrogen.  Nitrapyrin has been successfully used on millions of acres in the USA for over 20 years and soil nitrogen retention has been found to increase by over 28%, with significant reductions in nitrogen losses through greenhouse gas emissions and leaching.  This has also led to a 5% yield advantage in maize over 20 years.
Agrovista has been trialling N-Lock (Nitrapythin) in large scale field trials across a range of crops for the past two seasons with very promising results.  In 2014 the average yield response across a wide range of sites with winter wheat was 0.75% t/ha, with some sites significantly more.