According to the Potash Development Association (PDA), the optimal rate of nitrogen (N) for a crop will depend on many variables. One of these is the efficiency of use.
This can vary greatly depending on several factors, including the weather conditions around application, the state and health of the crop and particularly its root system, the product being applied, and the availability of other nutrients.
The greater the Nitrogen Use Efficiency (NUE) value, the more N is taken up by the crop.
As a consequence, the returns on the investment are likely to be greater. In addition, there will be less ‘wasted’ nitrogen that is susceptible to loss from the field potentially causing environmental harm.
Nitrogen use
Trials carried out by Yara in 2018 looked at the comparative NUE of winter wheat with differing nutritional regimes.
The findings showed that balanced crop nutrition, where the proper supply of macronutrients and micronutrients in a balanced ratio supplied throughout the growth of the crop, resulted in the highest level of NUE and the highest yields.
Although N is likely to give the greatest economic return on investment, even at the significantly higher prices, yield increases will not be gained, and therefore investment wasted, if N is not the most limiting factor.
Where N is supplied to a crop that has insufficient available potash, the nitrogen use efficiency will be reduced.
Management
More efficient N management, through the appropriate use of all other nutrients, can help to improve returns, sequester more carbon, and reduce the emissions of greenhouse gases (GHGs) such as nitrous oxide (N2O).
So, NUE should not only focus on N, as it is important, both financially and environmentally, to utilise all nutrients as efficiently as possible.
Although potassium may not have any environmental concerns related to losses to air or water, an adequate supply and soil reserve of potassium is an essential requirement for maximising NUE as sulphur is for the efficient use of N for protein synthesis.
Efficiency of uptake of potassium is largely driven by soil supply, differences in rooting, available levels of soil moisture and soil type, according to the PDA.
Potassium is available for plant uptake when held in soil solution, the concentration of which is generally low. However the mobility is also restricted.
Plant root systems have developed ways to overcome this lack of soil mobility, through root exploration and the release of exudates to help mine additional fractions of the soil.
