The Right Nitrogen Source

Not all nitrogen sources are created equal, and supplying your potato crop with the correct nitrogen sources - like all aspects of plant nutrition - is a balancing act.

Nitrogen is often applied at rates greater than potatoes can immediately absorb and utilize, and there are several considerations in deciding which form of nitrogen best suits your crop. Potatoes can utilize nitrate (NO3-), ammonium (NH4+), and urea nitrogen. Urea must be converted to ammonium inside the plant with the aid of urease. Urease is found throughout the potato plant (Witte, et al; 2001). Nitrate can be safely absorbed and stored for later use by the plant; while ammonium, when taken up in excess, can cause cell damage. Also, for ammonium to be utilized, the plant has to consume carbohydrates and energy which comes at the expense of plant growth and tuber yield. 

This doesn’t mean that ammonium is all bad. A mixture of nitrate and 8% - 20% ammonium nitrogen has been shown to be the optimum delivery of N for potatoes (Cao, Tibbitts; Univ. of Wisconsin 1993). This was later substantiated in 2000 by O Achilea, et al (see chart below). 


It is important to note, however, that even these small amounts of ammonium in the fertility program can interfere with calcium uptake, making potatoes more susceptible to calcium deficiency related disorders (Cao, Tibbitts; Univ. of Wisconsin 1993).

An additional benefit of nitrate nitrogen includes synergistic uptake of cations (eg K, Mg, Zn), whereas ammonium, being a cation, competes for uptake. Also, nitrate has a net neutral effect on soil pH (nitrate uptake actually raises the rhizosphere pH because the roots exude OH- or HCO3- anions to maintain charge neutrality) while ammonium drives pH down which can result in an  increase in the expression of Rhizoctonia solani.


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YaraLiva products provide readily available nitrate nitrogen to help provide a balanced approach to your nitrogen fertilizer regime. Additionally, the completely water soluble calcium is there to help offset any calcium uptake issues brought about by ammonium fertilization.


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