Ammonium Nitrogen May Offer Alternative to Nitrate Based Fertilization

27 Apr 2017 --- In order to alleviate current problems associated with nitrate-based fertilization, a research group are making new attempts to encourage a different type of fertilizer treatment, and have shown how ammonium nitrogen could offer an alternative.

Plants need nitrogen to grow, and intensive agriculture requires the input of nitrogen compounds. However, classical, nitrate-based fertilization is responsible for considerable environmental problems, such as the contamination of surface and underground water due to nitrate leaching, and the emission of greenhouse gases, owing to the effect of the micro-organisms in the soil that use the nitrate and produce nitrous oxide, a significant greenhouse gas.

“The inhibitors cause this ammonia to be in the soil for longer and this helps to mitigate nitrate leaching and also nitrous oxide emissions," explained Daniel Marino, researcher in the UPV/EHU's NUMAPS research group, which has conducted this study in collaboration with Dr Pedro Aparicio-Tejo of the UPN/NUP-Public University of Navarre

“This source of nitrogen can also be toxic for plants and lead to reduced growth than when nitrate is used. In our group we are studying the tolerance and sensitivity of different plants to this source of nitrogen.”

Seeking to go further into this subject, the researchers went on to study the proteome of a model plant, Arabidopsis thaliana.

“Without focusing on any protein in particular, we decided to see what differences were displayed by this plant within the synthesized proteins as a whole when ammonium or nitric fertilizers are applied,” said Daniel Marino.

When studying the type and quantity of proteins accumulated in the plants with each type of nutrition, "what seemed most interesting to us is that there were some proteins related to the metabolism of glucosinolates which accumulate in a greater quantity in plants receiving an ammonium input," stressed Marino.

Marino explained that in general, glucosinolates have two properties: they are natural insecticides and one of them in particular, glucoraphanin, has anticarcinogenic properties. Given that the experiments had been conducted using the plant Arabidopsis thaliana, a model plant widely used in research but of no commercial interest, they decided to repeat the experiment, "but this time with broccoli plants.”

“Although we did not manage to study the glucosinolate content in the part of the broccoli of greatest food interest, which is the flower, we saw that the leaves of the young plants accumulated a greater quantity of glucoraphanin when we added the source of nitrogen by means of ammonium than when we did so using nitrate,” explained Marino.

The research group is now continuing to work on this aspect and they have even been in contact with several companies that could be interested in them.

“We carried out field experiments where the system is much more complex, due, among other things, to the micro-organisms in the soil that also use ammonium as a source of nitrogen.”

“So in the field experiments we will also be interested in analyzing the glucosinolate content in the broccoli inflorescence, the part of the plant that is consumed most.”

“On the other hand, from a more fundamental point of view, we are also interested in knowing the effect that the glucosinolates could have on the ammonium tolerance of the plant itself," he explained.