The Importance of Testing for Nitrogen in Plant Material

By Atlantic Microlab

Why is testing for Nitrogen important in plant material? Nitrogen is a key ingredient necessary for plant growth. In fact, Nitrogen is generally considered the most significant component in the support of plant nutrition, and is part of the chlorophyll molecule, giving plants their rich green color. Chlorosis, or plant yellowing, is an indicator of Nitrogen deficiency. Since Nitrogen can shift throughout a plant, yellowing often occurs in mature growth more than in new growth, making Nitrogen concentration an interesting and informative study for scientists.

Researchers in the field of Agronomy, Botany, and Plant Sciences frequently discover that plants lack sufficient nutrition for healthy growth, and thus need plant and soil testing to determine the correct fertilizers to utilize in their fields. A precise analysis of soil and plant material is essential for healthy production. Understanding the exact levels of elements like Nitrogen in their samples is extremely beneficial.

The process of dividing the two atoms in a Nitrogen molecule is referred to as Nitrogen Fixation. Plants receive the required Nitrogen from the soil where it has been previously fixed by bacteria and archaea known as diazotrophs. Bacteria and archaea in soil and the roots of some plants maintain the capacity to convert N2 from the air to ammonia, breaking the recalcitrant triple bond of molecular Nitrogen. An assortment of microorganisms convert ammonia to other Nitrogen compounds that plants utilize in an easier fashion. Again, Nitrogen is an essential macronutrient for plant function and is a principal component of amino acids, which form the foundation of plant proteins and enzymes. So Nitrogen analysis in plants allows for the proper assessment of plant health, nutrient content, and environmental impact.

So how are samples best prepared for analyses? Having reasonably dried and homogenized material is a great start. Since water has mass, too much moisture left in any substance to be analyzed—whether  it’s a synthesized organic product, plant leaves, or soil—can  grossly distort the actual levels of Nitrogen in a sample. Lots of different drying techniques are useful, consisting of simple air drying, block drying (generally a sample is placed in a beaker and set on a temperature-controlled surface such as a hot plate), and vacuum oven drying. The level of drying is really dependent on how much moisture the sample contains, but one—or perhaps a combination—of these options will likely be a suitable choice. Next, a sample should be as homogenous as possible for the best analytical outcome. Grinding the sample into the smallest possible particles is a must, along with removing any foreign material. For example, in the case of analyzing Nitrogen in plant material, removing stems and any soil associated with the actual leaves or testing product is essential to getting the best results. Usually, if a sample is fairly homogenized and uniform, an analysis with Nitrogen levels above 1% can be achieved with only a few milligrams. Samples that are less homogeneous require larger sample weights.

So what about the actual analysis? There is no better analysis for Total Nitrogen than the Dumas Method of testing. It is fast, straightforward, and incredibly accurate when performed by a competent and reputable lab. So what exactly is the Dumas Method for Nitrogen analysis? Named after its discoverer, Jean-Baptiste Dumas, the method has been automated in recent years, and is the sought after technique for Nitrogen analyses in synthesized organic compounds, plant material, and even soils. Samples are weighed carefully on sensitive micro-analytical balances and subsequently combusted in pure Oxygen over catalysts such as Chromium Oxide or Copper Oxide at temperatures around 950 to 1000 degrees Celsius. Carbon dioxide, water, and various oxides of Nitrogen are produced, and oxides of Nitrogen are reduced to N2 by passing the gases over copper wires maintained at 650 to 700 degrees Celsius. The gases are swept through a chromatographic column with ultra-high-purity Helium where they are separated and detected by thermal conductivity, producing elemental Nitrogen in weight percent.

Clearly, Nitrogen testing for many substances provides researchers with valuable information, and since Nitrogen in plant material is a vital component, getting excellent data is crucial to understanding proper care and proper fertilization guidance, which would be incredibly difficult without accurate and precise analytical data. Atlantic Microlab has been performing such assays for over 50 years. So when it comes time to trust a reputable lab to perform your elemental analyses, let Atlantic Microlab take the hassle out of finding a fast, affordable and reliable lab to analyze your samples!