Certain common production practices put stress on the legume seedling, which in turn can reduce the nodulation process. For instance, conservation tillage may leave the soil cooler and more compacted than it would be under heavier tillage. Soil compaction and cool soil temperatures both reduce nodulation and, therefore, make inoculation more critical to production.

Without inoculation, soil that has never grown a particular legume before may exhibit no fixation since there are no bacteria present to infect the root. On land which has had the crop recently, the 'native' bacteria may provide some level of fixation, but often these bacteria are not optimal for peak yield potential. Inoculants allow for the addition of specialized, selected bacterial strains that increase the plant's ability to fix higher amounts of nitrogen.

Benefits of inoculation
By increasing the amount of nitrogen that is fixed by the plant, growers will receive a number of benefits over the short and long term. Inoculation prevents nitrogen deficiency without the need for farmer-applied nitrogen. Since nitrogen is commonly the limiting factor in legume yield, inoculants provide an economically attractive alternative to commercial nitrogen sources. Nitrogen application is an expensive, timeconsuming process, and the run-off from fields is under scrutiny by environmental agencies. The fixation process is very efficient, and the amount fixed is directly correlated with the rate of plant growth - nothing is wasted. Fertilization can result in some nitrogen being lost immediately. Inoculation reduces the risk that little or no fixation will occur (due to low populations of Rhizobia), or that the process will be inefficient (due to the poor performance of native bacterial strains). Inoculation also ensures that infection of the roots will begin quickly after germination, thus making nitrogen available to the plant early in its growth.

The yield advantage
Inoculating first-time fields offers the best chance to introduce proper Rhizobia into the field. (This is because the bacteria present in a field formerly used for a certain legume will not help a different legume.) First-time fields inoculated with Cell-Tech,® LIFTTM and Soil Implant®+ typically show large yield increases over uninoculated fields. High-quality products such as these deliver large doses of bacteria - they are often able to show significant yield increases over uninoculated fields that are under a regular rotation of that legume.

A plant's ability to host colonies of nitrogen-fixing Rhizobia bacteria in root nodules is the most significant difference between legumes and nonlegumes. The most economically significant legumes are soybeans, alfalfa, dry edible beans, peanuts, peas, lentils and clover. Being able to supply their own nitrogen, legumes are able to produce higher yields without additional nitrogen applications.

Non-legumes, however, often require the application of supplemental nitrogen fertilizer as a means of obtaining the appropriate amount of nitrogen for optimum plant growth. This major difference between legumes and non-legumes is advantageous from both ecological and economical points of view. Consequently, many researchers have made biological nitrogen fixation their top research priority.

Even though fixation from using inoculants happens underground, healthier-looking plants are a clearly visible sign that significant fixation is occuring.