Soil Health Tech Bulletin II (2017)

BIOLOGICAL SOIL HEALTH TEST: Microbial diversity is an excellent indicator of soil health (Nielsen and Winding 2002). They report that variation in microbial population or activities precede changes that can be noticed in some cases as early signs of soil degradation or amelioration. Water and nutrient supply from soil, particularly N and P, determine the plant growth both in natural and agro-ecosystems. It is important to understand that the above ground vegetation is the ultimate source of C for the microbes in the rhizosphere that, in turn, support the macro-fauna. Thus, it is important to understand that the above ground vegetation influences the below ground microbial community structure and soil properties (Orwin and Wardale 2005). A&L Biologicals research has shown that microbial popula ons require certain carbon sources that the plant must provide and maintain in the rhizosphere in order to sustain healthy beneficial populations of microorganisms.  A&L’s soil health test is designed to measure the important nutrient levels that are needed to support the plants ability to provide these essen al carbon sources to feed the soil biome.

From the past few years of study on unravelling the interaction of soil & plant physical, chemical and microbial parameters on soil & plant health through agricultural innovation program research, we found some interesting interactions of microbes on soil health, overall fertility and yield. The total microbial population in the soil, root, and rhizosphere measured through plating on selective nutritional media did not show any contribu on to the yield or the overall fertility. When we dissected these microbiome in subgroups such as Gram negative and positives we found some interesting facts. Gram negative bacteria such as Pseudomonas, Rhizobium, Azospirillum showed a strong positive correlation with the high productivity and the general fertility of the soil; thereby higher yield. Gram positive bacterial populations such as Bacillus species have strong positive correlation with the low productivity of the soil; thereby lower yield. Based on the in depth tests on several related aspects and findings, we developed a simple, fast, and affordable test to identify the indicators of soil health by measuring the key components. This biological test will complement the other physical and chemical soil tests to arrive at complete soil health information and for effective soil management and sustainability.

The following soil parameters influence the soil biome and from our research have a strong correlation to the relationship to the population of the indicator organisms that have a positive or negative in uence on crop performance. By increasing or reducing any of these indicators based on the ranges that have been established in our field research a grower can have a direct influence on the population of these organisms in both the bulk soil and the rhizosphere. Although other cultural practices such as crop rotation and addition of organics have a strong relationship to soil quality it still requires a good balance of nutrients available to the plant to provide the proper carbon source to attract and maintain these organisms.

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