Organic Fertilizers and Soil Biostimulants

Developing an effective organic lawn care regime involves a careful study of natural products' advantages and disadvantages.

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June 5, 2002

Integrated Pest Management (IPM) programs have been developed for almost all agricultural and ornamental crop production systems over the past two decades but only recently have IPM and organic management systems been considered a truly primary approach in professional turfgrass management. The reasons for the dramatic increase in organic approaches are centered upon public concern for the environment, which has resulted in legislation at both the state and federal level in reducing or eliminating pesticide and synthetic fertilizer usage.

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EcoOrganics' NitroSoy Max sprayable organic fertilizer

Although the industry has been “pushed” into using IPM and organic approaches, a multitude of research, as well as on-site experience, have shown that switching partially or even wholly to organic management techniques result in renewed and greatly increased turfgrass performance while reducing or eliminating pesticide and synthetic fertilizer usage.

Natural organic fertilizers are inherently low in available nitrogen levels, ranging, for the most part, from 2 to 8 percent with only blood meal and bat guano approaching the 10 to 12 percent levels. These relatively low nitrogen levels (compared to synthetic sources) make it necessary to apply inordinately high amounts of material to achieve the desired seasonal effects since all natural organics depend upon soil microbial activity for nitrogen/mineral release.

As such, when soil temperatures are low as in the spring and fall, release rates are limited at a time when cool-season turfgrasses are at their peak of performance and need higher levels of nitrogen in the development of root zones and lateral stems. This is particularly the case when using materials lower than 6 percent nitrogen and having a comparatively high C/N (carbon/nitrogen) ratio that would result even slower mineral release. To overcome this problem, the industry has developed “organically-based” fertilizers that increase levels of inorganic nitrogen added to meet the high nitrogen demands.

These “bridged” products have been successful but cannot be considered 100 percent naturally organic and can result in increased nitrogen loss through surface runoff and leaching to groundwaters, depending on how high the percentage of inorganic nitrogen. Inorganically “amended” materials also do not have the same ability to stimulate increases in soil microbial activities and populations so necessary for a healthy soil under reduced or limited pesticide programs.

It has been well-documented over the years that increased soil microbial populations and activity compete with and suppress the populations and activities of soil-borne plant pathogens. This results in significantly less disease occurrence and subsequent damage. Aside from temperature and adequate water levels, the amount and types of organic matter and fertilizers will have an extremely profound effect upon nutrient availability as well as disease suppression. Some types of organic amendments, particularly those with comparatively low carbon/nitrogen ratios, have been known to greatly suppress levels of disease incidence.

The literature published regarding the effects and potential use of organic fertilizers and amendments on professional turf, particularly in the last 10 years, is voluminous, but can be summarized as follows:

DISADVANTAGES AND ADVANTAGES

    Disadvantages:

  • Nitrogen levels too low to maintain higher performance turf, requiring a more rapid response.
  • Very high levels of material need to be applied to achieve desired results.
  • Almost all materials are applied in a pelletized, solid application which can easily be picked up during mowing events and take very long time periods to break down and release mineral nutrients.
  • Materials having high carbon/nitrogen ratios have extremely long residual times and may “bind” available nitrogen.
  • Seasonal effectiveness: organic fertilizers depend upon microbial activities for mineral release and, as such, on irrigated systems, are much more effective during the warm summer months and not adequate during the high growth fall and spring seasons.
  • Bulky to store and transport due to comparatively low nitrogen analysis.
  • May have a naturally foul smell.
  • Usually much more expensive compared to inorganics and urea.
  • Advantages:

  • Environmentally friendly: little or no nitrate leaching or runoff into ground or surface waters.
  • Increased soil microbial populations and activities.
  • Decreased disease incidence: due to enhanced competitiveness by increased soil microbial populations.
  • Decreased thatch accumulation: due to increased soil microbial populations.
  • Increased nutrient availability: due to enhanced decomposition by soil microbial populations.
  • Increased soil water holding capacity.
  • Little to no salt index making high temperature applications safe.

In view of the above listed disadvantages, the most desirable natural organic fertilizer would have the following properties:

1. The highest level of nitrogen available, preferably over 12 percent nitrogen.

2. The lowest carbon/nitrogen ratio possible, preferably under 20 for more rapid microbial breakdown and nitrogen availability, particularly during the spring and fall months.

3. Easy application, preferably a liquid soluble/flowable spray application to avoid particle pickup during mowing and to enhance response time.

4. High microbial populations and activities after application.

Until recently, the only way to approach the properties listed above was to blend an amended organically based material, which would have a base level of natural organic component mixed with a high nitrogen analysis inorganic or urea fertilizer. Unfortunately, although these materials meet plant nitrogen demands, they fall short with regard to increasing soil microbial activities/populations and decreasing disease incidence and are not in compliance with “natural organic” standards. These inorganic/organic blends also have much more potential for eventual nitrogen movement to ground and surface waters.

The only 100 percent natural organic that comes close to the above properties is blood meal, which has up to 12 percent nitrogen and can be suspended in water for spray applications. Unfortunately, blood meal is extremely expensive to produce, eliminating any feasible commercial use. One recently developed material, NitroSoy Max, meets the criteria outlined above.

This material has a high level of natural organic nitrogen at 15 percent, which is plant-derived from a complex series of extractions from soybeans. The material is composed of approximately 20 percent free amino acids and 70 percent short chain proteins and peptides which makes the material dispersible in water and, as such, very flowable allowing for liquid spray applications or additions to fertigation systems.

In addition, the protein content of products like NitroSoy Max is in excess of 90 percent, which gives it an extremely low carbon/nitrogen ratio of 1.8, making it a powerful soil microbial biostimulant.

Objectives and Methods:

The objectives of this report are to compare NitroSoy Max with a standard and comparable inorganic source having approximately the same analysis: milorganite, a popular composted sludge used extensively in the turf industry. Data were taken on overall turf quality every two weeks from experimental field plots of Providence and PennCross creeping bentgrass throughout the growing season of 2000.

Microbial activity and population analysis for these materials was obtained by sampling the soil profile three, seven and 10 days after each application of all materials, followed immediately by a standard plate count method of quantifying soil microorganisms. Rates of application were 0.1, 0.2 and 0.3 pounds of nitrogen per 1000 square feet, applied monthly on native soil sites and 0.3 pounds of nitrogen per 1000 square feet weekly on standard USGA sand greens and modified USGA sand greens mixed with 30 percent native silt-loam soil.

Conclusions:

Turf Quality Ratings:

Turf quality ratings for all soil types showed no differences between NitroSoy Max and inorganic treatments, indicating that a natural organic material can perform equally as well as an inorganic on widely divergent soil types, ranging from sandy to silt loam. The low carbon/nitrogen ratio of NitroSoy Max and the fact that the material is composed of highly degraded short chain protein/peptides and amino acids results in intensive soil microbial activity leading to an extremely rapid mineralization process and nitrogen availability levels approaching that of immediately available inorganic applications.

Soil Microbial Activity:

Applications of NitroSoy Max result in extremely rapid and large increases in existing soil microbial populations, compared to milorganite and inorganic nitrogen treatments. Populations resulting from product applications ranged from 600 to 800 percent higher than inorganic fertilizer or milorganite. This rapid response is again due to the low carbon/nitrogen ratio of the material as well as the fact that the product was applied as a flowable liquid spray (flowable powder), which would carry the material into the soil more effectively as well as have a much larger surface area for microbial activity.

Dr. William Torello is associate professor of plant and soil sciences at the University of Massachusetts and executive vice president for EcoOrganics. Dr. Haim Gunner is an emeritus professor of environmental microbiology at the University of Massachusetts, as well as president and chief executive officer of EcoOrganics. Dr. Ming Coler is an environmental microbiologist with extensive research experience in soil and acquatic eco systems, and chief financial officer and co-director of research for EcoOrganics.

EcoOrganics is located in Amherst, Mass., and manufactures NitroSoy Max sprayable organic fertilizer. For more information on organic lawn care and NitroSoy Max fertilizer, email Dr. Torello at wat@pssci.umass.edu.