The Process of Balancing Soils

 

The Process of Balancing Soil

 

Previously we discussed the importance of balancing soil inputs of carbon and nitrogen in maintaining a consistent return of plant residues into the soil profile, along with regulating the rate of soil organic matter decomposition by microbes. Maintaining the mutualistic relationship between plants and biology is critical to achieving a balanced soil environment and ultimately maximizing plant health. What I would like to do now is define the basic process of balancing soils by first identifying specific action steps, and then identify specific products that can help support those actions.

1.    Evaluation – Chemical, Physical and Biological Parameters

·        Chemically evaluate soils for accessibility (soil test), availability (paste extract) and mobility (tissue test) of plant essential nutrients. Additional parameters are TSOC (total soil organic carbon) and carbon to nitrogen ratio.

·        Physical evaluation of soil structure, texture, and % organic matter (humus) - Saturated Hydraulic Conductivity (infiltration rates) http://www.turfdiag.com/ plays a critical role in maintaining a balanced soil and is directly impacted by these three soil parameters.

·        Biological evaluation of plant biomass (rooting, thatch and shoot density), soil biological function and sustainability. The Solvita CO2 Burst Test https://solvita.com provides the opportuninity to measure soil biological activity - respiration.

·        Continually monitor and remediate as needed any excessive accumulation of bicarbonates and sodium in the soil profile.

2.    Chemical Balancing with Inorganic Foundation Minerals

·        Utilize granular and liquid applied minerals to balance base cation nutrients (Ca, Mg, K, Na, and H). Insure a sufficient supply of phosphorus, sulfur and adequate availability of trace elements.

 

3.    Maintain Adequate Soil and Plant Energy

·        Both soil microbes and plants need sufficient nitrogen (proteins) to sustain growth and return residues to the soil profile.

·        Adjust soil applications of synthetic nitrogen relative to the amount of active organic matter present in the soil. Foliar applications of nitrogen should be carefully adjusted to maintain plant health with only a minimal amount of tissue growth.

·        Synthetic sources of nitrogen are less dependent on biological activity and quicker to provide the desired plant response.

  

4.    Build a Supply of Stable Soil Organic Carbon

·        The controlled decomposition of soil organic matter provides a stable source of carbon, nitrogen and other plant essential minerals. Both carbon (carbohydrates) and nitrogen (proteins) provide microbes with food and energy for sustainability, as well as the ability to build new cells and grow.

·        When active soil organic matter is depleted, exogenous applications of soil stable carbon is necessary to maintain biological stability. These carbon sources can come from humic substances (i.e. humin, humic acid, and fulvic acid) or non-humic substances (i.e. amino acids, proteins, starches and sugars).

·        The ideal soil carbon to nitrogen ratio that favors the controlled decomposition of organic matter by microorganisms is 20:1.

5.    Biological Enhancement

·        Bio supplementation with Holganix can speed up the process of achieving a balanced diverse population of beneficial soil microorganisms.

·        The limiting factors for sustaining a biologically active soil are maintaining favorable environmental conditions and adequate food sources (active soil organic matter – carbon, nitrogen, hydrogen and oxygen).

  6.    Increase Saturated Hydraulic Conductivity of Sand Profile Greens

·        The key to increasing infiltration rates in sand-based profiles is enhancing the selective process of lignin degradation.

·        Lignocellulose is the essential part of cell walls of plants and is one of the most abundant organic sources. Lignocellulose is composed primarily of cellulose (24-54%), hemicellulose (11-38%), and lignin (6-31%). 

·        The presence of lignin in plant cell walls (lignocellulose) restricts microbial degradation mechanisms. Lignin limits the accessibility of existing microbial degraders to more biodegradable plant materials, such as cellulose and hemicelluloses. When this occurs, the rate of organic matter inputs can exceed microbial degradation resulting in an accumulation of non-biodegradable organic matter within the rhizosphere. In addition, when the breakdown of cellulose and hemicellulose into sugar is restricted, access to available energy (organic carbon) from the potential fermentation process is reduced.

·        It is the gradual accumulation of these recalcitrant forms of organic matter that have greatly reduced the functionality of USGA and modified sand-based green profiles over the years. It becomes dramatically more intense when dealing with the Ultra-Dwarf Bermuda plants, due to their inherent higher content of lignin in cell walls. USGA greens were not designed to optimize surface drainage, so when infiltration rates go from 6"/hour to .5"/hour in a span of 20 years, there in lies the problem. This then becomes a greater issue when irrigation water quality is challenged.

·        Aggressive core aerification and other cultural activities can provide a short-term enhancement of infiltration rates, but it is highly disruptive to the soil biomass (roots and beneficial biology), deleteriously impacting the biodegradation process – especially detrimental to maintaining important soil fungi populations.  

·        There is some hope in being able to cost effectively utilize lignolytic enzymes which have been shown to selectively breakdown lignin in sand based profiles. These particular enzymes are gaining momentum due to their role in bioenergy production (i.e. bioethanol), which would increase their eventual availability.
 

The above outlined process is the road map in achieving a balanced soil and ultimately maximizing plant health. Many of our high profile soils today are severely challenged from a combination of excessive use of synthetic nitrogen fertilizers, aggressive cultural activities and reduced quality irrigation water. The end result is we have soils that are severely depleted in both active and passive organic matter, reducing the ability of the soil to support a balanced biologically active population of beneficial microorganisms. Without the support of soil biology, plant health is at risk from both reduced nutrient and water access, as well as exposure to pathogens and parasites. When both the carbon and nitrogen cycle breakdown, the entire soil food web is in jeopardy and soils are no longer working for us.

 

Understanding Critical Soil Relationships - Carbon, Nitrogen, Organic Matter and Biology

 

When soils are functionally balanced, the soil biological community is constantly working hard not only to meet the plants short-term nutritional needs, but also enhance the soil microenvironment to insure plant health in the long-term. As managers of turf we are sometimes either impatient or feel obligated to catalyze many of these natural occurring processes with the intention of improving plant health. It is the unintentional consequences that sometimes can work against us.

Plant health is a direct function of the soil environment that immediately surrounds the roots – i.e. the rhizoshere. This dynamic zone is where critical interactions between plant and biology take place. Plants exchange exudates rich in sugars, amino acids and organic acids providing food for microorganisms. Microorganisms return the favor by supplying essential nutrients and other growth regulating substances directly back to the plant.
 

Along with plant exudates, microbes depend on both nitrogen and soil carbon for energy and for building structural components. The storehouse for both carbon and other essential nutrients is soil organic matter. The ability of microorganisms to slowly decompose active organic residues is important in mineralizing essential nutrients but also critical in the production of humus, that part of organic matter that is impervious to additional decomposition. Humus can dramatically improve structure, increase nutrient exchange capacity and enhance the water holding capacity of soils. Humus also provides important soil buffers to protect plant roots from soil pathogens and parasites.

Maintaining adequate soil carbon is the buffer that regulates the decomposition rate of organic residues by microbes, all the while protecting the mutualistic relationship it enjoys with the plant. Excess applications of synthetic fertilizer can reduce plant exudate production and diminishes the importance of naturally occurring nitrogen fixing bacteria. Without the benefit of plant exudates, microorganisms will begin feeding on exogenous soil nitrogen and begin the process of aggressively decomposing organic residues. Rapid breakdown of organic residues results in the volatilization of carbon (carbon dioxide) and nitrogen (ammonia) in favor of stable soil carbon, nitrogen and other humic substances beneficial to plant and soil health. The rapid recycling of carbon eventually results in a depleted soil unable to sustain a balanced functional biological community. Additional synthetic nitrogen applications will only serve to provide minimal plant uptake, dramatically increase nutrient loss through leaching and reduce the presence and activities of beneficial microorganisms. This condition is commonly referred to as “soil nitrogen burn-out”.

Managing the ratio of soil carbon to nitrogen is the key in controlling the process of building valuable soil organic matter and protecting the important contributions of rhizobacteria, mycorrhizae and other beneficial microbes. The ideal soil C to N ratio is 20:1, making carbon based inputs the dominate player in building a balanced soil. All natural organic and synthetic organic fertilizers have a carbon component, but not all meet the ideal soil C to N ratio. Meals are predominantly protein (16% nitrogen) and are closer to a 6:1, which favors excess nitrogen accumulation in the soil. Sludge is typically cooked at high temperatures, striating proteins and making them virtually unavailable as a practical carbon source. A good humified compost organic has a favorable C to N ratio (25:1) along with the added benefit of containing natural living biology (i.e. bacteria, fungi, protozoa, beneficial nematodes).

Healthy Grow http//www.healthy-grow.com/  represents a poultry compost derived from Pearl Valley egg production in Pearl City, IL. The indoor composting process is what separates the Healthy Grow product from others; producing a clean, granulated (90-180 SGN), homogenous, ammonia-free product that is very user and soil friendly. The base compost is 90% organic (OMERI certified) with a high contribution of carbon along with organic sources of phosphorus, potassium, calcium and other minerals making this the ideal product to energize and balance depleted soils.
 

Considering its natural ability to sustain carbon and support biological activity in the soil, Healthy Grow’s ability to feed soil biology fits nicely into the bio-inoculation concept of Holganix http://www.holganix.com/. Hence, Healthy Grow plus Holganix was created www.holganix.com/holganix-granular-with-healthy-grow. The combination of these two products provides all the benefits of a well composted organic fertilizer along with diverse beneficial biology, additional high carbon food and soil supplements contributed from Holganix. It gives end users an additional opportunity to experience the biological enhancement of Holganix but with a sustainable food source and all the additional soil building benefits of carbon, ultimately making the soils work for us.

  

Ongoing Field Trial - Profile Layer Remediation at Thunderbolt Pass GC (continued)

Situation: Functional profile quickly reaches saturation and begins to puddle after <.25" of rain. Profile remains at near saturation for >12 hours after initial rain event (EC >50%).



Situation: Due to reduced infiltration rates, profile is not capable of properly flushing and results in the accumulation of excess sodium (EC >.75) in top 2" of profile.

Situation: Anaerobic black layer at 5" depth in profile:

above BL - high lignocellulose biomass

below BL - clean sand (parent material)

Analytics: Establish baseline infiltration rates at varying depths throughout the soil profile prior to initiation of remediation protocol - Turf & Soil Diagnostics, NY

 

 

Analytics: Results of baseline infiltration rate analysis. Extremely restrictive water and air movement above the black layer (5" depth). Note that USGA recommendation is >6" (15 cm) / hr.

 

Application Protocol and Results: Field trial is currently underway. Application details, observations and results will follow in October 2015.

Case Study: Sudden selective turf loss on golf course putting greens in early August (continued)

 

 

Site Analysis – Basic Information
Site visit date: 08/17/15

Greens Profile Information:

Age: 20+ years

Location - Southern Indiana

Original Construction - sand modified with peat (90/10) – blended onsite

Original Established Cultivar Species - Penncross creeping bentgrass

Interseeded Cultivars - Crenshaw creeping bentgrass, Cato creeping bentgrass

Annual Bluegrass Contamination – 20 to 50%

Organic Matter Accumulation - distinct layer of organic matter accumulation down to 4” depth, did not appear to be anaerobic

Infiltration Characteristics - greens received .5” of natural precipitation the previous night and demonstrated reasonable uniform hydration throughout the profile

 

Situation:

On the weekend of August 1^st, greens demonstrated visual symptoms of moderate drought stress. In response to moisture stress, irrigation event duration and frequency was immediately increased.

Within two days after initiation of increased irrigation, rapid turf decline continued to the point of selective necrosis of Poa annua. A few days after the damage had stabilized, all greens were spiked and seeded with Pencross creeping bentgrass @ 1.5 lbs./M. At the time of my visit, 14+ days had elapsed without any sign of germination in the damaged areas.

 

On-Site Observations:

Turf loss appeared to be limited to Poa annua, but not all Poa was equally impacted.

Based on the pattern of necrosis, there was a direct correlation between the amount of turf loss and the environmental conditions associated with individual greens. Greens with poor air movement and less than full sun exposure experienced greater turf loss. These greens also exhibited higher populations of Poa annua.

There was also greater turf loss (Poa) on green surfaces or sections of greens that had a greater amount slope.

Green 13 best matched the above mentioned criteria (i.e. poor air movement, reduced exposure to direct sunlight and high % slope). , and did have the highest percentage of turf damage of all of the greens

Utilizing a POGO http://www.stevenswater.com/soil_moisture_sensors/ field diagnostic tool, we were able to verify that the highest EC readings were in fact on the higher sloped areas of green surfaces. These same areas also had lower moisture readings than surrounding areas of less slope.

Not being able to germinate bentgrass seed in 14 days under ideal conditions (temperature, moisture), also points to the suspicion of restrictive salt accumulation.

 

On-Site Initial Conclusion:

Visually assessing the damaged turf along with the input from the POGO, is that there was a distinct accumulation of soluble salt in the upper portion of the soil profile. Probably from a combination of poor quality irrigation water, the inability of the profile to properly flush and accumulation of sodium due to upward capillary movement within the profile driven by increased evapotranspiration rates.

The surface levels of salt accumulation were sufficient on the higher % slope areas to selectively shut down the root function of Poa annua plants due to reduced rooting depth – especially prevalent on greens impacted by environmental challenges (reduced light and air circulation).

Poa annua on the less sloped areas and not subjected to environmental challenges, was able to survive due to increased vertical movement of water down through the profile (effectively reduced the concentration of sodium in the upper soil profile) and maintaining a marginally healthier root system.

Bentgrass survived due to its selective tolerance to salt over Poa annua along with a more functional root system penetrating further down into the soil profile. The difference between surviving and dying depended on both plant tolerance and  concentration gradients in regards to salt accumulation within the soil profile. Furthermore, salt accumulation within the soil profile was a direct function of surface slope and infiltration permeability.

 

Field Testing Protocol:

Representative soil and irrigation water samples were gathered and submitted for the following tests http://www,loganlabs.com :

Basic Soil Test – nutrient accessibility

Saturated Paste Test – nutrient availability (bicarbonate, soluble salt, sodium)

Irrigation Water Suitability Test - conductivity, SAR, alkalinity, bicarbonate

Physical Infiltration Test – Saturated Hydraulic Conductivity at 0-4” and >4”

The results of these tests should provide a better understanding of the dynamics involved in this situation and provide a strategy for remediation.

 

Initial Field Recommendation – Pending Test Results:

  
Apply KaPre Exalt (Humic Acid penetrant) www.lidochem.com/Fertilizer-Product.../KaPre  @ 2.0 gl./acre + Holganix (biological  inoculant) http://www.holganix.com @ 2.4 gl./acre - pulse irrigation (frequent cycles with reduced duration) to gradually move sodium from surface to deeper into soil profile while minimizing surface runoff. Use POGO to verify achieving acceptable EC values. 

If EC is within acceptable range, spike and seed damaged areas as soon as possible.

Topdress seeding with Healthy Grow 2-4-3 Holganix (composted nutrition providing soil stable carbon and supplemental calcium) http://www.holganix.com/products/granular  @ 5 lbs./M.

Apply Command (penetrating surfactant) http://www.foliarpak.com @ 24 oz./acre + Root Guard (bio stimulants, mycorrhizae, other beneficial biology) http://www.foliarpak.com @ 2.0 gl./acre + Turbo MKS (soil available source of Mg, K, S) http://www.foliarpak.com @ 10 gl./acre – apply directly over the top of new seeding and water-in.

Continue to monitor EC levels with POCO and follow-up as needed with Cal-Pull (organic-amino acid chelated calcium) http://www.enp.com @ 5 gl./acre + Command @ 24 oz./acre + Holganix @ 2.4 gl./acre – water-in.

After germination topdress with Healthy Grow 2-4-3 Holganix @ 5.0 lbs./M

Enhance new seeding establishment with Amperage 12-0-0 (high energy food and essential nutrient supplement) http://www.foliarpak.com @ 1-2 gl./acre + Root Guard @ 1-2 gl./acre + AS Fusion 7-0-0 (liquid ammonium sulfate plus amino acid) http://www.foliarpak.com @ 2 gl./acre – apply every 7-14 days

Continue to monitor surface EC levels and continue to add supplemental potassium, magnesium and sulfur with monthly applications of MKS Turbo @ 10 gl./acre along with Holganix liquid @ 2.4 gl./acre until the cessation of photosynthetic activity (soil temperatures <40F).

Fall Aerification – incorporate Healthy Grow 2-4-3 Holganix @ 10 lbs./M and supplement with soluble gypsum @ 10 lbs./M

Soil and Irrigation Testing Results:

Soil and saturated paste reports by themselves are not indicative of the severity of the problem that currently exists. Elevated soil pH, moderately high bicarbonates, unbalanced soluble cations (% sodium > % potassium) are definitely potential issues, but not representative of the turf loss experienced. The disconnect lies in estimating average salt concentrations over a 4-5” profile depth vs. local concentrations at 1-2” depths – inconsistencies verified by POGO.

Irrigation water report demonstrated high alkalinity (highly buffered, elevated pH) and excess bicarbonate. Definitely a major indicator of potential soil and plant issues, especially during periods of frequent irrigation and elevated evapotranspiration, but by itself would not predict the dramatic turf loss scenario that occurred.

Poor water quality, reduced profile infiltration rates, challenged root function, increased surface drainage and high ET made for the perfect storm. Of all the factors influencing this unfortunate outcome, reduced profile infiltration is the most restrictive of all.  Enhanced profile infiltration is critical in building soil buffers, protecting the plant from less than ideal inputs. In older USGA and modified sand-based greens, it is a major hindrance  to implementing successful water management strategies - negatively impacting both plant and fiscal health.

It will be interesting to get the physical test results for current organic layer (upper profile) hydraulic conductivity and see how they differ from original construction values (lower profile).

Green 13 - moderately sloped, reduced air movement, >90%  Poa loss

 

 

Green 13 - profile, 4" organic layer, no algae indicates turf expired quickly (14 days ago)

 

 

Green 13 - bentgrass is virtually unaffected since rooting extends below high salt accumulation zone

 

 

Green 16 - very little slope, < 5% Poa loss within last 14 days

 

 

Green 16 - profile, 4" organic layer

 

 

 

Green 16 - unaffected Poa due to reduced sodium accumulation in upper profile, the presence of algae is indicative of previous turf damage

 

 

Green PP - moderate slope, 30% Poa loss (only in higher % sloped areas)

 

 

Green PP - POGO reading on high slope bentgrass area

 

 

POGO - Moisture / EC (very high salt)

Reduced slope areas had dramatically lower EC's (< .30)

 

Application Update:

 

08/26/15 
Initial application of Exalt @ 2 gl./acre + Holganix @ 2.4 gl./acre was made and watered-in.
EC's dropped from .65 to .35

Recommendation made by Kevin Wolfe to spike and inter-seed greens.

09/01/15 
Apply ENP Cal-Pull @ 5 gl./acre + Aquaduct @ 16 oz./acre - treat seeded areas and water-in.
         

09/04/15
Seed is germinating, but EC readings are going back up. Recommendation is for repeat application of Exhalt + Holganix +  Aquaduct