Managing Soil Profiles - Bicarbonates and Sodium (continued)

 

 

Reduced turf quality, non-functioning root system, water management issues and suspicious irrigation water quality all pointed to a potential build up of sodium within the soil profile. Reduced infiltration rates were inhibiting the ability of the profile to properly flush, even when exposed to natural rainfall.

 

 

The Soil Report Base Saturation % indicated that sodium was slightly elevated on green 18 (4.81%) along with a subsequent calcium deficiency (48.71%). Green 17 demonstrated reduced magnesium (4.22%). Both 17 and 18 were low in accessible phosphorus (<250 lbs./acre).  The Soil Report is a valuable tool in determining nutrient accessibility, but does not provide any information on availability of nutrients. Good tool for balancing Base Saturation.

 




 

The Saturated Paste Report paints a much clearer picture of what is going on in the soil solution. Using irrigation water to analyze soil saturation had a tremendous impact on both the pH (from 5.9 to 6.5 and 7.0 to 7.2) and in reducing availability of "good" Soluble Cations (Ca, Mg, K). It can be inferred from the dramatic movement of pH and Soluble Cations, that the irrigation water is extremely high in both pH and bicarbonates. High bicarbonates are causing calcium and magnesium to precipitate out in solution pulling them off soil colloids and reducing their presence as soluble cations. Sodium has taken advantage of this void and has therefore increased as a dominant soluble cation.  So much so, that it is negatively impacting plant and soil health.

Sodium is very aggressively over powering the other cations (Ca, Mg, K) in the soil solution as well as on the soil colloid – 30.91% (Grn 17) and 43.68% (Grn 18).  As the % saturation of sodium increases (>5%) it has a negative impact on soil aggregate stability, limiting the movement of water and air through the soil profile (especially in the upper horizons). As infiltration rates decrease we see salt accumulation begin to increase, having a negative impact on the ability of plant roots to access water and nutrients. This is especially noticeable on shallow rooted turf plants like Poa annua or newly germinating seedlings. With limited infiltration rates it becomes difficult to effectively flush the profile, greatly exasperating the problem. A sodic (sodium) issue can rapidly become a sodic-salt issue which then quickly impacts plant and soil health.

 

Reduced soil infiltration (air porosity <15%) as a result of high sodium and salts, will result in a severe decline of microbial activity in soils, dramatically reducing rooting depth, function and density. The fix is to dislodge sodium from soil colloids, replace it with calcium and relocate sodium beyond the root zone in the soil profile. Re-establishing the proper balance of Mg and K is also important. Adding supplemental mineral phosphorus to the soil will correct any potential phosphorus deficiency – this will also help to enhance rooting potential.

Sodic soils are typically higher in pH, lower in soil organic matter, lower in carbon and have reduced biological activity. Adding compost to high sodium soils can accelerate the remediation process by providing a sustainable food source for microbes. Carbon in compost is more liable and readily available for microbial use.The activity of microbes will help to reestablish soil aggregate stability, increasing the infiltration rate of soil profile and facilitate the leaching of sodium out of the root zone.

 

 

To expedite this process it is necessary to solid tine the greens to a depth that penetrates the organic portion of the profile (3"). Given the existing shallow roots, it would be too destructive to pull cores at this time, so care must be taken to minimize disruption of the upper soil profile (rhizospere).

 

Prior to this aeration event, apply a high rate of liquid humic acids (i.e. KaPre Exalt - 35% Humic Acids @ 2.5 gl./acre) + penetrating wetting agent (Foliar Pak Command @ 24-32 oz./acre). Immediately follow the application with a Pulse Irrigation Cycle – irrigate until puddling occurs, allow excess water to dissipate and repeat the process several times throughout an irrigation cycle. 

 

Repeat this application in 2-3 days before aeration.

 

As part of the aeration process, incorporate 5-10 lbs./M of a soluble fine granulated gypsum + 10 lbs./M of Healthy Grow Compost 2-4-3 Holganix. It can be applied in conjunction with sand topdressing, but it is important to get it worked well into the aerification holes and avoid surface stratification. Follow-up with a Pulse Irrigation Cycle.

 

At this point it is important to again take follow-up soil and water samples to verify soil sodium reduction and monitor additional nutrient deficiencies or imbalances.

 

If the Soil Report indicates a Base Saturation imbalance, mineralizing soils with Sul-Po-Mag, Gypsum or High Calcium Lime can be done in conjunction with a late fall aeration event. If phosphorus continues to demonstrates accessibility deficiencies (<250 lbs./acre), then MAP should be incorporated as well.

 

A late fall solid tine will also help with further cleaning up the soil profile. Leaving the holes open will facilitate flushing with natural precipitation over the winter.

A spring solid tine in lieu of coring would be beneficial.

Monthly venting (utilizing solid tines) during June, July and August along with incorporation of Healthy Grow Compost 2-4-3 Holganix would help prevent the build up of sodium. Regular applications of Root Guard, Bio 12-6-6 and Command in conjunction with Pulse Irrigation will also help in suppressing sodium accumulations during the summer months.

 

Avoiding excessive applications of high salt index fertilizers – compost based products are best (high carbon, low nitrogen, reduced salts).