I am studying some aternative ways to obtain a fertilizer and one of the hypothesis ends up containing a good amount of Na+ in it(half the amount of P and Mg). I am not an agrarian, but I always thought adding sodium to the field might disturb the hydric balance of the soil, or am I mistaken? I found some studies about the role of Na+ in soils but not so lucky in finding the effect of Na+ in fertilizers.
Does anyone know what may be the effect of adding a fertilizer containing Na+ in it's composition?
Depending on your soil the soil structure could be severely damaged. The hydraulic conductivity will decrease and crusting and hardening of the soil will occur. Sodium has one positive charge but will replace divalent Ca and Mg which provide a stronger bond, keeping the soil structure intact. When the replacement has taken place, it is mostly irreversible and once it rains heavily the sodium will wash out and the soil will slump, then the hydraulic conductivity will decrease. However, most fertilisers contain sodium and if you have high clay soil, and add Ca at the same time (lime) the damage will be limited. You can do hydraulic conductivity testing of your specific soil to see how much impact how much salt has. Coal Seam Gas companies do this all the time, testing how much their salty wastewater impacts the soil if they release it. I think a 10% reduction would be acceptable, although not ideal. The impact on the plants is caused by soil hardening, sodium toxicity and reduced water conductivity. Some plants are more salt-tolerant than others, but most plants will be impacted via reduced water availability and reduced root growth.
Denis Rodrigues
Sodium might not just come from fertilizer only. Consideration of other sources e.g. run-off, pesticides and breakdown of some minerals is needed. Also, plants have different tolerance levels to sodium toxicity. I think you need to dig a bit on specific plant species and their optimum levels
Friederike Susette Eberhard thank you for the informaiton on the soil. So even if the impact on the plants may depend on the plant itself, the soil may be severely affected by continuous input of extra Na+ through fertilizer. So I guess If I had another process leading to less Na+ concentration it would be better if I want that fertilizer to not be soil dependent.
Too much deposition could harm your soil and plant at the receiving ends
Denis Rodrigues yes, definitely less salt is always better, even if you want to grow plants that are quite salt-tolerant like tomatoes. I have never heard of sodium deficiency in plants, on the contrary, it prevents plants from taking up enough calcium and magnesium. Sometimes it is taken up when there is a potassium deficiency, and in this case, it is better than nothing.
I would recommend doing the hydraulic conductivity testing on a couple of soils in your area, there are many sites online that describe the method, for example, https://www.metergroup.com/environment/articles/how-to-measure-soil-hydraulic-conductivity-which-method-is-right-for-you/
It involves filling your soil in a PVC pipe piece with a fly net and filter paper, filling the air-dried soil in, dropping the pipe/soil set-up three times to compact it, measuring the height of the soil surface and then letting a set amount of fertiliser solution run through slowly over a couple of hours or days. Then you run the same amount of distilled water through and measure how much your soil has compacted. Once you have the results, you can decide if the impact is serious enough to change your formula. It might not have a strong impact at all.
It is known that Na element is not an essential for plant growth and it has many negative effects on the soil water relations, but using it with organic fertilizers or in organic soil along side with K fertilizers could minimize the negative effect of Na on soil and plant.
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