the soils I am experimenting with is highly sodic (high Na) with a pH of 8.3 to 8.6. When I checked the NH4+ and NO3- concentrations in the soil compared to a reference soil from an unaffected area, NH4+ of the test soil was similar to reference soils at all times; however, NO3- is gradually decreasing. I have two assumptions,
1) Sodicity/alkalinity induce denitrification
2) Sodicity/Alkalinity inhibit nitrification
1.The NH4+ should react to form NO2-, NO3- by nitrification, and NO3- react to form N2 by denitrification . If the NH4+ of affected area is the same as the unaffected area, then the high Na should contribution the soils alkaline (pH 8.3~8.6).
2.In the affected area ,if the nitrification, the NH4 react to form NO2, NO3, then the soils should become more acidic ( NH4+ react to form NO3- and H+), we need offer some alkaline to avoid the soil acidification. So I think the high Na (pH 8.3~8.6) maybe not the matter, the assumptions 1 is more reasonable.
3.The NO3- is gradually decreasing, I guess may the NO3- react to N2. You should to check the concentration of NH4+, and that should also gradually decreasing.
Dear Samadhi Gunathunga kindly refers to the link given below. It may helpful for understanding the relationship between pH and the denitrification process. Article The influence of soil pH on denitrification: Progress toward...
Symptoms and causes of salinity (high salt content), specific ion toxicity and sodicity (high sodium) are frequently confused. Each of these conditions can have adverse effects on plant growth, but they differ significantly in their cause and relative impact.
Saline and sodic soils both have high pH levels, with problems typically occurring at a pH of 7.8, or extremely alkaline conditions. The primary difference is that saline soils also have a high salt content, while sodic soils have high sodium content.
https://link.springer.com/chapter/10.1007/978-3-319-96190-3_1
The problems of primary soil salinity, soil sodicity and soil alkalinity are most widespread in the arid and semi-arid water management areas. but salt affected soils also occur extensively in sub-humid and humid water management areas, particularly in the coastal areas where the intrusion of seawater through estuaries, rivers and groundwater causes problems,Where the rainfall is approximately five to ten times less than the potential evaporation, salts derived from rock weathering, bio-cycling and atmospheric deposition may accumulate to relatively high levels in the soil.
High pH reduces the availability of some nutrients (zinc, iron, phosphorus). Signs of high soil pH include yellow stripes on middle to upper leaves (signs of zinc and iron deficiency); or dark green or purple coloring of the lower leaves and stems (signs of phosphorus deficiency). Saline soils cannot be reclaimed by chemical amendments, conditioners or fertilizers. A field can only be reclaimed by removing salts from the plant root zone by leaching, artificial drainage and managing accumulation.
Sodium affected soil can also be improved by continuing using high quality irrigation water, and good irrigation methods. Practices that improve water infiltration such as incorporation of organic matter (crop residues, manure, compost, green manure or cover crops) and deep plowing to disrupt restrictive clay pans and mixing calcium from deeper soil layers are also effective to reclaimed sodium affected soils.
This is such an issue , you will find literature simply flowing in journals , since nitrogen is the most crucial nutrient in relation to soil sodicity or alkalinity....
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