We have an experience reclaiming an abandon site of an oil and gas company in Indonesia, soil improvement has been done using humic subtance active product and of course organic fertilizer

It depends on the climate, soil type and growing zone. Many plants will build OM in alkaline soils. What pH are you thinking?

Hi Daniel Halsey

Thanks. pH values 8.5-10.

For alkaline soils, grow green manure crop such as Sunnhemp (Crotalaria juncea)  the field itself just similar to inter crop. Cut them  and mulch into the soil just before flowering (ie., in-situ). About 8 to 10 kg seeds are required per acre. Besides, their root nodules also fix atmospheric Nitrogen.

We used alfalfa and red clover for revitalization of  postflotation sediments with pH 8,5 high content of calcium and magnesium, these plants are growing very well since 2008 when they were sown. Accumulation of organic carbon proceeds and it is important all plants have high nodulation index., of course both plant should get some iron  by  foliar (Fe IDHA) or into substrate (Fe HBED ) that chelatin agents work fine in alkaline conditions in soil.

Alkaline soils, generally found to be low in hydraulic conductivity, high in sodium percentage and sodium absorption ratio. Which leads to imperfect drainage and low water retention capacity, an indicator of poor soil quality. Therefore to overcome these constraints, there is need to apply amendment like use of gypsum, use of water absorbent polymer (e.g. Pusa hydrogel), short duration crop, green manuring like growing of Dhaincha crop upto 50% flowering stage and incorporate it into field which could reduce sodium percentage over a peroid of time.

According to pable, determined the gypsum demand  of soil and application. After gypsum application give full irrigation. Or use organic mannure like compost , fym.

First there is a need to determine the cause of alkalinity before any especially chemicals amendment can be entertained that is to make use of the most effective agent. 

It is also very common in alkaline soil to have impeded infiltration, therefore improving water drainage through adequate cultural operation such as deep tillage assist the elimination of excess alkalis that are often in soil that need to be leached. 

Similar to acid soils, used of acidifying fertilizers such as ammonium phosphate, ammonium sulphate will assist in lowering the soil pH. 

Finally as proposed by others, organic amendment can help, but it is also possible that the same organic addition reduce significantly the capability to rid the excess bases from the soil given its ability to improve soil CEC. Moreover, the production of organic acids as a result of fermentative degradation can affect root growth and may also limit available soil oxygen due to excessive soluble organic loads in the soil.

Green manure Sunnhemp (Crotalaria juncea) in situ incorporation continuously for 3-4 seasons will provide very good reults

It is better and faster to firstly reduce or abate the dominant constraints of such alkaline soil by way of proper application of  amendments, such as gypsum. And then soil salts in the root zone should be horizontally flushed. Some practices such as phytoremediation should be also adopted in such a condition to match the amelioration to better improve the soil health.

 Simple and quick solutions are using Neem ( Azadirachta indica) Leaf powder or fresh crushed leaf 1kg per decimal and after  one month Neem seed  cake powder 1kg per decimal. This is the best organic solutions.