Dear Samuel,

Few studies have been conducted on the use of cow dung or agricultural manure or agricultural compost for the degradation (can say biodegradation) of oil contaminated soils. As manure/compost contains diverse group of microorganisms and have tendency to remediate the soil. Addition of cow dung in soil also enhance the physical and chemical properties by increasing its fertility (by adding nutrients), moisture absorbing capacity and more. 

If used in clay soils where water logging is a problem cow dung increases the porosity of soil of if the soil is porous not retaining the water such as sandy soils then cow dung acts as water holding carriers. 

I am sharing one article with you published on this theme. 

Thanks.

Kunal

Cow dung or Farm yard manure is an important source of organic matter in soils, especially in small-scale farming systems in Africa. Cow dung adds organic matter into the soil, basically the correct question to ask is what are the effects of organic matter in a degraded soil. Cow dung/ OM, helps to increase the soils buffering capacity, thus helping to regulate soil acidity.  For a degraded soil the soil physical properties are usually destroyed, because organic matter has declined in the soils.  This reduces soil aggregation and soil bulk density, water holding capacity and nutrient holding capacity. A soil without organic matter will only remain with the mineral component. The presence of organic matter ensures that soil biological properties are functional which is important for soil the soil system.

the effect of cow dung on soil is that it increases the geo-technical properties like bulk-density, dry density, increaesed water holding capacity, porosity, infltration

The soil automatically attracts earthworm to dwell wherever cow-dung is there

which further increases the fertility of soil

Addition of cow dung will increase the organic carbon content of degraded soil which may lead to the increasing activity of beneficial soil microorganisms.The activity of nitrogen fixing bacteria like Azotobacter(Azotobactor chroococcum )  etc. will increase and more atmospheric nitrogen may be accumulated in soil ,which may lead to increase available nitrogen content as well as the fertility status of soil. More over the availability of nutrients for the plants from the soil will also increase. Increased porosity of soil will also increase aeration in soil and produce a favourable condition for plant growth. 

The effects and their magnitude on are regulated by the dose, chemical composition and humfication degree of the cow manure applied... Since cow dug is a fresh organic materials, most of the effects are regulated by the rate applied, and they mostly act on soil chemical properties.... Humified materials applied in sequecend years may increase the CEC, water retention and can also improve the soil structrure. In terms of effects in soil chemical properties, fresh organic materials may increase the mineral N and soil N as a whole.. Substrate for organisms which could colonizes degraded soils coul also be increased... Again, all the effect are strongly regulated by the rate and accumulated charges of cow dug added to soils.  

Generally manure rates are high to promote changes in soil organic matter , mediated by microbial activity increase. However, in tropical conditions biochemical reactions are very intense and the carbon content increase in the soil is noticed in one or two years (depending on the applied dose), so a relatively short time beginning to reverse the degradation process.

Cow dung /FYM is an important source of organic fertilizer, useful in small scale farming . Cow dung adds organic matter into the soil,  helps to increase the soils buffering capacity and regulating soil pH ( decrease soil pH), provide secondary  and micro nutrients, thus  improve soil fertility, Increase the water holding capacity of soil, thus increase the growth of plant and sustain the productivity.

Degraded soil may be Alkali, Acidic and Saline in nature. Cow dung application increase the organic matter in the soil which regulate the soil reaction (pH). In acidic soil its application increase the pH where as in alkali soils it decrease the pH. and thus create favurable conditions for availability of maximum nutrients to plants (pH range 6.5 to 7.8). Of course it is beneficial to most of the physical & physico-chemical properties of soil.

Cowdung addition to degraded soil could bring changes to topmost layer of soil, deeper layers are less affected. Among readily observable characters soil pH would change, and as a result of manure addition the lighter and loosely held particles (that would otherwise blown away by wind) are glued together by this organic matter, thus wind erosion could be lessen. But for water erosion, the land surface has to be covered with vegetation.