Many scientists and farmers speak highly about the use of compost and mulch in soils. There are often soil and crop improvements attributed to using these organic additions but are they real benefits?
While there is a certain amount of quackery over many soil additives, with some very dubious clams being made for them, it is now considered that there is a reasonably comprehensive set of truisms that can be attributed to compost use, with compost consderd in a broad sense to also include organic mulches.
These benefits and soil improvements are seen in temperate regions in the US, Europe and Australia as well as in tropical regions, with the latter often seeing very big improvements as the soils are tending to be lower in soil organic matter anyway. Small additions of organic materials can mean big crop performance improvement.
The twelve well recognised benefits of compost are listed below.
The following list of compost benefits have been approved by the Association of American Plant Food Control Officials (AAPFCO). This organization is made up of state Department of Agriculture regulatory officials from every state in the US. These claims are permitted to be made, and are considered as valid, on compost labels, literature and websites in the US and are also relevant elsewhere.
a. Improves soil structure and porosity – creating a better plant root environment;
b. Increases moisture infiltration and permeability, and reduces bulk density of heavy soils – improving moisture infiltration rates and reducing erosion and runoff;
c. Improves the moisture holding capacity of light soils – reducing water loss and nutrient leaching, and improving moisture retention;
d. Improves the cation exchange capacity (CEC) of soils;
e. Supplies organic matter;
f. Aids the proliferation of soil microorganisms;
g. Supplies beneficial microorganisms to soils and growing media;
h. Encourages vigorous root growth;
i. Allows plants to more effectively utilize nutrients, while reducing nutrient loss by leaching;
j. Enables soils to retain nutrients longer;
k. Contains humus – assisting in soil aggregation and making nutrients more available for plant uptake;
l. Buffers soil pH.
There are many articles and newspaper stories about the benefits of compost - so if you are not using compost or any other organic additions such as mulch, why not? The photo shows mechanised compost production using a row turner.
In the tropics where rainfall is often in short higher intensity storms, surface mulches and composts provide a very effective surface barrier that prevents the dislodging of soil surface particles caused by the energy of impact of rain drops - this dislodgement commences the process of soil erosion. A mulch cover can greatly reduce that problem while also controlling the infiltration of the rain. "Cover"is a significant term in the universal soil loss equation [ USLE] used to calculate erosion, and is a factor that can be easily modified - as distinct from some of the other factors. And soil cover is why dense grassland or rainforest is less prone to erosion.
The carbon in the organic materials often remains in the soil for some time so it also contributes to sequestring carbon, although not always for really long periods. [ that is another complicated issue - you could read about biochar or terra preta soils]
Surface mulch and compost are great contributors to better soils and the products grown in them!.