Tropical soils, Temperate soils: What’s the difference and does it matter?
In the Advocate newspaper of 8th April 2013, there was an article captioned “Organic agriculture can boost restaurant sub-sector.” Immediately below the caption in bold font was the following statement: “In temperate countries like the UK, the organic matter content stood at 5%. In Barbados on the other hand….the organic matter content in most soils was less than one percent.” The statement also appeared in paragraph five of the article. In paragraph eight of the same article, the following appeared: “Conventional methods contribute to green house gas emissions and can cause inefficiencies in energy use..” The two statements were attributed to the National Co-ordinator of the United Nations Development Facility Small Grants Program (GEF SGP).
In biology there is a concept called the temperature quotient. The temperature quotient is a ratio of the velocity of a process at a given temperature to that at a temperature 10 °C lower. In biological systems the temperature quotient is about 2-3. This means that there is (using the lower figure) a doubling of the rate of a biological reaction for every ten degrees increase in temperature. This doubling effect occurs up to certain temperature beyond which, there is an adverse reaction due to effect of heat. Since tropical countries are hotter than temperate ones, one would expect tropical soils to have little or no soil organic matter. Obviously, if fresh vegetation or pen manure is added to tropical soils, initially, soil organic matter will be high. This, however, is only so for a short time. The duration of organic matter is further reduced in the presence of air and water. Another fact to be considered is the carbon /nitrogen ration of the added vegetation or manure. If the nitrogen content is too low, the rate of decomposition is retarded: the converse occurs if there is adequate nitrogen available. Pen manure or vegetation added to the soil is broken down by soil micro-organisms. Students of biology would have encountered in their studies the carbon and nitrogen cycles. Carbon dioxide and nitrogen are the ultimate products of the decomposition of manure and vegetation when added to soils as is the case when fertilizers are used.
I have stated in the past that, the majority of Barbadians are scientific illiterate and the article referred to, supports what I have been saying for years.
Robert D.Lucas, Ph.D.