There are a vast array of insects living in soils – and they have important jobs! Ants are fascinating as they create small trails in soils. They transport rocks, leaves, and wood, and anything with a manageable size, weight, and form. Seriously, insects are witty enough to conquer all the habitats around the planet, except for the open ocean. But, why select soils and how do they survive there?
Believe or not, soils are fantastic places to find insect specimens because of the relation between insects’ daily routines and the subsurface. For example, insects are part of the predator’s community that control the population of others. On the other hand, many of the terrestrial animals have an insectivorous diet granting a key role to insect’s populations as food source in the food chain.
At times, insect life on agricultural land can be harmful for crops. Some farms use pest biocontrol. Knowing the problem insect, farmers introduce an insect that eats the pest, and not the crop. This ecological service by insects is a way to control pests in a natural way at the same time preventing excessive application of pesticides to kill them.
There are many pests that have affected crops in my home of Puerto Rico. Once called caculos is harmful to sugar cane. Adults create tunnels close to the host plant to have food from foliage during day and protection in the soil during night. Another pest, Rhinoceros beetles, place their larvae on the ground to be fed by the roots of coconut palm trees.
Caculos and Rhinoceros beetles are now under control. Today, a pest called citrus root weevil, is a concern for citrus producers. The weevils bore holes in roots and stems reducing crop yield.
Incredibly, insects have a role in the soil nutrients cycles too. Some of these are nitrogen, phosphorus, potassium, calcium, and magnesium – all elements that interact with the insects at some point. Small amounts of these nutrients become available to be adsorbed by roots and microorganisms after the decomposition of soil organic matter.
Though little, insects’ life cycles have a big impact in soil’s physical condition. If you observe a piece of soil with stable structure, a soil aggregate, it is possible you can see small holes. Those could be a nest, refuge, or home for insects. When they die, the structures resulting from soil engineering by insects are resistant and effective to improve the pore space of soils. This in turn improves soils’ capacity to infiltrate water to the ground. For that, the ecological approach of integrated pest management promotes the diversity of insects and its benefit for agricultural resources like soils.
During field work mapping arable lands affected by salts and sodium, I was able to observe two beautiful events. The first one was the chance to find a Changa mole cricket (Scapteriscus spp.) during soil sampling. The second one was a “puddling event” by Aphrissa statira cubana, commonly named Migrant Sulphur or Pale Sulphur. Groups of these butterflies work to look for water and nutrients.
Without doubt, soil is full of life and insects. Take the chance to be surprised by nature, especially when you are in the soil. Just observe around you and discover what there is to be found.
Answered by Beverly Alvarez Torres, University of Puerto Rico
To learn more about the author’s research in soil mapping using electromagnetic induction, please visit this link: https://myagropostpr.wixsite.com/beverlyalvareztorres
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