NRS 212 – Introduction to Soil Science Fall 2018
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Application Problem #5
Please read and follow the rules provided in the Assignment Instructions
Pedro Greenjeans has been applying the
insecticide “Merit” to his lawn religiously every
spring for the past ten years. This practice was
recommended by his neighbor, Capt. Kangaroo.
The application of Merit has resulted in complete
control of the evil grubs that ruined his lawn.
However, it seems to have created a problem with
excess accumulation of thatch (he uses a
mulching mower) and the appearance of some
sort of fungal disease on the grass. Turning to the
Google for help, Pedro found the information on
the right. He showed it to the Captain, who
suggested that he just apply a fungicide to the
grass to get rid of the fungal infection.
1. The Captain’s wife, Tenille, a soil biochemist,
thinks that the accumulation of thatch is due to
inhibition of cellulase activity by “Merit”. Pedro’s
brother-in-law, who manages a vermicomposting
operation, tells him he’s sure that Merit’s toxicity
to Eisenia fetida and predatory insects is the
culprit.
What do you think is going on?
o Fungi and bacteria produce cellulase to hydrolyze cellulose. Cellulose
would slow down thatch decomposition causing thatch to build up. Also,
Eisenia fetida eats plant detritus and in the long term Merit can decrease
the number of Eisenia fetida. So, saying that its toxic to predatory insects
in not right.
2. Pedro has asked his friend, Guillermo Tell, a soil ecologist, to explain what he thinks is
causing the fungal disease. Guillermo tells him there are a number of possibilities: (1)
increased moisture at the soil surface due to thatch accumulation, (2) the thatch provides
C and nutrients to fungal pathogens, (3) a higher soil organic matter content from
increased inputs of plant detritus, and/or (4) suppression of fungivorous nematodes that
attack plant pathogenic fungi.
Which of these do you think is most reasonable? Explain.
o The most reasonable is that the accumulation of thatch increases moisture
in the soil. Fungi thrive under moist conditions.
______________________________________________________________________________
Application Problem #5
Please read and follow the rules provided in the Assignment Instructions
Pedro Greenjeans has been applying the
insecticide “Merit” to his lawn religiously every
spring for the past ten years. This practice was
recommended by his neighbor, Capt. Kangaroo.
The application of Merit has resulted in complete
control of the evil grubs that ruined his lawn.
However, it seems to have created a problem with
excess accumulation of thatch (he uses a
mulching mower) and the appearance of some
sort of fungal disease on the grass. Turning to the
Google for help, Pedro found the information on
the right. He showed it to the Captain, who
suggested that he just apply a fungicide to the
grass to get rid of the fungal infection.
1. The Captain’s wife, Tenille, a soil biochemist,
thinks that the accumulation of thatch is due to
inhibition of cellulase activity by “Merit”. Pedro’s
brother-in-law, who manages a vermicomposting
operation, tells him he’s sure that Merit’s toxicity
to Eisenia fetida and predatory insects is the
culprit.
What do you think is going on?
o Fungi and bacteria produce cellulase to hydrolyze cellulose. Cellulose
would slow down thatch decomposition causing thatch to build up. Also,
Eisenia fetida eats plant detritus and in the long term Merit can decrease
the number of Eisenia fetida. So, saying that its toxic to predatory insects
in not right.
2. Pedro has asked his friend, Guillermo Tell, a soil ecologist, to explain what he thinks is
causing the fungal disease. Guillermo tells him there are a number of possibilities: (1)
increased moisture at the soil surface due to thatch accumulation, (2) the thatch provides
C and nutrients to fungal pathogens, (3) a higher soil organic matter content from
increased inputs of plant detritus, and/or (4) suppression of fungivorous nematodes that
attack plant pathogenic fungi.
Which of these do you think is most reasonable? Explain.
o The most reasonable is that the accumulation of thatch increases moisture
in the soil. Fungi thrive under moist conditions.
