A paddy field of 8 hectares needs 100 kg of nitrogen on each hectare…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A paddy field of hectares needs kg of nitrogen on each hectare. Cyanobacteria supply kg of nitrogen to each hectare. Urea is nitrogen by mass.
- How many kg of urea hold kg of nitrogen?
- How many kg of urea does the farmer save on the whole field?
- How many kg of urea must the farmer still buy for the field?
Need a reminder? The key ideaShow
Rhizobium lives in the root nodules of legumes and fixes nitrogen. Azospirillum and Azotobacter are free-living nitrogen fixers. Mycorrhiza, as in Glomus, bring phosphorus from the soil. Cyanobacteria are autotrophic nitrogen fixers of paddy fields. Urea is about nitrogen by mass, so the mass of urea is the mass of nitrogen divided by .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Field: ha. Need: kg of nitrogen on each hectare. From microbes: kg. Urea: nitrogen.
Plan. Change each mass of nitrogen to a mass of urea by dividing by .
Step 1. For each hectare. kg of urea.
Step 2. For the field. kg of urea.
Step 3. Still needed. The nitrogen still needed is kg on each hectare, which is kg of urea. For ha: kg.
Answer: kg; kg; kg.
Check. kg, which is , the urea for the whole need.
Watch out. A real field does not use all the nitrogen that is supplied. These are teaching values.
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