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Nitrogen Fertilizer

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When running a nitrogen crop response model with 100kgN/ha fertilizer input I found that the amount of nitrogen in the top 90cm of the soil decreased compared to when zero nitrogen was added (66kgN/ha vs 93kgN/ha). No other variables in the model were changed (ie organic matter content, rainfall etc). the other results given by the model were:

For 100kgN/ha added - crop yield 3.9t/ha with %N content 3.52, N leaching below 90cm 94 kgN/ha

For 0kgN/ha added - crop yeild 1.99 t/ha with %N content 2.17, N leaching below 90cm 94 kgN/ha

I understand why the crop yeild and % N content went up in response to the added nitrogen but why did the amount of stored nitorgen in the soil go down - what am I missing about the nitrogen cycle that would explain this?

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Nitrogen dynamics in soil can be complicated by a number of factors. Plants only take up inorganic forms of nitrogen (NO3-, nitrate, and NH4+, ammonium), and other sources of nitrogen must be converted into one of these forms for use by plants. The conversion of ammonium to nitrite (NO2-) and then to nitrate is called nitrification. This process is carried out by soil microoranisms; all forms of nitrogen are eventually converted into nitrate. The ammonium form of nitrogen is held in the soil due to attraction between its positive charge and negatively charged clay particles and organic matter, and is obtained by plants by ion exchange with H+. The nitrate form is water soluble and is carried with soil water, so it can be lost if water percolates below the active root zone of the crop.

Your model estimates suggest that an ...

Solution Summary

Nitrogen's effect on soil is discussed.

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Purpose of Laboratory Investigations Hypothesis

In this lab, you will be observing the impact of mineral nitrogen fertilizer usage on maize's crop yield, which is measured in milligrams of dry mass harvested per 100 acres (1 hectare) during a 1-year period. Use the animation to help you come up with an answer to the following:

Complete a lab report using the scientific method.
Using the Scientific Method Lab

Using the M.U.S.E. link, review the background information and animation to complete your report. Use the Lab 1 worksheet for assignment instructions and data collection.

Both arable and nonarable land have been chosen as the experimental cultivation sites near the city of Melle, Germany, where the yield of maize was observed from 1990 through 1998. The climate variations have also been carefully recorded on equally sized lots of both types of land.Part 1: Using the lab animation, fill in the following data tables to help you generate your hypothesis, outcomes, and analysis:

Part 2: Write a 1-page lab report using the following scientific method sections:
Purpose
- State the purpose of the lab.
Introduction
- This is an investigation of what is currently known about the question being asked. Use background information from credible references to write a short summary about concepts in the lab. List and cite references in APA style.
Hypothesis/Predicted Outcome
- A hypothesis is an educated guess. Based on what you have learned and written about in the Introduction, state what you expect to be the results of the lab procedures.
Methods
- Summarize the procedures that you used in the lab. The Methods section should also state clearly how data (numbers) were collected during the lab; this will be reported in the Results/Outcome section.
Results/Outcome
- Provide here any results or data that were generated while doing the lab procedure.
Discussion/Analysis
- In this section, state clearly whether you obtained the expected results, and if the outcome was as expected.
- Note: You can use the lab data to help you discuss the results and what you learned.
Provide references in APA format. This includes a reference list and in-text citations for references used in the Introduction section.

Give your paper a title and number, and identify each section as specified above. Although the hypothesis will be a 1-sentence answer, the other sections will need to be paragraphs to adequately explain your experiment.
When your lab report is complete, post it in Submitted Assignment files.

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