Term
| why it is necessary to apply fertilizer at economic rates |
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Definition
| because in most Southeastern soils, the amount of N released from crop residues and soil organic matter is insufficient to obtain adequate crop yields |
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Term
| what an economic N rate is |
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Definition
| a rate that increases net income |
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Term
| some steps involved in determining economic N rates |
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Definition
-establishing field plots w/ different N rates
-analyzing the data taking into account the prices of the fertilizer applied and the crop produced |
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Term
| the objective of the Determining Economic N Rates exercise |
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Definition
| to acquaint you w/ a procedure commonly used to determine the optimum economic rate of N fertilizer to be applied to a given crop |
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Term
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Definition
| line that increases at a decreasing rate |
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Term
| equation for flat response curve |
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Definition
| Yield = a; where “a” is a constant |
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Term
| equation for a straight line response |
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Definition
| Yield = a + b(N rate); where “a” and “b” are regression coefficients |
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Term
| equation for a curvilinear response |
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Definition
| Yield = a + b(N Rate) - c(N Rate)2, where “a”, “b”, and “c” are regression coefficients. |
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Term
| the effect of adding N fertilizer when there's a flat response curve |
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Definition
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Term
| the effect of adding N fertilizer when there's a straight line response curve |
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Definition
| the increase in yield obtained by adding N should have a value that is greater than the cost of the fertilizer. |
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Term
| the effect of adding N fertilizer when there's a curvilinear response curve |
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Definition
the increase in yield obtained by each additional unit of N decreases as the rate of N increases.
recall the law of diminishing returns |
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Term
| when the addition of N fertilizer should be stopped |
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Definition
| when the value of the crop obtained by an additional N increase is equal to the cost of the fertilizer N added to obtain that yield increase. |
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Term
| relationship between yield value and cost of fertilizer when there's a straight line response |
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Definition
dY x Py > dN x Pn or
dY/dN > Pn/Py
thus, Pn/Py < b
where dY = increase in yield with application of a given rate of fertilizer N (dN)
Py = value of each unit of crop yield (for example lb, or bushel)
dN = N rate applied (lb N/A)
Pn = cost of 1 lb N/A
b= dY/dN, which is the slope of the straight line Y = a + b(N rate) |
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Term
| the ideal ratio to apply N fertilizer |
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Definition
| The ratio of fertilizer price to crop price has to be lower than the slope of the line for it to be economical to apply fertilizer N. |
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Term
| the relationship between N fertilizer input and crop output when there's a curvilinear response to fertilizer input |
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Definition
at first: dY x Py > dN x Pn
then: dY x Py = dN x Pn or
dY/dN = Pn/Py |
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Term
| when increasing the N fertilizer input on a curvilinear response curve should be stopped |
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Definition
| when the slope of the line is equal to the ratio of unit price of fertilizer N to unit price of the crop |
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Term
| why increasing the N fertilizer input on a curvilinear response curve should be stopped when the slope of the line is equal to the ratio of unit price of fertilizer N to unit price of the crop |
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Definition
| because dY/dN is the slope of the curvilinear equation |
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