Term
why it is necessary to apply fertilizer at economic rates 

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 


Term
what an economic N rate is 

Definition
a rate that increases net income 


Term
some steps involved in determining economic N rates 

Definition
establishing field plots w/ different N rates analyzing the data taking into account the prices of the fertilizer applied and the crop produced 


Term
the objective of the Determining Economic N Rates exercise 

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 


Term

Definition
line that increases at a decreasing rate 


Term
equation for flat response curve 

Definition
Yield = a; where “a” is a constant 


Term
equation for a straight line response 

Definition
Yield = a + b(N rate); where “a” and “b” are regression coefficients 


Term
equation for a curvilinear response 

Definition
Yield = a + b(N Rate)  c(N Rate)^{2}, where “a”, “b”, and “c” are regression coefficients. 


Term
the effect of adding N fertilizer when there's a flat response curve 

Definition


Term
the effect of adding N fertilizer when there's a straight line response curve 

Definition
the increase in yield obtained by adding N should have a value that is greater than the cost of the fertilizer. 


Term
the effect of adding N fertilizer when there's a curvilinear response curve 

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 


Term
when the addition of N fertilizer should be stopped 

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. 


Term
relationship between yield value and cost of fertilizer when there's a straight line response 

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) 


Term
the ideal ratio to apply N fertilizer 

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. 


Term
the relationship between N fertilizer input and crop output when there's a curvilinear response to fertilizer input 

Definition
at first: dY x Py > dN x Pn then: dY x Py = dN x Pn or dY/dN = Pn/Py 


Term
when increasing the N fertilizer input on a curvilinear response curve should be stopped 

Definition
when the slope of the line is equal to the ratio of unit price of fertilizer N to unit price of the crop 


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 

Definition
because dY/dN is the slope of the curvilinear equation 

