Table 2 Corn and Soybean Yield Models in Ontario 1959–2013 Using Fixed Effects Models with Alternative Effects of CO2 Concentration (a: N = 1594, b: N = 829) ***, **, and * indicate significant coefficients with significance level of 0.01, 0.05, and 0.1, respectively.

From: A Bio-Economic Crop Yield Response (BECYR) Model for Corn and Soybeans in Ontario, Canada for 1959–2013

Versions of Crop Yield Model

Corn Yield Model

(Dependent Variable = Grain Corn Yields)

Effects of CO2

No CO2 Effect

Linear CO2 Effect

Quadratic CO2 Effect

Independent Variables

Precipitation Before Growing Season

−0.1091***

−0.1088***

−0.08372**

(0.04055)

(0.04156)

(0.04095)

Precipitation During Growing Season

0.1697***

0.1697***

0.1631***

(0.01649)

(0.01646)

(0.01645)

Degree Days During Growing Season

0.1869***

0.1867***

0.1866***

(0.02179)

(0.02210)

(0.02160)

Corn Price Lagged One-Year

25.70***

25.71***

21.82***

(2.057)

(2.05)

(1.958)

Fertilizer Price Index

−71.29***

−71.33***

−92.88***

(8.952)

(8.789)

(9.069)

Trend

0.2906*

0.2563

2.737***

(0.1691)

(0.3211)

(0.4153)

Local CO2 During Growing Season

 

0.04453

−16.35***

 

(0.4454)

(1.77)

Square of Precipitation Before Growing Season

0.0002489***

0.0002483***

0.0001937**

(0.00008557)

(0.00008762)

(0.00008565)

Square of Precipitation During Growing Season

−0.0001594***

−0.0001595***

−0.0001517***

(0.00001669)

(0.00001668)

(0.00001733)

Square of Degree Days During Growing Season

−0.00006497***

−0.00006496***

−0.00006460***

(0.000009012)

(0.000009010)

(0.000008757)

Square of Corn Price Lagged One-Year

−4.002***

−4.000***

−3.589***

(0.3407)

(0.3424)

(0.3330)

Square of Fertilizer Price Index

22.59***

22.60***

28.90***

(2.755)

(2.723)

(2.821)

Square of Trend

0.02325***

0.02275***

−0.01624**

(0.002395)

(0.006010)

(0.007021)

Square of Local CO2 During Growing Season

  

0.02315***

  

(0.002384)

Interaction of Precipitation and Degree Days

0.0002266***

0.0002265***

0.0002201***

(0.00002119)

(0.00002121)

(0.00002066)

Adjusted R-Square

0.7869

0.7864

0.7919

F-Value

503.0

466.7

453.4

 

Soybean Yield Model

(Dependent Variable = Soybean Yields)

Effects of CO2

No CO2 Effect

Linear CO2 Effect

Quadratic CO2 Effect

Independent Variables

Dummy of 2001

−11.53***

−11.36***

−11.09***

(0.9217)

(1.000)

(0.9876)

Precipitation Before Growing Season

0.03554

0.03759

0.04349*

(0.02401)

(0.02498)

(0.02545)

Precipitation During Growing Season

0.07197***

0.07143***

0.07058***

(0.01073)

(0.01047)

(0.01048)

Degree Days During Growing Season

0.05434***

0.05310***

0.05020***

(0.007541)

(0.008941)

(0.009281)

Soybean Price Lagged One-Year

7.582***

7.607***

7.405***

(0.6085)

(0.6106)

(0.6094)

Fertilizer Price

−50.25***

−50.55***

−53.39***

(4.79)

(4.635)

(4.623)

Trend

0.03450

−0.05598

0.6310***

(0.07523)

(0.1765)

(0.2175)

Local CO2 During Growing Season

 

0.1208

−3.352***

 

(0.2431)

(0.7144)

Square of Precipitation Before Growing Season

−0.00005486

−0.00005929

−0.00007115

(0.00005219)

(0.00005418)

(0.0000553)

Square of Precipitation During Growing Season

−0.00005729***

−0.00005694***

−0.00005612***

(0.000009761)

(0.000009549)

(0.000009665)

Square of Degree Days During Growing Season

−0.00001680***

−0.00001649***

−0.00001522***

(0.000002806)

(0.000003148)

(0.000003289)

Square of Soybean Price Lagged One-Year

−0.5621***

−0.5635***

−0.5658***

(0.05585)

(0.05606)

(0.05649)

Square of Fertilizer Price

15.24***

15.34***

16.12***

(1.515)

(1.466)

(1.461)

Square of Trend

0.006238***

0.004846

−0.001959

(0.001078)

(0.003289)

(0.003687)

Square of Local CO2 During Growing Season

  

0.004658***

  

(0.0009189)

Interaction of Precipitation and Degree Days

0.00003381***

0.00003385***

0.00003522***

(0.000008023)

(0.000008022)

(0.000008045)

Adjusted R-Square

0.6529

0.6522

0.6535

F-Value

124.2

115.8

109.6

  1. The values in parentheses are standard errors. Precipitation before growing season means the precipitation in the 3 months prior to the start of the growing season. The growing season is defined as starting on the day following the last occurrence of −2.2 °C in spring and ending on the day preceding the first occurrence of −2.2 °C in fall. The degree days during the growing season refers to the degree days above 10 °C during the growing season. The crop price in Ontario and fertilizer price index in Canada is adjusted the inflation by annual all items CPI (2002 = 100). CO2 concentration is the combination of the proxy of CO2 (1959–2004) and actual CO2 (2005–2013) in Ontario.
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