Table IV. Multiple regression analyses of εc in six major food crops

The final model and ranking of variables included in the final model were determined using the lowest AICc . Variable coefficients and significance were determined using the final model.

CropVariable RankModel a AICc Coefficient (10−3)P
Peanut (n = 51) YOR, St , T −540.1<0.001
1 T −536.00.426<0.001
2 YOR −531.80.123<0.05
3 St −526.6−0.002380.12
Soybean (n = 117) YOR, [CO2], St , T −1,270.2<0.0001
1 T −1,231.8−1.04<0.0001
2 St −1,226.3−0.00824<0.0001
3 [CO2] −1,204.30.0524<0.05
4 YOR −1,201.30.02930.21
Rice (n = 102) St , T −1,133.8<0.0001
1 St −1,125.0−0.00960<0.0001
2 T −1,014.3−0.729<0.01
Wheat (n = 159) YOR, St , T −1,451.2<0.0001
1 T −1,447.9−0.746<0.001
2 YOR −1,438.40.105<0.05
3 St −1,437.8−0.002840.13
Sorghum (n = 23)1 St −228.3−0.007390.11
Maize (n = 149) YOR, T −1,347.8<0.0001
1 YOR −1,346.00.346<0.0001
2 T −1,344.00.521<0.01
  • a Independent variables included YOR, mean annual [CO2] during the measurement period, T, and available St . Water available as precipitation and irrigation was included when sample size changed by less than 10% after including it in the analyses. Density was included in maize analyses but was not in the selected model.