Table 1.

Type III sums of squares for rain-fed soybean yield

Model parameter	Degrees of freedom	Sums of squares	F value	P value†
Intercept	1	42,427,808	377.0	0.002
Year	1	97,894,399	869.8	0.002
County	253	51,990,756	1.8	0.002
Tmax	1	6,534,829	58.1	0.002
P/PET	1	160,418	1.4	0.226
Tmax2	1	6,465,343	57.4	0.002
P/PET2	1	1,086,772	9.7	0.01
W126	1	2,028,804	18.0	0.002
Year*county	253	52,677,918	1.9	0.002
Tmax*P/PET	1	3,579	0.0	0.832
Tmax*P/PET2	1	512,755	4.6	0.032
P/PET*Tmax2	1	20,533	0.2	0.652
W126*P/PET	1	2,834,395	25.2	0.002
W126*Tmax	1	2,534,975	22.5	0.002
W126*P/PET2	1	2,019,730	17.9	0.002
W126*Tmax2	1	2,688,000	23.9	0.002
Residuals	6,210	698,922,185

^†P values were determined by comparing the F value in the table to a null F distribution that was generated by a double bootstrap procedure that accounted for spatial correlation. Thus, the P value in the table is different from that of a standard F test.