Table 2.

Type III sums of squares for rain-fed maize yield

Model parameter	Degrees of freedom	Sums of squares	F value	P value†
Intercept	1	567,895,174	600.4	0.002
Year	1	1,720,503,651	1,818.9	0.002
County	283	888,816,636	3.3	0.002
Tmax	1	54,345,824	57.5	0.002
P/PET	1	380,084	0.4	0.546
Tmax2	1	63,688,564	67.3	0.002
P/PET2	1	5,869,113	6.2	0.016
W126	1	44,226,186	46.8	0.002
Year*county	283	900,103,436	3.4	0.002
Tmax*P/PET	1	1,638,230	1.7	0.21
Tmax*P/PET2	1	1,192,597	1.3	0.258
P/PET*Tmax2	1	2,259,738	2.4	0.12
W126*P/PET	1	1,943,883	2.1	0.134
W126*Tmax	1	51,755,969	54.7	0.002
W126*P/PET2	1	1,068,479	1.1	0.234
W126*Tmax2	1	54,124,209	57.2	0.002
Residuals	6,932	6,556,987,586

^†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.