Influence of Tropical Climate Parameters on Properties of Acid Sulfate Soils for Sustainable Oil Palm Cultivation

Table 8

Results of stepwise multiple regression analysis on climate and soil variables.

Climate parameter^a	Soil property^b	Adjusted R^2	F value	Regression equation^ab
Topsoil of Central Plain
SR	Cla	0.332	5.464	Cla = 1208.807SR − 21836.138
Subsoil-1 of Central Plain
SR	CEC	0.488	9.584	CEC = 160.904SR − 2964.165
Subsoil-2 of Central Plain
SR	pH1:1-H2O	0.567	12.788	pH-H2O = -12.160SR + 229.890
Rootzone of Central Plain
SR	Sil	0.513	31.591	Sil = -1246.185SR + 23500.175
WD	Acid-BC	0.114	4.719	Acid-BC = 33.102WD − 6697.325
Topsoil of Southeast Coast
MinT	Cla	0.456	8.552	Cla = 653.538MinT − 15356.974
Subsoil-1 of Southeast Coast
WVP	Cla	0.412	7.294	Cla = 12485.157WVP − 35328.988
Subsoil-2 of Southeast Coast
MinT	AWC	0.429	7.752	AWC = 20.222MinT − 458.125
SR	Exch-Mg	0.682	20.297	Exch-Mg = -51.119SR + 949.075
Rootzone of Southeast Coast
MinT	Cla	0.484	28.231	Cla = 686.109MinT − 16119.176
SR	Exch-Na	0.238	10.045	Exch-Na = -13.199SR + 245.424
SR	Sil	0.191	7.848	Sil = -240.493SR + 4811.905
WVP	Acid-BC	0.160	6.525	Acid-BC = 4053.929WVP − 11432.263

^aTopsoil = Ap; Subsoil-1 = Ap–60 cm; Subsoil-2 = 60–100 cm; Rootzone = top 100 cm; SR = daily solar radiation; WD = annual water deficit; MinT = annual minimum temperature; WVP = annual water vapor pressure. ^bAcid-BC = acid buffering capacity; Sil = silt content; Cla = clay content; Exch-Na = exchangeable sodium; CEC = cation exchange capacity; pH_1:1-H₂O = soil pH by water; AWC = available water capacity; Exch-Mg = extractable magnesium. ^,,Significance at 5%, 1%, and 0.1% alpha levels, respectively.