Effect of Land Application of Phosphorus-Saturated Gypsum on Soil Phosphorus in a Laboratory Incubation

Table 2

Treatments resulting from combination of phosphorus saturation level (expressed as a percent of the isotherm maximum) and gypsum application rate and the resulting application rates of phosphorus (P) and calcium (Ca), and their effect on soil water extractable P (WEP) and Mehlich 3 P (M3P) concentrations, averaged across time and soil type.

Treatment combination^†	Phosphorus saturation Level	Gypsum application Rate	P application rate	Ca application rate	Gypsum application rate	WEP^‡	M3P^‡
	% of maximum	(Mg ha^−1)	(kg ha^−1)		(Mg ha^−1)	(mg kg^−1)
LP-LG	25%	5.6	35	1232	5.6	4.5 b	61.9 c
HP-LG	75%	22.4	105	1232	22.4	7.1 b	70.4 b
LP-HG	25%	5.6	140	4928	5.6	6.6 b	76.2 b
HP-HG	75%	22.4	420	4928	22.4	20.8 a	117.3 a

^†LP−LG, low phosphorus—high gypsum; HP-LG, high phosphorus—low gypsum; LP-HG, low phosphorus—high gypsum; HP-HG, high phosphorus—high gypsum.
^‡Means followed by different letters were determined to be significantly different at 𝑃<0.05.