Chloride Fertilization Decreases the Dietary Cation-Anion Difference of Various Forage Species.

Chloride fertilization is known to increase Cl concentration and to decrease the dietary cation-anion difference (DCAD) of timothy but little information exists for other forage species. Eight forage species were sown at Normandin, QC, Canada (48°51'N, 72°32'W) in 2006 and 2007, and harvested in 2007 and 2008, respectively, to determine their response to two Cl fertilization treatments (0 and 140 kg Cl ha^-1 as CaCl₂) applied in a split application: 64% in early spring and 36% after first harvest. Each species was harvested twice a year at around their recommended harvest stage of development. The experimental design was a split-plot with four replicates; species as main plots and Cl fertilization as sub-plots. Forage Na, K, Cl, and S concentrations were determined and the DCAD (Na + K – Cl – S) was then calculated.

Forage DCAD (mEq kg-1 DM) of eight species fertilized or not with Cl.
		Spring growth (kg Cl ha-1)			Summer regrowth (kg Cl ha-1)
Species		0	90		0	50
Alfalfa		438	338		504	397
Red clover		486	307		612	375
Smooth bromegrass		387	309		471	264
Meadow bromegrass		376	298		504	335
Tall fescue		413	224		566	297
Timothy		369	213		298	121
Reed canarygrass		342	141		303	84
Kentucky bluegrass		217	127		226	138

Chloride fertilization decreased the DCAD of all forage species; this decrease ranged from 78 (smooth and meadow bromegrass) to 201 mEq kg^-1 DM (reed canarygrass) in spring and from 88 (Kentucky bluegrass) to 269 mEq kg^-1 DM (tall fescue) in summer. Species differed in their DCAD with legume species having the highest and timothy, reed canarygrass, and Kentucky bluegrass having the lowest. Producing forage with a DCAD lower than the target maximal value of 250 mEq kg^-1 DM is possible without Cl fertilization in Kentucky bluegrass and with Cl fertilization in timothy and reed canarygrass.