Partition of Mg in Forages as Affected by Fertilization, Species, Growth Stage, and Sample Preparation¹

Abstract

A 2‐year study was conducted in order to study the chemical form of Mg in different grass and legume species that are commonly used for livestock feeding in the Northeastern United States. Orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), and alfalfa (Medicago sativa L.) were treated with magnesium sulfate (MgSO4. 7H2O) and dolomitic limestone (CaCO3.MgCO3) at 280 kg Mg ha−1, or with no Mg fertilizer. The soil was a fine, loamy, mixed, mesic Hapludalf. Grass species received 34 or 224 kg N ha−1 as NH4NO3. In the 1st year samples were taken at four growth stages, prepared as fresh, oven‐dried or freeze‐dried herbage and partitioned into acetone soluble, water soluble, and acetone and water insoluble fractions. In the 2nd year samples were taken at two growth stages and prepared as fresh material only. Fertilization with MgSO4. 7H2O increased (P<0.01) total Mg concentrations in herbage compared to CaCO3. MgCO3 and no Mg treatments. High N fertilization of the grass species increased (P<0.01) total Mg levels compared to low N treatments. Magnesium as percent total Mg in each chemical fraction was affected (P<0.05) by forage species, stage of maturity and method of sample preparation and ranged from 0.7 to 24.8% (x̄ = 6.7%) for acetone soluble, 42.8 to 82.3% (x̄ = 65.7%) for water soluble, and 15.5 to 42.9% (x̄ = 27.6%) for acetone and water insoluble Mg fractions over all treatments. The proportion of total Mg in the water soluble fraction was higher (P<0.05) at mature growth stages for alfalfa and tall fescue compared to orchardgrass and the proportion of Mg extractable with acetone was less (P<0.0001) for dried compared to fresh sample preparations. Although fertilizer treatments affected total herbage Mg concentrations, there was no apparent effect of fertilization upon the chemical form of Mg in the plant.

Ruminal Solubility of Nitrogen and Minerals from Fescue and Fescue-Red Clover Herbage

“…The average solubility of Ca, Mg and K in our study showed good agreement with waterand acetone-soluble fractions of these elements in tall fescue, ryegrass and red clover (Todd, 1961;Grace et al, 1977;Shockey and Reid, 1984). It appears therefore that disappearance of these elements after 3 h of incubation is largely associated with the cell-soluble fraction and that any further disappearance will involve the insoluble, cell wall bound fraction.…”

Influence of the phenological stages on ionic alterations in aubergine plants (eggplant)

“…2) may have been due to marked fluctuations in some fractions of this element. Our findings for Mg 2 * behavior in aubergine are similar to those reported for other species by Mclntosh et al (1973) and Shockey and Reid (1984). In general, foliar Mg increased, with slight changes coinciding with different stages of plant development.…”

Applications in sustainable production

“…However, this does not mean that leaf levels of the Mg fractions cannot be high, since although the antagonistic effect does not facilitate the transport of the divalent cation it is not totally impeded (Addiscott, 1974), so dramatic nutritional changes do not occur and the rhythm of the plant is not greatly disturbed. In general, the levels of the different Mg fractions were similar to those obtained for other species (Shockey and Reid, 1984;López-Cantarero and Romero, 1993), with any differences, probably due to the growing conditions and particular nutritional requirements of each species.…”