Nitrogen Efects on Crested Wheatgrass as Related to Forage Quality Indices of Grass Tetany

Mayland, H.F. and Grunes, D.L. and Waggoner, H. and Florence, A. and Hewes, D.A. and Joo, P.K. (1975) Nitrogen Efects on Crested Wheatgrass as Related to Forage Quality Indices of Grass Tetany. Agronomy Journal. 67(3):411-414.

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Abstract

Nitrogen fertilization of forage is often accompanied by
an increased incidence of grass tetany. A field experiment
was established on two calcareous soils to evaluate
the effects of N fertilizer on forage quality indices of
grass tetany. Nitrogen, as NH₄NO₃, was applied at 0 and
150 kg N/ha in each of 2 years to separate plots. The
crested wheatgrass [Agropyron desertorum (Fisch.) Schult]
forage was harvested at regular intervals in the Spring
tetany period during 1968 through 1971. Forage was
analyzed for inorganic cations, N, total water-soluble carbohydrates
(TWSC), aconitic acid, higher fatty acids
(HFA), dry matter, and ash alkalinity — a measure of
total organic acids.

Nitrogen fertilizer increased the concentrations (equiv.
basis) of forage Mg and Ca more than the increase in K,
thus slightly reducing the K/(Ca + Mg) values when
compared to the unfertilized forage. However, forage
K/(Ca + Mg) values were usually less than the 2.2 value
above which the incidence of grass tetany increases rapidly.
The potential dietary benefits from the higher Mg
concentrations may have been offset by increased concentrations
of K, N, HFA, N/TWSC, and aconitic acid, since
these parameters are associated with decreased Mg availability
to cattle.

Low values for hypothetical blood serum Mg (calculated
from forage N, Mg, and K concentrations) coincided
with the occurrence of grass tetany in the field. The calculated
serum Mg values were lower in the N-fertilized
forage than in the control.

The aforementioned effects of N fertilization should
not deter the judicious use of N for optimizing forage
yields on semiarid ranges, since other research workers
have found that grass tetany losses can be reduced by
supplementing animals with Mg.

Item Type:	Article
NWISRL Publication Number:	0328
Subjects:	Irrigated crops > Grass forage > Chemistry Irrigated crops > Grass forage > Forage quality Mass Import - autoclassified (may be erroneous)
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:51
Last Modified:	15 Feb 2017 21:13
Item ID:	285
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/285