Potassium Fertilization Effects on Alfalfa in a Mediterranean Climate

Abstract

Potassium fertilization rates for alfalfa (Medicago sativa L.) have been increasing with intensive cropping systems or decreasing with policies that generally lead to reduced fertilizer inputs. In this case, nutrient buildup or maintenance of high soil test levels may not be desirable and drawdown of K reserves may be beneficial in the short term. The objective of this research was to evaluate the effects of potassium fertilization of alfalfa in areas of high soil exchangeable K levels and long growing seasons. A field experiment was established under irrigation from 1993 to 1997 in the Mediterranean environment of the Ebro Valley (Spain) on a silty clay loam soil. The treatments were five annual rates of K (0, 41.5, 83, 166, and 332 kg K ha-1) and two rates of K (166 and 332 kg K ha-1) applied prior to seeding on two alfalfa cultivars. The average annual dry matter (DM) yield was 21.5 Mg ha-1 and showed a small linear response to K fertilization (Pr > F = 0.0589). Total K removal in the herbage increased linearly with each rate of K and reached 1728 kg K ha-1 with the application of 332 kg K ha-1 yr-1, compared with 1546 kg K ha-1 without K fertilization. At the end of the experiment, soil ammonium acetate extractable K (Ke) increased little with K rates, and the differences were observed only in the first 30 cm of depth. Despite the uptake of 1546 kg K ha-1, soil Ke values did not change appreciably, suggesting that much of the K uptake was derived from the fertilizer and from nonexchangeable soil K fractions. Although K fertilization slightly increased alfalfa DM yields in this high testing Mediterranean soil, the economic benefit of this limited response does not justify the expense.

Full text

SOIL FERTILITY
Potassium Fertilization Effects on Alfalfa in a Mediterranean Climate
Jaime Lloveras,* Javier Ferran, Jaime Boixadera, and Jordi Bonet
ABSTRACT kg
⫺
1
, using short-season dormant or semidormant culti-
vars with reported annual DM yields of alfalfa that
Potassium fertilization rates for alfalfa (Medicago sativa L.) have
ranged generally between 10 and 15 Mg ha
⫺
1
in three
been increasing with intensive cropping systems or decreasing with
policies that generally lead to reduced fertilizer inputs. In this case,
to four harvests per season (Markus and Battle, 1965;
nutrient buildup or maintenance of high soil test levels may not be
Lutz, 1973; Smith, 1975; Rominger et al., 1976; Fixen
desirable and drawdown of K reserves may be beneficial in the short
and Ludwick, 1983; Barbarick, 1985; Alva et al., 1986;
term. The objective of this research was to evaluate the effects of
Sheaffer et al., 1986; Burmester et al., 1991; Razmjoo
potassium fertilization of alfalfa in areas of high soil exchangeable K
and Henderlong, 1997). The reported results of these
levels and long growing seasons. A field experiment was established
trials show that the effects to the applications of K varied
under irrigation from 1993 to 1997 in the Mediterranean environment
with production practices, growing conditions, and soil
of the Ebro Valley (Spain) on a silty clay loam soil. The treatments
K contents, ranging from no DM yield response with
were five annual rates of K (0, 41.5, 83, 166, and 332 kg K ha
⫺
1
) and
the application of 300 kg K ha
⫺
1
with a soil test level
two rates of K (166 and 332 kg K ha
⫺
1
) applied prior to seeding on
of 75 mg K kg
⫺
1
(Lutz, 1973) to a maximum response
two alfalfa cultivars. The average annual dry matter (DM) yield was
21.5 Mg ha
⫺
1
and showed a small linear response to K fertilization
with the application 448 kg K ha
⫺
1
for a soil with extract-
(Pr ⬎F⫽0.0589). Total K removal in the herbage increased linearly
able K of 55 mg K kg
⫺
1
(Rominger et al., 1976). These
with each rate of K and reached 1728 kg K ha
⫺
1
with the application
studies show that in general, K application increased
of 332 kg K ha
⫺
1
yr
⫺
1
, compared with 1546 kg K ha
⫺
1
without K
plant and soil K concentrations.
fertilization. At the end of the experiment, soil ammonium acetate
Although a survey of soil fertility and forage manage-
extractable K (K
e
) increased little with K rates, and the differences
ment specialists indicates that additional K is rarely
were observed only in the first 30 cm of depth. Despite the uptake
recommended when the concentration of exchangeable
of 1546 kg K ha
⫺
1
, soil K
e
values did not change appreciably, suggesting
K is greater than 300 kg ha
⫺
1
(about 150 mg K kg
⫺
1
)in
that much of the K uptake was derived from the fertilizer and from
the surface soil layer (Lanyon and Smith, 1985), the
nonexchangeable soil K fractions. Although K fertilization slightly
sufficiency levels for adequate soil K are much less clear
increased alfalfa DM yields in this high testing Mediterranean soil, the
economic benefit of this limited response does not justify the expense.
(Lanyon and Griffith, 1988). In fact, results from Colo-
rado (Barbarick, 1985), on soils with high levels of ex-
changeable K (from 308 to 335 mg K kg
⫺
1
) under irriga-
tion, found that application of 375 kg ha
⫺
1
of K increased
A
lfalfa fertilizer applications have been changing 4-yr DM yields from 52.7 to 55.6 Mg ha
⫺
1
, showing that
with production practices. They have been increas- alfalfa yield responses to K applied to a soil high in K
ing with more intensive cropping systems (Smith, 1975; are possible.
Lanyon and Griffith, 1988; Vough and Decker, 1992) In France, Ballif and Duthil (1976) obtained the high-
or decreasing and even withheld (Havlin et al., 1984; est alfalfa DM yields with applications of 166 and 325
Jouany et al., 1996; Swoboda, 1998) due to changes in kgKha
⫺
1
yr
⫺
1
, raising the 2-yr DM production from
agricultural and environmental policies (EU Commis- 15.4 Mg ha
⫺
1
to 17.6 Mg ha
⫺
1
. Soil exchangeable K levels
sion, 1993) that lead generally to lower prices. With in the top 20 cm of nonfertilized plots were reduced
reducing agricultural profits, nutrient buildup or mainte- from 270 to 80 mg kg
⫺
1
. Higher responses to K were
nance of high soil test levels may not be economically reported by Kafkafi et al. (1977), in irrigated eastern
desirable and drawdown of K reserves may be economi- Mediterranean conditions, where yields were raised
cal in the short term (Havlin et al., 1984; Mallarino et from 15.2 Mg ha
⫺
1
with0Kto20.9 Mg DM ha
⫺
1
with
al., 1991). Therefore, there is interest in designing field applications of 316 kg K ha
⫺
1
in a soil with initial K
experiments to evaluate the response to K fertilization values of about 180 mg K kg
⫺
1
.
in alfalfa, which has a high K requirement, in order to Although it is known that alfalfa can remove large
maintain high yields in intensive production systems amounts of K in intensive production systems, there are
(Lanyon and Smith, 1985). limited data on K fertilization from areas with high soil
Research involving applications of K for alfalfa has K levels (Havlin et al., 1984) or long growing seasons
been conducted mainly in the northeastern or midwest- with alfalfa dormancy ratings of 8 and 9 and crop yields
ern regions of the USA on soils responsive to this nutri- of 20 to 25 Mg ha
⫺
1
yr
⫺
1
under irrigation (Dovrat, 1993;
ent with soil test K levels between 30 and 230 mg K Kafkafi et al., 1977; Lloveras et al., 1998).
In the Mediterranean areas of southern Europe, pres-
UdL-IRTA, Av. Rovira Roure 177, 25198, Lleida, Spain. Received
1 Apr. 1999. *Corresponding author (jaume.lloveras@irta.es).
Abbreviations: DM, dry matter; K
e
, soil ammonium acetate extract-
able potassium.Published in Agron. J. 93:139–143 (2001).
139

140
AGRONOMY JOURNAL, VOL. 93, JANUARY–FEBRUARY 2001
were calculated on this basis. Ground (1-mm screen) plant
ent recommendations of between 200 and 350 kg K ha
⫺
1
tissue samples were analyzed for several nutrients. Total N
yr
⫺
1
are normally based on the amounts of K removed
was analyzed by a conventional Kjeldahl method. Potassium,
by the crop (Hidalgo, 1969; Le Gall et al., 1992). In this
Ca, P, Mg, B, Cu, Fe, Mn, and Zn contents were analyzed by
research we evaluated the effect of K fertilization on
inductively coupled argon plasma spectrophotometry (Poly-
alfalfa yield and nutrient uptake in irrigated production
scan 61E; Thermo Jarrell-Ash Corporation, Franklin, MA)
systems with high soil exchangeable K levels in a Medi-
after digesting the calcinated plant ashes with hydrocholoric
terranean climate.
acid.
Soil samples for determination of exchangeable K were
taken from every plot and from the 0- to 30- and 30- to 60-cm
MATERIALS AND METHODS
soil depths at the end of each growing season (prior to fertiliza-
The experiments were conducted under irrigation during tion). In addition, at the final sampling on December 1997,
four growing seasons (1994 to 1997) at the IRTA-University core soil samples also were taken from a 60- to 90-cm depth.
of Lleida research fields at Palau de Anglesola (Ebro Valley, Soil samples collected prior to planting were air-dried but all
Spain, 41⬚39⬘N, 0⬚51⬘E, altitude 180 m). The soil was an subsequent soil samples were analyzed as field moist samples.
Oxyaquic Xerofluvent, representative of the Ebro Valley, with Thus K data for the first year prior to seeding and from
a silty clay loam texture (397 g kg
⫺
1
clay). subsequent years unfortunately cannot be directly compared.
Analysis of a composite sample (0–30 cm depth) collected
from the experimental site revealed that pH (water) was 8.4,
available P was 14 mg kg
⫺
1
(Olsen method), available K was
RESULTS AND DISCUSSION
317 mg kg
⫺
1
(NH
4
OAc method), organic matter was 14 g kg
⫺
1
,
Forage Yields
and CaCO
3
equivalent was 310 g kg
⫺
1
. The exchangeable bases
Ca, Mg, Na, and K were 33, 4.91, 0.25, and 0.89 cmol
c
kg
⫺
1
Although the main effect of K was not significant in
respectively, whereas at 30 to 60 cm they were 33, 4.92, 0.27,
any year or for the total 4-yr production, the total 4-yr
and 0.53 cmol
c
kg
⫺
1
respectively. The total cation exchange
herbage DM yields showed a linear response (Pr ⬎F⫽
capacity was 39.06 and 38.7 cmol
c
kg
⫺
1
for the 0- to 30- and
0.0589) to K fertilization rates (Table 1). The mean of
30- to 60-cm depths, respectively. An estimation of minerals
the two highest rates (166 and 332 kg K ha
⫺
1
yr
⫺
1
) was
in the clay fraction with X-ray showed that illite was the
87.4 Mg DM ha
⫺
1
whereas the control and the 41.5 kg
dominant mineral (Roquero, 1979). The average temperature
K annual rate yielded a mean of 84.5 Mg DM ha
⫺
1
,
is 11.1⬚C and the average rainfall is 433 mm.
which is a difference of about 2.8 Mg DM ha
⫺
1
in 4 yr
The treatments were seven K fertilizer rates broadcast on
two adapted alfalfa cultivars, ‘Arago
´n’ and ‘P5929’ (dormancy
(0.70 Mg DM ha
⫺
1
per year). The lower yields observed
ratings 8–9). The fertilizer treatments, applied as KCl, con-
in the fourth year of production are common in the
sisted of five annual broadcast rates of 0, 41.5, 83, 166, and
irrigated areas of the Ebro Valley, mainly due to stem
332 kg ha
⫺
1
of K and two other treatments of 166 and 332 kg
nematode (Ditylenchus dipsaci) (Lloveras et al., 1994).
ha
⫺
1
of K prior to seeding. Fertilizer treatments following
The cultivar ⫻fertilizer treatment interaction was not
the initial preplant applications were topdressed in winter
significant, although ‘Arago
´n’ alfalfa yielded (89.7 Mg
(January). The crop also received an annual application of 44
DM ha
⫺
1
) significantly more than ‘P5929’ (82.3 Mg DM
kg P ha
⫺
1
. At seeding the plots were also fertilized with 3 kg
ha
⫺
1
). No significant yield differences were found when
Bha
⫺
1
,49kgMgha
⫺
1
, and 62 kg S ha
⫺
1
.
comparing annual fertilizer rates of 41.5 and 83 kg K
The experiment was seeded on 16 Sept. 1993 at a seeding
ha
⫺
1
yr
⫺
1
applied topdressed with the same total 4-yr
rate of 20 kg ha
⫺
1
in rows 20 cm apart. Plots were 1.5 ⫻6m.
amount of K applied at once at seeding (166 and 332
The previous crop was wheat (Triticum aestivum L.). Plots
were irrigated every 12 to 16 d from April to September,
kgKha
⫺
1
). This result suggests that in medium textured
receiving a total of about 900 mm of water per growing season.
soils, with the rates of K studied, all the fertilizer, at
The experimental design was a split-plot in space and time
least up to 332 kg K ha
⫺
1
, could be applied at seeding
(Steel and Torrie, 1980) with four replications. The K treat-
without any yield depression.
ments were the main plots and the alfalfa cultivars the sub-
The small yield increases obtained in this study (2.8
plots. The results were subjected to analysis of variance with
the General Linear Model procedure of the Statistic Analysis
Table 1. Alfalfa yield response to K fertilization. Mean of two cul-
System (SAS Institute, 1988).
tivars.
Alfalfa yield was determined by harvesting the whole plot.
Six cuttings were harvested each year at the mid to full flow-
Dry matter yields
ering stage, except for the first and the last cut of the year,
Cultivar
where the crop does not flower because of the photoperiod.
Treatment K 1994 1995 1996 1997 Total Arago
´n P5929
The first harvest was about mid-April and the last at the end
of October with a period of about 30 d between harvests
kg ha
⫺
1
Mg ha
⫺
1
(Lloveras et al., 1998). Insects were controlled by spraying
1 0 24.0 24.8 22.7 13.5 85.0 88.0 82.1
2 41.5 annually 23.7 24.8 21.9 13.7 84.0 87.8 80.3
0.1 kg ha
⫺
1
a.i. fenvalerate [cyano(3-phenoxyphenyl)methyl
3 83 annually 23.1 24.6 22.6 15.4 85.8 89.7 81.9
4-cholo-(1-methylethyl)benzeneacetate] two to five times per
4 166 annually 24.6 24.8 23.0 14.7 87.2 91.7 82.6
year. Weeds were controlled by applying 1 kg ha
⫺
1
a.i. hexazi-
5 332 annually 23.9 25.5 23.6 14.6 87.6 90.2 85.1
none [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-
6 166 at seeding 23.9 25.0 22.9 14.1 85.9 89.4 82.5
7 332 at seeding 23.7 25.2 22.3 15.1 86.4 90.8 81.9
2,4(1H,3H)-dione] in January. The alleys between blocks were
maintained weed free by rotary tilling.
Main K treatment effect NS† NS NS NS NS NS NS
Linear (Treatments 1 to 5) NS NS NS NS * NS NS
A 500-g wet sample of herbage was collected from each plot
at each harvest for moisture determination and subsequent
* Significant at the 0.05 probability level.
† Nonsignificant.
chemical analysis. Samples were dried at 70⬚C and DM yields

LLOVERAS ET AL.: K FERTILIZATION ON ALFALFA IN MEDITERRANEAN CONDITIONS
141
Table 2. Annual and 4-yr weighted average concentrations of K, N, P, Ca, and Mg in alfalfa herbage under K fertilization treatments.
Annual K concentration 4-yr weighted average concentrations
Treatment K 1994 1995 1996 1997 K N P Ca Mg
kg ha
⫺
1
gkg
⫺
1
gkg
⫺
1
1 0 24.3 16.8 14.4 16.2 18.1 30.7 2.33 22.9 3.27
2 41.5 annually 23.8 17.5 13.9 16.0 18.1 31.1 2.35 21.9 3.24
3 83 annually 25.0 18.3 14.9 16.8 18.9 30.9 2.38 22.8 3.24
4 166 annually 24.5 17.9 15.1 17.7 18.9 30.8 2.32 22.7 3.22
5 332 annually 25.5 18.2 16.4 18.2 19.7 31.0 2.31 21.9 3.06
6 166 at seeding 24.5 17.0 14.3 15.7 18.1 31.0 2.33 22.7 3.24
7 332 at seeding 25.6 17.8 14.3 16.4 18.8 30.7 2.37 22.6 3.24
Main K treatment effect * NS† ** ** ** NS NS NS **
Linear (Treatments 1 to 5) ** NS ** ** ** NS NS NS **
No.6and7vsNo.2and3 NSNS NS NS NSNSNSNSNS
* Significant at the 0.05 probability level.
** Significant at the 0.01 probability level.
† Nonsignificant.
Mg DM ha
⫺
1
in 4 yr) are similar to the responses re- exchangeable K, found that the K concentration of the
ported by others on soils high in K (Jones et al., 1974; tissue increased from 8.9 to 20.5 g kg
⫺
1
when K fertiliza-
Havlin et al., 1984; Barbarick, 1985). The yield increases tion rates increased from 0 to 448 kg K ha
⫺
1
.
in our study were lower than the increases reported by In this study, herbage K concentration differences
Kafkafi et al. (1977) in Mediterranean conditions. They between treatments varied little with the age of the
increased DM yields from 15.2 Mg ha
⫺
1
with 0 K fertil- stand, probably because the differences in soil test levels
ization to 20.9 Mg ha
⫺
1
with 498 kg K ha
⫺
1
in a soil with between K treatments also were small (Table 3). The
an initial K content of about 180 mg K kg
⫺
1
.total amount of K removed with the herbage increased
These results suggest that in high yielding conditions linearly with applied K (Table 4). Removal of K reached
alfalfa yield increases with K fertilization are very lim- 1728 kg ha
⫺
1
with the application of 332 kg K ha
⫺
1
yr
⫺
1
,
ited in soils with high exchangeable K levels. compared with 1546 kg K ha
⫺
1
for the 0 K fertiliza-
tion treatment.
Herbage Mineral Concentrations
Average P and Ca concentrations in the herbage were
not significantly affected by increasing K rates (Table
The average 4-yr K concentration in the herbage and 2). A linear decrease in Mg concentrations, however,
average annual concentrations in three of four growing was seen with K fertilization rates, as has been reported
seasons increased linearly with increasing K fertilization in other studies (Smith, 1975; Rominger et al., 1976;
rates (Table 2). The small increase in K concentration, James et al., 1995). The observed P, Ca, and Mg concen-
from 18.1 to 19.7 g kg
⫺
1
with increasing K fertilization tration values were similar to those of other studies
rates, is quite similar to the results reported Barbarick conducted in the Ebro Valley and in the USA (Heras
(1985) and Havlin et al. (1984) in soils high in K.
and Montan
˜es, 1974; Smith, 1975; Sheaffer et al., 1986;
On soils responsive to K fertilization, the tissue con-
James et al., 1995).
centration of K presented a much higher increase.
The K treatments did not affect the N concentration
Sheaffer et al. (1986), in a soil with 35 mg K kg
⫺
1
, found
of the herbage, which suggests that the supply of K was
that K tissue contents increased from 11.4 to 25.3 g kg
⫺
1
already adequate for maximum N
2
fixation (Collins et
when K fertilization rates increased from 0 to 334 kg K
ha
⫺
1
. Smith (1975), in a soil with about 128 mg kg
⫺
1
of al., 1986).
Table 3. Soil ammonium acetate extractable K (K
e
) concentrations at different depths (cm) during the experiment.
K
e
concentration
1994 1995 1996 1997 (final harvest)1993†
Treatment K 0–30 0–30 30–60 0–30 30–60 0–30 30–60 0–30 30–60 60–90
kg ha
⫺
1
gkg
⫺
1
1 0 426 283 188 272 211 226 182 261 213 144
2 41.5 annually 417 279 187 276 217 221 184 279 205 159
3 83 annually 442 271 192 271 221 235 196 272 212 148
4 166 annually 461 259 201 275 219 231 192 279 208 140
5 332 annually 447 317 202 308 222 250 207 315 219 165
6 166 at seeding 427 258 200 269 231 217 182 244 200 136
7 332 at seeding 427 315 198 279 222 228 194 262 208 147
Main effect – NS‡ NS NS NS ** NS ** NS NS
Linear (Treatments 1 to 5) – NS NS * NS ** * ** NS NS
No. 6 and 7 vs No. 2 and 3 – NS NS NS NS NS NS NS NS NS
* Significant at the 0.05 probability level.
** Significant at the 0.01 probability level.
† Initial soil test levels. Air-dried soil samples.
‡ Nonsignificant.

142
AGRONOMY JOURNAL, VOL. 93, JANUARY–FEBRUARY 2001
Table 4. Balance of K in K fertilization treatments, 1994 –1997.
riod) without reaching levels expected from nutrient
balance estimates.
Fertilizer
Treatment K inputs Uptake Balance
Havlin et al. (1984), also working in calcareous soils
but with a low K
e
(126 mg K kg
⫺
1
), found a substantial
kg ha
⫺
1
kgKha
⫺
1
1 0 0 1546 ⫺1546
buildup of K
e
for the high K application rates. But they
2 41.5 annually 166 1524 ⫺1358
also found that the K
e
for the treatment with 0 kg K
3 83 annually 332 1628 ⫺1296
ha
⫺
1
changed little with time, suggesting that the high
4 166 annually 664 1654 ⫺990
5 332 annually 1328 1728 ⫺400
illite content may account for the observed K buff-
6 166 at seeding 166 1561 ⫺1395
ering capacity.
7 332 at seeding 332 1631 ⫺1299
The results of this study showed that K fertilization
Main effect ** **
had a limited (p⫽0.059) effect on alfalfa DM yield in
Linear (Treatments 1 to 5) ** **
No.6and7vsNo.2and3 NS† NS
intensive Mediterranean production systems. However,
the economical benefit of this limited response to K by
** Significant at the 0.01 probability level.
† Nonsignificant.
alfalfa does not justify the cost of fertilization. The re-
sults also showed that rates of K usually considered high
were not sufficient to offset the K removed by the alfalfa.
Soil Extractable Potassium
Soil extractable K values prior to alfalfa seeding can-
ACKNOWLEDGMENTS
not be used together with the values collected in other
We express our gratitude to COPOSA (Comercializadora
seasons. The seeding year values were higher than in
de Potasa S.A.) who partially supported the study and in
any other year because in that year soil analyses were
particular to J. Salazar. We also thank J. Diaz Espada, J.
conducted only on dry samples, which often result in
Llobera, M. Baga, J. Del Campo, A. Lopez, J.L. Millera, J.A.
different values than determinations made with moist
Betbese, and R. Mestre from UdL-IRTA for their field and
soils (Mengel and Kirkby, 1980).
laboratory assistance as well as Dr. R. Salvador, A. Mallarino,
Soil K measured at the end of each of the four growing
P. Hinz, and I.C. Anderson of Iowa State University for their
seasons is shown in Table 3. The K
e
values in the 30-cm
technical and statistical assistance. Dr. F. Macias of the Uni-
depth showed significant linear effects with K fertiliza-
versidad de Santiago de Compostela provided the analysis of
tion, although with low slope. The increase in soil K
e
the clay minerals.
concentration in the 30-cm depth (24 to 54 mg kg
⫺
1
)
with the application of 332 kg K ha
⫺
1
yr
⫺
1
in the last REFERENCES
two growing seasons was small compared with the high
Alva, A.K., L.E. Lanyon, and K.T. Leath. 1986. Production of alfalfa
rate applied. The lack of significant differences or trends
in Pennsylvania soils of differing wetness. Agron. J. 78:469–473.
among treatments in soil layers below the 30-cm depth
Ballif, J.L., and P. Duthil. 1976. Recherche de l’equilibre potassium-
magnesium dans la fertilisation de la luzerne en Champagne cray-
suggests that although alfalfa is a crop with a high poten-
euse. Comptes Rendus Academie d’Agriculture de France 8:
tial for subsoil exploitation (De Nobili et al., 1990; Pe-
515–528.
terson and Smith, 1973), the upper 30 cm of soil was
Barbarick, K.A. 1985. Potassium fertilization of alfalfa on a soil high
most affected by K removal. Moreover, the highest rates
in potassium. Agron. J. 77:442–445.
of K did not significantly increase subsoil K
e
values. The
Burmester, C.H., G.L. Mullins, and D.M. Ball. 1991. Potassium fertil-
ization effects on yield and longevity of established alfalfa. Com-
average K
e
at the 0- to 30- or 30- to 60-cm depths did
mun. Soil Sci. Plant Anal. 22:2047–2062.
not change appreciably from year to year. These results
Collins, M., D.J. Lang, and K.A. Kelling. 1986. Effects of phosphorus,
suggest that alfalfa uptake or K fertilization scarcely
potassium and sulfur on alfalfa nitrogen-fixation under field condi-
influenced the K
e
levels.
tions. Agron. J. 78:959–963.
De Nobili, M., L.V. Antisari, and P. Sequi. 1990. K-uptake from
The balance between K uptake and fertilizer inputs
subsoil. p. 133–144. In IPI (ed.) Proc. of the 22nd Colloquium of
(Table 4) shows that 332 kg K ha
⫺
1
yr
⫺
1
(1328 kg K
the Int. Potash Inst., Soligorsk, Russia. 18–23 June 1990. Int. Potash
ha
⫺
1
in 4 yr) was not sufficient to offset the uptake of
Inst., Bern, Switzerland.
K. The differences in soil K
e
values in the 0- to 90-cm
Dovrat, A. 1993. Irrigated forage production. Developments in Crop
depth between plots that received no K fertilization and
Science 24. Elsevier Science Publ., Amsterdam, the Netherlands.
EU Commission. 1993. Our agricultural future. Official Publ. of the
the plots with the highest rates (332 kg K ha
⫺
1
yr
⫺
1
)
European Union, Luxembourg.
were, in the 90-cm depth, only 81 mg K kg
⫺
1
(699–618
Fixen, P.E., and A.E. Ludwick. 1983. Phosphorus and potassium fertil-
mgKkg
⫺
1
). This amount seems to account for most
ization of irrigated alfalfa on calcareous soils: I. Soil test mainte-
of the differences in the K balance between the two
nance requirements. Soil Sci. Soc. Am. J. 47:107–112.
Havlin, J.L., D.G. Westfall, and H.M. Golus. 1984. Six years of phos-
treatments (⫺1546 and ⫺400 kg K ha
⫺
1
), since 1 mg K
phorus and potassium fertilization of irrigated alfalfa on calcareous
kg
⫺
1
of soil represents about 11.7 kg ha
⫺
1
of K
e
for the
soils. Soil Sci. Soc. Am. J. 48:331–336.
90-cm depth, assuming a soil bulk density of 1.3 g cm
⫺
3
.
Heras, L., and L. Montan
˜es. 1974. Equilibrio y estado nutritivos de
The 198 kg ha
⫺
1
(1146–948 kg ha
⫺
1
) of nonaccounted
la alfalfa (Medicago sativa L.) cultivada sobre tres tipos de suelo.
K could come from nonexchangeable K forms, as
Anales de la Estacio
´n Experimental de Aula Dei. 12:146–155.
Hidalgo, F. 1969. El abonado de la alfalfa. Asociacio
´n de Investigacio
´n
pointed out by Lee and Metson (1977) and Vough and
para la Mejora de la Alfalfa, Zaragoza, Spain.
Decker (1992). Similar findings were reported by others.
James, D.W., C.J. Hurst, and T.A. Tindall. 1995. Alfalfa cultivar re-
Jounay et al. (1996), working with calcareous soils in
sponse to phosphorus and potassium deficiency: Elemental compo-
southwest France, reported that the K
e
content of non-
sition of the herbage. J. Plant Nutr. 18:2447–2464.
Jones, G.D., J.A. Lutz, and E.B. Hale. 1974. Effects of fertilization
fertilized plots declined only slightly (over a 25-yr pe-

LLOVERAS ET AL.: K FERTILIZATION ON ALFALFA IN MEDITERRANEAN CONDITIONS
143
and irrigation on yield and potassium content of alfalfa and on Markus, D.K., and W.R. Battle. 1965. Soil and plant responses to
available soil potassium. Commun. Soil Sci. Plant Anal. 5:155–163. long-term fertilization of alfalfa (Medicago sativa L.). Agron. J.
Jouany, C., B. Colomb, and M. Bosc. 1996. Long-term effects of 57:613–616.
potassium fertilization on yields and fertility status of calcareous Mengel, K., and E. Kirkby. 1980. Potassium in crop production. Adv.
soils of south-west France. Eur. J. Agron. 5:287–294. Agron. 33:59–110.
Kafkafi, U., R. Gilat, D. Yoles, and Y. Noy. 1977. Studies on fertiliza- Peterson, L.A., and D. Smith. 1973. Recovery of K
2
SO
4
by alfalfa
tion of field-grown irrigated alfalfa. Plant Soil 46:165–173. after placement at different depths in a low fertility soil. Agron.
Lanyon, L.E., and W.K. Griffith. 1988. Nutrition and fertilizer use. J. 65:769–772.
p. 333–372. In A.A. Hanson et al. (ed.) Alfalfa and alfalfa improve- Razmjoo, K., and P.R. Henderlong. 1997. Effect of potassium, sulfur,
ment. Agron. Monogr. 29. ASA, Madison, WI. boron, and molybdenum fertilization on alfalfa production and
Lanyon, L.E., and F.W. Smith. 1985. Potassium nutrition of alfalfa herbage macronutrient contents. J. Plant Nutr. 20:1681–1696.
and other forage legumes: Temperate and tropical. p. 861–893. In Rominger, R.S., D. Smith, and L.A. Peterson. 1976. Yield and chemi-
R.D. Munson (ed.) Potassium in agriculture. ASA, Madison, WI. cal composition of alfalfa as influenced by high rates of K top-
Lee, R., and J. Metson. 1977. Potassium removal from soil by lucerne dressed as KCl and K
2
SO
4
. Agron. J. 68:573–577.
over three years and the effect of potassium topdressing. N.Z. J. Roquero, C. 1979. The potential productivity of Mediterranean soils.
Agric. Res. 20:185–192. In IPI (ed.) Soils in Mediterranean type climates and their yield
Le Gall, A., J.D. Arnaud, P. Guy, H. Bousquet, A. Pflimlin, and Ph. potential. Proc. 14th Colloquium Int. Potash Inst., Sevilla, Spain.
Planquaert. 1992. La Luzerne Culture-Utilization. Groupement Int. Potash Inst., Bern, Switzerland.
National Interprofessionel des Semences-Institut Tecnique de l’El- SAS Institute. 1988. SAS/STAT user’s guide. Version 6.03. SAS Inst.,
evage Bovin-Institut Tecnique des Cereals et des Fourrages, Paris. Cary, NC.
Lloveras, J., J. Ferran, A. Alvarez, and L. Torres. 1998. Harvest Sheaffer, C.C., M.P. Russelle, O.B. Hesterman, and R.E. Stucker.
management effects on alfalfa (Medicago sativa L.) production and 1986. Alfalfa response to potassium, irrigation and harvest manage-
quality in Mediterranean areas. Grass Forage Sci. 53:88–92. ment. Agron. J. 78:464–468.
Lloveras, J., C. Pedros, and J. Soldevila. 1994. Effect of nematodes Smith, D. 1975. Effects of potassium topdressing a low fertility silt
in the seasonal forage production of alfalfa cultivars in irrigated loam soil on alfalfa herbage yields and composition and on soil K
areas of the Ebro Valley (Spain). p. 254–255. In Eucarpia/FAO values. Agron. J. 67:60–64.
‘Medicago’ Meeting, Lusignan, France. 4–8 Sept. 1994. FAO Steel, R.D., and J.H. Torrie. 1980. Principles and procedures of statis-
REUR Tech. Ser. 36. FAO, Rome. tics: A biometrical approach. McGraw–Hill, New York.
Lutz, J.A. 1973. Effects of potassium fertilization on yield and K Swoboda, R. 1998. Wasting money on fertilizer. Wallaces Farmer
content of alfalfa and on available subsoil K. Commun. Soil Sci.
123(15):15–16.
Plant Anal. 4:57–65.
Vough, L., and M. Decker. 1992. An alfalfa management program
Mallarino, A.P., J.R. Webb, and A.M. Blackmer. 1991. Soil test values
for optimun yields and quality. Better Crops Plant Food
and grain yields during 14 years of potassium fertilization of corn
and soybeans. J. Prod. Agric. 4:562–566. (Spring) 76:24–26.