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Ill. Yield and Quality Responses to Chloride

Ill. Yield and Quality Responses to Chloride

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some crops and cropping situations appear to have a greater potential than

others to benefit from its application.



Since the late 1970s, extensive C1- research has been conducted on

wheat and barley in the northwestern United States and the Great Plains of

North America. Many of these studies have shown beneficial effects of C1-,

and others have shown none. Factors influencing response probability

other than crop or cultivar will be discussed in Section V.

1. Cultivar Differences

It is clear that cereal crops not only differ in their potential for response

to C1- in the field (Fixen ef al., 1986b), but cultivars also differ in responsiveness. Average C1- responses across 5 site-years spanning 3 years for

three hard red spring wheat cultivars in South Dakota were 4 1 1, 330, and

7 kg grain ha-’ for “Butte,” “Marshall,” and “Guard,” respectively (Fixen,

1987). A screening of 15 cultivars at two locations resulted in response at

least at one location by 12 of the cultivars. “Guard” was again one of the

three cultivars that showed no response. Some but not all of the response

differences were explainable based on disease susceptibility.

Spring wheat cultivar differences have also been measured in Manitoba

(Mohr, 1992). Average grain yield responses to 50 kg C1- ha-’ across four

sites were 150, 137, 116, and - 16 kg ha-’ for “Biggar,” “Roblin,” “Marshall,” and “Katepwa” cultivars, respectively. “Katepwa” had also failed to

respond to C1- at eight sites in earlier studies and, like “Guard” in South

Dakota, appears to be a C1--nonresponsive cultivar.

The Cl- responsiveness of five spring barley cultivars was evaluated at

different sites for 2 years in eastern South Dakota (Gelderman ef al., 1988).

Average grain yield responses were 222, 200, 200, 49, and I 1 kg ha-’ for

“Robust,” “Hazen,” “Morex,” “Bowman,” and “Primus 11” cultivars,

respectively. Similar to spring wheat, some barley cultivars seem nonresponsive to C1- fertilization.

Similar barley cultivar differences in C1- response have been measured

in the Manitoba research referred to earlier (Mohr, 1992). Average response across four sites varied from 239 kg ha-’ for the most responsive

cultivar, “Heartland,” to -257 kg ha-’ for the least responsive cultivar,

“Bedford.” “Bedford” had responded positively at two out of eight sites in

earlier studies with an average grain yield response across all eight sites of

187 kg ha-’.



Differences in CI- response of hard red winter wheat cultivars have been

measured in Kansas (Bonczkowski, 1989). In a study of “Arkan,” a cultivar moderately resistant to leaf rust, and “Newton,” a leaf rust susceptible

cultivar, a C1- by cultivar interaction was detected in 1 out of 3 years.

Grain yield responses to 50 kg C1- ha-’ were 667 and 47 kg ha-’ for the

moderately resistant and susceptible cultivars, respectively. It appeared

that the leaf rust resistance in the moderately resistant cultivar was enhanced by C1- application.

2. Magnitude and Frequency of Yield Response

The largest reported wheat or barley yield increases to CI- fertilizers have

occurred on take-all-infested winter wheat grown in the northwestern

United States on moderately acid soils. For example, nine grain yield

increases reported in several studies conducted from 1980 to 1983 ranged

from 470 to 2 150 kg ha-’, with an average of 1076 kg ha-’ (Christensen et

al., 1981; Christensen and Brett, 1985; Powelson et al., 1985; Scheyer et

al., 1987). These responses were all determined by comparing (NH4)2S0,

to a rate of NH4Cl application giving an equivalent amount of N.

Addition of KCI to soils testing very high in available K in Saskatchewan, Canada, resulted in average yield increases of 342 kg ha-’ across 6

winter wheat sites, 192 kg ha-‘ across 18 spring wheat sites, and 128 kg

ha-’ across 9 spring barley sites (Wang, 1987). Durum yields were not

increased when averaged across 3 sites. Yield response was statistically

significant at 8 of the 36 sites. Wang (1987) suggested that response may

have been due to the lower osmotic potential caused by C1- uptake and the

resulting increase in plant turgor under moisture stress.

Wheat and barley grain yield responses to CI- fertilization over five

states in the Great Plains of the United States were recently summarized by

Engel et al. ( 1 992). The summary showed that significant C1- response

occurred in 42% of the 169 episodes over a wide range of environments

and yield potentials (Fig. 3). It is important to note that this summary

includes cultivars such as “Guard” spring wheat, “Primus 11” barley, and

“Newton” winter wheat, which are proved nonresponding or limitedresponding cultivars. Also included are sites testing high in soil C1-.

Responses in the Great Plains have generally been modest compared to

those measured in the northwestern United States (Engel et af.,1992). The

average significant response in Engel’s summary was 304 kg ha-’ whereas

the average response for all sites was 1 I7 kg ha-’. The average response for

all sites in the Saskatchewan studies ( Wang, 1987)was 184 kg ha-’. Thus it

is economically beneficial to be able to predict responsive situations. That

will be the topic of a later discussion in this review.







Control yield, kg/ha

Figure 3. Chloride yield response relative to control yields in the Great Plains. 0,

Nonsignificant; 0, significant (>67 kg ha-'). Each data point represents a cultivar X site X

year episode (Engel et a/.. 1992).

3. Mechanisms Involved in Yield Responses

Many of the responses summarized above were due to documented

suppression of root or foliar diseases or enhancement of host tolerance to

diseases, as discussed earlier. However, in many other cases responses

could not be attributed to disease effects (Bonczkowski, 1989; Engel and

Mathre, 1988; Engel and Grey, 1991; Fixen, 1987; Fixen et al., 1986b;

Goos et al., 1989; Mohr, 1992).

The nondisease mechanisms involved in these responses have not been

clearly demonstrated. However, possible mechanisms include effects of Clon plant development and resulting stress avoidance as well as potential

effects on plant water relationships. These were discussed earlier.

4. Quality Effects

Great Plains studies have demonstrated frequent improvements in

wheat and barley quality due to CI- application. Parameters influenced

include kernel weight, plumpness or volume, and test weight (Cholick ef

al., 1986; Engel and Mathre, 1988; Engel ef al., 1992; Mohr, 1992; Schumacher, 1990; Windels et a!., 1992). In some cases quality effects, espe-



cially kernel weight, have been more common than yield effects. In North

Dakota studies, barley kernel volume was increased in 6 out of 13 siteyears by application of KCl in situations wherein response to K+ was very

unlikely (Zubriski ef al., 1970). It has been observed in South Dakota that

CI- application can reduce the severity of late-season lodging in spring

wheat. Lodging reduction could be one mechanism for improvement of

grain quality.


Oat responsiveness to broadcast application of 187 kg KCl ha-’ was

compared to that in spring wheat and barley at 6 site-years in eastern South

Dakota (Fixen et al., 1986b).Wheat and barley responded significantly at 4

and 3 sites, respectively, but no oat responses were detected. Soil and plant

analysis as well as studies conducted the followingyear at nearby sites using

KNO, and CaCI, all indicated that responses were due to the C1- in the

KCI fertilizer. The authors concluded that oat was less responsive to C1than was wheat or barley but cautioned that the results could have been

influenced by the specific cultivars used for each species.

More intensive studies on the effects of C1- on oat cultivars were conducted by Gaspar (1988). The average grain yield responses to 64 kg CIha-’ across 5 site-years in eastern South Dakota were 160, 140, 110, 10

(nonsignificant, NS), and -40 (NS) kg ha-’ for the cultivars “Moore,”

“Benson,” “Ogle,” “Lancer,” and “Froker,” respectively. Yield responses

were due to increases in kernel weight. Neither the number of tillers nor

seeds per tiller were influenced by CI-. Parameters unaffected by CI- were

crown rust (Puccinia coronafa) infection, leaf relative water content, leaf

water potential, and stomata1 conductance.

Adjacent experiments evaluating the interaction of N and CI- showed a

slight reduction in crown rust infection from C1- at all 5 site-years and a

reduction in lodging in most cases, especially at high N rates (Gaspar,

1988). The reduction in crown rust was only 1% of the leaf area and was

considered agronomically unimportant. Solute potential and solute potential adjusted for full turgor were decreased by C1- addition, although the

decreases did not seem related to yield.


Published accounts of CI- effects on corn date back at least to 1958

(Younts and Musgrdve, 1958b).In field and pot experiments in New York,



increasing KCl rates decreased stalk rot incidence of corn whereas increasing K2S04or KP03 application had little or no effect.

Later studies in Wisconsin by Martens and Amy (1967a,b) showed that

both KCl and NH4Cl decreased pith levels of reducing sugars, decreased

natural root necrosis, and delayed death of corn plants, but increased stalk

rot when the stalks were inoculated with Diplodiu muydis (Berk). The

observation of delayed plant death is consistent with the findings of Younts

and Musgrave (1958b) that KCI reduced natural stalk rot. However, Martens and Amy ( 1967b) attributed the reduction to both K and C1, because

the effects of KC1 were much greater than the effects of NH,Cl.

The increased stalk rot in inoculated plants due to C1- application

reported by Martens and Amy (1967b) was thought to be due to the direct

injection into the stalk, which bypasses the normal advance of the pathogen from the roots. The researchers proposed that fungal growth in the root

and its advance into the stalk is delayed by both K+ and C1-, but subsequent growth in the stalk is more rapid.

Field studies in Wisconsin by Liebhardt and Munson ( 1976) evaluated

the effects of K+ and C1- on corn lodging where no KCI had been applied

for the previous 4 years. Potassium application resulted in an I800 kg ha-'

increase in grain yield and a reduction in corn lodging of 4896, whereas C1application had no effect on either yield or lodging.

Lack of significant yield response to C1- by corn was also measured in

South Dakota studies (Schumacher and Fixen, 1989). Broadcast-incorporated rates of C1- up to 5 10 kg ha-' failed to give significant yield response

for the year of application or the 2 years following the application year.

Grain moisture at harvest was significantly increased by C1- during the

third year. In the same study, spring wheat yields were significantly increased for the first 2 years.

Banding Cl--containing fertilizers near the corn row at rates higher than

those normally used has reduced grain yield and delayed maturity. Corn

growth in New York was delayed if KCI was applied in a band located

7.5 cm beside and 2.5 cm below the seed at C1- rates exceeding 50 to

100 kg ha-' (Younts and Musgrave, 1958a).Jackson el ul. ( 1 966) observed

reduced sweet corn growth and vigor following C1- application on a poorly

drained acid soil that contained Mn concretions in the Willamette Valley

of Oregon. The negative effect of C1- was attributed to an increase in Mn

availability and resulting Mn toxicity.

Research in Ohio showed no effect of NH4Cl applied in a band located

4 cm to the side and 4 cm below the seed at rates up to 100 kg ha-' (Teater

ef ul., 1960). A rate of I35 kg C1- ha-' decreased yields below those when

an equivalent amount of N was applied, but from non-C1- sources, in one

of two years. Broadcast application avoids these negative effects of C1- on



corn even at much higher rates of 500 to 600 kg ha-' (Schumacher and

Fixen, 1989; Teater ef al., 1960).

Studies in the greenhouse and field were conducted on poorly drained

Atlantic coastal soils to determine if C1- toxicity could be a problem for

corn (Parker ef al., 1985). No detrimental effects were measured even at

the highest rates in the studies (728 mg C1- kg-' soil in the greenhouse and

340 kg CI- ha-' in the field).

Studies evaluating the interaction between N and K sources suggest that

C1- increases the yield response of corn to enhanced ammonium nutrition

(Dibb and Welch, 1976; Teyker et al., 1992). In a 2-year field study Teyker

ef al. (1992) found no response to enhanced ammonium nutrition with

KHCO, or K2S04 as K sources, although grain yield was increased by 380

to 560 kg ha-' when KCI was used. A greenhouse study by Dibb and

Welch ( I 976) showed that the importance of KCI supplementation increased substantially when corn was grown with ammonium nutrition.

Teyker et al. (1992) suggest that the apparent higher CI- requirement

under enhanced ammonium nutrition compared to nitrate nutrition is

perhaps due the role of C1- as a counterbalancing ion and major osmolyte.

Although corn yield increases from C1- have been measured, there

appears to be less potential for corn to benefit from CI- application in the

field than is the case for cereal crops. When positive responses occur they

have been limited in magnitude.

Although data are limited, soybean and soybean diseases do not appear

to be responsive to application of CI- fertilizer. Studies in Missouri exploring the potential of CI- in KCI fertilizer for reducing soybean cyst nematode damage or cyst counts in the soil showed no reductions (Hanson ef

al., 1988). Likewise, Kansas experiments on the effects of K and CI- on

charcoal rot severity showed a lack of treatment effects (Granade et al.,


The major concern with CI- and soybeans is the potential for toxicity in

sensitive cultivars when grown in high CI- environments that accumulate

soluble salts. Considerable research has been camed out on this problem

on the poorly drained soils of the Atlantic Coast Flatwoods area of Georgia

(Parker and Gaines, 1987; Parker et al., 1986a,b, 1987).

The major cause of the problem is a water table that remains within I or

2 m of the surface and the fact that soil moisture is lost primarily by

evaporation and transpiration, which leaves CI- in the rooting zone. The



sandy texture and high K fertilizer requirements of the soils in the region

amplify the problem, which is worse in dry years than in wet years.

Dramatic differences in sensitivity to C1- toxicity exists among soybean

cultivars, with the sensitive cultivars being C1- accumulators and the tolerant cultivars being CI- excluders. Leaf scorch due to toxicity is just detectable at leaf concentrations of 8600 mg kg-' or seed C1- concentrations of

18,100 mg kg-l (Parker et af., 1986b). Growers have solved the problem by

use of Cl--tolerant cultivars.


Reduction in tuber specific gravity by CI-, especially when applied in

bands, has been a major issue in potato production (Berger ef af., 1961).

For this reason sulfate sources have often been the preferred form of K in

potato production.

Recent pot experiments have demonstrated that application of KCI as

compared to K2S0, delayed tuber development, increased plant turgor

pressure, and enhanced shoot growth (Beringer et af., 1990). These effects

suggested a less competitive shoot sink for K,SO,-treated plants and somewhat greater assimilate translocation to tubers.

Chloride application can also have beneficial effects on potato production. Oregon research has shown reductions in hollow heart with KCl

compared to K2S04and accompanying increases in yield and grade (Jackson and McBride, 1986). This research also revealed that a french fry

evaluation of tubers from experiments across 3 years showed that application of CI- did not affect uniformity of color or apparent "sugar ends."

Other studies have demonstrated reduction in frost damage in plots receiving 225 kg KCl ha-', presumably due to the 50,000 to 70,000 mg kg-l Cllevels in plant tissues (Jackson et af., 1982).

The role of CI- application in potato culture is likely dependent on a

number of factors, including end use of the tubers, disease pressures and

other stresses, and rate of K needed. Local research and experience on the

magnitude of the various potential effects of C1- need to be considered.


Soils high in C1- have reportedly produced better quality flax (Linum

usitatissimum L.) (Brioux and Jouis, 1938). Recent studies with five flax

cultivars resulted in a significant seed yield increase of 157 kg ha-' for one

cultivar and significant yield decreases of 119 and 144 kg ha-' for two

other cultivars from broadcast application of 135 kg KCl ha-' (Grady et

al., 1988). No consistent yield effects were measured during the second



year of the study. However, oil content was increased from 408 g kg-I for

the control to 4 12 g kg-I for the CI- treatments. Disease incidence was very

low for both years.

High soil nitrate levels late in the season reduce the concentration of

recoverable sugar in sugar beets (Beta vufgaris L.). The uptake antagonism

sometimes observed between CI- and nitrate offers a possible mechanism

for reducing the negative effect of high nitrate on recoverable sugar in beets

(Ludwick et al., 1980). Research in Washington has shown that C1- inhibition of nitrate uptake in sugar beets can lead to increased beet sugar

percentages (James ef af., 1970a). Colorado research showed no effect of

CI- fertilization on sugar concentration of irrigated beets; however, C1available to the crop from the soil and imgation water varied from 930 to

3810 kg ha-' for the sites used (Ludwick et al., 1980).

Sugar beets accumulate large quantities of C1- and uptake has been

highly correlated with soil C1- to a depth of 120 cm. In research conducted

in the Red River Valley of central North America, C1- uptake varied

among five sites and five N rates from 28 to 226 kg ha-' and 5 to 23 kg

ha-' for tops and roots, respectively (Moraghan, 1987). Chloride uptake

generally increased as fertilizer N rate increased. Moraghan pointed out

that the redistribution of soil C1- from below 60 cm to the surface soil by

the beet tops could influence the C1- relationships of subsequently planted


Coconut and oil palms have responded markedly to C1- fertilization on

low-C1- soils, typically occurring at distances greater than 20 to 25 km

from the sea (Ollagnier and Olivin, 1984; Ollagnier and Wahyuni, 1984;

von Uexkull and Sanders, 1986). Nut yield increases as high as 50% have

been measured. Optimum tissue C1- levels of 6000 to 7000 mg kg-l have

been proposed.


The only form of chlorine found in nature is C1-. Although other

oxidation states are possible and are important in some industrial processes, they are all unstable in the environment.




Four basic factors determine the amount of C1- available to crops growing in well-drained soils (Goos, 1987). They are (1) soil solution C1-, (2)

exchangeable C1- in the soil, (3) atmospheric deposition of C1-, including

irrigation water, and (4) fertilizer or manure C1-.



Due to the high solubility of C1- salts, most soil C1- is found in the soil

solution. Although some soil minerals contain very small amounts of C1-,

they generally do not contribute significantly to plant nutrition. Several

studies demonstrating high correlations between soil solution C1- and C1uptake by crops will be discussed later. Acid soils with clay mineralogy

dominated by 1 : 1 clays and oxides may have significant anion-exchange

capacity. Significant C1- can be held in anion-exchange sites in such soils

(von Uexkull, 1990).

Atmospheric deposition of Cl- varies greatly with geographic location.

Precipitation near ocean shores can annually contribute as much as 100 kg

CI- ha-' and drop to 20 kg ha-* just 200 km inland (von Uexkull and

Sanders, 1986). Atmospheric contribution in the midwestern United States

and Great Plains has been reported as being only 0.6 to 1.2 kg C1- ha-' per

year (Junge, 1963). Atmospheric inputs often increase near heavily industrialized areas where large quantities of coal are burned. Some imgation

waters contribute substantial C1- to crops (Fixen el al., 1986c) whereas

others contribute very little.

Chloride in the soil parent material, in precipitation, in soil drainage,

historical crop removal, and C1- applied in animal manure or fertilizers all

influence the quantity of C1- found in a particular soil. In North Dakota,

C1- levels are often high in soils derived from marine geological deposits, in

saline soils, where a shallow water table exists, and in low spots below long

slopes (Richardson et al., 1988).

The mobility of C1- in soils makes leaching the primary mode of C1- loss

(Schumacher and Fixen, 1989). As with any solute, actual leaching loss in

individual years is dependent on several interacting factors. Therefore,

persistence of C1- from fertilizer applications is difficult to predict except in

extreme situations.

Crop removal of C1- when only grain is harvested is typically very low

and has been reported as low as 0.05% of the dry matter in wheat grain

(Knowles and Watkin, 1931). Green forage, however, can remove substantial quantities of C1-, especially when growth occurs in a high-C1environment. At peak accumulation, spring wheat contained 18 and 6 1 kg

C1- ha-' on sites testing low and high in CI-, respectively (Schumacher,

1988). By crop maturity, C1- in the aboveground portion of the plant had

dropped to 50 and 43% of these values, respectively.




Fertilizer source comparisons have indicated that all common C1sources are equally effective (Fixen ef al., 1986b; Mohr, 1992). Common

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Ill. Yield and Quality Responses to Chloride

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