Air pollution and its impacts on wheat yield in the Pakistan Punjab

Environmental Pollution 88 (1995) 147-154 0 1995 Elsevier Science Limited

ELSEVIER

Printed in Great Britain. All rights reserved 0269-7491/94/$09.00

AIR POLLUTION AND ITS IMPACTS ON WHEAT YIELD IN THE PAKISTAN PUNJAB

A. Wahid,” R. Maggqb S. R. A. Shamsi,” J. N. B. Bellb & M. R. Ashmoreh* ‘Department of Botany, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590, Pakistan

hDepartment of Biology, Imperial College at Silwood Park, Ascot, Berkshire UK, SL5 7PY

(Received 23 August 1993; accepted 14 March 1994)

Abstract A study using open-top chambers ventilated with ambient or charcoal-jiltered air in the vicinity of Lahore, Pak- istan, has demonstrated a reduction of 46.7% and 34.8% in the grain yield for two cultivars of winter wheat (Triticum aestivum L.). The 6-h daily mean O3 concentrations were 254.5 nl litre-’ and on the basis of experience in North America and Europe, reductions in yield in the present study are substantially greater than might be predicted. The reasons for this discrepancy are discussed, together with implications for the suitability of a simple, relatively cheap, open-top chamber system for developing-country studies on the eflects of air pollution on crops.

INTRODUCTION

Ambient air pollution has been shown to reduce the growth and economic yield of a wide range of major crop species in North America and Europe. Such effects are currently attributed largely to the secondary photo-oxidant ozone (O,), which is widespread in many rural areas. The formation of ozone is influenced by major emissions of its precursors, nitrogen oxides (NO,) and hydrocarbons, of which the motor vehicle is the most important source. However, in some areas nitrogen dioxide (NO,), sulphur dioxide (SO,) and other air pollutants are also important in terms of crop yield.

The most detailed quantitative information on economic losses arising from air pollution has been obtained by the United States National Crop Loss Assessment Network (NCLAN). In this study, agricultural crops were grown to maturity in open-top chambers, ventilated with charcoal-filtered or ambient air, supplemented with extra 0, in some treatments in order to generate dose/response relationships. Outside plots were also set up to determine any impact on the crops by the chambers themselves. The NCLAN study, which included wheat, produced an estimate of around $3000 x IO6 annual economic loss in the United States as a result of 0, pollution on annual crops (Adams et al.,

*To whom correspondence should be addressed at: Centre for Environmental Technology, Imperial College of Science Technology and Medicine, 48 Prince’s Gardens, London, SW7 2PE, UK.

147

1988). In Europe, a similar study, using a standardised experimental protocol, has recently been completed, in- volving 12 sites in 10 countries. This study used a more restricted range of crops, but also included wheat (J8ger et al., 1994). Both the United States and European studies have shown clear evidence of ambient O3 pollution reducing wheat yield at some locations (e.g. Kohut et al., 1987; Fuhrer et al., 1989; Pleijel et al., 1991).

In contrast to the situation in the developed world, research into the impacts of air pollution on crops in developing countries is limited, and in most cases is devoted to fumigation experiments with high concentrations of SO,. However, industrialisation, urbanisa- tion and motor traffic are currently increasing on an unprecedented scale in many developing countries. The consequent air-pollution problems are serious, due to the absence of the kind of controls imposed on emissions in the developed world. A recent report on air nollution in twenty megacities, mainly in developing countries, highlighted indications of rapidly deteriorat- ing air quality, although in many cases reliable monitoring data are limited (WHOKJNEP, 1992). In contrast to Europe and North America, most developing countries are endeavouring to increase agricultural crop production to cope with high rates of population growth. These efforts may be seriously hampered by reduced crop production due to ambient air pollution.

This paper describes an experiment aimed at assessing the impacts of ambient air pollution on winter wheat at a location on the outskirts of Lahore, Pakistan. It is the first in a series of papers that will report on air pollution levels in the region and, in particular, their impact on agricultural production. The experiment grew wheat to maturity in open-top chambers, ventilated with ambient or charcoal-filtered air. Regular growth measurements and assessments of final-yield components were made. This is the first known investigation of this type conducted on the Indian subcontinent.

MATERIALS AND METHODS

The experimental site occupied a 21 x 15 m area in the Botanical Gardens of the Quaid-e-Azam Campus of the University of the Punjab, some 7.5 km south of the centre of Lahore. In 1985, Lahore had about 3.5 mil- lion inhabitants, a high volume of motor traffic and

148 A. Wahid, R. Maggs, S. R. A. Shamsi, J. N. B. Bell, M. R. Ashmore

some areas of light industry. The experiment site was 1500 m and 7 km from the nearest main road and industry, respectively, and was surrounded by agricultural areas to the west and south. Twelve plots were constructed on the site: eight were occupied by open- top chambers, the remaining four were unchambered control plots (OP). The chambers were constructed according to the design of Bell and Ashmore (1986), which has been used extensively in air-filtration studies at a number of locations in south-east England over the last thirteen years. These chambers are particularly suitable for use in the developing world; their simple, basic design can be constructed rapidly, using materials readily available locally. They are 1.5 m in diameter and height, consisting of an aluminium framework with polyethylene walls, with air supplied at three changes per minute via a vertical manifold. Four chambers were ventilated with ambient unfiltered air (UFA), while the other four were ventilated with air that had passed through an activated charcoal filter (FA). Both types of chamber were equipped with prefilters to remove dust. The fans and filters were sheltered in order to minimise any rise in temperature of the air entering the chambers. A metal fence was constructed around the entire site for security purposes.

The chambers were operated as closely as possible to the conditions prescribed under the European Open- Top Chamber Programme protocol (Jager, 1994). Microclimatic measurements were taken within and outside the chambers, to assist in interpreting the final results. Light intensity, relative humidity and air temperature were measured at crop height in one chamber and one outside plot at 0800, 1200 and 1600 h daily, using a light meter and a portable temperature-humidity probe. Dust was washed from the outside of the chamber walls on a regular basis. Ozone levels were monitored in one of each of the treatment plots (UFA, AA and OP) from 16 December 1991 to 11 January 1992. Having determined that there was little difference between ozone levels in UFA and AA, monitoring was switched to three of the eight chambered plots (one FA and two UFA) thereafter. Periodic sampling of replicate chambers revealed agreement for both O3 and NO2 levels. Sampling was carried out at crop height in the centre of the plots. The height of sampling was ad- justed to crop height accordingly and varied from 33345 cm at the end of active vegetative growth, depending upon cultivar and treatment.

In the absence of continuous monitors simple chemi- cal methods were employed. Ozone concentrations were monitored between 1000-1600 h three times per week, using the neutral buffered potassium iodide method (Saltzman & Gilbert, 1959). Interference from light was minimised by encasing the impinger vessel in black paper. No correction was made for interference from other pollutant gases. Comparisons between the KI method and a continuous ozone monitor at a site elsewhere in Lahore showed close agreement between the two methods. Mean NO2 concentration was determined over weekly periods using diffusion tubes

(Atkins et al., 1978) attached to chamber walls at heights of 75 cm in four of the eight chambered plots (two FA and two UFA). Difficulties were encountered in attempting to measure air concentrations of SO, using the acidometric method, probably due to interference by elevated levels of NH, arising from animal waste on nearby farms.

Two locally grown, currently recommended cultivars of Triticum aestivum L. were studied in the experiment, using seed obtained from the Ayub Agricultural Re- search Institute in Faisalabad, Pakistan. These were se- lected on the basis of a screening programme of ten Pakistan wheat cultivars, carried out by means of controlled 0, fumigation (80 nl litre ’ for 8 h per day for 7 days) at Imperial College, followed by assessment of visible injury. One cultivar (Pak-81) was relatively sensitive, while the other (Chakwal-86) was less sensitive to 0,. The screening fumigation resulted in 80 and 61% leaf-length injured, respectively.

Four plants of each cultivar were grown from seed in a sandy-loam soil in 30-cm-diameter clay pots, with four replicate pots in each plot, giving a total of 64 plants of each cultivar per treatment. The seeds were sown on 30 November 1991 and the chambers placed in position over the plots on 10 December 1991. The experimental plants were managed throughout the experiment according to local agricultural practices; plants were watered to excess every other day, and inter-plant distances of lo-12 cm were comparable with those in nearby agricultural fields. Cow manure was in- corporated into the soil at the start of the experiment and pesticides were avoided throughout.

Crop growth and development were monitored throughout the growing season by weekly measurements of plant height and numbers of tillers, and of numbers of live and senescent leaves. A single destruc- tive harvest was performed at crop maturity on 28-9 April 1992, with measurements of number of ears per plant, grains per plant, and spikelets per ear. Grain and straw dry weights were determined for each plant and the average ear and rachis lengths per plant were measured. Final harvest data were subjected to analysis of variance based on plot means.

RESULTS

Results of the routine measurements inside and outside the chamber showed relatively little impact upon mi- croclimate (Table 1). Light levels at crop height were, on average, reduced by 5% inside the chamber, while the mean air temperature inside the chamber was 1’ 1 “C higher than outside. Relative humidity was 1.4% higher inside the chamber. The 1’1°C increase in temperature inside the chamber was not related to light levels, but most likely was due to the heating effect of the fan and motor (Fig. 1).

The concentrations of ozone and nitrogen dioxide through the growing season are shown in Fig. 2. The mean 6-h concentration of 0, through the growing season was 35.6 nl litre-’ with a mean weekly NO,

Air pollution and its impacts in the Pakistan Punjab 149

Table 1. Mean monthly ambient air temperatures, light levels and relative humidities inside and outside the chamber environment. Values are means of values measured daily at OWO, 1200 and 1600 h

Month Air temperature (“C) Light intensity (Lux x 1000)

Relative humidity (%)

Inside Outside Diff. Inside Outside Diff. Inside Outside Diff.

December 17.59 16.55 +1.04 20.98 22.34 -1.36 70.58 69.34 +1.24 January 16-61 1544 +1.17 20.09 21.34 -1.25 65.96 64.34 +1.64 February 17.13 15.99 +1.14 24.78 25.99 -1.21 58.51 57.08 +1.43 March 23.54 22.36 +1:18 31.97 33.49 -1.52 47.00 45.66 +1.34 April 29.65 28.54 +l.ll 39.29 39.29 -1.56 41.06 39.58 +1.48

concentration of 23.3 nl litre-‘. The O3 concentration increased during the experiment from a mean concentration of 27 nl litre-’ in December and January to a mean of 39.5 nl litre-’ during March and April, whereas NO, concentration remained virtually constant. This increase in concentration coincided with an increase in monthly mean temperature. Filtration efficiencies were 85 and 65% for ozone and nitrogen dioxide, respectively. Concentrations of 0, and NOz at crop height were only l-2 nl litre-’ lower than those at 60 cm or 120 cm within the chambers, indicating little depletion of Oj concentrations by the crop. Ozone levels in the UFA plots were l-2 nl litre-’ below those recorded at a similar position in the OP plots.

Crop growth and development showed dramatic effects of treatment with increases seen in the rate of tiller production in both cultivars in FA compared to UFA and OP (Fig. 3); in cultivar Pak-81 this was apparent in mid-January, but in cultivar Chakwal-86 it did not begin until late January. Final tiller numbers were reduced by 25.9% in Pak-81 and 31.8% in Chak- wal-86 in UFA compared to FA. There was also an ac- celerated rate of senescence of the main stem leaves in UFA and OP when compared to FA (Fig. 4), which became apparent from mid-February in Pak-81 and late February in Chakwal-86. In both cultivars, the rate of leaf production on the main stem was unaffected by filtration, but was slower in OP than in the chambered plots (data not shown).

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15 20 25 30 35 40 45 Solar radiation (Lux x1000)

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Fig. 1. Relationship between solar radiation and temperature differences inside and outside chambered plots. Each value

is an average of three daily readings.

The results of the final harvest showed highly significant effects of treatment. Large yield losses in UFA were seen when compared to FA (Table 2) with total grain weight per plant showing reductions of 46.7% for Pak-81 and 34.8% for Chakwal-86. Reductions in straw weight were similar to reductions in total grain weight, 37% for Pak-81 and 35% for Chakwal-86. A substantial part of the yield reduction was due to reductions in the number of ears per plant, 20% for Pak-81 and 22% for Chakwal-86, respectively; this is largely a reflection of the reduced level of tillering in UFA in both cultivars. However, for Pak-81 there was also a 25% reduction

(a) Ozone

Unfiltered air

Filtered air

(b) Mrogm dioxide

I

January 1“““‘---7’..-.“,,.’ I - -

February March April

Date

40192 l/2192 4l4192 2ei92 Date of Tutm CoGzl

Fig. 2. Ozone and nitrogen dioxide concentrations (nl litre-‘) in filtered-air and unfiltered-air plots. Ozone concentrations represent a 6-h mean (1000-1600 h). Nitrogen dioxide values

are weekly means.


(a). cv. Pak-81.

?? Filtered air

+ Unfiltered air

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19/12/91 2ill92 16/l/92 30/l/92 13/2/92

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(b). cv. Chak-86.

I Filtered air

0 Open plots

+

19/12/91 02/01192 16/01192 3OlOll92 13102192

Date

Fig. 3. Effect of treatment on tiller development for cultivars Pak-81 and Chakal-86.

in the number of grains per ear in UFA, while the third major yield component, the lOOO-grain weight, was reduced by 11% in UFA in this cultivar. In contrast, the yield reductions in UFA for these two components were smaller in Chakwal-86 (12% in the number of grains per ear and 6% in lOOO-grain weight), accounting for the smaller overall yield reduction. It is important to note that the differences between filtered and unfiltered air were statistically significant for both cultivars and for all three yield components. The percentage reduction in

the number of spikelets per ear was similar to that in the number of grains per ear, suggesting that the effect of filtration was on spikelet production rather than numbers of grains produced per spikelet.

A number of parameters showed lower values in OP than UFA, although differences were small compared with those between chamber treatments. Grain yields in the OP were significantly reduced compared to UFA, by 10% for Pak-81 and 12.5% for Chakwal-86. The reduced yield was due primarily to reductions in the

10

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8

7

6

5

4

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Air pollution and its impacts in the Pakistan Punjab

(a). cv. Pak-81.

151

?? Filtered air

0 Open plots

+ Unfiltered air

2/I/92 3ON92 27l2i92 2613192 2314192

Date

(b). cv. Chak-86.

?? Filtered air

+ UnMered air

2/l/92 30/l 192 27/2/92 2613192 231492

Date

Fig. 4. Effect of treatment on main stem leaf senescence for cultivars Pak-81 and Chakwal-86.

number of grains per ear, rather than in the lOOO-grain weight or the number of ears per plant. The number of grains per ear in OP was significantly reduced compared to UFA, by 10% for Pak-8 1 and 15% for Chakwal-86.

DISCUSSION

This work has demonstrated the feasibility of using a simple. relatively cheap, open-top chamber system to test the effects of ambient air pollution on crops in a

developing country. Even under conditions where mean air temperatures approached 30°C towards the end of the experiment, temperature increases within the chambers remained small. In any filtration experiment in- volving comparisons of plant performance inside chambers, the environmental modification imposed by the chambers themselves (and consequently possible interactions with pollutant impacts) are inevitably criti- cised. In the present study, comparison of UFA with OP shows relatively small differences, and none at all in


Table 2. Treatment means for final harvest parameters of Pakistani wheat a~ltivars Pak-81 and Chkwal-86

Harvest parameter Cultivar

Pak-8 1 Chakwal-86

FA UFA OP FA UFA OP

Straw weight per plant (g) 9.28b 585a 5.53a 9.616 6.21a 5.88a Grain weight per plant (g) 25.80~ 13.75b 12.31a 31.78~ 20.69b 18.10a Number of ears per plant 3,986 3.18a 3.19a 3.86b 3,Ola 3.12a Average number of grains per ear 80,lOc 59.93b 53.71a 92.99~ 82.216 69.92a Average number of spikelets per ear 20.326 16.36a 14.36a 22.21c 19.46b 17.79a lOOO-grain weight (g) 81.50b 72.35a 71.75a 89.49~ 84.396 83.21a Total number of grains per plant 316~ 1906 171a 355c 2456 217a Average grain weight per ear (g) 6.53~ 4.346 3.86a 8.32~ 6.94b 5.82a

Treatment means followed by different letters within cultivars are significantly different from one another at PcO.05. [FA: filtered air; UFA: unfiltered air; OP: outside plot.]

the case of some growth parameters. This places further confidence on the validity of the results. Where differences were detected, for example on grain yield, they took the form of UFA>OP. This difference may possibly reflect the small increase in temperature inside the chambers. However, another factor may be the po- tentially adverse impacts of dusts, especially during the drier period of the year. Dust levels in the chambers will have been substantially lower than in the outside plots.

The relatively small differences in temperature and light intensity, and in plant growth, between the inside and outside of the chambers may be due to the com- pletely open-top design, without any type of frustrum, together with the higher solar angle. The ozone concentration in the UFA chamber was also only l-2 nl litre-’ below OP, while measurements indicated little evidence of a vertical gradient in the chamber at the planting density in this experiment. Despite the open-top design, overall filtration efficiencies were high, perhaps reflect- ing the relatively low ambient windspeeds at the site. Thus, overall, the design of these chambers appears highly suitable for work in regions like Lahore.

Both cultivars showed similar reductions in the number of ears per plant (20% for Pak-81 and 22% for Chakwal-86), which can be related to the reduced tiller development also shown in both cultivars in UFA. This delay in tiller production in UFA was first seen in late January, at the time when 0, concentrations began to increase, but this does not necessarily imply a causal relationship. Both cultivars also showed significant reductions in other yield components in UFA, but the reduction in UFA was smaller in Chakwal-86, both in the case of number of grains per ear (reduced by 12% in Chakwal-86, compared with 25% in Pak-81), and loo&grain weight (reduced by 6% in Chakwal-86, compared with 11% in Pak-81). These differences are of interest as an initial screening of cultivar sensitivity showed Pak-81 to be more sensitive to ozone than Chakwal-86.

In this study, the reductions in total grain weight were attributed to the combined effects of reductions in

three parameters: the number of ears per plant, the number of grains per ear and the lOOO-grain weight. It is of interest to assess whether the nature of the observed effects is consistent with those observed in fumigation experiments with the major air pollutants at the Lahore site. The reduction in IOOO-grain weight is consistent with observations by Heagle et al. (1979), Mulchi et al. (1986), Kohut et al. (1987), Pleijel et al. (1991), Fuhrer et al. (1989, 1992) and De Temmerman et al. (1992), following exposure of wheat to 03, although in the latter case there was no significant effect on overall grain yield. Fuhrer et al. (1989, 1992) also reported reductions in numbers of grains per ear, but not in numbers of ears per square metre. The absence of an effect on the latter parameter was also noted by Kohut et al. (1987) and Pleijel et al. (1991) and indicates some differences in the responses observed in the present work from field fumigation experiments with ozone.

The lack of any indication of adverse effects on growth before late January 1992, at which point 6-h mean 0, concentrations were starting to rise above 25 nl litre-‘, provides indirect support for 0, being responsible for the reductions in growth and yield. However, the effect of the substantial concentrations of nitrogen dioxide at this site cannot be excluded. Relatively few studies on O,/NO, interactions have been performed, but three recent studies by European workers on wheat, barley, rape and bean crops (Adaros et al., 1991a,b; Bender et al., 1991) have shown either additive or antagonistic effects in experiments with NO2 concentrations very similar to those recorded at Lahore. Furthermore, Adaros et al. (199 1) reported no negative effects of NO2 alone at these concentrations on the growth and yield of two European wheat cultivars in two successive seasons. This is consistent with other studies which show that adverse effects of NO2 on crop plants only occur at concentrations well above those found at the Lahore site. Never- theless, this issue cannot be finally resolved until controlled fumigation experiments are performed, expos- ing Pak-81 and Chakwal-86 to O3 regimes simulating those recorded in the chambers at Lahore, with or without addition of 20-30 nl litre? NO*.

Air pollution and its impacts in the Pakistan Punjab 153

This study has demonstrated remarkably large reductions in the grain yield of wheat, given the prevailing pollutant concentrations. Depressions of grain dry weight of between 35 and 47% in chambers ventilated with ambient air compared with charcoal-filtered air are considerably greater than nearly all of those reported from open-top chamber studies in Europe and North America. While the latter have shown examples of significant reductions at O3 levels with 7- or 8-h daily means of 4&50 nl litre-’ it_ should be noted that in the present investigation such concentrations were only reached in the latter part of the growing season. Furthermore, with one exception, the reported reductions in yield at such 0, concentrations have been less than half of those recorded at Lahore. For example, Pleijel et al. (1991) reported yield reductions in Sweden of 13% in two seasons with 7-h mean concentrations of 42 nl litre-’ and 44 nl litre-’ while Adaros et al. (1991a) working in Germany, reported yield reductions of 22% and 18% in two cultivars of wheat as a result of fumigation with an 8-h mean concentration of 48 nl litre-‘. In Switzerland, Fuhrer et al. (1989) have found 7-13% reductions in grain yield with 40 nl litre-’ O3 for 8 h per day, while in Belgium, De Temmerman et al. (1992) detected a 7.5% reduction after 38 nl litre-’ for 8 h per day. Most North American experiments have shown little effects at these concentrations but Kohut et al. (1987) found a 33% reduction in yield in a filtration experiment with one cultivar, Vona, in one particular year with a 7-h ozone mean of 41 nl litre-‘. It is worth noting that the European experiments involved spring cultivars; the North American studies used winter cultivars, but only placed the chambers over the crop from spring onwards.

The ambient levels of ozone and other pollutants at Lahore had a substantially greater impact on yield than would be predicted, on the basis of European and North American studies of wheat. The reasons for this are unclear. Local cultivars may be more sensitive, or local climatic conditions may lead to enhanced pollutant impacts. Another factor of possible relevance is that the experiment was carried out in winter with chambers in position from germination; in most other field experiments with winter cereals, chambers are positioned in the spring.

It is possible that pollutants other than those measured on-site may contribute to the observed effects. Continuous sulphur dioxide measurements have just begun in Lahore; early measurements at a site close to the city centre show a mean concentration of 5.9 nl litre-’ (24 h), and concentrations should be substantially lower than this at the experiment site. On the basis of experience in Europe, where a critical level of 11 nl litre-’ SO, has been adopted to protect the most sensitive crop species (Ashmore, 1994) these concentrations would not be expected to have any direct effect on crop yield. However, ammonia concentrations at the site may be significant, while the presence of other photo-oxidants associated with high levels of ozone, such as hydrogen peroxide and peroxyacetyl nitrate, cannot be excluded.

Finally, ozone levels were only measured between lOOO- 1600 h and this could have provided an unreliable estimate of ozone exposure. Data from the mobile laboratory in Lahore consistently show low 0, concentrations at night, with maximum hourly means typically between 1100 and 1500 h. On days with maximum hourly mean concentrations in the range of 60-80 ppb, 0, levels typically exceeded 40 ppb between 0900 and 1800 h. Thus there is evidence from the data available that our 6-h mean concentration does not provide a reasonable basis of comparison with data from Euro- pean and American studies using a 7-h seasonal mean.

The large yield effects may also be due to differences in cultivation techniques. The experiment was run according to local agricultural practices which are in stark contrast to the high-intensity, high-input agricultural practices seen in Europe and North America. The planting density, irrigation practices and low use of commercial fertilisers, along with the fact that the plants were grown in pots, make comparisons with other work difficult. Comparisons between field- and pot-grown crops elsewhere (Sk&-by et al., 1994) have indicated reduced sensitivity to ozone in pot-grown plants when compared to those in the field, possibly due to deficiencies in nutrient and water status. This could be offset in the current study by the lower planting density leading to a greater ozone exposure of indi- vidual plants.

Given all these factors, it is very difficult to be con- fident in making quantitative comparisons of our results with those obtained by workers in Europe and North America, or in identifying the cause of the observed discrepancies. Nevertheless, because we closely followed local agricultural practice, because pot-grown cereals are generally less sensitive to air pollution than field-sown crops, and because yield in the outside plots was only slightly lower than that in the unfiltered air chambers, we consider that our results do not overesti- mate the effects of ambient gases at this site

Resolution of the importance of the different pollutants in the observed effect will be central to any evalu- ation of the wider significance of these results from a single location. Measurements with diffusion tubes indicate that NO, concentrations decrease rapidly with increasing distance from Lahore, and the same would be expected for SO,. Thus, the study needs to be re- peated further away from Lahore, in order to assess its significance for crop losses in the region as a whole. If 0, is the only pollutant responsible for the observed effects, then it is likely that these large reductions in yield are widespread, in view of the medium distance dispersion of this pollutant; if other pollutants are important, this may not be the case. It should be noted in this respect that 0, injury has been reported on field- grown potatoes in the Indian Punjab, some 120 km east of Lahore (Bambawale, 1986).

The hitherto undetected substantial impact of air pollution at a semi-rural site in a developing country on a major agricultural crop must be a matter of great concern. If such impacts are widespread, and not just a

154 A. Wahid, R. Maggs, S. R. A. Shamsi, J. N. B. Bell, h4. R. Ashmore

result of particular features of the experimental site, the implications for agricultural production are consider- able not only for Pakistan but for many other countries. Pakistan is currently self-sufficient in grain production but the high rate of population growth may alter this situation. Air-pollution levels are likely to continue to rise over the coming decades in many developing countries; clearly their potential impact on agriculture needs urgent consideration.

ACKNOWLEDGEMENTS

The authors acknowledge gratefully the financial support of the European Commission via the Directorate General XII Scientific Co-operation Programme, and in particular, the interest and enthusiasm of the programme officer, Mr H. Denecke. We also would like to thank Professor Roger Perry of Imperial College for the organisation of a seminar at Lahore, in March 1989, which permitted the relevant UK/Pakistan links to be established and the research programme described in this paper to be formulated. Finally, we are grateful to the University of The Punjab for access to the Botanical Garden.

REFERENCES

Adams, R. M., Glyer, J. D. & McCarl, B. A. (1988). The NCLAN economic assessment: approach and findings and implications. In Assessment of Crop Loss from Air Pollu- tants, ed. W. W. Heck, 0. C. Taylor & D. T. Tingey, Else- vier, London, pp. 473-504

Adaros, G., Weigel, H. J. & Jager, H. J. (1991~). Concurrent exposure to SO, and/or NO, alters growth and yield responses of wheat and barley to low concentrations of 0,. New Phytol., 118, 581-91.

Adaros, G., Weigel, H. J. & Jager, H. J. (19916). Single and interactive effects of low levels of O,, SO, and NO, on the growth and yield of spring rape. Environ. Pollut., 72, 269-86.

Ashmore, M. R. (1994). Critical levels and agriculture in Europe. In Effects of Air Pollution on Agricultural Crops in Europe, ed. H. J. Jager, M. Unsworth, L. De Temmerman & P. Mathy. Air Pollution Research Report 46, CEC, Brussels, pp. 105-29.

Atkins. D. H. F., Healy, C. & Tarrant, J. B. (1978). The Use of Simple Dtjiision Tubes for the Measurements of Nitrogen Dioxide Levels in Homes Using Gas and Electricity for

Cooking. Report R9184. AERE, Harwell. Bambawale, 0. (1986). Evidence of ozone injury to a crop

plant in India. Atmos. Environ., 20, 1501-3. Bell, J. N. B. & Ashmore, M. R. (1986). Design and con-

struction of open-top chambers and methods of filtration (equipment and cost). In Proc. 2nd European Open-Top Chambers Workshop, Freiburg, September, 1986. CEC Brussels.

Bender J., Weigel, H. J. & Jager, H. J. (1991). Response of nitrogen metabolism in beans (Phaseolus vulgaris L.) after exposure to ozone and nitrogen dioxide, alone and in se- quence. New Phytol., 119, 261-7.

De Temmerman, L., Vandermeiren, K. & Guns, M. (1992). Effects of filtration on spring wheat grown in open-top field chambers at a rural site. I. Effect on growth yield and dry matter partitioning. Environ. Pollut., 77, l-5.

Fuhrer, J., Egger, A., Lehnherr, B., Grandjean, A. & Tschan- nen, W. (1989). Effects of ozone on the yield of spring wheat (Triticum aestivum L., cv. Albis) grown in open-top field chambers. Eviron. Pollut., 60, 273-89.

Fuhrer, J., Grandjean Grimm, A., Tschannen, W. & Shariat- Madari, H. (1992). The response of spring wheat (Triticum aestivum L.) to ozone at higher elevations. II. Changes in yield, yield components and grain quality in response to ozone flux. New Phytol., 121, 211-19.

Heagle, A. S., Spencer, S. & Letchworth, M. B. (1979). Yield response of winter wheat to chronic doses of ozone. Gun. J. Bat., 57, 1999-2005.

Jgger, H. J., Unsworth, M., De Temmerman, L. & Mathy, P. (1994). Effects of Air Pollution on Agricultural Crops in Europe. Air Pollution Report 46. CEC Brussels.

Kohut, R. J., Amundson, R. G., Laurence, J. A., Colavito, L.. van Leuken, P. & King, P. (1987). Effects of ozone and sulfur dioxide on yield of winter wheat. Phytopathology, 77,714.

Mulchi, C. L., Sammons, D. J. & Baenziger, P. S. (1986). Yield and grain quality responses of soft red winter wheat exposed to ozone during anthesis. Agron. J., 78, 593-600.

Pleijel, H., Sk&by, L., Wallin, G. & SelldCn, G. (1991) Yield and grain quality of spring wheat (Triticurn uestivum, cv. Drabant) exposed to different concentrations of ozone in open-top chambers. Environ. Pollut., 69, 151-68.

Saltzman, B. E. & Gilbert, K. (1959). Iodometric microdeter- mination of organic oxidants and ozone. Anal_vt. Chem., 31, 191420

Sk&by, L., Selldkn, G., Mortensen, L., Bender, J., Jones. M., De Temmerman, L., Wenzel, A. & Fuhrer, J. (1994). Responses of cereals exposed in open-top chambers to air pollutants. In Effects of Air Pollution on Agricultural Crops in Europe, ed. H. J. JBger, M. Unsworth, L. De Temmer- man & P. Mathy.

WHO/UNEP (1992). Urban Air Pollution in Megacities qf the World. Blackwell Publishers, Oxford

Air pollution and its impacts on wheat yield in the Pakistan Punjab

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