effect of irrigation on water use, water-use efficiency, growth and yield of mungbean

Field Crops Research, 31 (1993) 87-100 87 Elsevier Science Publishers B.V., Amsterdam

Effect of irrigation on water use, water-use efficiency, growth and yield of mungbean

R.K. Pannu and D.P. Singh Department of Agronomy, Haryana Agricultural University, Hisar-125004, Ha~. ana, India

(Accepted 1 July 1991 )

ABSTRACT

Pannu, R.K. and Singh, D.P., 1993. Effect of irrigation on water use, water-use efficiency, growth and yield of mungbean. Field Crops Res., 31: 87-100.

Mungbean ( Vigna radiata (L.) Wilczek) was grown on sandy loam soil (typic Ustochrepts) under four irrigation schedules: irrigation at cumulative evaporation from USWB Class A pan equal to 200 mm (I2oo), 300 mm (I30o), 400 mm ( 1400 ) and no post-sowing irrigation (Io) during a summer season (April-June) in India. The experiment was planned to study changes in soil water, growth and productivity in relation to irrigation schedules for efficient utilization of limited irrigation water in mungbean. Water use increased with frequency of irrigation and comprised 61, 55, 50 and 25% of pan evaporation during the growing season in I~oo, 13oo, I4oo and Io irrigation schedules, respectively. Water extraction decreased with soil depth in all the irrigation schedules. However, the plants extracted more water from deeper soil layers in the la0o and 14oo than in the 12oo and Io schedules. The highest water-use efficiency was recorded in Io, followed by Iaoo, 14oo and I2oo. The leaf area index, crop growth rate, biomass, seed yield and partitioning of dry matter from above-ground plant parts to grains were significantly higher in Ia0o followed by I4oo, I2oo and Io. The 14oo schedule had the highest harvest index. Seed yield was controlled primarily by pod density, while variation in seed size and grain number per pod had little influence on grain yield. The study has shown that irrigation at 300 mm pan evaporation is more beneficial, in terms of water economy and productivity, than the frequent watering at 200 mm pan evaporation in munghean.

INTRODUCTION

Mungbean is an important grain legume of South and South-East Asia. It is also grown to some extent in Australia and African countries. In Asian countries the short-duration photo-insensitive varieties are generally grown as a catch crop (between two main crops) in a double-cropping system (Singh, 1988 ). In India, it is grown as an irrigated crop during the summer dry season (i.e., April-June). The summer months are not only hot and dry but also have a short supply of irrigation water (Phogat et al., 1984a). Therefore, crops grown during this season have low productivity because of limited availability of irrigation water coupled with higher evaporative demand. Limited water

Correspondence to: R.K. Pannu, Dept. of Agronomy, Haryana Agricultural University, Hisar- 125004, Haryana, India.

0378-4290/92/$05.00 © 1992 Elsevier Science Publishers B.V. All rights reserved.

88 R.K, PANNU AND D.P. SINGH

supply in such an environment can restrict canopy development and reduce crop growth rate through its adverse effects on various morphophysiological processes (Phogat et al., 1984a,b; Muchow, 1985; Sinclair et al., 1987 ). Water deficit can also influence partitioning of dry matter from vegetative parts to grain (Singh et al., 1988). In non-irrigated cereal crops, the allocation of above-ground dry matter to grains may be affected by the difference in mo- bilization of both pre- and post-anthesis assimilates to grains (Passioura, 1986 ). Bidinger et al. (1977) have argued that such division about the mo- bilization of assimilates to the grain is only for the sake of convenience as in reality there is a pool of assimilates in the stem and elsewhere to which con- tributions and from which withdrawals are made. Such studies are, however, lacking in tropical grain legumes in general and mungbean in particular (Singh et al., 1988).

A few studies carried out recently have shown that mungbean tolerates drought to some extent either by early maturity or a stomatal system sensitive to higher vapour pressure deficit of the air (Pannu and Singh, 1988). These studies have, however, reported some contradictory results on responses of mungbean to irrigation. An increase in the frequency of irrigations enhanced evapotranspiration (ET) both in moderately hot (Muchow, 1985) and in very dry and hot environments (Phogat et al., 1984a), but the water-use efficiency (WUE) for dry-matter production remained static in the former and decreased in the latter. Water-use efficiency for grain yield was also unaf- fected by water deficits in the study of Muchow ( 1985 ). Moreover, frequent irrigation of 50-60 mm water in each irrigation at weekly intervals in a wet regime produced the highest grain yield of mungbean and other grain legumes (Muchow, 1985 ). However, there is some evidence that a mild moisture stress is desired to obtain higher productivity in grain legumes (Turner, 1990 ). Thus a detailed study is warranted to understand more clearly the relationship between morphophysiological processes and productivity under different irrigation schedules in mungbean. The present investigation is, therefore, di- rected to evaluate the effects of irrigation on moisture extraction patterns, ET, WUE, growth, partitioning of dry matter and grain yield in mungbean.

MATERIALS AND METHODS

Plant culture A field experiment was conducted on mungbean ( Vigna radiata (L.) Wil-

czek, cv. T-44) during the summer season of 1980 at Haryana Agricultural University, Hisar, India (29 ° 10' N latitude, 75 ° 46' E longitude). Weather conditions during the growing season are given in Fig. 1. Total rainfall was 26.5 mm. The experiment was laid out with four irrigation levels in a ran- domized block design using five replications. The gross plot size was 5.0 × 2.7 m and net harvested plot size was 4.0 X 2.1 m. The four irrigation levels were

EFFECT OF IRRIGATION ON WATER USE, GROWTH AND YIELD OF MUNGBEAN 89

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based on cumulative pan evaporation (CPE) from the USWB Class A pan evaporimeter, i.e. irrigation at CPE equal to 200 mm (I=oo), 300 m m (13oo), 400 mm (I4oo) and no post-sowing irrigation (Io).

The typic Ustochrepts soil was a sandy loam (62.0% sand, 20.4% silt and 17.6% clay), medium in fertility (208, 12, 369 kg ha -t available N, P, K,

90 R.K. PANNU AND D.P. SINGH

respectively in the top 30 cm soil layer) and alkaline (pH 8.0) in reaction. It retained 337 and 109 mm water at 0.03 and 1.5 MPa, respectively in the 0- 165 cm soil profile. The seeds were inoculated with a Rhizobium sp. Vigna culture just before sowing. A basal dose of 25 kg N and 17.5 kg P ha-1 was applied uniformly to the experimental area before the last harrowing. The crop was thinned after seedling establishment by retaining 15 plants m - 1 row length. The crop took 65, 73, 75 and 73 days to attain maturity in the Io, I4oo, I3oo and I2oo treatments.

Measurements Soil moisture content in the 0-15 cm soil layer was determined gravimet-

ricaUy and in the 15-45, 45-75, 75-105, 105-135 and 135-165 cm layers by a neutron moisture meter (Model 2651, Troxler Laboratories, NC, USA). Measurements of soil water content were made from sowing to harvest at weekly intervals and also before and after each irrigation. Water content of the upper 0-15 cm soil layer, determined on a dry-weight basis, was con- verted to a volumetric basis using bulk density ( 1.46 g/cm 3). For the other soil layers, a calibration curve was established to convert neutron counts to volumetric soil moisture content. A measured quantity of about 75 mm water was applied with the help of a Parshall flume at each irrigation. Details of irrigations are given in Table 1.

Evapotranspiration (ET) was calculated from the soil moisture, irrigation and rainfall data. Runoffand deep percolation losses below 165 cm soil depth were assumed to be negligible. Water-use efficiency (WUE = yield/ET) was calculated for each treatment.

Dry-matter accumulation was measured on a sample of five representative plants taken from each plot at weekly intervals starting from 20 days after seeding (DAS) until maturity. Samples were first dried in the sun and then at 65°C till constant weight in an air-circulated oven. Dry weight of above- ground plant parts (leaves, stems, pods, seeds) were recorded. Leaf area was measured on the five plants sampled for dry matter in each plot by an area

TABLE 1

Details of irrigation schedules in mungbean

Treatment Irrigation at No. of Total water Dates of irrigation pan evaporation irrigations applied (1980) values (mm) (mm)

I2oo 200 4 300 5 May, 28 May, 7 June, 20 June I3oo 300 3 225 16 May, 7 June, 24 June I4o o 400 2 150 28 May, 20 June Io No post-sowing 0 Nil -

irrigation


meter (LI3000, LI-Cor, NE, USA). From the leaf area and dry matter data, leaf area index (LAI) and crop growth rate (CGR) were calculated.

For yield studies, pods were threshed and weighed after drying in the sun. Pod number per plant, grain number per pod, pod length and 1000-grain weight were determined from ten plants sampled from each plot at maturity. From the net plot harvests, above-ground biomass and seed yield ( 14% moisture content) were recorded and harvest index (the ratio of seed yield to total above-ground biomass) was calculated. Statistical analysis of the data was done following procedures described by Panse and Sukhatme ( 1961 ).

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Soil water status, water use and its efficiency The soil moisture content increased with the frequency of irrigation and

decreased slowly during the crop season (Fig. 2 ), because of greater water use than its replenishment by irrigation. There was substantial decrease in soil water content during the grain filling stage (50-65 DAS) even in irrigated I3o 0

and I4o o plots. On 17 June 1980, the soil water potential (~soil, mean of whole soil profile) declined to the minimum value of - 0 . 6 0 and - 0 . 5 2 MPa in I4oo

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Fig. 2. Effect of four irrigation schedules on the soil moisture content (0-165 cm) during the crop season. Arrows indicate the dates of irrigation. The crop was sown on 17 April 1980.


TABLE 2

Effect of irrigation schedule on the moisture-use pattern from various layers of the soil profile

Irrigation Soil layers (cm) schedules

0-15 15-45 45-75 75-105 105-135 135-165

Total water use ( m m ) 12o 0 245 143 93 13oo 144 113 98 I4oo 139 96 78 Io 47 49 44 LSD at 5% 38 18 11

Water use/cm soil depth ( m m ) 12o 0 16.3 4.8 3.1 13oo 9.6 3.8 3.3 14oo 9.3 3.2 2.6 Io 3.1 1.6 1.5

37 35 20 82 55 22 58 63 31 37 28 11 10 08 04

1.2 1.2 0.7 2.7 1.8 0.7 1.9 2.1 1.5 1.2 0.9 0.4

Relative moisture use (%, based on water extraction m m / c m soil depth) 12oo 59.7 17.6 11.4 4.4 4.4 2.6 13o 0 43.8 17.4 15.1 12.3 8.2 3.2 I400 45.2 15.5 12.6 9.2 10.2 7.2 Io 35.6 18.4 17.3 13.8 10.3 4.6

and 13oo, respectively. During the growing season, ~btsoil declined to - 0 . 7 MPa in Io, but always remained above - 0 . 2 6 MPa in I2oo.

Soil water extraction decreased with depth (Table 2). Moisture use from the top 45 cm increased with frequency of irrigation but the plants in I3o o and I4oo extracted 67 and 60 mm more water from the sub-soil ( 75-165 cm) than did the frequently irrigated plants in I2oo. This suggests a substantial shift in the rooting pattern with moisture stress in mungbean.

Evapotranspiration did not differ significantly among the various irrigation schedules during the first 40 days of the growing season, but differences became apparent at later stages of growth (Fig. 3 ). The total water use during the crop season in I200, 1300, 1400 and Io treatments was 574, 514, 466 and 217 mm (Table 3 ) corresponding to 7.5, 6.7, 6.1 and 3. l mm average daily water use in the respective irrigation treatments. This amounted to 6 l, 55, 50 and 25% of Class A pan evaporation.

Water-use efficiency differed among irrigation schedules, but there was no consistent relation with irrigation (Table 3). Based on the seed yield and above-ground biomass, non-irrigated plants (Io) had the highest WUE, followed by those of the I3oo, I4o o and I2oo schedules. The frequently irrigated plants in I2oo utilized water least efficiently.

Crop growth and partitioning of dry matter Leaf area index (LAI) was affected by crop age and irrigation schedule

(Fig. 4). In Io and 12oo, LAI increased slowly from the vegetative to the pod

E F F E C T O F I R R I G A T I O N O N W A T E R USE, G R O W T H A N D Y I E L D O F M U N G B E A N 93

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Fig. 3. Effect of four irrigation schedules on cumulative evapotranspiration in mungbean during the crop season. Arrows indicate the dates of irrigation. The crop was sown on 17 April 1980.

TABLE 3

Effects of irrigation schedule on yield components, seed yield, above-ground biomass, harvest index, evapotranspiration (ET) and water-use efficiency (WUE) of mungbean

Parameters Irrigation schedules LSD at 5%

I200 1300 I4oo lo

Pod length (cm) 5.85 Pod number/plant 10.46 Grain number/pod 6.09 1000-seed weight (g) 33.32 Seed yield (Y, kg/ha) 1141 Above-ground biomass 3309

(dm, kg/ha) Harvest index (%) 34.5 ET (mm) 574 ET/Pan evaporation 0.61 WUEv (kgha -~ mm -I ) 1.99 WUEdm (kg ha- ~ mm- l ) 5.77

5.86 6.03 4.90 0.56 15.47 14.07 8.37 4.94 7.12 6.43 4.89 1.37

31.64 32.51 29.05 1.08 1608 1330 837 175 4860 3654 2541 503

33.1 36.4 32.9 0.9 514 466 217 74

0.55 0.50 0.25 0.08 3.13 2.86 3.85 0.36 9.45 7.86 11.70 1.17

9 4 R . K . P A N N U A N D D . P . S I N G H

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Fig. 4. Effect of four irrigation schedules on leaf area index in mungbean. Arrows indicate the dates of irrigation. The crop was sown on 17 April 1980.

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Fig. 5. Effect of four irrigation schedules on crop growth rate of mungbean. The crop was sown on 17 April 1980.

filling stage (56 DAS) and then declined rapidly to maturity. On the other hand, leaf growth continued until about 70% pod maturity (62 DAS ) in I40o and until crop maturity in I300. Among irrigated plants, highest LAI was recorded in I300, followed by the Loo, I2oo and Io treatments.


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Fig. 6. Effect of four irrigation schedules on dry-matter accumulation in leaves, stems and pods of mungbean. Arrows indicate the dates of irrigation. Each point is the mean value (n = 25 ) per plant. The crop was sown on 17 April 1980.

In general, crop growth rate (CGR) was slow during the initial vegetative stage but increased at a rapid rate from flower initiation till about 50% pod formation and started to decline thereafter through to crop maturation (Fig. 5 ). The peak values of CGR lasted for only a short time (6 to 12 days) in the


various irrigation schedules. Similar to LA/, maximum CGR was recorded in I3oo, followed by I4oo, 12oo and Io.

There was a consistent increase in the dry weight of leaves and stems from the vegetative stage to crop maturity in I2oo, 13oo and 14oo (Fig. 6 ). In Io, weights of stem and leaf declined during grain filling. In all irrigation schedules, pods grew at a rapid rate from pod initiation to about 75% pod formation, but thereafter the rates of pod growth slowed until crop maturity. In absolute terms, above-ground dry matter was highest in I3oo, followed by I4oo, 12oo and Io treatments. Among vegetative parts, irrigated plants had more biomass in leaves than stems. At harvest, grains comprised 34.5, 33.1, 36.4 and 32.9% of the total above-ground plant dry weight in 12oo, I3oo, I4oo and Io, respectively. The corresponding values for dry matter in pods were 50.0, 48.0, 51.8 and 47.1%, in leaves 27.3, 24.8, 24.5 and 27.5%, and in stems 24.6, 27.1, 23.5 and 25.6%. These results suggested that reproductive and vegetative plant parts were roughly equal in weight in mungbean.

Seed yield and its components Biomass and seed yield were affected significantly by irrigation schedules

(Table 3). The highest seed yield recorded in 13o 0 was 20.0, 17.3 and 48.0% higher than that obtained in I2oo, 14oo and Io, respectively. Reductions in total dry-matter yield in I4oo, I2oo and Io were 24.8, 31.9 and 47.7% ove r I3o o. The 13o 0 also recorded highest values of various yield attributes, followed by I4oo, I2oo and Io. There was 47.9 and 16.9% increase in number of pods per plant and grains per pod, respectively, in I3o o ove r frequently irrigated 12oo. Differ- ences in harvest index were small between different irrigation schedules, ex- cept for I400 which had a significantly higher harvest index than other treatments (Table 3).

DISCUSSION

Irrigation schedules influenced the water status of the soil profile, ET and WUE in mungbean. An increase in the frequency of irrigation resulted in higher soil moisture content and greater ET. Frequent wetting of the upper surface layer exposed to the hot atmosphere in 12oo created a higher vapour pressure gradient between the crop canopy and the atmosphere, which might have caused a relatively larger loss of the water from the soil surface than in other schedules. On the other hand, the low leaf area index coupled with low stomatal conductance (Pannu, 1981 ) were mainly responsible for low ET from the severely stressed plants. This was reflected in the highest WUE in Io, which had the lowest seed and biomass yield (Table 3).

The plants in I3o o and 14oo extracted more water from the sub-soil (75-165 cm) than the frequently irrigated 12oo and non-irrigated Io plants, probably because of the differences in rooting depth and density, water potential gradient and canopy development (Burch et al., 1978; Taylor and Klepper, 1978 ).


At a minimum value of -0 .52 MPa ~//soil 1 day before irrigation (17 June 1980) in 13oo, the sub-soil still contained 58 mm of usable water ( 15.4% on volume basis), which was adequate to maintain high ET and CGR in I3o 0 (Figs. 3 and 5 ). The water r e s e rve 13o 0 plants also had the second highest WUE at the highest level of grain yield (Table 3 ). These results are, however, not in agreement with those reported by Muchow ( 1985 ). He found no effect of irrigation on WUE in mungbean, either on the basis of seed yield or dry- matter production. Such differences in WUE could arise from either different approaches of irrigation scheduling and/or genotypic differences in partitioning of dry matter from vegetative parts to grains in mungbean (Stanhill, 1986; Singh et al., 1988 ).

Crop growth rate (y) was linearly related to LAI (x) (y= 2.7497 + 0.5354x; r2=0.72) as reported for cowpea and mungbean by Phogat et al. (1984b). The peak rates of CGR recorded in this study were relatively high (46.6 g m - 2 day- 1 in I3oo ) but these were within the limits of those reported by Mon- teith (1978) (39 and 54 g m -2 day -1 in C3 and C4 species) and Tanaka et al. (1966) (55 g m -2 day -I in rice). In a tropical environment with high interception of radiation by a canopy, it is possible to attain relatively high CGR for short periods even in C3 species (Tanaka et al., 1966). The low CGR recorded in the non-irrigated Io treatment was mainly due to reduced leaf growth from the initial vegetative stage until pod formation and increased leaf senescence thereafter through to crop maturity (Fig. 4). Fre- quently irrigated I2oo plants, however, had substantially lower LAI and CGR than less frequently irrigated 13o 0 and Iaoo plants. The exact cause of growth suppression in the 12oo is not known, but the absence of a large reproductive sink (flowers and pods) might be one of the major causes. Sheldrake and Saxena ( 1977 ) found that when pod development was reduced, delayed or prevented, the dry-matter accumulation by the plants was substantially reduced.

The irrigated plants had relatively more allocation of dry matter to leaves than stems. The reverse was true for non-irrigated plants. This suggests that stressed plants mobilised less assimilate to leaves with a consequent reduction in leaf area and water loss from crop canopy. The loss of leaf and stem weight of Io plants during pod filling stage might be due to translocation of some photosynthates from these vegetative parts to grains (Turner, 1986 ). It is interesting to note that the distribution of above-ground dry matter in stems, leaves, pods and grains was influenced by less than 5% over large range of water supply. Harvest index also differed 3.5% (from 32.9 to 36.4%) among four irrigation schedules (Table 3 ). This suggests that there is little difference in mungbean in partitioning of dry matter to different plant parts under var- ied situations of water availability. In the environmental context, a mild stress with the application of irrigation at 300 mm pan evaporation provided the longest reproductive phase with fairly larger photosynthetic green surface and


reproductive storage capacity to attain higher allocation of dry matter to grains in mungbean.

The highest biomass and seed yield was registered in 13oo, followed by I4oo, 12oo and Io (Table 3). The seasonal mean values ofLAI (x) were able to ex- plain about 90% of the variations in grain yield (Y~) (Y~= - 3.5667 + 9.3550 x; r2=0.92) and about 97% of that in above-ground biomass (YD) (Yb=--22.6209+28.6318 X; r2=0.97). Reductions in yield with the decrease in the frequency of irrigation from 13o 0 to I o were due to the adverse effects of moisture stress on leaf area (Fig. 4 ), canopy photosynthesis (Pannu, 1981 ), CGR (Fig. 6) and different yield attributes (Table 3 ). These results are in conformity those reported by Singh et al. ( 1987 ) for chickpeas. Though frequent watering in 12oo improved soil and plant water potential, it had adverse effects on stomatal conductance (Pannu, 1981 ) and induction of flowering and pod setting. However, a mild stress and/or better soil aeration by irrigating mungbean at 300 mm pan evaporation promoted flowering and pod setting. Such results have also been reported in coffee by Alvim (1960) and in lupin by Turner (1990). Alvim ( 1960 ) suggested that water stress reduces growth inhibitors responsible for flower bud dormancy. There is a need to investigate hormone levels in grain legumes.

Among the yield attributes, the number of pods per plant was most sensitive followed by seed number per pod and seed size. A multiple regression analysis suggested that pod density per plant had a dominant role in influenc- ing seed yield. The variation in seed yield per plant could be explained by including in multiple regression analysis one variable (number of pods per plant) 97.5%, two variables (number of pods per plant and seed size) 97.7% and three variables (number of pods per plant, number of grains per pod and seed size) 99.9%, respectively. The higher contribution of pod density to- wards grain yield has also been reported for mungbean (Muchow, 1985; Pannu and Singh, 1988 ) and chickpeas (Singh et al., 1987 ) under variable supply of irrigation water. However, no compensation in terms of increased seed size by reduction in pod number per plant was recorded in severely stressed plants of Io as reported for mungbean by Muchow (1985). This might be due to differences in the severity of moisture stress and in the cultivar used in this study.

In conclusion, the application of irrigation at 300 mm pan evaporation re- suited in 75 mm saving of irrigation water and gave 41% higher grain yield than frequent watering at 200 mm pan evaporation. A mild stress by irrigating at 300 mm evaporation not only promoted flowering and pod development, but also higher WUE, LA/, CGR and yield components. During the growing season, soil water use under the 13o 0 treatment at a 2-3 week interval of irrigation was 55% of pan evaporation. This simple approach of scheduling irrigation (based on pan evaporation) could also be employed for efficient


uti l izat ion o f l imited water resources to attain higher product iv i ty o f mungbean in As ian and other countries .

REFERENCES

Alvim, P. de T., 1960. Moisture stress as a requirement for flowering in coffee. Science, 132: 354.

Bidinger, F., Musgrave, R.B. and Fischer, R.A., 1977. Contribution of stored pre-anthesis assimilate to grain yield in wheat and barley. Nature, 270:431-433.

Butch, G.J., Smith, R.C.B. and Mason, W.K., 1978. Agronomic and physiological responses of soybean and sorghum crops to water deficits. II. Crop evaporation, soil water depletion and root distribution. Aust. J. Plant Physiol., 5" 169-177.

Monteith, J.L., 1978. Reassessment of maximum growth rates for C3 and C4 crops. Exp. Agric., 14: 1-5.

Muchow, R.C., 1985. Phenology, seed yield and water use of grain legumes grown under different soil water regimes in a semi-arid tropical environment. Field Crops Res., 11: 81-97.

Pannu, R.K., 198 I. Development of water stress and its recovery in mungbean. M.Sc. thesis, Haryana Agric. Univ., Hisar, India, 147 pp.

Pannu, R.K. and Singh, D.P., 1988. Influence of water deficits on morpho-physiological and yield behavior ofmung ( Vigna radiata (L.) Wilczek). In: S. Shanmugasundaram (Editor), Proc. 2nd International Symposium on Mungbean. Asian Vegetable Research Development Center, Taiwan, Publ. No. 88-304: 253-259.

Panse, V. and Sukhatme, P.V., 1961. Statistical method for agricultural research workers, 2nd Publ. Indian Council of Agric. Res. Agric. Circ. No. 843, 328 pp.

Passioura, J.B., 1986. Resistance to drought and salinity: Avenues for improvement. Aust. J. Plant Physiol., 35:299-319.

Phogat, B.S., Singh, D.P. and Singh, P., 1984a. Responses of cowpea ( Vigna unguiculata (L.) Walp) and mungbean (Vigna radiata (L.) Wilczek) to irrigation. I. Effects on soil-plant water relations, evapotranspiration, yield and water use efficiency. Irrig. Sci., 5: 47-60.

Phogat, B.S., Singh, D.P. and Singh, P., 1984b. Responses of cowpea ( Vigna unguiculata (L.) Walp) and munghean (Vigna radiata (L.) Wilczek) to irrigation. II. Effects on CO2 exchange, radiation characteristics and growth. Irrig. Sci., 5:61-72.

Sheldrake, A.R. and Saxena, N.P., 1977. Growth and development of chickpeas under progres- sive moisture stress. In: H. Mussel and R.C. Staples (Editors), Stress Physiology in Crop Plants. Wiley-Interscience, New York, NY, pp. 465-483.

Sinclair, T.R., Muchow, R.C., Ludlow, M.M., Leach, G.J., Lawn, R.J. and Foale, M.C., 1987. Field and model analysis of the effect of water deficits on carbon and nitrogen accumulation by soybean, cowpea and black gram. Field Crops Res., 17:121-140.

Singh, D.P., Singh, P., Sharma, H.C. and Turner, N.C., 1987. Influence of water deficit on the water relations, canopy gas exchange and yield of chickpea (Cicer arietinum). Field Crops Res., 16: 231-241.

Singh, P., Singh, D.P., Kumar, A., Chaudhary, B.D. and Thakural, S.K., 1988. Response of munghean-black gram hybrids under water stress conditions. Proc. 2nd International Sym- posium on Mungbean. Asian Vegetable Research Development Center, Taiwan, Publ. No. 88-304:263-271.

Singh, R.B., 1988. Trends and prospects for mungbean production in South and South-east Asia. Proc. 2rid International Symposium on Mungbean. Asian Vegetable Research Devel- opment Center, Taiwan, Publ. No. 88-304: 552-559.

Stanhill, G., 1986. Water use efficiency. Adv. Agron., 39: 53-85.

1 0 0 R.K. PANNU AND D.P. SINGH

Tanaka, A., Kawano, K. and Yanaguchi, J., 1966. Photosynthesis, respiration, and plant type of the tropical rice plant. I.R.R.I. Bull. Los Banos, 7: 1-50.

Taylor, H.M. and Klepper, B., 1978. The role of rooting characteristics in the supply of water to the plants. Adv. Agron., 30: 99-128.

Turner, N.C., 1986. Crop water deficits: A decade of progress. Adv. Agron., 39:1-51. Turner, N.C., 1990. The benefits of water deficits. In: S.K. Sinha, P.V. Sane, S.C. Bhargava and

P.K. Aggarwal (Editors), Proc. Int. Congress Plant Physiology, New Delhi, India, 15-20 February 1988. New Art Press, New Delhi, pp. 806-815.

effect of irrigation on water use, water-use efficiency, growth and yield of mungbean

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