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:4MiDn J. Plant Physiol., Vol. XXX. No.4, pp. 372-379, 1987
CROP'STAND AND PRODUCTIVITY OF EARLY SOWN RAIN FED (BARANI) WHEAT
A.K. BAGGA. N.V.K. CHAKRAVARTY AND O.P.S. TOMAR
Division of Plant Physiology Indian Agricultural Research Institute
New Delhi-llOOl2
SUMMARY
Early sown rainfed wheat suffers losses in germination, seedling establishment and grain yield due to higher temperatures prevailing at sowing time. As the advanc ing of sowing date of rainfed wheat is considered to be beneficial in view of the availability of ,larger amounts of stored soil moisture from the preceding monsoon, the present work was carried out to see whether the adverse effects of temperature could be mitigated by using 0) suitable plant type or (ii) higher seed rates. A variety i.e.• Hindi 62 known for its relatively better performance under early sown rainfed condition and another high yielding V3.riety HD 2329 were subjected to three sowing dates i.e .• early, normal and late, and three seed rates i.e., 80, 120 and 160 kg/ha.
Though the seedling establishment was reduced in early sowing, higher seed rates increased it considerably. Higher seed rate plots which had larger leaf area and heavier crop stands but lower soil moisturl at 90 days from sowing and lower water potential and transpiration rate of the flag leaf, gave grain yields similar to the lower seed rate plots.
Hindi 62 produced higher productive shoot number and grain yield than HD 2329 in the three sowings. The former variety was also characterised by a larger leaf area and a longer duration from sowing to maturity. Based on these results suggestions have been made about a wheat plant type for early sown rainfed condition.
INTRODUCTION
Rainfed (barani) wheat in India is sown early in the robi season to take advantage of the soil moisture stored in the root zone from the preceeding rainy season. There is, however, a limit to advancing the sowing date of rainfed wheat as the prevailing temperatures are on the higher side for the wheat plant and are harmful to the germination as well as early growth. Wheat sowings in the rainfed areas have therefore to wait till the temperatures declined to a level at which they are least harmful.
In spite of the above slated obstacle in advancing the sowing date, the large amounts of water which would be available to the rainfed wheat crop if sown early
CROP STAND AND PRODUCTIVITY OF RAINFED WHEAT 373
"in the season has attracted the attention of agric,ultural scientists (Bagga, 1986). It is believed that this water can be beneficially used provided the problem of unfavourable temperature could be overcome either by selecting suitable plant types -or through manipulation of cultural practices. The present study was initiated with the objective to find out if the loss in crop establishment and consequent grain production under early sowing dates could be compensated by i) increasing the "seed rate and (ii) by using a variety known for its relatively better performance.
Of the two varieties used in this work, Hindi 62 possess characteristics more -close to those mentioned above as compared to HD 2329 Both the varieties were -sown on three dates viz., early, normal and late for rainfed conditions with three 'seed rates in each sowing. It was expected that a comparison of the responses of
the two varieties to sowing dates and seed rates would yield important information -on the possibilities of advancing the date of sowing in the rainfed areas.
MATERIAL AND METHODS
Two wheat (Triticum aeslivum L.) varieties viz., Hindi 62 and HD 2329 were 'Sown during rabi 1983-84 under rainfed conditions on the sandy loam soils of the Indian Agricultural Research Institute farm. The crop was sown on 20.10.'83 ,(early-DI), 4.11.'83 (normal-D1) and 19.11.'83 (late-D]). Due to the rainfall on
10.10.'83 (37.2 mm) and 14.10.'83 (4.4 mm), the sowing could be started from 20.10.'83 onwards. Three seed rates viz., 80 kg/ha (SI), 120 kg/ha and 160 kg/ha ,(S3) were employed and the crop was sown in randomized block design with four replicates, the plot size being 6 x 2.3 m with row to row spacing of 23 em and N,P,K, "Were applied at the ratio of 50,30 and 30 kg/ha respectively at sowing time.
Observations were recorded on (a) seedling count per metre row length on 18 days after sowing (b) leaf water potential and transpiration rate of the flag leaf using bench press apparatus and auto pormoter, respectively (c) leaf area from 0.5m row length at anthesis stage from all the four replicates using electronic leaf area ,meter (d) the number of productive shoots from one metre row length in all the replicates (e) grain yield from 1m2 area in all the replicates and (f) soil moisture
"from two replicates in the root zone upto 90 em death at 30 and 90 days after sowing using screw auger for soil sampling. The soil moisture was determined .gravimetrically. The data on meteorological parameters viz., maximum and mini. mum temperatures were collected from the daily recordings on the meteorological .observatory located 400 m east of the experimental site.
RESULTS AND DISCUSSION
'Temperature aud erop establishmeut
374 . A.K. BAGGA ET AL.
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40
20
HINDI 62
HD2329
Fig. 1 (a) : Seedling number and (b) leaf area of Hindi 62 and lID 2329 under early (DJ, normal (DJ and late (Da) sowing with three seed rates, Sl (80 kg/ba), Sl (120 kgfba) and Sa (160 kg{ba) under rainfed rabi season 1983-84.
7his reduction in seedling number resulted presulDably from poor germination or death of the germinated plant. Since the soil moisture in the upper layers was· more or less si~ilar in the three sowings, the above lOiS in seedling number could be attributed to higher temperature conditions prevailing under early sowing. As temperature· dependence of respiration is exponential and the critical temperature for respiration is lower for early growth stages (Yudina et. al., 1982), it is likely that the increased respiratory activity caused by higher temperatnres in the early sowing exhausted seedlings which resulted in higher mortality rate as compared to· later sowings which faced relatively milder temperature conditions (Fig. 2).
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CROP STAND AND PItODUC11VlTY OF ItAINFED WHEAT
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fold increase in plots with 160 kg/ha seed rate as compared to the plots with 80 kg{ ba seed r a t e . '
The plots with higher seed rates also showed higher leaf area in both -<:u1tivars (Fig. I b) and were characterized by baving heavier crop stand (based on -visual ranking). -Among sowings, however, the two varieties behaved differently • .Hindi 62 displayed larger leaf area in early sowing but it was the reverse in HD 2329 which had higher leaf area in later sowings. The two varieties obviously presented two different types of adaptive responsese to early sown conditions. Whereas in Hindi 62 the leaf development was favoured, it was adversely affected
in the variety HD 2329.
:Soil moisture depletion leaf water potential and transpiration
The depletion of soil moisture from 90 cm depth was evident even at 30 days .after sowing but a deOnite pattern related with the treatments was seen only at
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March AprilStandard
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Fig. 2 : Mean daily maximum and minimum temperatures of standard weeks during the
crop growtb period (1983-84). Duration of vegetative period (up to anthesis) and maturity of Hindi 62 HD 2329 are depicted at tbe top, Db DI and Da represent early, normal and late sowings, respectively.
In the early sowing, the water potential and transpiration rate of the flag: leaf were lower in plots with higber seed rates (Table I). These plotes also develop ed heavier crop stands as already mentioned above. It is understandable then,.
that under the warmer conditions of early sowing, the higher seed rate plots exhausted the soil moisture faster and showed lower values of transpiration rates. as compared to low seed rate plots. Higher seed rate plots were thus subjected to·
CROP STAND AND PRODUCfIVlTY OF RAINFED WHEAT 377
Table I : Transpiration rate and water poteDtial of :8.ag leaf, ear number and grain yield of Hindi 62 and HD 2329 under fainfed cUltivation
Dl Ds D, Dl Da Da
(Seed rate 80 kg/ba) Hindi 62 HD 2329
Grain yield (g. m-2) 207 186 88 165 160 152
Ear no. m-l row length 70 64 56 44 51 54
Transpiration rate (ug. em-II-l) 2.24 1.88 2.05 2.05 1.86 2.05 Water potential (-bar) 16.0 17.0 15.0 20.0 18.0 15.5
(Seed raIl! 120 kg/ha)
Grain yield (gm_2) 196 193 182 140 150 133
Ear no. ml row leDgth 75 75 72 40 46 59
Transpiration rate (ug em-II-l) 2.46 2.05 1.79 2.37 2.02 1.94 Water potential (-bar) 16.0 18.0 14.5 21.5 19.5 14.5
(Seed rale 160 kg/ha)
Grain yield (g.m-2) 209 225 193 143 140 142
Ear no: m-l row length 74 101 70 41 39 49
Transpiration rate (ug. em-lei) 1.82 2.11 2.21 1.83 2.19 2.26 Water potential (-bar) 20.0 17.5 15.5 21.0 20.5 17.0
Dit D, and Ds=EarJy. normal and late sowiDgs.
Note : Only variety was Significant at 5% P in case of ear number (CD=7.2) and grain yield (CD =25.9).
Grain production
The grain yield was not affected either by advancing the sowing date or by increasing the seed rate (Table 1). When the number of productive shoots (ear number per metre row) is considered, which was similar between the plots with different seed rates, it becomes obvious that the plots with higher seed rates and with heavier crop stand could not produce a matching proportion of ears. Thus, the crop which was sown earlier with normal seeds rate (80 kg/ha) had more soilmoisture for use but failed to produce more grain yield because of a poor crop stand and a lower productive shoot number as compared to the later sowings. In case when the seed rates were increased, there was considerable improvement in seedling number and crop stand, but again this did not help as there was a faster de.pletion of soil moisture causing increased soil water stress which resulted in failure to sustain enough ear heads for higher grain yield.
378
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Table. II : Soil moisture (%) in wbeat varieties at 30 or 90 days arter sowing 3OD.4.S
Depin (em) VISI ViSa VIS, V.SI V.S. V.S,
Dl
~30 8.4 7.8 7.S 8.S 6.S 8.0
-3Q.:-60 9.0 8.9 8.8 9.8 6.8 9.0
~90 10.4 13.0 12.S 9.8 9.S 9.8
90-120 14.8 14.S 13.S 12.8 12.S 12.S
D.
0-30 8.4 8.0 7.4 9.S 7.S 9.0
3()...6() 8.8 6.' 8.2 9.S 8.8 10.0
60-90 11.S 9.S 8.2 13.S 9.S 11.S
90-120 14.S 14.0 13.S 14.S 12.S 13.S
Da
~30 8.4 7.8 8.4 8.8 8.4 9.0
3()...6() 9.0 8.S 10.0 9.S 9.4 10.0
~O 10.S 11.0 11.0 (lo,s 9.8 10.S
90-120 12.0 12.S 13.0 12.S 12.S 13.0
DI 90DAS
~30 6.8 6.8 6.0 7.8 S.9 8.9
3()...6() 8.7 8.3 S.8 9.1 6.2 8.8
~90 9.7 13.4 9.9 9.0 9.2 9.0
90-120 14.1 14.3 11.8 12.1 II.'J 13.0
D.
~30 7.S 6.4 8.7 8.3 6.4 8.7
3()...6() 7.S 8.0 9.9 8.2 6.4 9.9
~90 7.S 12.4 9.9 8.6 8.7 8.7
90-120 9.9 12.4 12.4 11.1 12.4 12.4
D.
~30 8.4 7.4 6.4 8.7 6.4 8.7
3()...6() 8.1 S.7 6.4 8.7 6.4 9.9
~90 11.1 8.6 6.4 8.7 6.4 9.9
90--120 13.6 13.S 11.1 14.9 11.1 12.4
VI=Hindi 62; V.=HD 2329; DIt D.and D,=Eary, normal and late sowing respectively, Sit S., S,=80, 120 and 160 ki/ha seed rate.
Saini et al., (1986) reported that the slow ear differentiation and development in Hindi 62 was less sensitive to a range of temperatures which offers explanation for longer vegetative period of this variety under rainfed conditions. These characteristics of Hindi 62 .when viewed in the ligbt of results obtained in the present work provide a basis for suggesting desirable characters for plant type for early sown rainfed condition. ThUl, a suitable plant type for advancing the date ofsowing in the rainfed areas should have :
. (a) capacity to estab~ a good crop stand initially,
(b) slow growtb in the ensuing period,
"
CROP STAND AND PR~DUCnVlTY OF B.AJNFED WHEAT '379
For fulfillingth.e requirement at (a) above, the piant must possess heat tolerance for germination and early seedling growth stages which should relate to temper~tures prevailing during sowing time. Since germination is a soil based process, soil temperatures upto 5 cm dc;pth
win
also matter in this case. The point at (b) above' envisages a plan~. type havin~ 11.I~w vegetativegrpwth so that the ear development is pushed into cooler periods of the seasOn, ensuring the'formation of a relatively bigger 'sink: especially in respect of grai~ number. Higher tempera ture and w~ter stress are known to adversely affecte the grain number per ear in wheat (Asana et. al.. 1955; Asana and Mani, 1958; andBagga
and Rawson, 1977). The proposed slower veBetative growth will redUce the water loss from the crop, The implications of point made at (c) above are quite obvious as the favourable effects of c+r conditions OD grain yield are well known. Theauthors fully agree with Asana (1968 and 1976) who while suggesting a model for wheat plant type for minfed cultivation considered
till
9 2 ' 25°C (maximum) to be the satisfactory temperature for grain development. In. addition to the above suggested characteristics, the plant type should also possess drought resistance qualities i.e. high water use effiiciency, low water requirement and capacity to extract soil moisture from deeper soil layers.
REFERENCES
Asana, R.D. (1968), Growth habits of crops of non-irripted .lI'Cas. Important characteristics of plant types, Indian Pmg. 18 : 25-27.
Asana, R.D. (1975). Physiological approaches to breeding of drought resistant crops. I.C.A.R. Tech. Bulletin (Agric) No. 52, Indian Council of Agricultural Research, New Delhi.
Asana, R.D. and Mani, V.S. (1958). Analysis of drought resistance in crop plants U. The influence
of soil drought on the relationship between yield and ear characters in wheat (field
experiments). Indian J. Genet. Pl. Breed. 18: 187-98.
Asana, R.D., Mani, V.S .. PiIlay, K.P. and Gahlot, LN.S. (1955). Analysis of drought resistance in crop plants. I. The influence of soil drought on the relation between yield and ear characters in wheat (pot culture). Indian J. Genet. PI. Breed. 15: 59-79.
Baga, A.K.(1986). Investigations on wheat physiology. In: Twenty five years of coordinated wheat research. 1961·86. Ed. J.P. TandclD and A.P. Sethi •• Wheat Project Directorate. All India Coordinated wheat Improvement Project. I.C.A.R. I.A.R.I. New Delhi 110012.
Bagga, A.K. and Rawson, H.M. (1977). Contrasting response of some morphologically similar wheat cultivars to temperatures appropriate to warm temperate climates with hot summers : A study in controlled environment. Australian. J. Plant Physiol. 4: 877·87.
Saini, A.D., Dadhwat, V.K .• Pbadnawis, B.N. and Nanda. R. (1986). Influence of sowing dates on pre.anthesis phenology in wheat. Indian. J. Argic. Sci. 56(7) : 503·11.
Yudina, 0.5., Leina, G.D. and Berez in. B.V. (1983). Temperature dependence of respiration in
some spring wheat cultivars from the middle Volga region. Fiziotogiya Biokhimeya
