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Abstract E.xpt. St a, in Xalubia Governorate, A,R. of Egypt to investigate the effect of soil moisture stress (SMS) as well as skipping one irrigation at different stages of plant age on growth, yield, yield components and grain quality characters of tne local wheat cultivar (Bakha 8). The first and second experiments were conducted in 1978 I 19 season and the third and fourth in 1979/80 season. The first and third experiments were performed to study the effect of SMS, while the second and fourth to study the effect of skipping one irrigation at different stages of plant age. The experimental design of each experiment was randomised complete block desigen in four replications. The treatments were as fallowa:- I, The effect of soil moisture stress (first and third e.rpt.): 1. Irrigation after 40% depletion of available soil moisture, i.e. AMD = 40%. 2. Irrigation after 60% depletion of available soi3. Irrigation after 80% depletion of available soil moisture i.e. AMD = 80%. 4. Irr:l.gction after 100% depletiGn of available soil moisture for a week i.e. afte~ one week of 100 % AJJD. All the treatments started at tillering stage, II. The effect of drough at different stages of plant age (second and fourth expt.): A: Sb: irrigations ~the first at planting, the second at tillering, the third at the beginning of spike initiation, tl;e Lmrth at heading, the fifth at flowering and the sLI:t\1 at Dough stage, B: Fi .,, irrigations: the s,n~ as ”A” except slcil-YPing an .. ·c·rigation at tille:dng .ltq;e. io::t stage. ” ,,, r: s ”A” except skipping ’, __ iii:g of spikes initiat- D: Five irrigatiOll’: the same as ”A” except skipping ~~ ir~igation at heading stage. E: Pive irrigations: the aa::e as ”J..” e::::e;:-t st;:i;:;:~ ~,; an irrigation at flowering stage.lh Five irrigations: the sa.Illl!l as ”A.” except skipping a.n irrigation at dougl:t stage. The planting dates were 30/11/1978 and 1/12/1979 for the first and second season, respectively. Irrigation water was measured by portable water meter. Soil samples were taken Just before ae well as 48 hr. after every irrigation to determine the water consumptive use. The quantity of irrigation water was added to rais the soil moisture content to the field capacity. The most important results for this investigation could be summarized as follows: I. Effect of soil moisture a tress (SMS) ”first and third e.xpt.”; 1. Exposing wheat plants to high moisture stress ranging from irrigation after 40% depletion of available soil moisture to after a week of lOo% depletion of’ available soil moisture depressed flag leaf area, plant length and spike length. 2. The relationship between soil moisture content and each of flag leaf area, plant length, spike length and number of tillers without spikes was ourvilinJ. Exposing wheat plants to tb.e :f’.:J:rtner -;;~ntoa c.epressed yield and yield components characters i.e. number of spikes per plant, number of spikelets per spike. number of grains per spike, number of uafertile florets per spike. total number of florets per spike, fertility percentage. 1000 kernlea weight • grain yield and straw yield. 4. The combined data revealed that the differences between irrigating the plants at 40% AMD and 60% AMD were not significant for the number of spikes per plant, the number of spikelets per spike, the number of grains per spike and the 1000 kernels weight. In addition, the differences between irrigating the plants at 40% AYD, 60% AMD and 80% AMD were not significant for the number of spikes per plant and number of spikelets per spike. I 5. The r>,lationships between soil moisture content at the irrigation time and each of number o:f’ spike per plant, number of spikelets per spike, number of grains per spike• number of unfertile florets per spike, total number of florets per spike, 1000 kernels weight, grain yield and straw yield were6. Increasing depletion of available soil moisture before irrigation ranging from 40% to after one week of 100% depletion of AK depressed some grain qualit1 ob.aracters, i.e. the hectol.i:ier 110igttt,. fi:al t: r>ar percentage and ash percentage. On the contrar.r, other grain quality cBaracters i.e. fine middlings percentage, middlings percentage (Bran% ), crude protein peroe~t~ge, sedimentation value, wet gluten ~~ ~ percentage, dry gluten percentage and do11gll properties ( dough energy. dough extensibility, dough elasticity and tBe ratio of elasticity ,to extensibility ) increased with increasing depletion of A.M. before irrigation. 7. ’!’he relationships between each of th.e grain quality characters ( excluding dough properties ) and soil moisture content at the irrigation time were curvilinear. ll a. Irrigation requirements ( IR ) tended to decrease wi tb. increase in soil moisture stress from the low moisture stress up to tb.e bigll stress i.e. :f’rom irrigating after 40% depletion of A.M. up to irrigating one week after 100% depletion of A.M. ~verage values of !R of the two seasons were 4087, )259 , )J21 and 2421 m’/faddan when the plants wer~ ..irrigated after 40~, 60%, 80% and 100% ( for one week ) depletion of the available soil moisture, 9. Average consumptive use of the two seasons tended to decrease with increase in SMS before irrigation. Average seasonal oonaumpti ve use values were 78.4 • 63.4, 66,8 and 52,1 ems when the plants were irrigated after 40%, 60%, 80% and 100% for a week depletion of A.M. respectively. 10. Maximum consumptive use ( c.u. ) ae well as coll£1umptive use coefficient (K) of,wheat plants were obtained duri:og March. 11. Averages of water use efficiency ( 1lUE ) i.n kg. grains/m> water were o.65).o.ns. 0.0# a.Qd O.i.ll for the irrigation treatments after 40%, 60%, 80% and after one week of 100% depletion of AM, respectively; II, Effect of drought conditions at different stages of plant age:- 1. Exposing wneat plants to drought at tillering stage or at the beginning of spike initiation reduced flag leaf are~ compared with the other treatments. Minimum value of flag leaf area was obtained by irrigating Wheat plants 5 times skipping one at the2. Exposing wheat plants to drought at tillering stage or the beginning of spike initiation stage or heading stage had a significant reduction effect on plant length. Delaying wheat plant expo sure to drought i.e.” at flowering stage or dough stage had no significant effect on plant length. 3. Exposing wheat plants to drought at the beginning of spike initiation stage as well as at heading stage reduced significantly the spike length. Minimum spike length was obh.ined by cposi.Jlg wi:l.eaX plant to drought at heading stage_ 4. Number of tillers without heads increased sig.nificanlty by exposing wheat plants to drought at the beginnjng of spike initiation or at heading stage. 5. H. i.nimum. number of tillers per plant was obtained by exposing wheat plants to drought at tillering stage; lj’ I 6. Exposing wheat: plants to drought at tile tilleri.ng stage (B) or at the beginning of spike initiation (C) or at heading stage (D) reduced significantly the number of spikes per plant, the number of spikelet a per spike and tile number of grains per spike compared w itb. the control (A). Minimum number ofspikes per plant was obtained~ Tre&~ (el. w~ile minimum number o~ t~e spikelete perspike and grains per spike were obtained from treatment (D). 7. Number o~ un:fertile florets per spike was decrea-• sed significantly by exposing wheat plants to drought at the beginning of apike initiation where as it increased significantly by exposing the plants to drought at heading stage. s. Exposing wheat plants to drought at tillering stage (E), or at the beginning of spike initiation stage (C) resulted in a significant reduction on tb.e total number of florets per spike. Minimum number of florets per spike was obtained by treat .... ment (C)~ 9. Fertility percentage was reduced clearly with exposing wheat plant to drought at heading stage (D). ’I 10. Erposing wheat plants to drought at flowerillg stage (E) or dough stage (F} reduced significantly the l.OOO kernels weight. Minimum value was scored with treatment (F). 11. Grain yield was reduced significantly with ski¥ping one irrigation during one of the plant lifestages i.e. treatments 13, o, D, E and F• Minimu.m reduction was oocured with skipping an irrigation at heading stage. 12. Straw yield was reduced significantly wit~ exposing wheat plants to drought at the ’tillering stage or at the beginning of spike initiation stage (0). Minimum value was obtained with treatment (O). 13. The hectoliter weight decreased significantly with skipping an irrigation at dougl:l stage (D). 14. Exp9sing wheat plants to drought at B.llY’ stage ( B, 0, D, E or F ) reduced significantly the fine flour pe:t’oentage • MaximQI!I value was oocured with skipping an irrigation at dough stage (D). 15. Exposing wheat plants to drought at an,y stage of plant age ( B, 0, D, E or J.i’ ) increased siga1fioant11’ the :f’ine 11!Liddli.tlgs percentage. Var!m•mr increase oocu.red ~th ek1pp:f.ns: an :i.rJ:oj,p:t::f..aA at; u._ stage~ 16. Skipp~g an irrigation at the tillering stage (B) or the beginning of spike initiation (0) or the heading stage (D) or the dough stage (F) increased significantly the bran percentage. Maximum increase oocured with treatment (F).17, Skipping an irrigation at the heading (D) or the dough stage (F) increased significanlty the crude protein. Maximum increase occured with treatment ( D )~ lti. Exposing Wheat plants to drought at the beginning of spike initiation stage (C) or heading stage (D) or floweriAg stage (E) or dough stage {P) increased s:l.gnificanl ty the sedimentation value, Maximum value obtained with treatment (F). 19. Exposing wheat plants to drought at the heading stage (D) or dough stage (F) increased significantly the wet gluten percentage. Maximum increase occured with treatment (D). 20, Dry gluten percentage increased significantly with skipping an irrigation at the heading stage (D) or the dough stage (F). While skipping an irrigation at the tillering stage (B) decreased ’Signi:ficantly the d:r7 gluten perc~~Uttage. K•x:imum increase ooca.red with treable.nt (D). 21. Exposing wlleat plants to @ought at the heading stage increased significantly the ash percet~tage while it decreased significantly with skipping an irrigation at flowering stage (E).22. Irrigation requirements (IR) of wheat plants which were iJ:’l.”igated si% ti.mes {J.) e.:.c.eeai! Umae :u:::igated :N.ve ti-mes b,r skippi-ng one :f.1’riga;Uon ai: 11- llering stage (B) or the beginning of spike initiation stage (C) or the heading stage (D) or the flowering stage (E) or at the dough stage (P). Average values of IR of the two seasons were 2568.6• 2337;0, 2204.6, 2268.2 1 2356.4 and 1970.4 m3/faddan for treatments A. ( control ) , :B, C, D, I and P, respectively. 23. Consumptive use of water (ou) for the plants which were irrigated sir times (A) exceeded those irrigated five times by skipping one irrigation at the ~illering stage (B) or the beginning of spike initiation stage (C) or the heading stage (D) or the flowering stage ( E) or at dough stage (F}. Average seasonal ( cu ) values were 52.4, 4J.s. 4J.O, 39.5, 42.8 an~!J7,8 ems for treatments A (control), . ’ B1 . C,D, E and ’P respeotivel,v< · 24. The period of maximum water use values corresponding closely to the heading, flowering and dough stages of all treatments. J.finimum eu was obtained with irrigating wheat plants five times ezoluding an irrigation at the dough stage {l!’). lfarliiWDc.u. as well as consumptive use coefficient (K) of wheat plants for all treatments were obtained during March. 25. Consumptive use coefficient (K) of wheat plants which irrigated six times exceeded those irrigated five times. It was 0,875, 0.721• 0.6~7, 0,629, 0.714 and 0.652 .ror treatments A(control), B, C, D, E and F, respectively. 26. Jverages of water use efficie::~cy ( WUE )• in kg, er”.ns/mJ \~’ter were 0.744. 0.806, 0.703; o •. 655; 0.797 and O.o02 for the treatments A (control), B, C, D, E and F, respectively~ |