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MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



photoperiod, and decrease in light intensity at 

 the base of plant. 



Wimmera ryegrass, unlike the aggressive bar- 

 ley grass, does not persist in pastures. Because 

 of its desirable properties, such as large yields 

 of easily harvested and easily sown seeds and 

 lack of awns and sharp pointed fruits, reasons 

 have been sought for its poor persistence and for 

 its almost inevitable replacement by barlej 7 grass 

 on both acid and alkaline soils. 



Smith's comparative studies (4-1, 43) showed 

 that frost affected barley grass more than Wim- 

 mera r} T egrass. When frosts were recorded, pure 

 barley grass swards had less herbage after 66 

 days than after 32, because of leaf loss from 

 frost damage. In the absence of frost, barley 

 grass produced more tillers after defoliation and 

 higher yields than Wimmera ryegrass did in the 

 winter and early spring — periods when feed 

 shortages are likely in southern Australia. 



Tiller densities of intact plants of barley grass 

 and Wimmera ryegrass were similar in spring, 

 but in frequently cut plants there were more 

 tillers of barley grass, especially at low-sowing 

 densities. Densities of n~egrass four times greater 

 than those of barley grass were frequently re- 

 quired to give equivalent yields of dry matter. 



Both species produced more tillers as a result 

 of nitrogen applied early, but nitrogen applied 

 late during stem elongation had no effect on 

 barley grass tiller production, though it signifi- 

 cantly increased tiller number in Wimmera rye- 

 grass. This suggests that the low production of 

 tillers by ryegrass after defoliation, particularly 

 when growing with barley grass, may be due to 

 a deficiency of nitrogen. 



As Wimmera ryegrass approached maturity, 

 the growth rate was greater than that of barley 

 grass, and final yields of the two grasses were 

 similar. Smith (Jfi) considers that the heavier 

 seed of barley grass is a factor in its higher pro- 

 ductivity during the first 7 to 8 weeks of growth. 

 Initial growth of wheat (Williams 1$) and sub- 

 terranean clover (Black 8) depends on seed re- 

 serves. 



Pennisetum typhoides (bulrush millet) is a 

 cross-pollinated, summer-growing annual of po- 

 tential value as first-year companion species for 

 Townsville stylo in cattle pastures in northern 

 Australia. Bulrush millet is more a crop than a 



pasture plant but it is the only tropical annual 

 grass for which morphological data have been 

 obtained in Australia. 



The main features of its seasonal growth and 

 development and its response to defoliation at 

 different times are shown in figures 4 and 5, taken 

 from Begg (7). 



Seedlings emerged 4 days after sowing in mid- 

 January. Tillering began in the second week 

 when the main shoot had 4-5 unfolded leaves 

 and continued rapidly until the fifth week, when 

 tillering ceased at full light interception by the 

 canopy. By this time, the main shoot had 6 to 7 

 fully expanded leaves. Floral initiation took 

 place in February, and internodes elongated 

 rapidly, with consequent elevation of apical meri- 

 stems, from then until flowering, 12 to 14 weeks 

 after emergence. As in temperate species, the 

 onset of reproduction, the period of rapid inter- 

 node elongation, was marked by a high rate of 

 dry matter production. 



Recovery from cutting was high in the early 

 and vegetative stages of growth. In contrast, the 

 grass made poor recovery from cutting during 

 internode elongation when growth was rapid and 

 shoot apices were above cutting height. 



At this time and particularly in the 7- to 

 8-week period, little or no new tillers developed 

 from basal buds. Begg reasoned that axillary 

 tillers failed to develop because of a low re- 



Dry matter yield 



Leaf area index 



Tiller number 



Height of apical meristem 



(Jan) (Jan) (Feb) (Feb) (Mar) (Mar) (Apr) (Apr) (May; 

 14 28 11 25 11 25 8 22 6 



Weeks after emergence 



Figuke 4. — Bulrush millet. Seasonal growth and develop- 

 ment and changes in height of shoot apex. (After 

 Begg, 7.) 



