Effect of time of planting on the Growth and Development of Annual Medics (Medicago spp.) in Eastern Wyoming.

M.J. Walsh, J.M. Krall and R.W. Groose
Department of Plant Sciences, University of Wyoming, Laramie, 82071-3354

Annual medic pastures have been used successfully for many years in ley-farming systems in areas with Mediterranean type climates around the world (Crawford et al., 1989). The ability of these pastures to produce high levels of quality forage under rainfed conditions has substantially improved as well as stabilised farm productivity of these regions. Annual medics appear to be highly suited for production in ley-farming systems in the dryland farming regions of North America. However, there is a need to determine the effects of the North American summer growing season on their phenological development. Thirteen annual medic varieties/species were evaluated for dry matter, pod and seed production as well as days from emergence to flowering and maturity at 3 times of planting in the 1997, growing season in Eastern Wyoming. Days to flowering and harvest are taken from the respective times of emergence which were for T1 20/5/97, T2 9/6/97 and T3 28/7/97. The dry matter production of the medic cultivars was related to the length of their growth and development period where increased periods resulted in higher levels of dry matter production (See Table). The Australian developed cultivars produced lower dry matter levels and had restricted pod and seed productions when compared with the winter hardy medic species (M. Rigidula, M. Rigiduloides and M. Lupulina). This was due to the generally shorter growth and development periods of the Australian cultivars, which were up to 2 months shorter than those of the winter hardy medics. The time to flowering from emergence for these Australian cultivars was also substantially shorter in the Eastern Wyoming than has been previously recorded under Australian conditions.

Table. Days to flowering and harvest and dry matter production of 13 annual medic varieties/species in Eastern Wyoming.
Variety   
Species         
Days to flowering      
Days to harvest
Dry matter
(t/ha)
Pod production
(1000 pods/m2)
T1
T2
T3
Australia*
T1
T2
T3
T1
T2
T3
T1
T2
T3
George
M. Lupulina
56
51
48
107
101
98
5.1
2.3
1.2
14.9
6.5
0
Sava1
M. Scutellata
41
36
27
71-80
58
51
48
1.3
1.7
1.8
1.5
2.0
0.9
10344
M. Rigidula
78
70
Frost
121
121
98
8.6
8.2
3.3
1.7
0
0
Santiago1
M. Polymorpha
43
38
41
71-183
71
6 0
76
1.1
0.9
1.8
1.3
8.5
0
Orion1
M. Sphaerocarpas
51
46
34
66
7 3
69
1.0
1.1
1.3
1.5
1.0
0
Caliph1
M. Truncatula
41
36
34
71-148
58
6 0
69
0.9
1.0
3.5
4.5
4.9
1.5
Herald1
M. Littoralis
43
38
41
101-110
10 0
8 7
76
3.3
4.9
2.1
12.3
11.3
0.5
Paraggio1
M. Truncatula
56
60
Frost
>110
91
87
76
3.9
5.6
3.0
6.0
3.2
0
119R-P
M. Rigiduloides
44
60
Frost
121
101
98
7.8
1.3
2.7
4.0
0
0
LSD (p=0.05)
3.5
3.0
2.2
6.5
6.4
ns

* Days to Flowering in Australia (Crawford et al., 1989)
1 Indicates Australian developed cultivars

Reference

Crawford, E.J., Lake, A.W.H. and Boyce, K.G. (1989). Breeding annual Medicago species for semiarid conditions in southern Australia. In Advances in agronomy, Vol. 42, academic press, Inc. pp. 399-437.

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