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Determination of sowing times for sod-seeded crops on the central tablelands of New South Wales

P.M. Dowling

Agricultural Research & Veterinary Centre, Forest Road, Orange, 2800

Limitations imposed by terrain and soil effectively restrict use of agricultural land on the central tablelands to grazing enterprises. Cropping as an alternative to grazing might be considered if reliability could be improved. Further, the adoption of sod-seeding techniques would allow greater flexibility at planting. However, planting time with this technique is influenced by the timing of germinating rain, and where crops are to be sown, by cultivar and probability of frost incidence at flowering. An initial step in the development of a cropping system is to ensure that a range of crops and cultivars adapted to the environment is available for planting over an extended period. A field experiment aiming to determine earliest sowing times for a number of crop/cultivars is described here.


Ten crop/cultivars (Table 1) were sod-seeded on 27 April and 17 June 1983 onto plots pretreated with glyphosate (2 1 ha-1) two weeks before each planting. Layout was a randomised block design with four replicates. A thermograph with a soil probe (2 cm depth) was used to estimate mean daily temperature.

Results and Discussion

Degree days accumulated between seedling emergence (E) and flowering (F) (Table la), and flowering dates (Table lb) for each planting were used to calculate a planting time where flowering would coincide with the mean date of the last heavy frost (14 October (I)).

Table 1. Degree-days, flowering dates, estimated earliest planting dates and yield of ten crop/cultivars sod-seeded at Orange, 1983.

Planting dates adjusted on this basis provided dates ranging from 15 March for Maple peas to 18 June for Marnoo rape, a period of 14 weeks (Table lc). To ensure greater flexibility of the technique it will be necessary to extend the range of planting dates from early March through to the end of July, another six weeks. Choice of cultivars with a greater vernalization requirement, and grazing will permit earlier plantings while strictly long day plants could be considered for late winter-early spring plantings. The earliest planting dates (Table lc) can only be regarded as approximate, however because of the influence of other factors on flowering time. In addition species such as rape and peas have extended flowering periods and would not be expected to be as adversely affected by frost at flowering.

In 1983 frosting appeared to have little affect on flowering as reflected by yield of Marnoo rape and Dun peas (Table 1d). The last heavy frost occurred on 8 October.

1. Foley, J.C. 1945. Bull. No. 32. Commonwealth Meteorological Bureau. 142 pp.

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