Soybean Seed Yield as Affected by Time of Sowing in a Cool Temperate Environment

ABSTRACT

Experiments were conducted over two seasons (1999/ 2000 and 2000/2001) at Canterbury, New Zealand (Lat. 43°38'S, Long. 172°30′E) to study the effect of time of sowing on soybean (Glycine max (L.) Merrill.) seed yield and yield components. Four cool-tolerant cultivars (Northern Conquest (Group V) and Maypole, Alta and March (Group VII)) were sown at three dates (15 November, 7 and 29 December) in 1999 and two of the cultivars (Northern Conquest and March) were sown at four dates (2 and 17 October, 1 and 16 November) in 2000. Seed yield was 277 g m r² for the mid November 1999 sowing, but was significantly decreased for the two December sowings because the shorter time for plant development meant production of fewer pods per plant and reduced seed weight. Cultivar Northern Conquest yielded less than cv. March for the 15 November sowing, but out-yielded it for the 29 December sowing. The yields of the other two cultivars were intermediate. In the second season, seed yield ranged from 224 to 269 g m r² but did not differ with sowing date, while cv. March out-yielded cv. Northern Conquest only at the first sowing. The number of pods per plant was the major determinant of seed yield in both seasons. Sowing between mid-October and mid-November would enable the crop to accumulate the dry matter required to allow a good seed yield.

Key Words:

• Glycine max
• cultivar
• cool tolerance
• seed yield components