Planting date and suboptimal seedbed temperature effects on dry bean establishment, phenology and yield

Seedbed temperatures below 15°C are detrimental to dry bean germination and emergence. This field study was conducted to determine the effects of suboptimal seedbed temperatures on dry bean emergence, and the cumulative effects of suboptimal seedbed temperatures during emergence on crop phenology and yield. Selected dry bean cultivars were planted in mid- and late May when seedbed temperatures were below and above the suboptimal temperature (15°C), respectively, at Saskatoon, SK. Emergence, cumulative thermal units to anthesis and maturity, seed yield, yield components and percent frost-damaged seeds were evaluated in 1999 and 2000. The final seedling count at 30 d after planting was 81% for the mid-May planting and 94% for the late May planting. However, the difference in plant stand was not statistically significant. Year-to-year differences in weather influenced the response of dry bean to planting date for maturity and seed yield. The mid-May planting produced the highest seed yield in 1999, when the two indeterminate cultivars in the late May planting failed to mature prior to the mid September frost. The mid-September frost also resulted in a high percent frost-damaged seeds for the late May planting. In 2000, when the first fall frost was in late September, maturity and seed yield of dry bean cultivars were equivalent for planting dates. The mid-May planted dry bean cultivars will result in higher seed yield and quality compared to the conventional late May planting in years with an early fall frost. Key words: Dry bean, seeding date, low temperature, emergence, maturity

Low temperature emergence potential of short season corn hybrids grown under controlled environment and plot conditions

One important reason for limited progress in selecting corn (Zea mays L.) with superior cold tolerance during germination and early growth is the unpredictable occurrence of cold, wet test springs. Breeders need an efficient laboratory test paralleling field emergence under such climatic conditions. Laboratory screening data from 30 corn hybrids with under 2400 corn heat unit ratings were compared to field emergence data in Atlantic Canada to evaluate the usefulness of a laboratory test as an indicator of cold tolerance. Hybrids were ranked by mean percent emergence using 1985–1989 field data collected from seven locations in the Atlantic region. From daily observations on seed germinated in a germinator at 11 °C, mean times to 50% root and coleoptile initiation, and 1-cm coleoptile were calculated using probit analyses. Field emergence ranked from 1 (highest percent) to 30 was compared to ranking of time to 50% 1-cm coleoptile in the laboratory (one represented most rapid growth). Of the top 15 hybrids (by 1-cm coleoptile), 11 fell in the top half of the hybrids ranked by field emergence. Removal of hybrids with low numbers of field observations, all made during the unusually warm spring of 1989, improved the comparison. These results indicate that time to 50% production of a 1-cm coleoptile is a useful screening parameter to select corn hybrids with superior cold tolerance during germination and early growth.Key words: Corn, maize, low temperature tolerance, emergence