The inspiration to reassess method and timing for establishing alfalfa (Medicago sativa L.) is meteorological data documenting that current Polish winters are milder than several decades ago, when management recommendations were worked out for this crop. Additionally, prolonged periods of spring drought occur more frequently, posing significant challenges to the development of alfalfa seedlings under a companion crop. The hypothesis was made that as climatic conditions change, the traditional practice of spring sowing with a barley (Hordeum vulgare L.) companion crop may become higher risk, and direct sowing later in the season when rainfall is more dependable would provide advantages. From 2010 to 2014 three series of experiments were carried out over the establishment year and first production year. Establishment success and yield performance of alfalfa sown with a barley companion crop in April was compared to alfalfa direct sown in May, June, July and August. Plant density, overwinter survival, and diameter of the upper taproot from sowings performed in the period April to late July were similar. Plant density with August sowing was significantly higher, but taproot diameter was smaller than in plants sown earlier in spring or summer. Plants from all sowing treatments overwintered well, with the greatest stand loss of only 15% occurring with August sowing. In the first production year, mean dry matter yields were similar for alfalfa sown in the period from April to late July, averaging 11.7 Mg. ha⁻¹. First production year yield associated with August sowing was significantly lower, at 8.88 Mg. ha⁻¹. In the years and locations of this study, the alternative of direct sowing alfalfa up to late July resulted in similar establishment success to the traditional practice of sowing with a barley companion crop in early spring.
This study, conducted in the period 2006-2008, involved an evaluation of yield and commercially useful traits of red cabbage grown from seedlings produced from seeds sown at three different times (the second decade of April, the third decade of April, and the first decade of May). Seedlings were produced in multicell trays in an unheated greenhouse and in a nursery bed from seeds sown at the same time. The experiment included 6 red cabbage cultivars (‘Huzaro F1’, ‘Kalibos’, ‘Langedijker Polana’, ‘Rodeo F1’, ‘Roxy F1’, ‘Zelox F1’). After cabbage heads were harvested in the second decade of October (in each year), total and marketable yield as well as head weight and the head shape index were determined. Red cabbage yield was shown to be significantly dependent on the cultivar, time of sowing, and method of seedling production. Among the cultivars studied, the following proved to be the most productive, irrespective of the other experimental factors: ‘Zelox F1’ (marketable yield averaged 398.11 kg×100 m-2), ‘Roxy F1’ (marketable yield averaged 368.82 kg×100 m-2), and ‘Rodeo F1’ (marketable yield averaged 331.59 kg×100 m-2). The cultivar ‘Kalibos’ was characterized by the lowest marketable yield (on average 257.09 kg×100 m-2). Delayed sowing (to produce seedlings) by 10 and 20 days, compared to the earliest sowing time, had a significant effect on the reduction in total and marketable yield. Irrespective of the time of sowing, the production of seedlings in multicell trays did not have a significant effect on higher head weight. But the influence of the cultivar was significant – heads of the highest weight were found in the yield of the cultivar ‘Zelox F1’ (head weight was on average 1.71 kg). The head shape index was more than 1 and on average it did not exceed 1.35. The cultivar ‘Kalibos’ had the most elongated heads (with a conical shape), while cabbage heads in the cultivar ‘Langedijker Polana’ were closest to the spherical shape.