The area under sweet corn is increasing in Poland due to increased consumption and suitability for cultivation in all regions of the country. However, sweet corn is sown on different dates in these regions. A field experiment was carried out in the years 2006-2008 at the Experimental Station in Zawady (52º03’ N; 22º33’ E). It was conducted to examine the effect of three sowing dates (26th April, 10th May and 24th May) and covering with non-woven PP on the yields of three sweet corn cultivars (Sweet Nugget F1, Rana F1 and Sheba F1). Weather conditions in 2007 and 2008 were more favourable for sweet corn growth compared with the year 2006, when high air temperatures were accompanied by very low precipitation from mid-June to late July. In 2007 and 2008, higher early, total and marketable yields were produced (by 29 and 13%, 50 and 44%, as well as 72 and 74%, respectively), and more ears were harvested (by 40-45%), too. Moreover, with a delay in the sowing date, kernel yields harvested in these years were twice as high as in 2006, when weather conditions contributed to more rapid maturation of ears and to an increase in the percentage share of early ear yield in the total yield. What is more, over the study years, on average both the total and marketable yields of ears increased with the delayed sowing, however only in the coldest 2008 this increase was significant. Unlike in 2008, delayed sowing in 2006 caused a decline in the number of ears and kernel yield. An application of non-woven PP increased the yields, the share of early yield in the overall yield of marketable ears and the number of ears. Covering was most beneficial in cooler years for the first sowing date. The highest ear and kernel yields were obtained for ‘Sweet Nugget F1’. Differences between the cultivars were observed for the first sowing date.

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