Organic manuring is suggested to be necessary in sweet corn cultivation. It is not always possible to use farmyard manure due to economic, production or technical reasons. Catch crops used as green manures can be an alternative source of organic matter. A field experiment was carried out in central-eastern Poland to investigate the effect of phacelia and amaranth catch crops used as green manures on sweet corn growth and yields. Catch crops were sown at three dates: 21^st July, 4^th and 18^th August, and incorporated in late October. Sweet corn was cultivated in the first year following manuring. The effect of the green manures was compared to farmyard manure applied at a rate of 40 t∙ha^-1 and a non-manured control. Of the catch crops examined, the highest yield of fresh and dry matter was obtained for phacelia sown on the 21^st of July (33.6 t∙ha^-1 f.m. and 6.3 t∙ha^-1 d.m.) and 4^th of August (33.7 t∙ha^-1 f.m. and 5.5 t∙ha^-1 d.m.). A delayed sowing date of phacelia seeds, from 21^st of July to the 18^th of August, caused a decrease in the quantity of fresh matter and dry matter by 26 and 37%. Amaranth sown on the 21^st of July produced 26.2 and 5.3 t∙ha^-1 fresh and dry matter. Delaying the sowing date of amaranth seeds by 14 and 28 days decreased the yield of fresh and dry matter by 18 and 55–58%. There were found similar effects on yield of farmyard manure, phacelia and amaranth catch crops sown on the 21^st of July. Delaying the sowing date of catch crops by 2 and 4 weeks decreased the marketable yields of corn cobs by, respectively, 16.2 and 28.9% for phacelia and by 12.8 and 24.4% for amaranth. The average weight of marketable corn cobs cultivated after farmyard manure, phacelia and amaranth catch crops sown on the 21^st of July and phacelia sown on the 4^th of August were similar. Biological productivity of corn cobs following farmyard manure and the catch crops examined (except amaranth sown on the 18^th of August) was similar and ranged from 66.5 to 72%. ‘Chalenger F₁’ produced marketable cobs with a higher average weight but with lower biological productivity than ‘Sweet Wonder F₁’.

145-159