Organic manuring have significant influence on the sweet corn growth. Important element of sweet corn agrotechny can be catch crops cultivated on the ploughing down. A field experiment was carried out at the Zawady Experimental Farm near Siedlce. There was investigated the effect of green manures applied as sunflower catch crops on changes in the content of dry matter, ascorbic acid, total sugars and monosaccharides in sweet corn . The sunflower was sown at three dates: the 21^st of July, 4^th of August and 18^th of August. The effects of catch crop green manures was compared to the effect of farmyard manure (40 t·ha^-1) and the control. Sweet corn cultivated in control and after catch crops sown on the 18^th of August content more dry matter in kernels then cultivated after farmyard manure. Catch crops sown on the 21^st of July and 18^th of August reduced ascorbic acid content in corn compared to farmyard manure and the catch crop sown on the 4^th of August. Sweet corn cultivated following farmyard manure and catch crops sown on the 21^st of July and 4^th of August had a higher content of total sugars compared with corn following the sunflower catch crop sown on the 18^th of August. An average content of monosaccharides in sweet corn after sunflower catch crop sown on the 21^st of July was higher than in corn cultivated following farmyard manure.

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