The secondary effect of sunflower (Helianthus annuus L.) catch crop in sweet corn (Zea mays L. var. saccharata) cultivation

A field experiment was carried out in central-eastern Poland (52°06’N, 22°55’E) to investigate the effect of a sunflower catch crop used as green manure sown on three different dates (21^st July, 4^th and 18^th August) on sweet corn yield and growth. The ‘Challenger F₁’ and ‘Sweet Wonder F₁’ corn cultivars were cultivated in the first year following organic fertilization. Sunflower was plowed in the third week of October. The effect of the catch crop’s green manure was compared to farmyard manure applied at a dose of 40 t ha^-1 as well as a control without organic manuring. The biomass quantity and the amount of macroelements absorbed with the sunflower catch crop sown on the 21^st of July was similar to the quantity absorbed with farmyard manure applied at a rate of 40 t ha^-1. The quantity of organic mass and macroelements absorbed with the sunflower sown on the 4^th of August was smaller by 20%, and by 50% for the 18^th of August set, compared with the corn treated with farmyard manure. The effects of farmyard manure and sunflower catch crop sown on the 21^st of July on the yield were similar. The marketable yield of cobs of corn plants cultivated following farmyard manure treatment and catch crop sown on the 21^st of July amounted to 12.6 and 12.4 t ha^-1, respectively. An application of sunflower sown as a green manure on the 2^nd and 3^rd date prior to corn cultivation decreased marketable cob yields by 8% and 25% as compared to the farmyard manure. The corn cobs cultivated following the sunflower sown on the 21^st of July and treated with farmyard manure had the greatest mass. The corn cobs cultivated with farmyard manure were characterized by the highest biological productivity (72.1%); similar was the cob production of corn cultivated with catch crops sown on the 21^st of July and the 4^th of August. The ‘Challenger F₁’ and ‘Sweet Wonder F₁’ yields were similar. ‘Challenger F₁’ produced cobs with higher mass whereas ‘Sweet Wonder F₁’ produced cobs characterized by greater biological productivity.