Growing corn as an extra energy crop in grassland based forage systems in Latvia

The aim of this study was to demonstrate the potential of a range of corn hybrids (Zea mays L.) for making energy dense silage in Latvian conditions, which are marginal for corn growing. Field trials were carried out at the Research and Study Farm 'Vecauce' (latitude: N 56 degrees 28', longitude: E 22 degrees 53') from 2002 to 2004. Altogether 33 different corn hybrids according to their earliness bred in the Ukraine were evaluated. Two hybrids bred in Germany ('Loft', 'Anna') were used as checks. Hybrids were grouped according to earliness and characterised by FAO number from 140 to 350. Year effects on results were substantial hence demonstrating that the main factor in Latvian conditions determining good results is temperature (2002 - the best suited year; average DM yield - 16.0 t ha(-1) with a high density of com-cobs - 5 10 g kg(-1); 2004 - the worst results due to a cool season - DM yield 8.77 t ha(-1), com-cob density 315 g kg(-1)). Lack of precipitation could affect quality of forage substantially in very few years (2003; average DM yield - 14.03 t ha(-1) with the density of corn-cobs only 337 g kg(-1)), too. Effect of hybrid earliness was more important in unfavourable years. To avoid poor harvests in such years one should recommend specific hybrids for use in Latvian conditions. Despite some difficulties, especially in cool seasons for bulk yield, we can sustain recommendation to grow corn in Latvia for energy dense silage making.