The influence of cultivar, weather conditions and nitrogen fertilizer on winter wheat grain yield
Winter wheat (Triticum aestivum L.) is one of the most productive and significant cereal species in Latvia used for food grain production. The aim of the research was to e valuate winter wheat grain yield depending on nitrogen fertilizer rate, crop - year (meteorological conditions) and cultivar and determine the impact and interaction of research factors on grain yield. Field experiments with winter wheat cultivars ‘Bussard’ and ‘Zentos’ were conducted at the Latvia University of Agriculture, Study and Research farm Peterlauki during a three year period (2009/2010, 2010/2011 and 2011/2012). Nitrogen (N) was applied (N60, N90, N120, N150 kg ha - 1 ) in spring after resumption of v egetative growth. Assessment of both winter wheat cultivars showed that crop - year, cultivar, nitrogen fertilizer, crop - year × cultivar had a significant (p < 0.05) impact on grain yield. Nitrogen fertilizer did significantly (p < 0.05) affect the grain yie ld of winter wheat, treatment with N90 showed of yield increase, compared to N60, while further use of increasing amounts of N fertilizer did not increase grain yields significantly. Results suggest, that winter wheat grain yield by 34% depended on cultiva r, by 33% on crop - year (weather conditions), and by 13% on crop - year × cultivar. Influence of the nitrogen fertilizer effect was small – 3%. Medium strong positive correlation was found between HTC in the vegetation period from winter wheat heading to grai n ripening.