THE SOWINGS DATE IN RELATION TO THE QUALI TY AND YIELD OF GRAIN OF WINTER-WHEAT

The investigations were carried out in a field experiment established by the Research Institute of Agroecology and Soil Management at Hrusov any near Brno in 1986 to 1988. The locality is situated in the maize g rowing region, average annual temperature being 9.1-degrees-C, annual sum of precipitation 484 mm. Three varieties of winter wheat were chos en for the experiment - Vala, Hana and Slavia and three dates of sowin g: Ist early, IInd timely, IIIrd late. During vegetation, essential au tumn and spring fertilizers were combined with foliar fertilizers (nit rogen and phosphorus) in four variants. Tab. II shows that the best da te of sowing was the IInd one i.e. timely sowing in the agrotechnical term, for five of the eight studied indicators (grain yields and level of proteins, bulk weight, thousand-kernel weight (TKW) and the propor tion of full grains). Late sowing significantly decreased the grain yi elds, bulk weight, thousand-kernel weight the proportion of full grain s, i.e. those characters, closely associated with grain yields. Tle re duced content of proteins and gluten as quoted by some authors, did no t appear to be significant in our case. On the contrary, late sowing s ignificantly increased the values of sedimentation and the swelling nu mber of gluten, both of which characterize the better baking quality o f wheat. Early sowing, compared with the most favourable timely sowing , gave lower values for most of the characters, particularly lower gra in yields, bulk weight and crude-protein content. The weather of the i ndividual years considerably affected the absolute values of the studi ed characters. In 1988, being a drier and warmer year (precipitation 3 62.8 mm, average annual temperature 9.1-degrees-C), the values or bulk weight (838 g), thousand-kernel weight (45.05 g), and proportion of f ull grains (93.2 %), were the highest, with grain yields being 7.38 t. ha-1, while in 1987, which was a more humid (598.9 mm) and colder (8.2 -degrees-C) year, the yields of grain were the highest (8.69 t.ba-1), the values of volume weight and TKW being lower (i.e, 770.8 g and 37.0 9 g, respectively). The high yield of 1987 was apparently achieved nam ely due to the high stand density and smaller size of grains as compar ed with 1988. In 1987, when the yields were the highest compared with 1986 and 1988, the baking quality was significantly the lowest in term s of the content of proteins (I 2.25 %), wet gluten (24.3 %) and sedim entation quality (28 ml). Tab. IV confirms the negative correlation be tween grain yields and baking quality in the studied set and gives the values of correlative coefficientS. On average, the most favourable s owing date, even despite the different characters of the individual ye ars, was found to be the timely IInd date. The variety affects the bak ing quality, i.e. the content of proteins, gluten and especially the s edimentation value and swelling number of gluten. The Hana variety pro ved its high quality. The different response of the varieties to the s owing dates was not very marked, the IInd date was found to be the mos t favourable. The effect of the individual years affected the variabil ity of the quality characters studied. The least marked was the effect of fertilization, as given in Tab. III, what was due to the relativel y small difference among the variants of fertilization applied. The co ntribution of this factor in terms of the date of sowing was very low. The survey of relationships between the indicators of quality and gra in yields of wheat expressed by the correlation coefficients r showed a positive highly significant relationship between the yield and the b ulk weight and the proportion of full grains, significant between yiel d and TKW, i.e. characters associated with the size and weight of kern els, while the relationship regarding the indicators of the internal q uality affecting the baking quality of wheat, in our case the content of proteins, gluten and the sedimentation value