Dynamics of maize growth before harvest

Dynamics of growth can be investigated in the total dry matter as well as i n different parts of maize plant. Vrzal (1993) presents the highest values in the rate of growth (CGR) 18.28 g.m(-2).d(-1) during the growing season w hat corresponds to high yields of dry matter. In the years 1995 to 1997 tri als at the Research Station of the Faculty of Agronomy of Czech University of Agriculture in Praha, Cerveny Ujezd, were established to verify the dyna mics of maize growth in the period of ripening. 24 hybrids in three differe nt early groups (eight hybrids in each) (FAO 200-220, 230-250 and 260-280) of similar properties in each group were investigated. Average of precipita tion for 30 years was 493 min, 333 mm during the growing season. The length of the growing season was 150 to 160 days. October 11 can be considered as the first frosty day for the average of the years. Experimental plots were arranged by the method of randomized blocks of the size of harvest area 17 m(2) in four repetitions. Intervals of observations were 8 to 12 days. Res ults in tables are average for the investigated years. The most intensive g rowth of grain weight was recorded in the starting phases of growth, at the beginning of milk ripeness (Tab. I). High significance between different g roups of hybrids according to FAO number was found. Insignificant differenc e in the growth of grain weight was recorded on day 172 from seeding. The h ighest rate of maize grain was measured in the hybrids of the FAO group 230 -250 and 260-280 in the phase of the beginning of milk ripeness (Tab. II). In the group of hybrids 200-220 the highest rate of growth was found in the phase of wax ripeness (the phase of the beginning of milk ripeness was not studied in these hybrids). The development of the rate of grain growth is in congruency with the literary data (Volodarskij, 1975). The CGR Value was ranging from 8 to 15 g.m(-2).d(-1) and in the period of wax ripeness was s ignificantly lower. Statistically significant values were recorded at the p hase of wax to full ripeness. Maximum grain weight growth occurred in milk wax ripeness, in further phases of the development it was lower. In the per iod of maize harvest in milk wax ripeness in most hybrids the basis for gra in yield was created and nutrient concentration in total mass was recorded. The growth of the total weight of maize plants and CGR are presented in Ta bs III and IV. High statistical significance was reported in samplings on d ays 172 and 182 from seeding. The decrease of dry matter weight closely cor relates with the decrease of growth rate (Tab IV). In this period the growth rate decreased even to negative values of CGR wha t can be explained by less favourable meteorological conditions. High stati stical significance between different groups of hybrids according to the FA O number was found. In evaluation of the grain and whole plants growth rate it can be said that in different groups of earliness of hybrids the growth rate was approximately identical. The difference between hybrids was recor ded by comparison of hybrids in one group of earliness which was, however, in the boundary of significance but the curve of the growth rate was almost the same in the studied dates what is also confirmed by literary results ( Vrzal, 1985; Petr, 1980) according to them the pattern of curves was depend ent on the earliness of investigated hybrids. The green matter increase in the period of maize ripening is given in Tab VIII, Plant weight grew during the growing season to the phase of the beginning of milk to milk wax ripen ess. Dry matter increased due to ripening but the green matter weight of pl ants was falling.