THE SIZE AND THE SHAPE OF GRAINS IN THE R EGULATION OF MAIZE STAND EMERGENCE

Emergence is, without any doubt, at least for agronomist, important ma tter, though variable one, and therefore an indicator hard to be defin ed. Breeders do not like it, however, the growers are interested in it . For them the stand uniformly and completely emerged is always a symb ol of a good start and promising production hope towards new vegetatio n. Emergence was one of indicators in the trial with so-called starlin g cultural practices of maize hybrids. In this trial the effect of som e factors manipulated just at the very beginning of the stand - the si ze and the shape of grains, sowing depth and date, this all at the app ropriate hybrids of various earliness of ripening was investigated. We differentiated the course of emergence with the number of continuousl y emerged plants N(DELTA) in about two thirds to three fourths of the standard length of the time needed for a complete emergence of the sta nd, and also the final state of emergence - emergence with final numbe r of emerged plants N(f). The effects of these number as partial funct ion f1 and f2 were synthesized by addition into the resulting function f based on the principle of expression of the loss L:f((L)) = (k - N( DELTA)) : N(f), where k is the number of sown grains (Fig. 1). From a practical point of view, we consider the losses of L as the situation, where L less-than-or-equal-to 1; if L = 0-0.3 (low losses), if L = 0. 3-0.7 (medium losses), and if L = 0.7-1.0 (big losses). A dynamic aspe ct predominated (approximately N(DELTA)) at the relatively low average value of loss L = 0.33 for the whole trial and three years in evaluat ion of emergence by means of above-mentioned function f. The highest e ffect on emergence exerted the sowing date and grain shape: the worst emergence was observed at an early sowing date, flat grains had signif icantly higher emergence compared with round grains. As the effect of the most stable factor is concerned during the mentioned three-year pe riod on the emergence, it was sowing date (stable fourth place). Mediu m depth h2 derived from the double of TKW (HTZ in g): h2 = 2 . HTZ : 1 00 (in cm). However, for early sowing date depths were uniform h1 = 3 cm, h2 = 4 cm, h3 = 5 cm. Generally, with growing depth, the number of emerged plants is growing too. The grain size was the second stronges t factor, but simultaneously with it, the least stable. With greater g rain, the higher final emergence and lower variability in the number o f emerged plants. The earliness of the hybrid was the second most stab le, but at the same time the weakest factor in the emergence of stand. Regarding the emergence the best were medium-early hybrids. Good emer gence, however, is not the only ideal for a grower. It is well documen ted by confrontation presented in Tabs I and II, partially explaining at least the modest attitude of creators of hybrids to this phase of t he stand development. The final result of stand emergence is for the g rower in practice living under the conductor's baton of detailed cours e of weather an obligatory rule. This is an evident difference compare d with the breeder's approach. The results presented here based on eme rgence confirmed justification, at least on the practical level, for g rading the grain yield not only according to healthy (valuable) propor tion and waste, but also to grade further the healthy proportion itsel f.