Influence of sowing dates on the productivity of maize on common chernozem of Northern Kazakhstan

The studies determined the optimal sowing time for maize hybrids of different maturity under the conditions of the forest-steppe of Northern Kazakhstan. Field experiments were carried out in 2015-2017 at North Kazakhstan State University named after M. Kozybaeva. The availability of soil with mobile P2O5 is low (29 mg/kg), average is N-NO3 (15.8), mobile K2O is high (415 mg/kg), the content of humus is 5.7%, pH (aq.) - 7.0. When sowing on May 15-17, the least prolonged vegetation period was observed, which was less than the periods of May 10-12 and 20-22 by 1-10 days. Field germination in the experiment was 79.3-91.4%, while in early-maturing it is higher than in late-maturing hybrids. Late-seeding plants on May 20-22 generally reduced field germination. The tallest plants were formed when sowing on May 20-22, with mid-late hybrids exceeding the height of early - maturing ones up to 31 cm, and mid-early ones up to 17 cm. Early-maturing hybrids had a smaller leafage (26.4-28.6%) compared to mid-early (27.6-29.8) and mid-late (30.3-31.3) hybrids, but with a larger share of ears (28.5-29.1 and 19.8-20.3%, respectively). The best sowing period for the studied maize hybrids was May 15-17: both early-maturing and mid-early hybrids formed the highest yield of 31.8-41.9 t/ha. In this option, the yield of Knezha hybrid 511 amount to 40.7, of Turan 150 SV to 40.9, of Kazakhstansky 435 to 41.9 t/ha, which is significantly higher than that of the hybrids Moldavsky 257 SV - 31.8, Omka 130 - 37.2 t/ha. Only Turan 150 SV managed to form a vegetative mass suitable for silage (with a dry matter content of more than 25%) at one sowing period, i.e. May 15-17. In this option, this hybrid formed the largest collection of dry matter in the experiment with 10.37 t/ha, Turgayskaya 5/87 with 9.92 t/ha, which is higher than the other hybrids ranging from 7.20 to 9.40 t/ha. At the optimal yield period of May 15-17, the protein concentration increased by 0.30-1.00% in comparison with early sowing on May 10-12.