STALK LODGING RESISTANCE OF CORN HYBRIDS DEPENDING ON THE PLANTING DATE
Authors: Palamarchuk Vitalii , Kolisnyk Oleh 
Published: January 2020

Purpose. To study the effect of the planting date on the number of the lodged stalks, place of stem breaking and productivity of corn hybrids of various maturity groups. Methods. Field, laboratory, statistical. Results. In the studies, three planting dates were studied, in particular, early date with the soil temperature regime (STR) at the seeding depth of + 8°С, mid date with STR – + 10°С and late date with STR – + 12°С for corn hybrids of different maturity groups (early group – Kharkivskyi 195MV, DКС 2870, DКС 2960, DКС 2949, DКС 2787, DКС 2971 (st), mid-early group – DКС 3476, DКС 3795, DКС 3472, DКС 3420, Pereiaslavskyi 230SV, DКС 3871 (st) and mid group – DК 391, DКС 3511, DК 440, DКС 4964, DКС 4626, DК 315 (st) and their effect on the productivity and number of the lodged stalks after a 15-day overripe in the field after full maturity of kernels. According to the research results, the number of lodged stalks in the group of early hybrids was 11.1%, in the group of mid-early hybrids – 9.0%, and in the group of mid hybrids – 6.2%. So that hybrids with a longer growing season had higher lodging resistance than early forms due to better developed mechanical tissue of the lower stem. A significant change in the number of the lodged stalks was observed in the maturity groups depending on the genetic features of the hybrid (factor B). Hence, over the years of research, in the group of early hybrids, the smallest number of the lodged stalks, was observed in such hybrids as DKC 2960 – 4.9% and DKC 2971 – 7.4%, in the group of mid-early hybrids – DKC 3476 – 4.6% and Pereiaslavskyi 230SV – 8.2%, and in the group of mid hybrids – DKC 4964 – 3.6%, DKC 4626 – 4.9%, DK 391 – 5.1% and DK 440 – 5.8%. The research results also established the effect of the planting date on the productivity and number of the lodged stalks in the studied corn hybrids. Thus, on average over three years, under early planting, the number of the lodged stalks in the group of early hybrids was 17.1%, in the group of mid-early hybrids – 14.3%, and in the group of mid hybrids – 10.4%, whereas when applying the second planting date the number of the lodged stalks was 10.5%, 7.3% and 6.1%, while under late planting date – 5.6%, 5.4% and 2.2%, respectively, for the early, mid-early and mid hybrid group of hybrids. Conclusions. Therefore, according to the research results it can be concluded that later planting date reduces both the total number of the lodged stalks (by 8.2-11.5%) compared with the early sowing and the number of plants that have lodged below the place of cob formation (by 6.6-9.9%). The smallest number of the lodged stalks (6.2%) was observed in the hybrids of the mid group of maturity compared to the mid-early group (9.0%) and early group (11.1%) of hybrids. The same was observed with the number of the plants that have lodged below the cob –
3.3%, 5.8% and 6.0%. There has been established the dependence between the yield and number of the lodged stalks depending on the planting time, so that the yield ranged within 8,4-9,4 t/ha in the group of early hybrids under early planting , 7.2-8.7 t/ha under mid one, 6.4-7.7 t/ha under late one, and the number of fall lodged stalks – 17.1%, 10.5% and 5.6% respectively under early planting, mid planting and late planting, in the mid-early group – 9.7-10.9 t/ha, under mid planting – 8.7-10.0 t/ha, late – 7.2-8.6 t/ha, and the number of the lodged stalks – 14.3%, 7.3 % and 5.4% and mid hybrids –11.5, 10.2 and 9.2 t/ha and 10.4, 6.1 and 2.2%, respectively. According to the factor analysis, it has been established that the planting date makes a significant contribution (17% of the total contribution) to the lodging resistance of plants of corn hybrids. The number of the lodged stalks varies considerably depending on the conditions of heat and moisture supply. An increase in the number of the lodged stalks was observed in 2012 (11.6%), compared to 2011 (10.8%) and 2013 (3.9%) due to the moisture deficiency during the growing season of corn that year.