Nodule number and weight on soybean roots depending on seeding rates and row spacings

Abstract

Objectives. To describe the effects of different combinations of row spacings with seeding rates on the variability of the root nodule number and fresh weight on soybean roots in the Eastern Forest-Steppe of Ukraine.

Materials and methods. The studies were conducted in the field grain-intertilled crop of the Department of Plant Production of the ERPC «Opytnoye Pole» of KhNAU nd. a V.V Dokuchaev in 2015–2018 in accordance with conventional methods. The multiple-factor experiment was carried out by split-plot method in four replications. The first order plots were two soybean varieties (factor A): Annushka and Bayka. The second order plots were three row spacings (factor B): 15, 45 and70 cm, and the third order plots were five seeding rates (factor С): 800, 900, 1,000,000, 1,100,000, and 1,200,000 seeds/hа.

Results and discussion. Of the factors under investigation, the seeding rates had the greatest influence on the variability of the root nodule number on plant roots. The average root nodule number on roots of ten plants varied from 48.1 to 83.7, depending on the year, variety and row spacing. With a gradual increase in the seeding rate in increments of 100,000 seeds/ha, the gain in the parameter gradually decreased. With an increase in the seeding rate was from 1,100,000 to 1,200,000 seeds/ha, the root nodule number on plant roots increased insignificantly.

The investigated row spacings also significantly changed the root nodule number on plant roots. A common pattern was a decline in their number, as the row spacing increased. It is rationally attributed to the feeding area narrowing, since with the same seeding rate, the plant number per row with a row spacing of45 cmwas three times as much as that with a row spacing15 cm, and in the experiments with a row spacing of70 cm, it was 4.6 times as much.

In all the study years, the largest root nodule weight on roots of ten plants by the anthesis completion was recorded for variety Baika with the maximum seeding rate of 1,200,000 seeds/ha in combination with a15 cmrow spacing. In particular, the root nodule weight on roots of ten plants in this experiment was 9.35, 16.50, 6.60, and3.90 gin 2015, 2016, 2017, and 2018 respectively.

Conclusions. We found a pattern in the increase in the root nodule number and weight on soybean plant roots when the seeding rate increased. With its gradual increase from 800,000 to 1,200,000 seeds/ha, the gain in the parameter became less promiment.

With a reduction in the plant nutrition area due to the row spacing expansion and, accordingly, a greater plant density in the row, the gain in the root nodule number and weight on plant roots decreased, as the seeding rate increased.

The dominant role of weather conditions in the variability of symbiotic activity parameters has been established. Over 85.0% of the total variability in the root nodule number and weight on soybean plant roots was due to the influence of this factor. Of the studied technological elements, the seeding rate had the greatest impact on the variability of these parameters, and varietal features – the least.