The main aim of our research was to analyze the change of the soybean productivity, depending on varieties, cultivation methods and a seeding rate.

The experiment scheme had three factors:

1.  Varieties: Romantyka and Ustya;

2.  Cultivation methods: without cultivation, mechanical cultivation, chemical cultivation;

3.  Seeding rates: 600, 700, 800 and 900 thousand/ha.

A soybean was sowed in 15 cm distance between rows by a common line method in the third ten-day period of May. The crop cultivation methods were used for each test example by different means, according to the scheme rate. Two test examples were cultivated by before shoots and after shoots drilling method in concordance with the mechanical cultivation method. The chemical cultivation method, aimed to lessen the weed amount and carried out at the experiment test examples, was done due to the sprinkling plant leaves with the herbicides in the 3^rd phase (the herbicides that were used for the research: Basagran (bentazon – 48 % ) – in a normal state 2 l/ha and Fyuzilad Super (fluazifop-p-butyl – 12.5 % ) – in a normal state 2 l/hа.

The soybean varieties Romantyka and Ustya gave the worst yield at the test example areas with no weed control. It was noted that when the varieties sowing rate was increased from 600 to 900 thousand/ha, they gave better yield. The mechanical cultivation method, used for Romantyka, enlarged the yield in 2.1 times in comparison with the test examples without care. It meant that natural weed growth lessened the yield on 52 %. The sowing rate productivity with 600 thousand seeds/ha at the level with 1.83 thousand/ha was formed. The yield productivity, enlarged to 0.22 thousand/ha, was the result of the increasing in the sowing rate to 700 thousand/ha. Being increased in the sowing rate to 800 thousand/ha, the agrophytocenosis compression influenced on the productivity improvement – 0.16 thousand/ha. The next compression with a maximum seed sowing rate 900 thousand/ha influenced on the productivity rate – 1.96 thousand/ha. It also showed that an interspecific soybean competition existed, it had a negative influence on the sawing rate and lessened the yield productivity rate on 0.25 thousand/ha in comparison with the test examples where the sawing rate was 800 thousand/ha.

The chemical cultivation method, used for Romantyka, gave worse yield in comparison with the mechanical method. The average productivity was lessened on 0.02 thousand/ha. The average productivity was increased in 2.21 times in comparison with no cultivation method. The minimum sowing rate 600 thousand/ha in combination with the chemical method, used for Romantyka, gave the yield at the level of 1.82 thousand/ha. Being increased in the sowing rate to 800 thousand/ha, the next agrophytocenosis compression influenced on the yield lessening (2.03 thousand/ha). A maximum seed sowing rate (900 thousand/ha) had influence on the yield, continuing to lessen it on 0.1 thousand/ha.

The soybean variety Romantyka (with the sowing rete 800 thousand/ha) gave the highest productivity – 2.21 thousand/ha at the test areas, cultivated by the mechanical care method. The best result of the soybean sowing yield (2.16 thousand/ha) was gained due to the seed sowing (with 700 thousand seeds/ha) at the test areas, cultivated by the chemical care method.

The soybean varieties Ustya gave better yield, which was 2.3 times higher at the test example areas, cultivated by the mechanical method, than at the areas with no weed control, it meant that yield loss through the weed growth was 57 %. The sowing rate with 600 thousand seeds/ha gave the yield with the level 1.82. The increase in the sowing rate to 700 thousand seeds/ha had influence on yield productivity and it was enlarged on 0.29 % thousand/ha. The next compression (800 thousand/ha) afforded opportunity to increase yield productivity only on 0.12 % thousand/ha. The maximum seed sowing rate with 900 thousand/ha influenced Ustya’s yield productivity and it was enlarged on 0.17 thousand/ha.

The chemical method gave 12 % higher yield than the mechanical care method. The yield productivity was 2.19 thousand/ha. It provided the yield productivity on 0.2 thousand/ha, increasing the sowing rate to 700 thousand/ha.

The next compression with 800 thousand seeds/ha influenced on the increase of the yield productivity to 2.62 thousand/ha, it meant that the difference between the yield productivity was 0.23 thousand/ha. Increasing the sowing rate to 900 thousand seeds/ha, we had the value of 2.53 thousand/ha, it meant that the seed compression didn’t have a good influence on the soybean yield in other words it was lower on 0.09 thousand/ha than at the area with sowing rate 800 thousand/ha.

Ustya (the soybean varieties) gave the best yield (2.62 thousand/ha) due to the chemical care at the test example areas with the seed sowing rate 800 thousand/ha. The next seed sowing concentration (to 900 thousand/ha) provided the increase the interspecific soybean competition but it lessened the yield productivity. The mechanical care method gave the best yield (2.4 thousand/ha) at the test example areas with the seed sowing rate 900 thousand/ha.

Ustya’s soybean sowing had better reaction to the compression than Romanyka. The optimal soybean sowing rate for Romanyka due to the line sowing was 700–800 thousand seeds/ha. The optimal soybean sowing rate for Romanyka – 800-900 thousand/ha. It was worth noting that the yield productivity was higher at the test example areas with no weed control and Romanyka had better competitive ability with the weed than Ustya.

Key words: soybean, varieties, seeding rate, crop cultivation method, productivity.