To improve the technology of winter wheat cultivation it becomes more relevant to discuss the issue of enhancing crop microelement nutrition, which is very important when mineral fertilizers are applied at a higher rate than the one accepted in the zone. Chornozem (black) soils in general, and southern ones in particular, have a neutral or slight alkaline response, i.e. most of the microelements are slow movable and in fact are not available for the plants.

The efficiency of the microelement application uppermost affected by the form they are in. Recent experiments prove that the most efficient form of microelement transportation to the plants is complex compounds of metals with organic ligands – chelates. The most common chelators are organic acids with carboxyl groups: ethylendiamintetraacetic (EDTA), diethylentryaminpentaacetic (DTPA), dihydroxybutylendiamintetraacetic (DBTA), ethylendiamindisuccinic (EDDA); phosphonic acids – oxyethylendendiphosphonic (OEDF) and nitryltrymethylenphosphonic (NTF).

The research aims to study the effect of forms and ways of zinc application on the yield formation and grain quality of soft winter wheat on the southern chornozems (black soils). 

The experiments were carried out on southern chornozems, low-humus heavy loamy well-cultivated.

The size of a sown plot is 120 m², that of a record one is 50 m², replication is fourfold. Fertilizers were applied in a form of ammonium nitrate, granulated superphosphate and potassium salt, and also superphosphate with zinc complexonate (0.75 %). Vegetative winter wheat fields were treated with the solutions of zinc salts with help of a manual sprayer. An experiment scheme was given when the results were presented. Black fallow was the predecessor of winter wheat, cv. Knopa.

The efficiency of microelement was studied when it was applied in the form of zinc sulfate, chelate form, where oxyethylendendiphosphonic (OEDF) oxyethylendendiphosphonic (OEDF), superphosphate with zinc chelate on OEDF basis were used as ligand (0.75 %)

Monitoring and analyzing were done according to the conventional methods in compliance with a standard technique. Statistical processing of the received results was done using a package of applied software Excel and Statistika, the methods of dispersive, correlative and regressive analyses.

When N₉₀P₆₀K₄₀, which contained superphosphate modified with zinc complexonate based on OEDF, was applied, the yield increase was 20.2 % as compared with the variant without fertilizers, including 6.4 % – due to zinc. It is advisable to apply zinc in the form of its complexonate with OEDF, the yield increase is 0.15 cwt/ha, as compared with zinc sulfate, and a share of the effect of this factor is 14.0 %. The application of zinc complexonate under pre-sowing cultivation at a rate of 2.0 kg/ha had no benefit over one-time treatment of the plants at the phase of tillering at a rate 250 g/ha, but doing this treatment at a phase of shooting resulted in a serious yield increase (0.20 t/ha at SSD 0.95 = 0.18).

Foliar application with the solution of zinc complexonate (250 g/ha) increases the grain yield of winter wheat with the highest effect from a two-time treatment at tillering and shooting phases; the increase ranges from 0.20 to 0.54 t/ha. The efficiency of Zn application by 75.7-96.0% in arid conditions of the south of Ukraine is defined by hydrothermal conditions of spring vegetation, and a microelement helps winter wheat plants develop resistance to a temperature stress. A grain zinc concentration in the experimental variants ranged from 18.4 to 22.1 mg/kg (in the control it was 14.5 mg/kg).

Key words: zinc, winter wheat, vegetation phases, quality, southern chornozem.