Hormone balance and shoot growth in wheat (Triticum durum Desf.) plants as influenced by sodium humates of the granulated organic fertilizer

Humic acids are formed in soil during decomposition of organic residues and are capable of increasing plant productivity. Plant growing widely utilizes application of the most soluble preparations on the base of sodium and potassium humates possessing hormone-like activity. Humic substances are capable of stimulating plant growth in very low concentrations that determines the necessity of targeting their uptake by plants. Such a possibility is provided by placing fertilizers in the direct vicinity of the seeds. The effect of incrustation of Nitrofosque granules with sodium humate (SH) on the crop yield of spring durum wheat has been shown previously. In the present experiments, the data on the changes in growth and hormone content of wheat plants (Bashkirskaya 27 cv.) treated with SH included into the granules of organic-mineral fertilizer (OMF) are reported for the first time. Granules of fertilizers without SH and those containing 1.25×10-2 %, 2.5×10-2 % and 5×10-2 % of humic preparation (of the granule mass) were placed at the distance of 2-3 cm from the 1-day seedlings planted into the soil. OMF was obtained from poultry waste (chicken manure) and dolomite and SH was extracted from brown coal. Plants that obtained neither humates nor OMF served as the control. Leaf length and transpiration (according to the decline in the mass of vessels with plants) were measured starting from the third day after sowing. Leaf samples for determination of hormones with enzyme-linked immunoassay were sampled on day 9 and leaf area and plant mass were measured on day 21 after sowing. OMF granules without SH stimulated leaf elongation resulting in their significantly longer length compared with the control (42, 156, 187 and 274 mm against 47, 167, 199 and 294 mm, p £ 0.05) detected in the first leaves 3, 6 and 8 days after sowing and 14 days after sowing in the second leaves. Meanwhile an increase in the OMF dosage did not increase their length significantly compared to the lower dose. Addition of humic substances to the OMF granules increased the promotive effect of the preparation on the leaf elongation most clearly manifested in the case of intermediate SH concentration (2,5×10-2 %), which significantly increased the leaf length during the time of registration (3, 6, 8, and 14 days after sowing) compared to the application of OMF without SH (6, 11, 13 mm increment of the first leaves and 9.4, 9, 22 mm of the second leaves, р ≤ 0.05). Unlike OFM without SH, which application did not change the shoot mass and leaf area, combination of OFM with intermediate SH concentration increased shoot mass (from 538 to 583 mg, р ≤ 0,05). Leaf area was significantly greater than in the control in the case of intermediate and maximal SH concentration (increments were 385 and 283 mm2, р ≤ 0.05). Thus, addition of SH to OFM increased the effectiveness of the OFM action of growth characteristics. Accumulation of nitrogen in the shoots of the wheat plants supplied only with OFM without SH did not differ from the control, while combination of OFM with SH resulted in accumulation of nitrogen at the level (by 8-15 %, p ≤ 0.05) higher than in the control. Application of OFM without SH did not influence the content of studied hormones (auxins, cytokinins and abscisic acid - ABA), while addition of SH to the granules of fertilizers resulted in significantly higher concentration of abscisic acid (ABA) and cytokinins in the shoots, the 1.6-2.8 ng∕g-1 increment (1.5-1.8 times) and 3.8-4.9 ng∕g-1 increment (1.5-1.7 times) (р ≤ 0.05). Concentration of indole acetic acid (IAA) with intermediate SH concentration was higher than in the control (40 against 15 ng∕g-1, р ≤ 0.05). The results obtained by us allow attributing increased effectiveness of fertilizers in the case of their supply with humates to their effect on the hormonal content. Increased content of hormones with promotive type of action is likely to enable activation of plant growth, while accumulation of ABA limits water losses by transpiration. The results of these laboratory experiments indicate perspectives of application of OMF containing sodium humates according to technology developed by us. Furthermore, the obtained data are of importance for revealing fundamental mechanisms, by which the action of humic compounds is manifested, in particular at the level of hormonal balance in plants.