The Agriculture Ministry is holding the seminar on issues development of technology of leguminous crops like lens and pea using organomineral fertilizers
, compost, biological products, as well as their procession and storage, the ministry reports.
However, various HS-based products have appeared in the market in the last years, which are usually extracted from peat or leonardite, enriched or not with nutrients and registered at the Ministry of Agriculture, Livestock and Food Supply (MAPA) as organic fertilizers, organomineral fertilizers or soil conditioners, although they are commercialized as plant biostimulants (Benites et al., 2006; Zandonadi & Busato, 2012).
Considering that HSs can favor the cultivation of plants, the soybean crop will also benefit from their application; however, it is notable the need for studies aiming to establish an ideal dose of the organomineral fertilizer.
Thus, this study aimed to evaluate the effect of the application of doses of organomineral fertilizer enriched with HSs on the growth, development, mineral nutrition and yield of soybean cultivated under water stress conditions.
The organomineral fertilizer was enriched with humic substances extracted from peat through chemical fractionation using 0.5 mol [L.sup.-1] KOH and acidification with 2 mol [L.sup.-1] [H.sub.2][PO.sub.4], without subsequent purification.
At each soil moisture level, there were increments and all of them followed a quadratic model as a function of organomineral fertilizer doses (Figures 1A to 1E).
Under this condition (with water stress) and compared with the control (without the application of organomineral fertilizer) at the highest accumulations of biomass observed in the stages of flowering and physiological maturation (harvest), there were increments from 13 to 16% in RDM, and from 18 to 32% in SDM.
The reduction in the values of production parameters, observed after the peak of production of certain variable (around 5 mL [dm.sup.-3]), may have been due to the deleterious effects caused by the high dose of the organomineral fertilizer (Figures 1A to 1E).