Natural Organic Residues Enriched with Ca and Mg: Application in Lettuce Grown with Water Blade

Abstract

Natural organic residues (NOR), a residue from extracting organic matter from soils with NaOH, has shown to be an interesting and promising environmental adsorbent, due to its high surface area and porosity, in addition to the diversity of functional groups. In this context, this work developed a material from NOR enriched with Ca^II and Mg^II and evaluated its application in lettuce crops irrigated over water in sandy and clay soil. NOR was extracted from a soil collected in Alagoas, Brazil, with 25% organic matter content. The nutrients were inserted into NOR by adsorption in a multielement solution of Ca^II and Mg^II (10 mg L^-1) at pH 8.0. The highest adsorption rate of NOR (78.92 and 55% for Ca^II and Mg^II, respectively) occurred at pH 8.0. The characterization of NOR showed a content of organic matter (OM) = 15.40, C/H ratio = 0.185 and E₄/E₆ = 2.18 and characteristic bands of OH, C=C and Si-O stretching were observed in the samples. Lettuce cultivation with NOR was conducted in a protected environment for sandy and clayey soils. The results obtained demonstrate the influence of nutrients adsorbed in NOR and water blade on lettuce cultivation, especially in its variables of commercial interest.

Keywords:
humic substances; irrigation; nutrients; Lactuca sativa L.