Organic and mineral fertilization: Effects on physical characteristics and boron dynamic in an agricultural soil

The mineral and organic fertilizations on lettuce (Lactuca sativa L.) cultivation were investigated to understand the correlations between soil physical and mechanical indexes and boron (B) dynamic (adsorption, desorption, fractions) in soil. The fertilization with compost (derived by wine-producing residues) and integrated fertilization (compost plus ammonium nitrate) increased the soil workability, as do the extent of aggregation, the water retention, and the cation exchange of the soil. The physical (colloids index, Ic) and mechanical (shear resistance, ) properties showed a significantly higher value in compost and integrated fertilization plots. The biomass application to the soil influences the sorption B behavior, which is related to the soil shear strength and the compaction susceptibility; the Langmuir maximum adsorption for B was positively related with plastic deformation (De) and dry bulk density (Db) and negatively related to water infiltration (Wi), , and compressibility index (Cs). The B desorption was not modified by the variation on soil mechanical resistance; no correlation was found between B desorption index and physical-mechanical parameters of the soil. The B fractions, not readily available for plants, occluded in aluminium (Al) and iron (Fe) oxyhydroxides (Ox-B) and organically bound (OM-B), were negatively correlated with colloid index (Ic), Wi, tau, and moisture content (U), and were positively correlated with De, Db, and compressibility index (Cp, related to organic-matter content of the soil).