Abstract

ZAMUDIO-GONZALEZ, B. et al. Loss of Nitrates and Salt Accumulation in Soil by Drip Irrigation with Nitrogen. Terra Latinoam [online]. 2011, vol.29, n.3, pp.239-248. ISSN 2395-8030.

There are prediction models about the nitrates movement in the humidity fronts of homogenous soils or preferred flow in structured soils, but it is unknown the dynamics of leaching of the NO3 - applied in drip irrigation associated with the washing of K+, Na+ and changes of pH, electrical conductivity (EC) and sodium adsorption relationship (SAR) for different nitrogen sources. Soil columns were established with soil and subsoil from Sonora, Mexico. The infiltration and drainage required to wash out the salts with irrigation by flooding with alkaline water (A) and water with agronomic gypsum and sulfuric acid (Am) was evaluated. The nitrates and changes of EC, pH, K+, Na+ and SAR from 12 leachates were measured equally to simulate fertirigation by drip with 310 mg L-1 of NO3 - in 4 mm water layers. Seven commercial sources of N were used. The conclusions were: a) the infiltration in soil was higher with Am than with A, but the wash out of salts, NO3 -, K+ and Na+ were similar, b) subsoil leached 10 times more NO3 - than soil, c) fertilizers with NO3 - showed only one peak of nitrates leached associated with humidity front since third fertigation, and the fertilizers with ammoniac sources showed two and three peaks of nitrates since the third fertirrigation, d) with Am pH values were less alkaline with Mg(NO3)2 in soil and with KNO3 and CO(NH2)2 in subsoil, e) the EC in subsoil was higher with (NH4)2 SO4 and Am, f) the K+ is more leachable in soil when adding gypsum water, Mg(NO3)2 and (NH4)2SO4, g) the salts (EC) and sodium (SAR) were increased with NaNO3 with alkaline water (A), h) there were associations with high nitrate concentrations in humidity fronts in the subsoil but not in soil by drip irrigation.

Keywords : nitrogen fertilizers; soil amendments; water movement; drainage.