Crescimento de melão, características químicas de solos e lixiviados sob irrigação com águas salinas.

Abstract

Soils of arid and semi-arid regions may present salt accumulation damaging to plant growth, due to either natural salinization processes or human contribution by inadequate irrigation management. At the Brazilian Northeast, climactic conditions are favorable to salt accumulation in soil. The Assu/Mossoró agricultural production center, in this region, has shown high productive potential for irrigated fruit production for exportation, but the irrigation waters may have high salt content. Without an adequate water quality control, increasing salt accumulation may happen, which could lead to soil degradation by salinization. This work aims to evaluate Assu/Mossoró, RN, agricultural production center soil degradation under irrigation with increasing electrical conductivity (CE) levels, and sodium adsorption rates (SAR), when cultivated with cantaloupe. The work was conducted in a greenhouse at the Environmental Sciences Department of Semi-Arid Rural Federal University. Four soil types, traditionally used for cantaloupe production, were used and irrigated with solutions corresponding to eight CE (CE = 100, 250, 500, 750, 1250, 1750, 2250 and 3000 μS/cm) and two SAR (SAR = 4 and 12) levels, as salinity treatments, corresponding to the irrigation waters used in the Northeast, with low sodification risk, especially in the studied area. So the experiment was a factorial arrangement of 4 x 8 x 2 (four soils, eight CE and two SAR), with three replicates, and 192 experimental units, on a randomized block design. Plant (fresh and dry matter production, and nutritional composition) and soil (CE, saturation extract pH, soluble elements, exchangeable cations, cation exchange capacity, and clay mineralogical composition) variables were evaluated. Fresh and dry cantaloupe production wasreduced with increased water salinity in two succeeding crops, leading to plant death a few days after transplanting in the second cycle. Increased water salinity enhanced Ca, Mg, Na, K and Cl plant accumulation, as well as soil pH, CE, and soluble and exchangeable Ca, Mg, Na and K contents. Saline water use increased salinity andsodicity of the four studied soils, diminishing cantaloupe growth.