Effect of tillage and application of gypsum In a No-Till field under supplementary irrigation with sodium bicarbonate waters

Supplementary irrigation is widespread in the Humid Pampa of Argentine, where the main source of water for irrigation has elevated content of sodium bicarbonate. The combination of irrigation and rain increases the sodium absorption ratio of soil (SARs), consequently raising the clay dispersion and reducing infiltration. The water quality standards for irrigation indicate that SARs values ​​should remain below 3.5. An alternative to mitigate these disadvantages is the application of a gypsum amendment. This study targeted the following objectives: measure the impact of tillage and the addition of gypsum on: infiltration, bulk density, sodium content and crop yield in a soil (Argiudoll and petrocalcic Paleudoll association) under no-till with supplementary irrigation. One treatment consisted of applying a gypsum liming of particle size less than 3 mm. After application, the plots were tilled to a depth of 15 cm. Sunflower (Helianthus annuus L.) was seeded 30 days after the completion of the amendment. Applying gypsum improved water infiltration into the soil. Tillage treatment without adding gypsum reduced SARs and increased infiltration the same way as tillage and gypsum treatment. This can be attributed the dissolution of native or precipitated carbonate by irrigation water. Tilled treatments, with or without amendment, had higher yield compared to no-till treatment.