Sulphuric acid application to the irrigation water corrects iron-chlorosis on calcareous soils

The majority of crops that grow on alkaline and calcareous soils show serious chlorosis problems. To correct these problems, several strategies have been used, such as genetic improvement, agronomic practices, foliar fertilizers and soil acidification; but none of them offer an alternative to correct the original problem. The objective of this research was to study the effect of acid fertilizer solutions applied both to the irrigation water and to the soil. This research was conducted under greenhouse and field conditions. The pots were treated with three levels of Hsub2 Sosub4 (AS) 0, 15 and 30 L hasup-1, three levels of FeSOsub4·4Hsub20 (SF) 0, 10, and 20 kg hasup-1 and five application frequencies (FA), applied on the irrigation water using sorghum as the indicator crop. Under field conditions during three years the rotation wheat-sorghum was used. The dosages studied were AS 15 L hasup-1, SF 20 kg hasup-1, ZnSOsub4 (SZ) 5 kg hasup-1, MnSOsub4 (SM) 2 kg hasup-1 and two FA in the irrigation water and directly to the soil 0.5 and 1.0 t hasup-1 of AS and a control, giving a total of 11 treatments. In both studies a randomized complete block design was used with three and two replications. The SF application with industrial AS to the irrigation water corrected sorghum iron chlorosis. The levels of 20 kg hasup-1 SF with 15 L hasup-1 as at one FA was the best treatment under greenhouse and field conditions, also the best wheat and sorghum productions were obtained with those dosages. The application methodology of commercial AS at low dosages alone or with SF, SZ or SM on the irrigation water, can be used on calcareous soil to correct deficiencies without serious management technical problems, it is more efficient and cheaper than the direct application of 1.0 t hasup-1 of AS (1800 kg hasup-1) on the soil En suelos de origen calcareo y reaccion alcalina (pH 7.3 a 8.5) la mayoria de las especies que en ellos se cultivan presentan graves problemas de clorosis. Para corregirlas se han utilizado varias estrategias: mejoramiento genetico, practicas agronomicas, fertilizacion foliar y acidificacion del suelo; ninguna ofrece alternativas que de origen resuelvan el problema. El objetivo de la investigacion fue estudiar el uso de soluciones fertilizantes acidificadas, que se aplicaron tanto en el agua de riego como al suelo. La investigacion se desarrollo en invernadero y campo. En invernadero las macetas se trataron con tres niveles de H2SO4 (AS); 0, 15 y 30 L hasup-