Use of polyacrylamides and irrigation on hydric management of lettuce (Lactuca sativa L.)

Abstract

In San Ramón Farm, located 5 km south of Villarrica, Chile, a research was carried out between November 2002 and February 2003, with the purpose of studying the effect of different hydric treatments on lettuce production. A soil conditioner (hydrogel) was applied to: roots of seedlings at transplant time, to soil (prior to the transplant) and applied together to roots and soil, with bare root transplant as control. Irrigation and no irrigation was an additional factor, generating a total of eight treatments under study. Parameters measured were: percentage of established plants, plant diameter, number of leaves/plant, complete plant weight, leaves weight, root weight and days from transplant to harvest. All parameters were measured at harvest time. The experimental design was a complete block, with 3 random blocks with 8 treatments each. Results were subjected to Anova and Tukeys’s multiple comparison test. The analysis of percentage of established plants showed no significant differences. Largest diameters were obtained with hydrogel applied only to soil and to roots and soil. For number of leaves, the largest values were obtained with gel applied to soil and to roots and soil. Irrigation, increased significantly the number of leaves. In regard to weight of complete plant, leaves and roots weights, a significant difference was found in favor of gel, as the largest weights were associated to the application of this product to soil and to roots-soil. For roots weight, a significant interaction was found, and gel applied to soil without irrigation (T7) produced the highest weight. By applying gel to soil and to soil and roots, average value of plant vegetative cycle were shorter than with bare root transplant. Irrigation also shortened average cycles. An economic evaluation showed that soil application of hydrogel, without irrigation (T3) produced the higher profit, with a net present value of $ 18.489.426. The IRR´s were all higher than the discount rate used, so investment is attractive irrespective of the project option used.