Evaluacion del uso de desecante (Diquat) en un cultivo de frejol para semilla de exportacion.

A trial was done to evaluate the effect of the desiccant Diquat (Reglone) on moisture loss, yield and quality in export bean seeds. The experiment was carried out at the Experiment Station of ANASAC (Agricola Nacional S.A.) located in Graneros, 76 km south of Santiago. The bean cultivar used was 2172 from Royal Swis (Holland enterprise) and the desiccant, from ICI (Imperial Chemical Industries). The experimental design was completely randomized with 7 treatments and 5 replications. The treatments were established according to different maturity stages. Five of them were sprayed with the desiccant at 5 to 10%, 15 to 20%, 25 to 30%, 35 to 40% and 45 to 50% of dry pods. The other two treatments were not sprayed (controls), and the plants were pulled out at 15 to 20% and 45 to 50% of dry pods. At the determined maturity stages, the plants were sprayed with 2,5 l/ha of Diquat and 400 l/ha of water. From this day and until the seeds reached the threshing moisture (14 to 15%), their moisture content was measured daily. When the seeds reached the threshing moisture, samples were taken to determine purity, yield, germination, vigour and weight of 100 seeds. It was determined that the use of the desiccant Diquat does not reduce the days to harvest. No effect was found on the quality variables. The results showed that pulling out plants or spraying them with the desiccant from 15 to 20% of dry pods (55% of moisture in seeds) does not reduce the yield. In this sense, it is important to take advantage of pulling out the plants at the initial maturity stages so that, without affecting yield, the seeds are not subject to higher temperatures and sunburn for prolonged periods. Pulling out plants or spraying the desiccant to plants at earlier maturity stages (5 to 10% of dry pods) reduces the yield significantly. Since these are export seeds, it is not recommended to pull out plants at advanced maturity stages (more than 20% of dry pods) because the germination percentage may decrease to less than 85 which is the minimum required.