Tuberous root yield of Dahlia variabilis Wild (Desf.) under different agronomic management practices

Abstract

The Dahlia variabilis Wild (Desf.) is considered the Mexican national flower and their exploitation is mainly for ornamental purposes. Recent studies have shown that the tuberous roots dry weight of this species contains from 38 to 53% of a polysaccharide of fructose called inulin. The consumption of this compound does not elevate the levels of glucose in the blood of human beings, making this polysaccharide an attractive product for the food industry. This fact has helped to diversify (1) the production of Dahlia variabilis and (2) research towards the production of their roots. The aim of this study was to evaluate the effect of phosphorus fertilization, planting density and leaf removal on dry matter production of roots of Dahlia variabilis. In spring-summer 2009, two experiments were established. In the first study, we evaluated four phosphorus levels (0, 60, 100 and 120 kg P2O5/ha) and four planting densities (2.5, 3.12, 4.16 and 6.25 plants/m2) under a factorial arrangement in a randomized complete block design with four replications. In the second study, the source-sink relationship was evaluated defoliating different plant strata. The treatments were: undefoliated (t1), defoliated the lower stratum (t2), the intermediate stratum defoliated (t3), defoliated the upper stratum (t4), defoliated the lower and middle strata (t5), defoliated the lower and upper strata (t6), defoliated the middle and upper strata (t7), and completely defoliated (t8). These treatments were distributed in a randomized complete block design with four replications. The results showed significant differences in the factors phosphorus and planting density. The highest production of root dry matter (345 g/m2) was achieved with 120 kg/ha of phosphorus and 6.25 plants/m2. Leaf removal revealed that the middle and lower strata (66%) satisfied the “sink” from the root.