Effect of Tithonia diversifolia Mulch on Atta cephalotes (Hymenoptera: Formicidae) Nests
The addition of mulch biomass from Tithonia diversifolia (Hemsl.) Gray prior to seeding may improve bean production. We evaluated the response of two Costa Rican bean cultivars (Chirripo Rojo, Negro Huasetco) to the retention or removal of T. diversifolia biomass with respect to soil chemical characteristics, and bean biomass, nutrient content, root architecture, and fungal structures. There were no significant differences (p < 0.05) between bean cultivars and their influence on soil characteristics. Soil pH, Ca and Mg were significantly lower (p < 0.05) at bean harvest in both biomass removal and retention treatments compared to those at the time of bean sowing, whereas exchangeable acidity was significantly greater (p < 0.05) at bean harvest. Bean shoot nutrient concentration differed significantly between cultivars but not between biomass retention or removal treatments except for Mg. Pod, leaf and stem biomass, root characteristics, and the number of root fungal structures (entry points, vesicles, arbuscules) were significantly different (p < 0.05) between bean cultivars and mulch biomass treatments. Results showed that T. diversifolia biomass positively influenced bean shoot and root characteristics, and suggested that the addition of mulch may have added relatively large quantities of P and K to the soil and stimulated the uptake of these nutrients.