EVALUATION THE NITROGEN NEEDS AND EFFICIENCY OF RHIZOBIA STRAINS TO PROVIDE NITROGEN TO CHIPILIN (Crotalaria Longirostrata HOOK. AND ARN.) FEBRUARY OF 2013 FATIMA DEL ROSARIO CAMARILLO CASTILLO, B.A., AUTONOMOUS UNIVERSITY OF CHAPINGO M.A., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Francis X. Mangan Chipilin (Crotalaria Longirostrata) is a leguminous plant native to Central America and Southern Mexico and used in the preparation of traditional dishes in this region. Starting in 2009, farmers in Massachusetts have been growing chipilin with a weekly production of 800 kg∙ha-1. However, as much as 300 kg∙ha-1 of nitrogen has been necessary to apply to the soil in order to obtain a marketable leaf quality. With the goal to determine the nitrogen requirements of chipilín and to quantify the capacity of selected stains to infect and provide nitrogen for this crop, two-field experiments were conducted at the UMass Research farm at Deerfield, Massachusetts, in an occum fine sandy loam soil (coarse-loamy, mixed, mesic Fluventic Dystrudept) soil as a randomized complete bock design with five replications. For the field trial in 2011, nitrogen rates were (kg∙ha-1): 40, 80, 120, 160, 200 and 240 and 0, 40, 80, 120, 160, 200, 240 and 280 in 2012 in combination with four Rhizobia strains: Bradyrhizobium sp. (Vigna), Rhizobium leguminosarum biovar, Bradyrhizobium USDA 3384 and no Rhizobia were the treatments. Based on the results obtained, nitrogen fertilizer application of 80 kg∙ha-1 was economically sufficient for chipilin to reach optimum yield. However higher nitrogen rates are needed to obtain marketable leaf color and quality. Additionally a greenhouse experiment set up as a factorial experiment with five replications was conducted with seven nitrogen concentrations (mg N∙L-1)-; 0, 26.25, 52.5, 105, 157.5, 210 and 262.5 mg∙L1 and the three Rhizobia strain for the previous experiment plus Bradyrhizobium USDA 2370 as treatments. Results suggest from Bradyrhizobium USDA 3384 is not an efficient strain for chipilin, and Rhizobium leguminosarum biovar potentially may provide the most nitrogen of the strains evaluated. In the greenhouse trial, nodules number per plant decreased with the increase in nitrogen applications, but this was not the case in the field trial in 2012. Nodules were found on the root of chipilin plants in the control. This is suspected to be due to one of the following possibilities: Rhizobia inoculum presence in the seed, Rhizobia in the soil (in the field trial) or contamination during the setup of the experiment.