Intercropping Legumes for Weed Management and Nitrogen Fixation in Organic Papaya in Costa Rica.

Intercropping cover crops increases agroecosystem diversity and provides multiple agronomic and ecological benefits. Weed control and nitrogen (N) fixation are considered important contributions by intercropped legumes in organic papaya (Carica papaya L.) plantations in Costa Rica. In order to evaluate the effect of cover crops on weed control, nutrient release and competition with papaya plants, an experiment was carried out on the Atlantic low lands of Costa Rica in 2014. Three legumes, Vigna radiata, Crotalaria spectabilis and Pueraria phaseoloides, were sown 7 weeks after papaya plants were transplanted into the field. The control treatment consisted of the usual weed slashing implemented on the farm. Vigna radiata and C. spectabilis percent cover was 85% and 90%, respectively, 10 weeks after the cover crops were seeded, whereas P. phaseoloides establishment was unsuccessful possibly because heavy rains washed the seeds away. Weed aboveground biomass was 90% and 66% lower in the V. radiata and C. spectabilis plots, respectively, compared to the control. Dry matter of V. radiata and C. spectabilis contained 3.1% and 4.9% N, which represented an estimated contribution of 70 and 181 kg N ha^-1, respectively. There were no differences among treatments of papaya plants height, stem diameter, number of leaves and number of fruits. These results show that intercropping legumes is a feasible strategy for weed control and nitrogen fixation during the establishment phase of organic papaya plantations.