Contents of macronutrients and growth of ‘BRS Marataoã’ cowpea fertigated with yellow water and cassava wastewater

Abstract Agricultural utilization of yellow waters associated with cassava wastewater is a sustainable technique, since it allows reduction of costs related to acquisition of industrialized fertilizers and minimizes the environmental pollution caused by the inadequate disposal of these effluents. In this context, this study evaluated the macronutrient macronutrient content and growth of cowpea fertigated with yellow water associated with cassava wastewater and NPK as source of nutrients. The experiment was set up in a greenhouse located at Campus I of the Federal University of Campina Grande. The experimental design was completely randomized, composed of five treatments characterized by: fertigation with mineral fertilizers, in the form of NPK; organic fertigation composed of human urine, cassava wastewater, human urine plus cassava wastewater; and organo-mineral fertigation composed of urine, cassava wastewater and mineral phosphorus, with four replicates. At 36 days after sowing, the following parameters were determined: contents of nitrogen, phosphorus, potassium, sulfur and the variables number of leaves, plant height, stem diameter, leaf area, shoot fresh matter and shoot dry matter. The use of yellow waters promotes significant increases for growth and production variables for nitrogen and potassium contents mainly, as well as for growth and production variables. The contents of nitrogen, phosphorus and potassium were higher than the levels considered as adequate for the cowpea crop. The use of human urine and cassava wastewater have potential to meet the needs for the main macronutrients required by cowpea and the irrigation via fertigation with these biofertilizers positively influences the development of cowpea.