The impact of biofertilizers with diazotrophic bacteria and fungi chitosan on melon characteristics and nutrient uptake as an alternative for conventional fertilizers

• A modern and economic biofertilizer was modeled to increase plant yield.
• The biofertilizer increases nutrients by Acidithiobacillus inoculation.
• The biofertilizer was enriched in N by the diazotrophic bacteria.
• The new biofertilizer increments soil quality.
• The NPK biofertilizer has potential as alternative to mineral fertilizers.

Fertilization is one of the most important factors to improve plant characteristics and nutrient uptake. Biological N2 Fixation (BNF) is a process of great importance in crop production systems, to enhance sustainability and prevent land degradation in modern agriculture. The impact of the biofertilizer (NPKB) produced from PK rock biofertilizer mixed with earthworm compound enriched in N by free living diazotrophic bacteria and of the bioprotector (NPKP) with chitosan from Cunninghamella elegans were investigated in a field experiment with melon. The study compared the influence of biofertilizers with soluble fertilizers (NPKF) on the melon characteristics and nutrient uptake. The experiment was conducted (February–April 2012) in the Bahia state, Brazil, and the treatments were NPKP (4 t ha−1); NPKP (8 t ha−1); NPKP (12 t ha−1); NPKB (8 t ha−1); NPKB (12 t ha−1); and NPKF (soluble mineral fertilizers) at the recommended rate for irrigated melon. A control with an earthworm compound (20 t ha−1) that was not inoculated with diazotrophic bacteria was added as a comparison. The results demonstrated a positive effect of NPKP and NPKB, especially when applied at a higher rate (12 t ha−1), which increased the commercial characteristics of melon compared with the soluble fertilizer applied in the recommended rate. Nutrient uptake in the melon fruits indicated a significant difference among the different fertilizer sources and the best results were displayed with NPKB and NPKP applied at the highest rate (12 t ha−1), especially for total S-SO4−2. Therefore, NPKP and the NPKB are potential alternatives to soluble fertilizers (NPKF).