Efficiency of foliar application of zinc oxide nanoparticles versus zinc nitrate complexed with chitosan on nitrogen assimilation, photosynthetic activity, and production of green beans (Phaseolus vulgaris L.)

•The foliar application of nanoparticles+Chitosan increased biomass and production in green beans.•ZnO nanoparticles accelerated the maturation process of the plants, reaching their harvest time in a shorter time.•Nanoparticles can reduce the amount of fertilizer to be used without affecting crop yields.•ZnO nanoparticles could be used as nanofertilizers to maximize the productivity of agriculture crops. The individual application of ZnO nanoparticles and chitosan improve the growth and production of crops, compared to conventional fertilizers, their effectiveness is higher, and the doses can be reduced. However, there is little information regarding foliar application of ZnO nanoparticles complexed with chitosan and its effect on crop physiology. Therefore, the aim of the present study was to evaluate the efficiency of foliar application of zinc oxide nanoparticles versus zinc nitrate complexed with chitosan on the assimilation of nitrogen, photosynthetic activity, and production of green bean cv. Strike. Two sources of zinc were foliar-applied: zinc nanoparticles and zinc nitrate at doses of 0, 25, 50, and 100 ppm with and without chitosan. The results obtained indicate that the foliar application of Zn nanoparticles at 25 ppm and zinc nitrate at 50 ppm were the most efficient doses in favoring biomass accumulation and production. The addition of chitosan favored the biomass, production, and the parameters related to photosynthesis, especially when combined with zinc nitrate while the combination with ZnO nanoparticles presented a possible chelation of the nanoparticles, delaying the release of Zn. Finally, the best nanoparticle treatment was ZnO (25 ppm), which had similar results to the 50 ppm NZN treatment. This indicates that ZnO nanoparticles can reduce the amount of fertilizer to be used without affecting crop yield, so they could be used as nanofertilizers to maximize the productivity of agriculture crops. Finally, this indicates that more in-depth studies are required to know the physicochemical properties of ZnO nanoparticles complexed with chitosan and its effect on the physiology and biochemistry of plants.