Environmental, agricultural and economic implications of the use of nano-agrochemicals for a sustainable food production of Brassica oleracea var. capitata L.

The traditional use of agrochemicals causes environmental pollution and global public health problems. The fact that plants use only a part of the agrochemicals added to the soil makes them ineffective. The frequent application of excessive doses of fertilizers to soils can lead to risks of environmental contamination, mainly of aquifers and surface waters. This opens up new technological challenges that can be applied to agriculture and food production to meet the needs of the population. The use of nanoagrochemicals (NAC) is recent and there are insufficient studies to provide information on their potential impact on the environment. In this study, NACs were synthesized by simple, rapid, economical, and sustainable methods to evaluate their potential impact on the soil-water system and in the cabbage (Brassica oleracea var. capitata L.)  crop. The main objective of this study is to synthesize urea-hydroxyapatite and potassium sulfate NACs for application in soils as nanofertilizers, in order to reduce agricultural inputs, to achieve more environmentally friendly agrochemicals and to evaluate from an economic point of view the cost-effectiveness of the use of these nanomaterials in agriculture versus the traditional use of agrochemicals. For this purpose, the aforementioned nanoparticles were synthesized and characterized. Subsequently, a field assay was carried out in experimental plots of 4 m² in which four different treatments with NAC and traditional fertilizers were applied (in quadruplicate): (i) urea-hydroxyapatite NAC; (ii) potassium sulfate NAC; (iii) urea-hydroxyapatite NAC and potassium sulfate NAC; and (iv) non-nanoparticulate traditional fertilizer treatments; and two doses: (i) an optimum dose according to the usual fertilizer contents (NPK) used for this crop.; and (ii) half the optimum dose.  Soils were sampled at the beginning and end of the assay for characterization. The crop was closely monitored throughout the growing period and at the end of the crop cycle, the cabbages were harvested for size, weight, yield, and nutrient content determination. An economic-financial analysis was also carried out comparing the yield of the use of NAC versus the use of traditional fertilizers. The main results showed that the treatment with NAC at half the dose showed similar yield (number of cabbage harvested: 93), size (diameter) (35.3 ± 2.1 cm), and weight (0.38 ± 0.08 kg) values as the cabbages treated with traditional fertilizers (yield: 91; size: 34.8 ± 1.5 cm; weight: 0.41 ± 0.10 kg). Thus, NAC applied at half dose was efficient for the production of this crop. The analysis of cost-effectiveness proved that the treatment cost with NAC at half dose was lower than the treatment with optimal doses of traditional fertilizers, which indicates that the use of these NAC can be profitable and minimizes the input of fertilizers to the soil.

Acknowledgements

This research was supported by the grants to research groups in the Campus of Ourense (InOu 2022). Daniel Arenas-Lago thanks for the postdoc grant Juan de la Cierva Incorporación 2019 (IJC2019-042235-I).