2.1 Experimental design
SP1308 product was the SPF used in this study, which is applied widely in a sugarcane field in Guangdong Province. SP1308 contains two main components: clothianidin, which is a pesticide, and an animal-derived amino acid solution used as a bio-fertilizer. SP1308 contains clothianidin (1%) (AccuStandard Company, USA), organic fertilizer (amino acid solution mainly including animal hair protein, 64 mL/kg), and excipients (aminocellulose 30 g/kg, gelatin 20 g/kg, and kaolin 940 g/kg, all produced by Damao company, Tianjin, China). Clothianidin ((E)-1-(2-chloro-1,3-thiazol-5-ylmethyl)-3-methyl-2-nitroguanidine), is a second-generation neonicotinoid insecticide; it is a white crystalline compound with the molecular weight of 249.68 and has the lowest water solubility (0.327 g/l) among the neonicotinoids (Hirano et al., 2015). Clothianidin was determined to be a more persistent insecticide than imidacloprid and thiamethoxam in the soil of tropical sugarcane agroecosystems (Ramasubramanian et al., 2013). It was reported to have excellent plant systemicity, broad-spectrum activity, and confer high crop safety (Uneme & Hideki, 2011). In addition to the insecticide effects, it has beneficial effects on the initial growth of sugarcane, increasing the total weight of plants and plant height, improving the root system, and even minimizing the effects of drought stress on the sugarcane (Endres et al., 2016).
The experimental design was comprised of four groups, including (1) SPF (pesticide and fertilizer mixed with excipient), (2) a pesticide control (SP, pesticide mixed with excipient, but with no fertilizer added), (3) a fertilizer control (SF, fertilizer mixed with excipient, but with no pesticide added), and (4) an excipient control (SA, with neither pesticide nor fertilizer added), and one control blank (SK), with four replicates of each group.