Fig. (3) Effects of different organic and biological treatments on the NO₃^- (mg L^-1) concentrations of soil leachates under greenhouse plant growth. CK: control; NPK: 100% chemical fertilizer; S2: (20 g of spent grain/ kg soil); S1: (10 g of spent grain / kg soil); M2: (20 g of compost/ kg soil); M1: (10 g of compost/ kg soil); M1S1: mix between M1 and S1; A1: Azospirillum inoculation; A1S1: A1 + S1; A1M1: A1+M1. The standard deviation (n = 3) was analyzed using a one-way ANOVA.