Commercial humic substances stimulate tomato growth

A greenhouse experiment was conducted to investigate the effects of two commercial lignite-derived, humic substance-containing products (K-humate and K-fulvate) on tomato yield and nutrient uptake in soil and sand cultures. Seeds of tomato (Acadia cv. field busm) were grown in pots filled with soil and sand media and pretreated with a basic nutrient solution (control) and two levels of the K-humate and K-fulvate (equivalent to 0, 8 and 80 L ha^-1): low rate and high rate, respectively. A foliar treatment was included using only the low rate. Plant growth response as indicated by the fresh/dry biomass and incorporation of macro and secondary nutrients (N, P, K, Ca, Mg, S) into shoots were measured. Low rates (8 L ha^-1) of K-humate and K-fulvate application on growth media and in foliar treatments resulted in significant (p < 0.001) increases in fresh/dry biomass of shoot and fruits and increased nutrient uptake. Effects at high rates (80 L ha^-1) of treatment were less beneficial but still demonstrated significant (p < 0.001) improvement over the controls. The highest increases in major nutrient (NPK) uptake resulted from the humate foliar application in soil and from the fulvate foliar treatment in sand culture, which were well correlated with increased fresh/dry biomass of shoots and fruits. The results from this study demonstrate that both the K-fulvate and K-humate commercial products derived from lignite can potentially be employed to improve and sustain soil fertility, increase crop productivity and yield, and improve/correct plant nutrient deficiency by foliar applications during growth.