Row Crop Response to Commercially Available Humic Acid Products.

Humic acid products are being marketed with increased frequency and intensity for use in row crop production.  These products claim, among other things, to increase both crop yield and plant uptake efficiency of soil and fertilizer nutrients.  Our objective was to evaluate these claims by examining how Hydra-Hume (HH), a granular humic acid product, rate influenced rice (Oryza sativa) and soybean (Glycine max) yield and tissue nutrient concentrations.  In 2010, rice and soybean trials were established on a Calhoun silt loam that received 0x, 1x (45 kg HH/ha, recommended rate), 5x, and 10x rates of Hydra-Hume DG. For rice, each HH rate was applied with four combinations of P (0 or 29 kg P/ha) and N (0 and 112 kg N/ha), which will be referred to as NP rate.  Rice dry matter accumulation and nutrient concentration was determined at early heading for rice receiving each of the four HH rates that received no P and 0 and 112 kg N/ha.  The soybean trial evaluated the effect of HH rate. Hydra-Hume rate had no effect on rice (P=0.5902) or soybean (P=0.9196) yield.  Only NP rate, averaged across HH rate, affected rice yield (P<0.0001).  Rice receiving no N and 0 or 29 kg P/ha produced low mean yields of 2821 to 3100 kg/ha (LSD0.05=269), respectively, which were lower than rice fertilized with 112 kg N/ha (7081 kg/ha) or 112 kg N plus 29 kg P/ha (7610 kg/ha).  Whole-plant concentrations of P, K, and Mn concentrations were increased in rice that received 112 kg N/ha, averaged across HH rates. Neither the main effect of HH rate nor its interaction with NP rate affected rice (aboveground) nutrient concentrations.  Results suggest that HH did not benefit rice or soybean yield or enhance nutrient uptake by rice.