Influence of Lignite Humic Acid on the Micronutrient Availability and Yield of Blackgram in an Alfisol.
Ramasamy Natesan, S. Kandasamy, S. Thiyageshwari, and P. Murugesa Boopathy. Tamil Nadu Agricultural Univ, Lawley Road Post, Coimbatore, India
The importance of soil organic matter in the maintenance of soil fertility is well recognized. They have multi faceted activities in influencing the soil properties and greatly facilitate the judicious dose of fertilizers for the promotion of crop growth. Humate materials are widely distributed organic carbon containing compounds which play a direct role in determining the production potential of a soil. Humic acids have two main components viz., humic acid and fulvic acid and the mixture is generally known as humic acid. Humic matter has shown to increase the uptake of nutrients, can incorporate iron into chelated complex maintaining its availability to plants although insoluble form. The present study is carried out to assess the effect of humic acid (HA) on the availability of micronutrients and in an Alfisol. A pot experiment was conducted with BN-3 Black gram (Vigna mungo) as test crop in an Alfisol. There were seven treatments were carried out in triplicates in a randomized block design comprising of 0.1 % HA foliar spray, seed soaking with 1% HA, soil application of 10, 20, 30 and 40 kg ha-1 of HA and a control. The yield was recorded and DTPA extractable Fe, Cu, Zn and Mn were analysed in the post harvest soil samples. The results on the blackgram seed yield indicated that humic acid application significantly increased and yields from 7.23 to 9.46 g pot -1. The increased yield of seed may be due to hormonal effect of humic acids which also act as a respiratory catalyst and increased cell permeability. Humic acids also contain quinone groups, which act as a growth regulating substances. Contributing to the increased yield. Among the various levels of humic acid, 20 kg ha-1 recorded significantly higher seed yield of 9.46 g pot-1 and the least was recorded by the control. Among the methods of application, soil application of humic acid performed better than seed soaking and foliar spray. The availability of DTPA extractable micronutrients in the post harvest soil sample was higher due to HA application than the control. Soil application of 20 kg ha-1 of HA resulted in higher availability of Cu (3.11 mg kg-1), Mn (11.67 mg kg-1), Fe (12.61 mg kg-1) and Zn (1.72 mg kg-1). The positive effect of HA in increasing the availability of micronutrients may be due the its priming effect to increase water soluble amounts of micronutrients after addition of HA, which led to chelation and subsequent release of micronutrients. From the research results, it can be concluded that soil application of 20 kg HA ha-1 to blackgram increased not only the grain yield, but also the availability of DTPA extractable micronutrients. Confirmatory results were obtained in the field experiment.