Abstract

A sand culture study was conducted with 12 treatments. Sieved, acid washed and autoclaved sand was used to exclude microbial contamination. Five amino acids viz., glutamic acid, aspartic acid, glycine, cystine, tryptophan and their mixture as nitrogen source in Hoagland solution which served as the reference treatment and also as a source of all other nutrients. There were treatments where 50% nitrogen was supplied through Hoagland and remaining 50% was through glutamic acid, glycine and their mixture. Green and dry foliage yield, root biomass and photosynthetic rate were highest with Hoagland solution indicating that inorganic nitrogen was most suited. About 50 to 95% dry matter yield obtained by Hoagland solution could be produced by amino acids. An incubation study with the same sand used in the above pot study indicated that the nitrification rate of amino acids was 14 to 30% at 30 days, suggesting the direct absorption of amino acids by maize plant. Nutrient contents in the leaf and their uptake by the plant showed that their values were within the normal range irrespective of their nitrogen source. Maximum sulphur content was obtained when cystine was the sole source of nitrogen. Inclusion of 50% nitrogen as inorganic nitrogen or foliar spray of 1% amino acid did not have any distinct advantage in utilization of organic nitrogen. The results showed that the inorganic nitrogen was utilized better than that of organic nitrogen. At the same time, fairly good amount of organic nitrogen was absorbed and utilized.