Effects of humic acid and organic matter on quantitative yield and macro-element absorption in rice (Oryza sativa L.)

Abstract

This research intended to study the effects of various levels of humic acid and organic matter forming the substrate for rice seeds of the Tarom cultivar to germinate and for seedlings to grow. For this purpose, an experiment was conducted using split-plots base on randomized complete block design with three replications in the Research Field at Dasht-e Naz in Sari in 2015. Four mixed substrates of clay soil and organic matter (100% soil, 90% soil+10% organic matter, 80% soil+20% organic matter, 70%+ 30% organic matter) were applied as main plot, and four application levels of humic acid (2, 4, 6, and 8 ppt) as sub plot. Results showed that increases in the organic matter content of the substrate improved the seed yield, in which the maximum seed yield obtained in the mixture containing 10% organic matter (1485 g/2m²) and in the treatment of applying humic acid at 6 ppm (1477 g/m²). Moreover, the largest seed yield under the interaction effects of organic matter and humic acid (1800 g/2m²) was achieved at the organic matter content of 10% and humic acid concentration of 6 ppt. Seed nitrogen concentration improved with increases in the organic matter content, with the highest seed nitrogen concentration (1.673%) observed under the interaction effects of 30% organic matter and humic acid at 6 ppt. In addition, when the organic matter content of the substrate was raised, seed phosphorous content improved, with the maximum seed phosphorous content (0.20%) obtained under the interaction effects of 20% organic matter and application of humic acid at 6 ppt.