Effects Of Humic Acid On Adsorption Characteristics Of Potassium And Rice Growth

For establishment of humic acid (HA) on K+adsorption model, and get the optimum application amount and concentration of humic acid at different growth stages of rice, the Humic acid sample extracted and purified from Heilongjiang lignite was conducted in this experiment. Adsorption parameters of HA to K+were measured, and the effects of HA on seed germination and vegetative growth and nutrient uptake and anti-aging of rice were explored. The results are as follows.(1) The pH, initial concentration of K+and reaction time affect the adsorption of HA on K+. The adsorption amount of HA on K+was low at acidic condition, then the adsorption amount reached the highest6.07mg·g-1at pH7. The adsorption capacity of HA on K+increased with the initial concentration increasing of K+in the pH5.0-pH7.0conditions. The adsorption HA on K+reached saturation when K+initial concentration was120mg·L-1. The adsorption capacity of HA on K+increased with time prolonged, it basically reached saturation after120min. The adsorption rate slowed down with the time prolonged, and it accorded with the Langmuir adsorption model.(2) The effect of HA on seeds germination of rice was that low concentration stimulated seed germination and high concentration inhibited seed germination. The germination rate, germination potential, germination index and seedling length increased with the concentration of HA increasing in50mg·L-1-200mg·L-1concentration range. The growth stimulation began to decline when HA concentration greater than200mg·L-1. HA inhibited the seed germination when its concentration was greater than500mg·L-1, and the inhibition gradually enhanced with the increase of its concentration. Therefore, the appropriate concentration of HA for rice seed soaking should be200mg·L-1.(3) HA stimulation effect on rice growth was closely related to the concentration of HA. Rice plant height, biomass, chlorophyll content and roots activity were highest when the concentration of HA150mg·L-～200mg·L-1at tillering and booting stages,200mg·L-1～250mg·L-1at grain filling stage respectively. While HA inhibited rice growth when its concentration was higher than300mg·L-1.(4) HA enhanced the anti-aging ability of rice. The effects of HA on the three kinds enzymes activities of SOD, POD and CAT were not significant at tillering stage of rice, but it significantly improved the activities of three kinds enzymes above in booting and grain filling stage with concentration of150mg·L-1～300mg·L-1, and the activities of the three kinds enzymes increased by16.8%～20.1%,11.6%～23.1%,12.1%～18.7%, respectively.(5) HA promoted the uptake of nutrient elements in rice. The improvement was particularly significant at50μmol·L-1of low potassium, but it decreased at200μ mol·L-1of moderate potassium and1000μmol·L-1of high potassium. HA promoted the nutrients accumulation of rice. The increasing ratio of Fe and Mg were the most significant by more than15%, and it followed by Na, P and Mn by more than10%, then Cu, Zn and Ca by less than10%.