Abstract:

This experiment explored the feasibility of attapulgite plus an organic matrix as a carrier of bacterial fertilizer and the optimal amount of bacterial liquid to be added when making bacterial fertilizer. Different amounts of attapulgite （5%， 7.5%， 10%； F₁， F₂ and F₃， respectively） were added to an organic matrix as the carrier for bacterial fertilizer， and then different quantities of bacterial liquid （25%， 27.5%， 30%） were added to make solid bacterial fertilizer. The shelf life of bacterial fertilizer was evaluated and the growth-promotion effect of the bacterial fertilizer was verified by measuring plant traits of alfalfa（Medicago sativa） in a pot experiment， for the various attapulgite and bacterial liquid addition treatments. It was found that 180 days after preparation， the effective viable count of all the different bacterial fertilizer carrier formulations was more than 2×10⁸ cfu·g^-1， and the number of miscellaneous bacteria was less than 3×10⁶ cfu·g^-1. The number of alfalfa nodules was the highest （62.7 per pot； 317.8% higher than control plants with no bacterial fertilizer added） under the treatment combination F₃+30% bacterial liquid. The above-ground and below-ground biomass and chlorophyll content of alfalfa under the treatment comprising F₂+25% bacterial liquid were increased by 46.5%， 86.2% and 54.9%， respectively， while the total root length， total root surface area， root tip number and root bifurcation number were increased by 87.7%， 108.4%， 96.2% and 252.0%， respectively， compared with the control plants. However， when data were analyzed by multivariate membership function， the treatment comprising F₂+25% bacterial liquid was found to have the best effect on the growth of alfalfa.

Key words: attapulgite, bacterial fertilizer carrier, alfalfa, plant growth-promoting characteristics