Abstract:

 In order to solve the problem that straw mulching inhibits seed germination and seedling growth, biofertilizer was made by inoculating Piriformospora indica solution on rice straw and the activity of the biofertilizer and its effect on rice seed germination and seedling growth were discussed to provide theoretical basis for the application of straw mulching and biofertilizer. In this study, two kinds of biofertilizer were made using straw and peat as carriers, and the toxicity of the two carriers on Piriformospora indica and the change of the number of viable colony forming units (CFU) during the storage period of the biofertilizer was detected to determine whether straw was a suitable carrier for Piriformspora indica. Then, two kinds of fertilization (biofertilizer as base fertilizer and seed soaking with biofertilizer extract) with three fertilizer treatments [straw treatment (ST), biofertilizer treatment (BF) and conventional fertilization as control (CK)) and five seed soaking treatments (four biofertilizer extract gradients of 25%, 50%, 75% and 100%, and sterile water as control (CK)] were set up to treat the seeds of Lvhan 1. Then, the comparative analyses of the germination indexes, agronomic traits, root morphology and physiological indices under different treatments were conducted, and the fertilization effect was evaluated, and finally the appropriate fertilization concentration and fertilization method were selected. Results showed that: (1) the number of viable CFU was significantly increased by 2.89 times and 1.89 times during 0~6 days after inoculation on straw and peat carriers, respectively (P<0.05). During the 180 days of straw carrier-based Piriformospora indica biofertilizer stored at room temperature (25℃) , the number of viable CFU of the biofertilizer showed a trend of first increased and then decreased with the extension of storage time. The number of viable CFU was significantly increased by 32.08% and 31.13% at 30th and 60th day, and significantly decreased by 61.23%, 96.60% and 98.70% at 120th, 150th and 180th day than that of the initial (P<0.05). (2) Compared with straw treatment, plant weight, stem length, root length, projection area, surface area, root activity, the contents of both chlorophyll a and chlorophyll b were significantly increased under biofertilizer treatment. (3) Rice seed germination was inhibited by biofertilizer extract, and the inhibition effect was strengthened with the increase of concentration of the extract. Biofertilizer extracts of different concentrations showed different effects, namely low concentration promoted growth and high concentration inhibited growth, on germ length, radicle length, seedling root morphological indices, stem length, longest leaf length and plant weight, and they were obviously promoted by 25% biofertilizer extract. However, germ length, root morphological indexes and plant weight were significantly reduced by 34.07%, 43.53%−63.97% and 19.51% by the original extract solution(100%), respectively (P<0.05). This study showed that combined with straw mulching, the biofertilizer made by inoculating Piriformospora indica solution on straw-carrier was a suitable rice planting strategy. Mixing compound fertilizer and Piriformospora indica biofertilizer at 3:1 and seed soaking with 25% biofertilizer extract were two fertilization methods and fertilization concentrations appropriate to both rice seed germination and seedling growth.

Key words: Piriformospora indica, Biofertilizer, Carrier, Toxicity, Viable colony forming unit, Growth promoting effect