Nitrogen Fixation Of Hybrids Of Caucasian Clover × White Clover And The Responses To Nitrogen And Potassium

There are escaped type white clover population distributed in the Daxinganling forest area of Inner Mongolia.The white clover population has excellent environmental adaptability and nitrogen fixation ability,and has been used as male parent material to hybridize with Caucasian clover to form a large number of hybrid progeny strains.To purify the white clover rhizobia for the inoculation of the study material,the nitrogen fixation after rhizobia inoculation of hybrid F1 generation was observed,and the effects of nitrogen and potassium on the growth of F1 generation strains were surveyed through testing.In this experiment,culture conditions for white clover rhizobia(initial pH of the culture medium,culture temperature and shaker speed)were screened and the rhizobia was purified.The rhizobia culture conditions were designed by single factor and two factors,with the operation repeated 3 times;nitrogen and potassium elements were treated by two factors and repeated 3 times,F1 generation strains and their parents were subjected to nitrogen and potassium application at different levels,and the effects of nitrogen and potassium application at different levels on physiological indexes and the root system of the plants were studied;the rhizobia inoculation experiments were carried out on the F1 generation strains and 2 parents.The gemmiparous seeds were transplanted into the sterile venniculite,and received 3 treatments,i.e.no rhizobia inoculation,activiation of rhizobia inoculation and deactivation of rhizobia inoculation,3 times repeated,the effects of 3 treatments on the root system and dry weight of the plants were observed.the nitrogen content of the plants was determined by elemental analyzer to detect whether they had nitrogen fixation ability.The results showed:1.Under the condition of single factor treatment,the optimal culture condition of the white clover rhizobium was that the initial pH value for the culture medium was 7.0,the culture temperature was 25 ? and the shaker speed was 180r/min.Under the condition of both factors treatment,when the temperature and the initial pH value were independent variables,the temperature was 25 ? and the pH value was 7.0,it was suitable for the growth of rhizobium;when the shaker speed and the initial pH value were independent variables,the shaker speed was 160r/min and the pH value was 7.0,it was suitable for the growth of rhizobium;when the shaker speed and the temperature were the independent variables,and they were 160r/min and 25 ?respectively,it was suitable for the growth of rhizobium.2.After treatment with different nitrogen and potassium elements,the physiological indexes and root indexes of the plants were increased and then decreased with the increase of nitrogen application rate and potassium application rate,and under the treatment of nitrogen and potassium,in the plants,nitrogen was the main influencing factor,and parents responded more strongly to nitrogen and potassium.3.After inoculation with rhizobium,F1 generation strains and Caucasian clover still showed the loss of nitrogen fixation,and the enhanced nitrogen fixation of white clover after inoculation with rhizobium.