Study On Effects Of Applying Supperphosphate Fertilizer And Inoculation With Rhizobia On Growth And Forage Quality Of Alfalfa

Alfalfa (Medicago sativa L.) is a famous species for the production of high-quality forage in Shandong area. But it is susceptible to a variety of stresses that can combine to reduce dry matter yield and forage quality. A field trial was carried out in Shandong area in order to investigate the effects of a superphosphate fertilizer application and inoculation with rhizobia on growth and forage quality of alfalfa.The results showed that basic phosphorus fertilizer application increased significantly (p<0.05) nodulation rate, root nodule number and weight per plant. Beacause biological nitrogen fixation (BNF) was closely associated with root nodule number and weight per plant; phosphorus fertilizer application could significantly improve BNF of alfalfa. After application, germination rate, percentage of plant set, overwinter survival, plant No. per sq.m, branch number, plant height, stem diameter and leaf area index of alfalfa were all dramatically increased (p<0.05). All these factors resulted in remarkably increasing of dry matter yield. Applying additional phosphorus fertilizer also improved significantly growth situation of alfalfa. And the factors that resulted in increases of dry matter yield are the same as above-mentioned.Phosphorus fertilizer had a very marked effect on forage quality of alfalfa. After application, photosynthesis and water-soluble carbohydrate of alfalfa were all significantly (p<0.05) increased with the increasing of chlorophyll content of leaf, and in vitro dry matter digestibility was increased markedly result from the increasing of leaf yield after phosphorus treatment. But P-topdress had less effect on forage quality of the 2nd cut of alfalfa because it was too long to be effective after application probably.It is concluded from the results that alfalfa grown in the Yellow River Delta should be applied 750kg/hm2 basic superphosphate fertilizer (to Zhongmu No.1), and in Dezhou area should be applied 750kg/hm2 superphosphate fertilizer (basic or top application) to Zhongmu No. 1 or 1175kg/hm2 superphosphate fertilizer (basic or top application) to Gold empress, among which Zhongmu No.1 had the highest yields and Gold empress had the best quality forage.Inoculation with rhizobia could also significantly (p<0.05) improve nodulation situation of alfalfa. After inoculation, nodulation rate was increased 3~20% higher thanthat in un-inoculation plot. Root nodule number and weight per plant were all increased significantly (p<0.05) too. Rhizobia inoculation also had better effect on growth and forage quality of alfalfa. The results showed that rhizobia inoculation significantly (p<0.05) increased germination rate and plant No. per unit, then improved growth situation and dry matter yield. But the effects of inoculation were less significant than that of superphosphate fertilizer application.