Effect Of Different Levels Of Phosphate And Rhizobium Vaccination On Growth And Nutrient Absorption Characteristics Of Seedling Stage Alfalfa

In order to discuss nitrogen and phosphorus nutrition and the effect of rhizobium inoculation,and avoid eliminate interference of externalities, the experiment was in the laboratory and used sandculture method. Nutrient solution was used to control accurately the8phosphorus levels:0,50,100,250,500,1000,1500,2000μmol/L. The experiment studied the effects of phosphorus levels andrhizobium inoculation (12531) on growth, photosynthesis, root morphological characteristics,nodule nitrogenase activity, plant nitrogen and phosphorus content and nitrogen absorption ofalfalfa under conditions where N was either added or absent. The results are listed as follows:(1) In the nutrient solution without nitrogen, rhizobium inoculation (12531) obviouslyincreased nodulation and nitrogen fixation, nodule number and weight, root length, root surface area,average root diameter and root volume of alfalfa. At the same time, root activity and nitrogenaseactivity were better, and plant total nitrogen content obviously increased, which promoted allgrowth indexes of aboveground and below ground and increased biomass of alfalfa. Meanwhile,rhizobium inoculation obviously promoted photosynthetic capacity, absorption and accumulation ofnitrogen and phosphorus, yield and quality of alfalfa.(2) In the nutrient solution with sufficient nitrogen, rhizobium inoculation (12531) increasednodule number and nodule weight of alfalfa, but not so obvious as in the nutrient solution withoutnitrogen. The same indexes at the same phosphorus level which in the without N and with N wereclose. Visibly, rhizobium inoculation to some extent makes up the lack of nitrogen of the nutrientsolution without nitrogen. At the same phosphorus level, the growth indexes were the worst at thetreatment of without nitrogen and rhizobium inoculation, and the treatment of rhizobiuminoculation without nitrogen and sufficient nitrogen without rhizobium inoculation are in the middle,and the treatment of rhizobium inoculation with sufficient nitrogen were the best.(3) In terms of yield, the treatment of without nitrogen and rhizobium inoculation was themost sensitive to phosphorus. The best phosphorus levels were between500-1000μmol/L. Thebest phosphorus levels of rhizobium inoculation without nitrogen and sufficient nitrogen withoutrhizobium inoculation were between1000-1500μmol/L. The best phosphorus levels of rhizobiuminoculation with sufficient nitrogen were between1500-2000μmol/L.(4) At the same nitrogen level with or without rhizobium inoculation, phosphorus promoted growth, photosynthetic capacity, and nitrogen fixing capacity of alfalfa. Seen from this experiment,between the phosphorus levels500-1000μmol/L, photosynthetic capacity and nitrogen fixingcapacity of Medicago sativa var. Gannong No.3alfalfa were the best. While these two indexes playa key role in absorption and accumulation of nutrient, and determine the yield and quality of alfalfa.Proper phosphorus level promotes root growth, increases effective nodule number, nitrogen andphosphorus content and nitrogen uptake of alfalfa irrespective of inoculation or N fertilizer(5) Level of sensitivity for organs of alfalfa at the same treatment were different. Compare alltreatments comprehensively, and seen from the demand for phosphorus of different organs of alfalfa:For plant height and blade number, phosphorus level500μmol/L was the best; For leaf area andchlorophyll content, phosphorus level1500μmol/L was the best; For nodule number and noduleweight, phosphorus level2000μmol/L was the best. Under the condition of this experiment,phosphorus level between1000μmol/L-1500μmol/L were the best. Between this phosphorus level,nitrogenase activity, amount of nitrogen and yield were the best. There was no positive benefit toincrease P level. When phosphorus level exceeded1500μmol/L it was bad for normal growth ofalfalfa. Nitrogenase activity, amount of nitrogen and yield were lower at phosphorus level2000μmol/L than1500μmol/L. In terms of photosynthesis, nitrogen fixation efficiency and yield scopeof this experiment, phosphorus level1500μmol/L was the best.(6) Compare all treatments and indexes comprehensively, the treatment of rhizobiuminoculation with sufficient nitrogen at phosphorus level1500μmol/L was the best.