Differences between Bradyrhizobium strains NC92 and TAL1000 in their nodulation and nitrogen fixation with peanut in iron deficient soil

The effects of Bradyrhizobium (strains NC92 and TAL1000) and Fe supply on nodulation and nitrogen fixation of two peanut (Arachis hypogaea L.) cultivars (cv. Tainan 9 (Fe inefficient) and cv. 71-234 (Fe efficient)) grown under Fe deficient conditions (imposed by adding 40% CaCO₃ to a ferruginous soil) were examined in a glasshouse experiment. When inoculated with TAL1000 without Fe, both cultivars had low shoot N concentration, very low nodule numbers and weight and no measurable acetylene reduction activity per plant. Inoculation with NC92 without Fe increased all these parameters substantially; addition of Fe with NC92 had no further effect on N concentration but doubled nodule number, weight and acetylene reduction activity per plant. Addition of Fe with TAL1000 increased all parameters to the same level as Fe+NC92, indicating that the poorer nodulation and N₂ fixation of TAL1000 in the absence of Fe, resulted from a poorer ability in getting its Fe supply from the alkaline soil. The nodules from all treatments with measurable activity had the same specific acetylene reduction activity suggesting that Fe deficiency limited nodule development.The results support previous suggestions that Bradyrhizobium strains differ greatly in their ability to obtain Fe from soils and that selection of Fe efficient strains could complement plant breeding in the selection of legume crops for Fe deficient soils.     

Some characteristics of symbiotic nitrogen fixation,yield, protein and oil accumulation in irrigated peanuts (Arachis hypogaea L.)

Summary The potential of peanuts for symbiotic nitrogen fixation is considerable and under optimal edaphic and climatic conditions it reached 222 kg N₂/ha, which was 58% of the nitrogen accumulated in the plants. The effect of the Rhizobium inoculation on crude protein accumulation in the yield (kg/ha) was 3–4 times greater than its effect on the yield of pods and hay. There was an inverse relationship between the protein and oil content in the kernels.Seasonal changes in nitrogenase activity in the nodules were determined by the acetylene reduction method during two growing seasons. Under favorable conditions the specific activity of the nitrogenase reached a very high level (up to 975 moles C₂H₂ g dry wt nod/h) and the total activity (moles C₂H₄/plant/h) was also high in spite of the relatively poor nodulation (weight and number). The high activity was drastically reduced (to 75 moles C₂H₄ g dry wt nod/h) due to exceptionally hot and dry weather, which occurred in the middle of the second half of the growing season. It appears that N₂-fixation (nitrogenase activity) is more sensitive to these unfavorable conditions, than is nodule growth. Maximum nitrogenase activity was observed during the podfilling stage; until 50–60 days after planting, nitrogenase activity was very low.     

Groundnut (Arachis hypogaea L.) cultivars for cultivation on calcareous soils

Summary Studies of incubation experiments showed that the phosphorus turnover under aerobic decomposition in soil starts with a non-biological process, which is rapid and probably due to chemical fixation. The present study allowed a distinction to be made between chemical fixation and biological immobilisation of added phosphorus with special reference to the effects of addition of energy material in the process of biological turnover. Invariably, both glucose and cellulose additions resulted in an increase in phosphorus immobilisation. Comparatively, cellulose acted slowly on phosphorus turnover, with the prospect of more immobilisation in long term experiments. re]19730416