Effect of Phosphorus Supply Levels on Nodule Nitrogen Fixation and Nitrogen Accumulation in Soybean (Glycine max L.)

Abstract

The specific mechanism by which phosphorus affects nodule nitrogen fixation and nitrogen absorption in soybeans remains inconclusive. To further quantitatively analyze the effect of phosphorus on nodule nitrogen fixation and nitrogen accumulation in soybeans, this experiment was carried out under sand culture conditions. The experiment consisted of six phosphorus supply levels (1 mg/L, 11 mg/L, 21 mg/L, 31 mg/L, 41 mg/L, 51 mg/L). The acetylene reduction method and 15N tracer method (50 mg/L (NH4)2SO4) were used to determine and analyze the nodule growth status, nodule nitrogenase activity, nitrogen content, and nodule nitrogen fixation rate at initial flowering (R1 stage), initial pod (R3 stage), seed filling (R5 stage) and maturity stages (R8 stage). The results are described as follows: 1. The nitrogen fixation of soybean nodules at different growth stages has different requirements for phosphorus supply levels. The initial flowering stage and seed-filling stage were 31 mg/L–41 mg/L, and the initial pod stage was 51 mg/L. 2. The nitrogen source in different parts of soybean showed different trends with different growth periods and phosphorus supply concentrations. Among them, from the initial flowering stage to the seed filling stage, the main body of the nitrogen supply of soybean shoots in the low phosphorus treatment (1 mg/L–31 mg/L) gradually changed from fertilizer nitrogen to nodule nitrogen fixation, while the main body of the nitrogen supply of soybean shoots in the high phosphorus treatment (41 mg/L–51 mg/L) always showed nodule nitrogen fixation and was transformed into fertilizer nitrogen at the mature stage. The main nitrogen supply to the roots of soybean at different levels of phosphorus supply from the initial flowering to the initial pods and maturity stage was fertilizer nitrogen, and the main nitrogen supply at the seed filling stage was nodule nitrogen fixation. The nitrogen supply to the main body of soybean nodules was constantly nodule nitrogen fixation. 3. Different phosphorus supply levels significantly affected the nitrogen fixation of soybean nodules (R2 ≥ 0.803), and both the acetylene reduction method and the 15N tracer method could be used to determine the nitrogen fixation capacity of soybean nodules. This study indicated the optimal phosphorus supply level of nodules in different growth stages of soybean and clarified the main body of phosphorus supply in different parts of soybean at different growth stages, which pointed out the direction for further improving the utilization efficiency of soybean nitrogen and phosphorus fertilizer.

The Influence of Organic-Mineral Foliar Fertilizers on Soil Mineral Nitrogen, Nitrous Oxide Emissions and Crop Productivity

“…Thus, our data are confirmed by the results of studies on the effectiveness of fertilizers based on a complex of microelements with amino acids or humic substances, as well as nitrogen fertilizers, in direct dependence on provision of soil with other nutrients, primarily mobile phosphorus [64,65].…”

Effects of Co-Inoculating Saccharomyces spp. with Bradyrhizobium japonicum on Atmospheric Nitrogen Fixation in Soybeans (Glycine max (L.))

“…IAA has been reported to play a significant role in nodule development and legume-rhizobia interaction [ 42 , 43 ]. NNP and NDW have also been reported to decrease with the decline in available P [ 30 , 31 ]. This might explain the higher NNP and NDW values under the treatments which had either of the yeast isolate (T3, T4, T5, and T6) relative to T1 and T2 ( Table S3 ).…”

“…The NNP and NDWP enhancement due to co-inoculation might be caused by the increase in root length and mass, thus increasing the number of effective sites for nodulation and infection sites for the bacteria. On the other hand, when the emphasis is put on the P solubilization abilities of the yeast isolates, soil P availability to soybeans has also been reported to enhance the capacity of root nodules, promoting N 2 -fixation [ 30 , 32 ]. Therefore, the overall impact of the yeast isolates on nodule N 2 -fixation also stems from the importance of P and its effects on host plant growth, nodule formation, nodule growth, nodule function, and nodule metabolism [ 32 ].…”

“…The can also help to improve soil health and may influence plant growth indirectly by encouraging the growth of other plant growth-promoting rhizo-microorganisms through the production of plant growth hormones such as indole-3-acetic acid/auxins (IAA), polyamines, vitamin B 12, protein, organic acids, soluble, and volatile exudates as well as solubilizing inorganic P and iron [ 19 , 26 , 28 , 29 ]. These PSMs have also been reported to enhance N 2 -fixation, nodulation, root growth, nutrient uptake, and disease tolerance in different plants [ 30 , 31 , 32 , 33 ]. Furthermore, some studies have shown that dual inoculation of these plant growth-promoting microbes improves plant growth relative to the sole inoculation of only one [ 34 , 35 ].…”

The Importance of Mineral Elements for Sustainable Crop Production

“…Li et al [8] conducted a detailed investigation into the effects of varying P supply on soybeans using a split-root system. In a related study, Li et al [9] further researched the optimal P levels necessary for effective nodulation, N fixation activity, and plant N accumulation in soybeans. Both studies highlighted the complex interplay between P supply and soybean growth.…”