Seasonal critical concentration and relationships of leaf phosphorus and potassium status with biomass and yield traits of soybean

Abstract

Analysis of uppermost fully expanded leaves is useful to detect a deficiency of mineral nutrients such as phosphorus (P) and potassium (K) in soybean. Although, the leaf P or K status aids in fertilizer management, information on nutrient seasonal relationships with growth and yield traits at maturity are limited. To investigate this, soybean was grown under varying P or K nutrition under ambient and elevated CO 2 concentrations. Results show significant relationships of the relative total biomass and yield-related traits with the foliar P and K concentrations measured several times in the season across CO 2 levels. However, the relationships established earlier in the season showed that the growth period between 25 and 37 d after planting (DAP), representing the beginning of flowering and pod, respectively, is the best for leaf sampling to determine the foliar P or K status. The leaf P and K status as well as the critical leaf P (CLPC) and K (CLKC) concentrations for traits such as seed yield peaked around 30 DAP (R2 stage) and tended to decline thereafter with the plant age. The CLPC and CLKC of seed yield indicate that the leaf P and K concentration of at least 2.74 mg g -1 and 19.06 mg g -1 , respectively, in the uppermost fully expanded leaves are needed between 25 and 37 DAP for near-optimum soybean yield. Moreover, the greatest impact of P and K deficiency occurred for the traits that contribute the most to the soybean yield (e.g., relative total biomass, seed yield, pod and seed numbers), while traits such as seed number per pod, seed size, and shelling percentages were the least affected and showed smaller leaf critical concentration. The CLPC or CLKC for biomass and seed yield was greater under elevated CO 2 24-25 DAP but varied thereafter. These results are useful to researchers and farmers to understand the dynamics of the relationship of pre-harvest leaf P and K status with soybean productivity at maturity, and in the determination of suitable growth stage to collect leaf samples.

Exploring phosphorus fertilizers and fertilization strategies for improved human and environmental health

“…Reich et al (2010) reported the net photosynthesis rates to increase with increasing leaf P content, whereby 90% of their data points were below a leaf P concentration of 0.27% by weight. Maximal biomass and grain yield are also reported for soybean at leaf P concentration of 0.2-0.3% by weight (Singh et al 2018). Photosynthesis reaches A max at about 0.2-0.3% P by weight, with no clear relation between leaf P and A max at higher P levels where photosynthesis is likely no longer affected by P (Shane et al 2004).…”

Effect of Fast Dissolved Phosphorus Fertilizer on the Growth, Seed Product, and Phosphorus Uptake Efficiency of Soybean (Glycine max L.)

“…Subsequently, the element in the fertilizers is indispensable for plant growth, especially to synthesize adenosine triphosphate (ATP) compounds, an organic compound that plays an important role in various energetic reactions in metabolic processes (Marschner, 2012). Singh et al (2018) stated that the seed yield of soybean was maximal when P concentration of the leaf reached 0.2-0.3% by weight.…”

Foliar application of phosphite reduces grain weight of soybean facing postflowering phosphorus deficiency

“…(2017) and Singh et al. (2018). Before starting the treatments, deionized water was applied in excess to remove residual P in the rooting medium from previous fertigations.…”

“…During the first week, NS had 25% of the final ionic strength (see below), being doubled in the subsequent two weeks until reached 100% of the final ionic strength. NS was free of nitrogen and the other nutrients were in the following concentrations: in mM, 0.5 P; 3.5 potassium (K); 5.0 calcium (Ca); 1.3 magnesium (Mg); 1.3 sulfur (S), and in µM, 41.6 boron (B); 0.1 cobalt (Co), 1.0 copper (Cu); 46.7 iron (Fe); 10.0 manganese (Mn), 1.3 molybdenum (Mo), 0.1 nickel (Ni), and 3.5 zinc (Zn) (Singh et al., 2018; Zambrosi, 2016).…”