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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Adaptive Cropping Systems Laboratory » Research » Publications at this Location » Publication #344249
Title: Seasonal critical concentration and relationships of uppermost fully expanded leaf phosphorus and potassium status with biomass and yield traits at maturity in soybean

Author
item SINGH, SHARDENDU - University Of Maryland Eastern Shore (UMES)
item Reddy, Vangimalla
item Sicher Jr, Richard

Submitted to: Journal of Plant Nutrition and Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2018
Publication Date: 5/8/2018
Citation: Singh, S.K., Reddy, V., Sicher Jr, R.C. 2018. Seasonal critical concentration and relationships of uppermost fully expanded leaf phosphorus and potassium status with biomass and yield traits at maturity in soybean. Journal of Plant Nutrition and Soil Science. https://doi.org/10.1002/jpln.201700392.
DOI: https://doi.org/10.1002/jpln.201700392

Interpretive Summary: The analysis of soybean leaf is useful to detect deficiency of mineral nutrients such as phosphorus and potassium, and aids in the fertilizer management. However, information in regard to the best time of leaf sampling during soybean growth periods, which correlates well with the yield at maturity, is limited. To investigate this, the seasonal leaf phosphorus and potassium concentration and yield were measured in soybean grown under a range of phosphorus and potassium fertilization. Through the correlation of soybean productivity with leaf phosphorus and potassium status, this work showed that growth period between 25 and 37 days after planting was the best for leaf sampling to determine the leaf phosphorus and potassium status. These results are useful to researchers and farmers to understand the relationship of soybean leaf phosphorus and potassium status with soybean productivity during the growing season and in determination of the growth period to collect leaf samples.

Technical Abstract: Analysis of uppermost fully expanded leaves is useful to detect 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 their seasonal association with the growth and yield traits at maturity are limited. To investigate this, soybean was grown under varying P or K nutrition under ambient and elevated CO2 concentrations. Results showed significant relationships of total biomass and yield related traits with the foliar P and K concentrations measured several times in the season across growth CO2 levels. However, the relationships established earlier in the season showed that the growth period between 25 and 37 days 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. The CLPC and CLKC of seed yield indicated that the leaf P and K concentration of at least 3.0 mg g-1 and 19.6 mg g-1, respectively, in the uppermost fully expanded leaves are needed between 25 and 37 DAP for the near optimum soybean yield. The degree of response to the leaf P and K status for traits tended to either differ (e.g., biomass, seed yield, seed protein, and oil) or were similar (e.g., seed size, seed per pod, shelling percentage). The CLPC or CLKC for biomass and seed yield was greater under elevated CO2 about 25 DAP but varied thereafter. The biomass accumulation, pod and seed numbers, and seed yield were more sensitive to P and K deficiency showing greater mean CLPC (2.67 – 3.07 mg g-1) and CLKC (17.8 – 19.0 mg g-1) compared to the traits such as shelling percentage, seeds per pod, seed size, and harvest index that exhibited substantially lower CLPC (0.88 – 2.05 mg g-1) and CLKC (10.6 – 12.3 mg g-1).