Changes in sulphur content, uptake, internal efficiency index, harvest index and N:S ratio in pea plants from the four-leaf stage to full maturity

Sulphur is an important macronutrient for legume plants because it influences the formation and functioning of root nodules, the activity of enzymes reducing molecular nitrogen to available forms for plants, the formation of storage proteins, and in effect, ultimately the yield and quality of the crop. Sulphur should be adequately available for these plants during the entire growing period, because it is poorly redistributed from older organs to younger ones. Therefore it is appropriate to determine suitable parameters illustrating sulphur management by the pea plant throughout the growing period and accumulation in various organs.

In a two-year study, we determined the sulphur content (Sc), sulphur uptake (Sup), sulphur internal efficiency index (SIE), sulphur harvest index (SHI), and N: S ratio in six development stages of pea according to Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale: BBCH 14, BBCH 33, BBCH 55, BBCH 65, BBCH 75 and BBCH 90. Analyses were performed for the root and aerial part, and at the fully ripe stage, for seeds as well. The plants were fertilized with sulphur and nitrogen before sowing at rates of 34 kg·ha^− 1 S and 30 kg·ha^− 1 N, both in the form of ammonium sulphate (NH₄)₂SO₄.

In most cases, the pea parameters were influenced by both the development stage and the year of the study, but not all of them were significantly influenced by the cultivar. The values of the measured parameters for the whole mass of peas ranged: Sc from 2.70 to 5.02 g S·kg^− 1 dw, N:S from 8.5 to 11.5, Sup from 1.19 to 18.45 kg S ·ha^− 1, SIE from 205 to 305, and SHI calculated for whole aerial mass from 0.49 to 0.98 (0.45 calculated for seeds in 90 BBCH). Sc, Sup and SHI calculated for whole pea plants increased between BBCH 14 and BBCH 33, while the N: S ratio and SIE decreased. Sc decreased from BBCH 33 stage to BBCH 75, while Sup, SIE and SHI increased, and the N: S ratio did not change significantly. Between BBCH 75 and BBCH 90, there were no significant changes in any of the parameters of sulphur management.

All tested parameters of sulphur management indicated adequate supply of sulphur to the pea plants throughout the growing season.