Abstract

Mustard (Brassica juncea) and sesame (Sesamum indicum L.) are important oilseed crops in India. Both crops may benefit from sulfur (S) application. Polysulphate™ is the trade mark of the natural mineral ‘polyhalite’, which consists of four key plant nutrients - sulfur (S), potassium (K), magnesium (Mg), and calcium (Ca). In the present study, the effects of basal application of Polysulphate on the performance of mustard and sesame crops were examined in two distinct experiments. Each experiment included six fertilization treatments: T₁ - recommended doses of nitrogen (N) and phosphorus (P) (K omitted); T₂ - recommended NPK dose as control; T₃-T₅ - recommended NP + Polysulphate application at 20, 30, and 40 kg ha^-1, respectively, with compensation to the recommended K level; and, T₆ - recommended NPK + gypsum (with S dose equivalent to T₅). Potassium shortage reduced mustard and sesame grain yield by 12 and 17%, respectively, as compared to the control. In both crops, basal S application through Polysulphate brought about significant gains in grain yields with a linear response to the S dose, up to about 33% more at 40 kg S ha^-1, as compared to the control. Sulfur application appeared to increase the whole plant biomass, affecting most yield parameters, including oil concentration. Thus, mustard and sesame oil yields increased to 1,095 and 505 kg ha^-1, 39% and 43% more than the control, respectively. Sulfur application significantly increased K uptake by the plants, indicating a synergistic relationship between the two elements. Furthermore, S and K are translocated to the grains and are possibly involved in oil biosynthesis. It is concluded that S application at a macro-element dosage level significantly increases yields of oilseed species, such as mustard and sesame. The advantages of Polysulphate over gypsum as a basal fertilizer are discussed.