​Effect of Levels and Sources of Sulphur on Growth and Yield Attributes of Sesamum (Sesamum indicum L.) under Rainfed Condition of Nagaland

Sesamum is known by different names such as simsim, sesame, biniseed, gingly, till and gargelim and is also called as the “Queen of Oilseeds”. Sesamum has the highest oil content (46-64%) among the oilseed crops with 25% protein. Sulphur is an important component of plant amino acids, proteins, vitamins as well as enzyme structures which influence the productivity, quality of oil seed and total oil content. Oilseed crops are especially sensitive to sulphur deficiency because their demand for sulphur is quite high and produces seeds with a high yield of protein with relatively large quantities of sulphur containing amino acids (Zhao et al., 1997). Among all the sulphur supplying sources, gypsum and elemental sulphur are most abundantly used in sulphur deficient soils. The response of sesamum to sulphur fertilization for the production of higher yield was up to 40 kg S ha^-1 (Nagavani et al., 2001 and Kathiresan, 2002). Therefore, this study was undertaken to realize the importance of sulphur and its proper fertilization for better growth, yield and quality of sesamum crop.

A field experiment was conducted at the experimental farm, Department of Agronomy, SASRD, Nagaland University, during the Kharif season of 2019 to study the effect of different levels and sources of sulphur on sesamum. The experiment was laid out in randomized block design (RBD) with three replications and ten treatments viz; T₁ (control), T₂ (10 kg gypsum ha^-1), T₃ (20 kg gypsum ha^-1), T₄ (30 kg gypsum ha^-1), T₅ (40 kg gypsum ha^-1), T₆ (control), T₇ (10 kg elemental sulphur ha^-1), T₈ (20 kg elemental sulphur ha^-1), T₉ (30 kg elemental sulphur ha^-1) and T₁₀ (40 kg elemental sulphur ha^-1).
       
The soil of the experimental farm was categorized as clayey loam. The recommended dose of N, P and K fertilizer (30 kg ha^-1 urea, 60 kg ha^-1 SSP and 30 kg ha^-1 MOP) was applied as a single basal dose followed by the treatments as per viz., (T₁-S₁L₀), (T₂-S₁L₁), (T₃-S₁L₂), (T₄-S₁L₃), (T₅-S₁L₄), (T₆-S₂L₀), (T₇-S₂L₁), (T₈-S₂L₂), (T₉-S₂L₃) and (T₁₀-S₂L₄), where, T= Treatment, S₁= Gypsum, S₂= Elemental Sulphur, L₀= 0 kg ha^-1, L₁= 10 kg ha^-1, L₂= 20 kg ha^-1, L₃= 30 kg ha^-1, L₄= 40 kg ha^-1. The seeds were pre- treated with Bavistin @2g kg^-1 of seed and sown manually in lines and then covered them with soil to make it favorable for germination. Seed were sown at the rate of 4 kg ha^-1. From each plot five plants were selected randomly for recording the observations on growth attributes of the crop. At harvest, yield data of grain and stover of sesamum was recorded.

Growth attributes of sesamum
 
The crop growth attributes in terms of plant height (cm), leaf area index, plant dry weight (g plant^-1) and crop growth rate (g m^-2 day^-1) were significant among different treatments (Table 1).  The plant height was highest in T₁₀ (40 kg Elemental sulphur ha^-1). Plant height was not influenced significantly by sources and levels of sulphur at 30 DAS which might have been due to the young age of the seedlings. At 60 DAS, the highest plant height was recorded by T₁₀ (162.00 cm) and the lowest height (138.67 cm) was recorded by T₂. At 90 DAS, T₁₀ showed the highest plant height whereas T₁ (control) showed the lowest plant height.
 

       
The sources and levels of sulphur were not found to influence significantly on LAI of sesamum. Significantly highest plant dry weight at 30, 60 and 90 DAS was recorded in T₁₀. The lowest plant dry weight at 30, 60 and 90 DAS was recorded in T₆ (control). The application of nutrients in higher amounts and source of sulphur (elemental sulphur) might have resulted in the highest accumulation of total dry matter. The crop growth rate (g m^-2 day^-1) was recorded significantly highest in T₁₀ at 60 DAS-harvest (Deshmukh et al., 2010). At 30-60 DAS and 60-90 DAS, T₁₀ recorded highest crop growth rate. The lowest CGR value was recorded at T₁ (control) followed by T₆ (control) respectively where no sulphur treatment was applied.
 
Yield attributes of sesamum
 
The yield attributes in terms of number of capsules plant^-1, number of seeds capsule^-1, length of capsule, seed yield (kg ha^-1), stover yield (kg ha^-1) and harvest index (%) were significant among the treatments (Table 2). T₁₀ (89.33) recorded the highest number of capsule plant^-1 which was followed by T₉ (87.33) and were statistically at par. However T₁ (control) recorded the lowest number of capsule plant^-1 (62.00). The data on length of capsule as affected by different treatments showed that the longest capsule was recorded in T₁₀ (2.86 cm), while the shortest capsule (1.90) was recorded at T₁ (control). Application of elemental sulphur at increased levels gave a superior result. The highest number of seeds capsule^-1 was recorded in T₁₀ (70.67) while the lowest number of seeds capsule^-1 was recorded at T₁ (control) [57.33] which were statistically at par with T₆ (control) [58.67]. The variation in the different levels and sources of sulphur application did not give any significant effect on test weight of sesamum. The seed and stover yield reductions were observed more with T₁ (control) over other treatments (315.04 and 1222.44 kg ha^-1 respectively).
 

       
The stover yield and seed yield was found to be highest in T₁₀ (40 kg elemental sulphur ha^-1) with 2338.5 kg ha^-1 and 623.36 kg ha^-1 respectively. The harvest index was found to be maximum in T₁₀ (40 kg elemental sulphur ha^-1) which was statistically at par with T₉ (30 kg elemental sulphur ha^-1) and T₁ (control) with 12.75% recorded the lowest.

From the above result, it can be concluded that the treatment T₁₀ (40 kg elemental sulphur ha^-1) recorded the highest in plant height, plant dry weight (g plant^-1), CGR (g m^-2 day^-1), number of capsules plant^-1, number of seed capsule^-1, length of capsule, seed yield (kg ha^-1), stover yield (kg ha^-1) and harvest index (%). The present study showed that elemental sulphur is a better source of sulphur as compared to gypsum under rainfed condition of Nagaland and that sesamum yield also increases with increased level of sulphur application upto 40 kg ha^-1.