Residual effect of different sources and levels of sulphur on growth, yield attributes and yield of mustard (Brassica spp.)

Introduction

Mustard (Brassica spp.) is an important oilseed crop cultivated widely during the rabi season and contributes substantially to edible oil production. Sustaining productivity of mustard under intensive cropping systems requires efficient management of plant nutrients. Among the essential nutrients, sulphur has particular importance in oilseed crops because of its role in plant growth, protein synthesis and reproductive development. Adequate sulphur availability is therefore important for obtaining optimum growth, yield attributes and seed yield. Continuous cultivation and intensive fertilizer use may alter the availability of secondary nutrients in soil. Sulphur removed by crops can contribute to depletion of available sulphur, particularly in soils having initially low sulphur status. The residual availability of sulphur applied to one crop may, therefore, become important for the succeeding crop in a cropping sequence. The residual effect of sulphur is influenced by its source and level of application. Elemental sulphur undergoes oxidation in soil before becoming available to plants, while ammonium sulphate supplies sulphur in a comparatively readily available form along with nitrogen.

Consequently, the amount and source of sulphur applied to a preceding crop may influence the quantity of sulphur remaining in the soil and its availability to the succeeding crop. Mustard has a relatively high nutrient requirement and is considered responsive to balanced nutrient management. In a rice-mustard cropping sequence, sulphur applied to the preceding rice crop may provide a residual nutrient contribution to the succeeding mustard crop. However, the magnitude of this residual effect may also depend on the fertilizer supply to mustard itself. Therefore, the present investigation was undertaken to study the residual effect of different sources and levels of sulphur on growth, yield attributes and yield of mustard (Brassica spp.).

Materials and Methods

Experimental site

A field experiment was conducted during the rabi seasons of 2021-22 and 2022-23 at the Instructional-cum-research farm, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh, India. The mustard crop was grown as the succeeding crop after rice to evaluate the residual effect of different sulphur treatments imposed on the preceding rice crop. The experimental soil was Kanhar soil, characterized by low organic carbon, low available nitrogen, medium available phosphorus, high available potassium and low available sulphur. The soil reaction was neutral, with a pH of 7.1.

Experimental design and treatment structure

The experiment was laid out in a split-plot design with three replications. The experiment comprised nine main-plot treatments representing the residual effect of sulphur management treatments applied to the preceding rice crop and three sub-plot fertilizer levels applied directly to the succeeding mustard crop. The gross plot size was 2.25 m × 5.5 m. These treatments were applied to the preceding rice crop, and their residual effects were evaluated in the succeeding mustard crop.

Main-plot treatments: residual sulphur management

Sub-plot fertilizer treatments

The succeeding mustard crop received three fertilizer levels:

The recommended fertilizer dose for mustard was 100:80:40 kg N:P₂O₅: K₂O ha⁻¹.

No sulphur was directly applied to mustard.

Crop establishment

The mustard variety Chhattisgarh Sarson was used. The crop was established by direct sowing in lines at a spacing of 45 × 10 cm during the rabi seasons of 2021-22 and 2022-23.

Fertilizer management

The recommended fertilizer dose for mustard was 100:80:40 kg N: P 2 O 5: K 2 O ha -1 . Fertilizers were applied according to the three sub-plot fertilizer treatments, viz. no RDF, 50% RDF and 100% RDF.

No additional sulphur was applied directly to mustard. Thus, the sulphur response observed in mustard was considered to represent the residual effect of sulphur applied to the preceding rice crop.

Observations recorded

Observations were recorded on plant growth, yield attributes and yield of mustard.

Growth observations

• Plant population (no. m -2 )

Yield observations

Observations were recorded during both experimental years and mean values were calculated for interpretation.

Statistical analysis

The experimental data were statistically analysed according to the procedure appropriate for a split-plot design with three replications. The effects of residual sulphur treatments, fertilizer levels and their interaction were evaluated at the 5% probability level. Where applicable, critical differences were used for comparison of treatment means.

Results and Discussion

Growth parameters 3.1.1 Plant Population

Plant population (no. m -2 ) of mustard influenced by the residual sulphur treatments was non-significant. Among the residual treatments, T 8 recorded the highest mean plant population at harvest (26.77), followed by T 7 (26.76), whereas T 9 recorded the lowest (25.03). Among fertilizer levels, F3 recorded the highest mean plant population (26.42), followed by F 2 and F 1 . The relatively higher plant population under the superior treatments may be attributed to better nutrient availability and crop establishment.

Plant height

Plant height increased progressively with crop growth and was favourably influenced by the residual sulphur treatments. T 8 recorded the highest mean plant height at later stages, reaching 173.39 cm at harvest, followed by T 7 (166.50 cm), whereas T 9 (absolute control) recorded the lowest (145.56 cm). Among fertilizer levels, F 3 (100% RDF) recorded the highest plant height (171 cm) followed by F 2 (163.54 cm) and F 1 (143.07 cm). The improvement may be attributed to better nutrient availability and utilization in the succeeding mustard crop. Similar improvement in plant height is reported by Tarafdar et al. (2019) [7]

Number of branches plant⁻¹

The number of branches plant -1 increased with crop growth. T 8 recorded the highest mean values, particularly at 60 DAS (5.56) and 90 DAS (11.70), whereas T 9 recorded the lowest. Similarly, F 3 recorded the highest number of branches, followed by F 2 and F 1 . The greater branching under residual sulphur and adequate fertilizer supply indicates improved vegetative development. The results are in agreement with the findings of Singh (2017) [6] .

Dry matter accumulation

Dry matter accumulation increased markedly with crop age. T 8 recorded the highest mean dry matter accumulation at, with 51.04 g plant -1 at 60 DAS, 70.56 g plant -1 at 90 DAS and 74.26 g plant - 1 at harvest, followed by T 7 , whereas T 9 recorded the lowest values. F 3 also recorded the highest dry matter accumulation (74.49 g plant -1 at harvest). The response indicates a favourable residual effect of sulphur on biomass production. Similar findings also reported by Chandel et al. (2002) [2] .

Yield attributes 3.2.1 Number of siliquae plant -1

Residual sulphur significantly influenced siliquae production. T 8 recorded the highest mean number of siliquae plant -1 (146.39), followed by T 7 (141.78) and T 5 (139.11), whereas T 9 recorded the lowest (125.28). Among fertilizer levels, F 3 recorded the highest value (145.79), followed by F 2 and F 1 . Greater siliquae production T 8 may be associated with better vegetative growth and reproductive development. The results are in agreement with the findings of Rao and Shaktawat (2000) [4] .

Number of seeds siliqua -1

The number of seeds siliqua⁻¹ was highest under T 8 (15.69), followed by T 7 (14.96) and T 5 (14.62), while T 9 recorded the lowest (12.32). F 3 recorded the highest mean value (15.24) compared with F 2 (14.14) and F 1 (12.49). Improved sulphur nutrition may have favoured reproductive development and seed formation. Similar findings also reported by Rao and Shaktawat (2000) [4] .

Siliqua length

Siliqua length was highest under T 8 (5.08 cm), followed by T 7 (4.82 cm) and T 5 (4.66 cm), whereas T 9 recorded the lowest (3.74 cm). Fertilizer application also increased siliqua length, with F 3 recording 5.08 cm, followed by F 2 (4.39 cm) and F 1 (3.56 cm). The significant interaction between residual treatment and fertilizer level indicates that siliqua development was influenced by their combined effect. Rao and Shaktawat (2000) [4] Tarafdar et al. (2019) [7] are on the same opinion.

Test weight

The residual sulphur treatments significantly affected test weight. T 8 recorded the highest mean value (5.03 g), followed by T 7 (4.96 g) and T 5 (4.91 g), whereas T 9 recorded the lowest (3.89 g). F 3 recorded the highest value (5.01 g), followed by F 2 (4.36 g) and F 1 (3.94 g). The higher seed weight under T 8 indicates improved seed development under favourable residual nutrient availability. Similar findings also reported by Rao and Shaktawat (2000) [4] Tarafdar et al. (2019) [7] .

Yield 3.3.1 Seed yield

Seed yield was significantly influenced by the residual sulphur treatments. T 8 recorded the highest mean seed yield (16.53 q ha - 1 ), followed by T 7 (16.00 q ha -1 ) and T 5 (15.59 q ha -1 ), whereas T 9 recorded the lowest (12.71 q ha -1 ). T 8 and T 7 were statistically at par. The higher seed yield under T 8 may be attributed to its favourable effect on plant growth, siliquae production, seeds siliqua -1 and test weight. The results are in agreement with the findings of Tarafdar et al. (2019) [7] Singh et al. (2008) [5] .

Stover yield

Stover yield followed a similar trend. T 8 recorded the highest mean stover yield (40.07 q ha -1 ), followed by T 7 (38.31 q ha -1 ) and T 5 (37.53 q ha -1 ), whereas T 9 recorded the lowest (29.65 q ha -1 ). The greater stover production was consistent with the higher vegetative growth and dry matter accumulation under the superior residual sulphur treatments. Singh (2017) [6] is on the same opinion.

Harvest Index

Harvest index was not significantly influenced by residual sulphur treatment. Numerically, T 8 recorded the highest mean harvest index (30.34%), followed by T 5 (30.13%), whereas the differences among treatments were relatively small. Thus, the residual sulphur effect was expressed more strongly through seed and stover production than through harvest index.

Conclusion

The present investigation demonstrated that different sources and levels of sulphur applied to the preceding rice crop exerted a measurable residual effect on the growth, yield attributes and productivity of succeeding mustard. Among the residual treatments, 40 kg S ha -1 through ammonium sulphate (T 8 ) generally recorded the highest growth and yield attributes and the highest mean seed yield (16.53 q ha -1 ) and stover yield (40.07 q ha -1 ), while the absolute control (T 9 ) recorded the lowest performance. T 7 , comprising 30 kg S ha -1 through ammonium sulphate, generally followed T 8 and was statistically at par with T 8 for seed yield, whereas T 5 , comprising 40 kg S ha -1 through elemental sulphur, was another comparatively superior treatment. Direct application of fertilizer to mustard also improved crop growth, yield attributes and yield, with 100% RDF generally performing better than 50% RDF and no RDF. The residual effect was particularly evident in plant height, branching, dry matter accumulation, siliquae production, seeds siliqua -1 , siliqua length, test weight and seed yield. Therefore, under the conditions of the present investigation, application of 40 kg S ha -1 through ammonium sulphate to the preceding rice crop, followed by adequate fertilizer management of the succeeding mustard crop, was the most promising nutrient-management approach for enhancing productivity of mustard in the rice-mustard cropping sequence.

References

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