Studies on synergistic interaction of different sources and levels of sulphur on growth of black soybean

Introduction

Black soybean (Glycine max L.) cultivation holds significant importance in the agricultural sector, valued for its nutritional benefits and versatile nature. Within the realm of crop productivity, the role of sulphur as an essential nutrient cannot be underestimated. Sulphur plays a pivotal role in various physiological processes of plants, including protein synthesis, enzyme activation, and chlorophyll production, all of which are integral to the growth and development of black soybean crops. The availability of sulphur in the soil is crucial for ensuring optimal plant health and productivity Sharma et al. (2019) [8] . The productivity of black soybean can be influenced by the type and quantity of sulphur sources present in the soil. Different sources of sulphur, such as elemental sulphur, sulphate salts (e.g., Epsom salt), and organic sources like compost or manure, offer varying forms of sulphur that impact plant growth differently. Elemental sulphur, for instance, acts as a slow-release form that necessitates microbial activity for conversion into plant-available sulphate, potentially requiring a longer time to manifest visible results in crop performance. In contrast, sulphate salts provide an immediate source of sulphate that is quickly available to plants, leading to a rapid growth response. Organic sources of sulphur contribute sulphur in complex forms, facilitating gradual release over time and potentially improving soil structure and microbial activity (Devi et al., 2012) [1] . Furthermore, the levels of sulphur in the soil play a critical role in black soybean productivity. Insufficient sulphur levels can result in reduced protein synthesis, chlorophyll production, and overall growth of the plant, ultimately leading to lower yields. Conversely, optimal sulphur levels support healthy plant growth, enhance nutrient uptake, and contribute to the potential for increased yield. However, excessive levels of sulphur can be detrimental, causing toxicity symptoms such as leaf yellowing, decreased photosynthesis, and stunted growth in black soybean plants Sarkar et al., (2002) [6] .

Materials and Methods

The field experiment was conducted during summer (Kharif) season of 2023-24, at the Agriculture Field of Himalayan University, Jollang, Itanagar, Arunachal Pradeh. The Crop Research Farm is located in Jullang on the university campus, situated ar 27.14°N latitude and 93.62°E longitude, and an altitude of 320 meters above sea level. The site belongs to the Eastern Himalayan region, and the agro-climatic zone falls under the sub-tropical zone of Arunachal Pradesh. It was undertaken with the objectives to assess the performance of Black Soybean crop and to assess the performance in Kharif seasons. Epsomite + Sphalerite at 15 kg S ha⁻ 1 T8 (S3L2)

Epsomite + Sphalerite at 30 kg S ha⁻ 1 T9 (S3L3)

Epsomite + Sphalerite at 45 kg S ha⁻ 1

The various methods for calculation of growth parameters are given below Plant height (cm) Plant height was taken in cm from the growth level to the tip of the plant from randomly selected 5 (five) plants in each individual plot and these plants were tagged for subsequent observation. A total of 3 (three) observation 30 DAS, 60 DAS and 90 DAS were recorded from the same plants in each plot and the average height of plant in each treatment was worked out for each observation.

Number of leaves per plant

The total number of leaves per plant was recorded 30 DAS, 60 DAS and 90 DAS and average number of each leaf per plant was calculated.

The fresh weight of plants refers to the weight of the plant or plant parts immediately after harvest, including the water content present in the product.

The dry weight of a plant is the weight of the plant after all its water content has been removed. This is typically done by drying the plant material at temperatures higher than ambient temperature until all moisture is evaporated.

Crop growth rate (CGR)

The method was suggested by Watson (1956) [10] . The CGR explains the dry matter accumulated per unit land area per unit time (g m -2 day -1 )

Where, W 1 and W 2 are whole plant dry weight at time t 1t 2 respectively, ρ is the groundarea on which W 1 and W 2 are recorded. CGR of a species are usually closely related to interception of solar radiation.

Relative growth rate (RGR)

The term was coined by Williams (1946) [11] . Relative Growth Rate (RGR) expresses the total plant dry weight increase in a time interval in relation to the initial weight or dry matter increment per unit biomass per unit time or grams of dry weight increase per gram of dry weight and expressed as unit dry weight / unit dry weight / unit time (g g -1 day -1 )

Where, W 1 and W 2 are whole plant dry weight at t 1 and t 2 respectively and t 1 and t 2 are time interval in days.

Results and Discussions 1. Plant Height (cm) 30, 60, 90 DAS At 30 DAS the maximum increase in plant height was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 15.43 cm and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 14.50 cm was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg Sha -1 ). Lowest plant height was observed in treatment T 4 S 2 L 1 -(Iron Pyrite 15 kg S ha -1 ) i,e.,13.96 cm. At 60 DAS the maximum increase in plant height was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 35.43 cm cand T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 34.53 cm was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest plant height was observed in treatment T 4 S 2 L 1 (Iron Pyrite 15 kg S ha -1 ) i,e.,33.96 cm. At 90 DAS the maximum increase in plant height was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 65.56 cm and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 64.50 cm was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha - 1 ). Lowest plant height was observed in treatment T 4 S 2 L 1 (Iron Pyrite 15 kg S ha -1 ) i,e., 64.03 cm. . The higher plant height recorded in T 3 S 1 L 3 (Gypsum 45 kg S ha-1 ) plot may be attributed to the beneficial effects of gypsum on soil structure and water retention. Gypsum application can enhance soil conditions, promoting improved nutrient uptake and overall growth stimulation for the plants. This, in turn, may have led to the observed increase in plant height in the specified treatment group and recording lower plant height in T 4 S 2 L 1 (Iron pyrite 15 kg S ha -1 ) could be a result of the negative impact of iron pyrite on soil quality, such as acidity or toxicity, leading to hindered nutrient uptake and growth inhibition for the plants (Dixit et al., 2009) [3] . The probable reason for the higher length of black soybean leaves in treatment T 3 (S 1 L 3 Gypsum 45 kg S ha -1 ) compared to the lowest length in treatment T 4 S 2 L 1 (Iron Pyrite 15 kg S ha -1 ) could be due to the varying effects of gypsum and iron pyrite on the soybean plants. Gypsum, being calcium sulfate, may have positively influenced leaf growth due to its impact on soil structure and nutrient availability. On the other hand, iron pyrite, being a source of sulfur and iron, may not have provided the necessary nutrients or conditions for optimal leaf growth, leading to shorter leaves. Factors such as soil pH, nutrient uptake, and plant response to these amendments could also play a role in the observed differences (Sangale et al., 2004) [7] . The probable reason for the higher no.of leaves in T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) could be due to the positive effects of gypsum on plant growth, such as improved soil structure, increased nutrient availability, and enhanced root development.

Gypsum may have promoted healthier and longer leaves in this treatment compared to others. On the other hand, the lowest recording for leaf length in T 4 S 2 L 1 (Iron Pyrite 15 kg S ha -1 ) could be attributed to the negative impact of iron pyrite on plant growth. Iron pyrite may have adverse effects on soil quality, nutrient uptake, and overall plant health, leading to shorter and less healthy leaves in this treatment (Dhageet et al., 2014) [2] .

At 30 DAS the maximum increase in fresh weight was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 6.51 g and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 6.27 g was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest fresh weight was observed in treatment T 4 S 2 L 1 (iron pyrite 15 kg s ha -1 ) i,e., 5.31 g. At 60 DAS the maximum increase in fresh weight was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 21.57 g and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 17.99 g was found to be statistically at par with S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest fresh weight was observed in treatment T 4 S 2 L 1 -(Iron Pyrite 15 kg S ha -1 ) i,e.,12.13 g. At 90 DAS the maximum increase in fresh weight was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 32.11 g and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 227.43 g was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest fresh weight was observed in treatment T 4 S 2 L 1 -(Iron Pyrite 15 kg S ha -1 ) i,e.,15.27 g. . The higher fresh weight in T 3 (S 1 L 3 Gypsum 45 kg S ha -1 )could be due to the positive impact of gypsum on plant growth, resulting in increased water and nutrient absorption, improved photosynthesis, and enhanced overall plant vigor. Gypsum may have facilitated better growth conditions, leading to higher fresh weight measurements in this treatment.

Conversely, the lowest fresh weight recording in T 4 (S 2 L 1 Iron Pyrite 15 kg S ha -1 ) may be attributed to the detrimental effects of iron pyrite on plant development. Iron pyrite can lead to soil acidification, reduced nutrient availability, and toxicity to plants, resulting in stunted growth and lower fresh weight measurements in this treatment (Zou et al., 2018) [12] .

At 30 DAS the maximum increase in dry weight was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 5.46 g and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 4.78 was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest dry weight was observed in treatment T 4 (S 2 L 1iron pyrite 15 kg S ha -1 ) i,e., 4.13 g. At 60 DAS the maximum increase in dry weight was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 20.20 g and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 16.89 g was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest dry weight was observed in treatment T 4 S 2 L 1 -(Iron Pyrite 15 kg S ha -1 ) i,e.,10.06 g. At 90 DAS the maximum increase in dry weight was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e.

31.06 g and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 25.47 g was found to be statistically at par with S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest dry weight was observed in treatment T 4 (S 2 L 1 -Iron Pyrite 15 kg S ha -1 ) i,e.,13.35 g. The higher dry weight in T 3 S 1 L 3 (Gypsum 45 kg S ha-1 ) could be a result of the beneficial effects of gypsum on plant growth, such as improved soil structure, enhanced nutrient availability, and better water retention. Gypsum may have created optimal growing conditions, leading to increased biomass accumulation and higher dry weight measurements in this treatment. Conversely, the lowest dry weight recording in T 4 S 2 L 1 (Iron Pyrite 15 kg S ha -1 ) may be due to the adverse impact of iron pyrite on plant productivity. Iron pyrite can induce soil toxicity, hinder nutrient uptake, and impede plant growth, resulting in reduced biomass accumulation and lower dry weight measurements in this treatment (Varun et al., 2011) [9] . A sigmoidal but marginal decrease in CGR was observed during the successive growth intervals. At 30-60 DAS the maximum increase in CGR was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 0.49 g m -2 day -1 and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 0.40 g m -2 day -1 was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha - 1 ). Lowest CGR was observed in treatment T 4 S 2 L 1 -(Iron Pyrite 15 kg S ha -1 )i,e.,0.20 g m -2 day -1 . At 60-90 DAS the maximum increase in CGR was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 0.36 g m -2 day -1 and T 9 S 3 L 3 (Epsomite+ Sphalerite 45kgSha -1 ) i,e., 0.29 g m -2 day -1 was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest CGR was observed in treatment T 4 S 2 L 1 -(Iron Pyrite 15 kg S ha -1 ) i,e.,0.11 g m -2 day -1 . The probale reason for higher crop growth rate in T 3 S 1 L 3 Gypsum 45 kg S ha -1 ) could be attributed to the positive effects of gypsum on plant growth and development. Gypsum may have enhanced nutrient availability, improved soil structure, and promoted overall plant health, leading to a faster rate of crop growth in this treatment. Conversely, the lower recording for crop growth rate in T 4 (S 2 L 1 Iron Pyrite 15 kg S ha -1 ) may be a result of the negative impacts of iron pyrite on plant growth. Iron pyrite can adversely affect soil quality, inhibit nutrient uptake, and hinder plant growth, resulting in a slower rate of crop growth in this treatment compared to others (Hitsuda et al., 2015) [5] .

The observations on realtive growth rate (g m -2 day -1 ) of black soybean recorded at different intervals (30-60, and 60-90) was statistically analysed and is being presented in table no.7 and graphically depicted in figure no.2 A sigmoidal but marginal decrease in RGR was observed during the successive growth intervals. At 30-60 DAS the maximum increase in RGR was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) i,e. 0.043 g m -2 day -1 and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 0.042 g m -2 day -1 was found to be statistically at par with T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ). Lowest RGR was observed in treatment T 4 S 2 L 1 -(Iron Pyrite 15 kg S ha -1 ) i,e.,0.29 g m -2 day -1 . At 60-90 DAS the maximum increase in RGR was observed and recorded in treatment T 3 S 1 L 3 (Gypsum 45 kg Sha -1 ) i,e. 0.0143 g m -2 day -1 and T 9 S 3 L 3 (Epsomite+ Sphalerite 45 kg S ha -1 ) i,e., 0.0136 g m -2 day -1 was found to be statistically at par with T 3 S1L3 (Gypsum 45 kg S ha -1 ). Lowest RGR was observed in treatment T 4 S 2 L 1 -(Iron Pyrite 15 kg S ha -1 ) i,e.,0.0094 g m -2 day -1 . The probale reason for higher relative growth rate in T 3 S 1 L 3 (Gypsum 45 kg S ha -1 ) may be due to the positive impact of gypsum on plant growth. Gypsum could have improved nutrient availability, enhanced soil moisture retention, and stimulated overall plant development, leading to a faster relative growth rate in this treatment. Conversely, the lower recording for relative growth rate in T 4 S 2 L 1 (Iron Pyrite 15 kg S ha -1 ) could be attributed to the adverse effects of iron pyrite on plant growth. Iron pyrite may have inhibited nutrient uptake, caused soil toxicity, and restricted plant development, resulting in a slower relative growth rate in this treatment compared to others (Hitsuda et al., 2015) [5] . Treatments RGR (g m 2 day -1 ) 30-60DAS 60-90DAS T1 S1L1-Gypsum 15 kg S ha -1 0.033 0.0102 T2 S 1L2-Gypsum 30 kg S ha -1 0.041 0.0134 T3 S1L3-Gypsum 45 kg S ha -1 0.043 0.0143 T4 S2L1-Iron Pyrite 15 kg S ha -1 0.029 0.0094 T5 S2L2-Iron Pyrite 30 kg S ha -1 0.031 0.0099 T6 S2L3-Iron Pyrite 45 kg S ha -1 0.037 0.0113 T7 S3L1-Epsomite+ Sphalerite 15 kg S ha -1 0.039 0.0126 T8 S3L2-Epsomite+ Sphalerite 30 kg S ha

Conclusion

Understanding the effects of different sulphur sources and levels on the productivity of black soybean is essential for agricultural practitioners seeking to maximize crop yield and quality. By discerning the nuanced interactions between sulphur availability and plant growth, farmers can make informed decisions regarding sulphur management strategies to optimize black soybean productivity. T 3 S 1 L 3 (Gypsum 45 kg S ha-1 ) showed the most notable improvements in plant height (cm),, number of leaves plant, fresh weight and dry weight (g). T 3 S 1 L 3 (Gypsum 45 kg S ha-1 ) was also observed best in CGR (g m -2 day -1 ) and RGR (g g -1 day -1 ).Through further research and implementation of sustainable sulphur management practices, the cultivation of black soybean crops can be enhanced, contributing to the overall sustainability and success of agricultural systems.

Acknowledgement

AcknowledgementI would like to extend my heartfelt gratitude to my thesis advisor, Dr.Kasinam Doruk, for her unwavering support, expert guidance, and valuable feedback throughout every stage of this research. Her patience, encouragement, and mentorship have been pivotal in shaping the direction and quality of this thesis. I am truly grateful for her dedication and belief in my capabilities. I also appreciate the assistance provided by the technical staff and the financial support received from my parents, which made this study possible.

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