Effect of nitrogen and boron on available nutrients in sesame (Sesamum indicum L.) and harvested soil

A field experiment was carried out at the Soil Science research field of Sher-e-Bangla Agricultural University (SAU), Dhaka-1207, Bangladesh to study the nutrient uptake of sesame plant and available nutrient condition of soil after harvesting of sesame. Sesame variety BARI Til-3 was used as test crop. The experiment consisted of two factors. Factor A: Nitrogen levels (N0-3): N0: 0 kg N/ha (control), N1: 50 kg N/ha, N2: 60 kg N/ha, N3: 70 kg N/ha; Factor B: Boron levels (B0-2): B0: 0 kg B/ha (control), B1: 2 kg B/ha, B2: 3 kg B/ha. The experiment was carried out in two factors Randomized Complete Block Design (RCBD) with three replications. From the study, it was found that nutrient uptake of sesame plant and the nutrient concentration in post-harvested soil such as total N, available P, exchangeable K, available S and available B was increased with the increasing of nitrogen up to a certain level and boron supply. For the combined application of nitrogen and boron (60 kg N/ha and 3.0 kg B/ha) was found suitable to uptake maximum N, P, K, S and B by the sesame plant and to available the highest nutrient concentration in post-harvested soil. 
Res. Agric., Livest. Fish.6(2): 203-213, August 2019


INTRODUCTION
Sesame (Sesamum indicum L.) belongs to the family Pedaliaceae is one of the vital oil crops, which is widely grown in different parts of the world. It is grown for seed and oil for thousands of years and today its major production areas are the tropics and the subtropics of Asia, Africa, East and Central America. In Bangladesh, it is locally known as 'til' and is the second important produced edible oil crop (Mondal et al., 1997). Sesame is a versatile crop having diversified usage and contains 42-45% oil, 20% protein and 14-20% carbohydrate (BARI, 2012). In 2015-2016 the crop covered an area of 99,592 acres in Bangladesh with the production of 36,921 metric tons (BBS, 2017). The climate and edaphic conditions of Bangladesh are quite suitable for sesame cultivation. Yield and quality of sesame seeds are very low in Bangladesh. Deficiency of soil nutrient is now considered as one of the significant constraints to successful upland crop production in Bangladesh (Islam and Noor, 1982). To attain suitable production and quality yield for any crop it is necessary to apply proper management with ensuring the availability of an essential nutrient in proper doses. Generally, a considerable amount of fertilizer is required for the growth and development of sesame (Opena et al., 1988). Nitrogen is a structural constituent of chlorophyll and protein therefore, the adequate supply of nitrogen is beneficial for both carbohydrates and protein metabolism as it assists cell division and cell enlargement, resulting in more leaf area and thus ensuring good seed and dry matter yield (Ibrahim et al. 2014). On the other hand, excessive application of nitrogen is not only uneconomical, but it can prolong the growing period and delay crop maturity. Excessive nitrogen application causes physiological disorder (Obreza and Vavrina, 1993).
Boron is one of the crucial micronutrients required for plant growth and productivity. It plays a vital role in cell wall synthesis, RNA metabolism, and root elongation as well as phenol metabolism. Also, boron involved in pollen and tube growth (Srivastava and Gupta, 1996). Kalyani et al., (1993) noticed that boron applied as boric acid increased the plant height, relative growth rate, net assimilation rate and leaf area index. Boron is a micronutrient essential for healthy growth of pollen grains, sugar translocation and movement of growth regulators within the plant (Hamasa and Putaiah, 2012). Photosynthetic activity and metabolic activity enhanced with the application of boron (Sathya et al., 2009). Boron's involvement in hormone synthesis and translocation, carbohydrate metabolisms and DNA synthesis probably contributed to additional growth and yield (Kalyani et al., 1993). The objectives of this study were to find out the nutrient concentration in seeds and stover of sesame, and nutrient status of harvested soil due to the application of nitrogen and boron. Through this experiment farmers can get optimum dose of nitrogen and boron fertilizer for sesame cultivation.

Study area and time
The experiment was conducted during the period from February to May 2016 at the research field of Soil Science of SAU. The location of the experimental site is located at 23 0 74 / N latitude and 90 0 35 / E longitude and an elevation of 8.2 m from the sea level (Mostofa et al., 2019).

Soil Condition and weather
The soil of the experimental field belongs to the Tejgaon series under the Agroecological Zone, Madhupur Tract (AEZ-28) and the General Soil Type is Deep Red Brown Terrace Soil. A composite sample was made by collecting soil from the field at a depth of 0-15 cm before the initiation of the experiment. The collected soil was air-dried, grounded and passed through 2 mm sieve and analyzed for significant physical and chemical parameters. The initial physical and chemical characteristics of the soil are presented in Table 1. Details of the meteorological data during the period of the experiment was collected from the Bangladesh Meteorological Department, Dhaka (2016) are presented in Table 2.

Planting material
Seeds of BARI Til-3 were used as a test crop for the study and those were collected from Bangladesh Agricultural Research Institute, Gazipur-1701. This variety was developed by BARI and released for cultivation in the year of 2001 (BARI, 2012). It is a non-hairy medium-sized plant with primary and secondary branches with the high potential plant.

Experimental design and layout
The experiment was laid out in two factors Randomized Complete Block Design (RCBD) with three replications. Each block was divided into 12 plots where 12 treatment combinations were allotted at random. The size of the plot was 2.5 m × 1.5 m. The distance between two blocks and two plots was 50 cm each.

Fertilizer application
Manures and fertilizers that were applied to the experimental plot presented in Table 3 (BARI, 2012). The total amount of Cowdung, TSP, half of the MOP, total zinc and sulfur were applied as basal dose during the time of land preparation. The rest amount of MOP and the total amount of urea (as per treatment) were applied in two installments at 15 and 30 days after seed sowing.

Crop Management
All intercultural operations such as irrigation, thinning, gap filling, weeding and plant protection measures were taken as per when needed. The pods were harvested depending upon the attaining good sized and the harvesting was done manually. Enough care was taken during harvesting.

Parameters determined
The data were collected from the inner rows of plants of each treatment to avoid the border effect. In each unit plot, ten plants were selected at random for data collection. Data were recorded on the following parameters.

Collection and preparation of samples
Seed and stover samples were collected after threshing and finely grounded by using a Wiley-Mill grinder to pass through a 60-mesh sieve. Then the plant samples were dried in an oven at 70 0 C for 72 hours and grounded by a grinding machine to pass through a 20-mesh sieve. Then the samples were analyzed for determination of N, P, K, S and B concentrations.

Determination of N, P, K, S and B from samples
N concentration of the sample was determined followed by the Micro Kjeldahl Method (Page et al., 1982). Phosphorous and Potassium concentration in samples was determined as described by Olsen et al., 1954 andPage et al., 1982. Sulphur concentration in samples was determined as described by Page et al., 1982 andHunter, 1984. Boron concentration in samples was determined as described by Hunter, (1984).

Post-harvest soil sampling
After harvesting of the sesame, soil samples were collected from each plot at a depth of 0 to 15 cm. Soil samples of each plot was air-dried, crushed and passed through a two mm (10 meshes) sieve. The soil samples were kept in a plastic container to determine the physical and chemical properties of soil.

Soil analysis
Total N content of the soil was determined followed by the Micro Kjeldahl Method (Page et al., 1982). Soil pH, organic matter and Exchangeable K were measured as described by Page et al., (1982). Available P was measured as described by Olsen et al., 1954 andPage et al., 1982. Available B was measured as described by Hunter, (1984).

Statistical analysis
The data obtained for different parameters were statistically analyzed by using Statistix 10 (Statistix, 2013) computer package program to find out the significant difference of different levels of nitrogen and boron. The significance of the difference among the treatment means was estimated by the Least Significant Difference (LSD) at 5% level of probability (Gomez and Gomez, 1984).
Interaction effect of nitrogen and boron showed statistically significant variation in terms of N, P, K, S and B concentration in stover. The maximum concentration in stover for N (0.54%), P (0.30%), K (1.67%), S (0.26%) and B (0.013%) were observed from N2B2, while the minimum concentration in stover for N (0.25%), P (0.15%), K (1.17%), S (0.13%) and B (0.006%) were found from N0B0 treatment combination (Table 7). N, P, K, S and B concentration in sesame seed and stover increased with the increasing of the nitrogen level up to 60 kg N/ha; thereafter N, P, K, S and B concentration decreased in seed and stover with increasing nitrogen level (Kumawat et al., 2000;Shehu, 2014). In case of boron, the concentration of N, P, K, S and B in seed and stover increased with the increasing of boron level. Boron has positive effect on nutrient uptake by plant and improves nutrient use efficiency, nutrient demand and supply (Bariya et al., 2014). A positive relationship was observed with nitrogen and boron while up taking mineral nutrients (N, P, K, S and B). Boron concentration was higher in seeds than stover and its concentration in seed increase with increasing boron application (Bubarai et al., 2017).   Total N Total N of post-harvest soil showed statistically significant differences due to different levels of nitrogen, boron and combined interaction. In case of nitrogen levels, the highest total N of post-harvest soil (0.073%) was observed from N2 which were statistically similar to N1 and N3; and lowest (0.050%) was observed from N0 ( Figure 1). In case of boron levels, the highest total N of post-harvest soil (0.070%) was recorded from B2 which was statistically similar to B1 and lowest (0.058%) was recorded from B0 ( Figure 2). In the case of interaction, the highest total N of post-harvest soil (0.078%) was observed from N2B2 and lowest (0.041%) was observed from N0B0 ( Figure 3).   (Table 8 and 9).

Organic matter
Organic matter of post-harvest soil showed statistically non-significant due to different levels of nitrogen, boron and combined interaction (Table 8 and 9).

Available P
Available P of post-harvest soil showed statistically significant differences due to different levels of nitrogen, boron and combined interaction. In case of nitrogen levels, the highest available P of post-harvest (34.98 ppm) were observed from N2 which were statistically similar to N3 and N1; and lowest (27.25 ppm) was observed from N0. In case of boron levels, the highest available P of post-harvest soil (32.51 ppm) was recorded from B2 which were statistically similar to B1 and lowest (29.47 ppm) was recorded from B0 (Table 8).
In the case of interaction, the highest available P of post-harvest soil (36.53 ppm) was observed from N2B2 and lowest (24.43 ppm) was found from N0B0 (Table 9).  Exchangeable K Exchangeable K of post-harvest soil showed statistically significant differences due to different levels of nitrogen, boron and combined interaction. In case of nitrogen levels, the highest exchangeable K of postharvest soil (0.144 me%) was observed from N2 which were statistically similar to N3 and N1; and lowest (0.129 me%) was observed from N0. In case of boron levels, the highest exchangeable K of post-harvest soil (0.143 me%) was recorded from B2 which were statistically similar to B1, whereas the lowest (0.130 me%) was recorded from B0 (Table 8). In the case of interaction, the highest exchangeable K of post-harvest soil (0.152 me%) was observed from N2B2 and the lowest (0.120 me%) was found from N0B0 (Table 9).

Available B
Available B of post-harvest soil showed statistically significant differences due to different levels of nitrogen, boron and combined interaction. In case of nitrogen levels, the highest available B of post-harvest (0.277 ppm) were observed from N2 which was statistically similar to N3 and N1; and lowest (0.244 ppm) was observed from N0. In case of boron levels, the highest available B of post-harvest soil (0.303 ppm) was recorded from B2 which were statistically similar to B1, and lowest (0.185 ppm) was recorded from B0 (Table  8). In the case of interaction, the highest available P of post-harvest soil (0.320 ppm) was observed from N2B2 and the lowest (0.163 ppm) was observed from N0B0 (Table 9).
In post-harvest soil available total N and available B increased with the increasing of nitrogen level up to 60 kg N/ha thereafter decreased with increasing nitrogen level except available P and exchangeable K. In case of boron supply available total N, available P, exchangeable K and available B increased in soil with the increasing of boron level (Petridis et al., 2013). For soil pH and organic matter percentage, nitrogen and boron levels were found non-significant; but numerically both soil pH and organic matter percentage were increased with increasing nitrogen and boron level. Nitrogen was applied from the source of Urea, as a result Urea hydrolysis increased with the increasing Urea concentration up to a maximum was reached and soil pH was increased; thereafter with increasing Urea concentration (70 kg N/ha) hydrolysis decreased and ultimately soil pH was decreased (Cabrera et al., 1991).

CONCLUSION
From the above experiment, it was found that combined application of Nitrogen and Boron @ 60 kg N/ha with 3.0 kg B/ha influenced the uptake of maximum nutrient by sesame plant (BARI Til-3) and also increased available nutrients of harvested soil.