Bangladesh Agron. J. 2023, 26(1): 48-55 ESCALATION OF GROWTH AND YIELD IN MUNGBEAN BY SINK MANIPULATION: AN APPROACH FOR MINIMIZING POD PICKING EPISODE A.H.M.M.R. Talukder1*, F. Ahmed1, I.M. Ahmed1, S.N. Mahfuza1, A.F.M.S. Ahsan1, N. Mokarraoma1, M.K. Shahadat2, L. Nahar3 1Plant Physiology Division, Bangladesh Agricultural Research Institute, Gazipur-1701, Bangladesh 2On-Farm Research Division, BARI, Daulatpur, Khulna, Bangladesh 3Department of Agricultural Botany, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh *Corresponding author, Email: motiurbari@yahoo.com (Received: 14 July 2023, Accepted: 15 September 2023) Keywords: Mungbean, sink manipulation, pod picking, growth, yield Abstract Farmers’ frequently experience difficulties with their mungbean (indeterminate type) crops harvests due to continuous picking that prolong the pod-picking episode and cause an economic crisis. To solve these issues, deflowering strategies (sink manipulation) were employed in this study following the randomized complete block design. A series of deflowering strategies were started from 40 days after sowing (DAS) to 55 DAS; resulting reduced pod production as well as pod picking episode (3 to 4 times) with 6.8-36.8% seed yield compared to control. The minimum seed yield reduction was 6.8%; deflowering at 55 DAS; with the maximum gross margin Tk.112,800 ha−1. Considering relative yield, yield reduction, and gross margin, 50 or 55 days produced flower (which would be matured within 60-65 DAS) could be considered for obtaining the economic seed yield. Introduction Growth and production of crops are closely related to the potency of sources and sinks as well as their equilibrium condition (Zhang and Flottmann, 2018, Smith and Stitt, 2007). However, to increase mungbean productivity, it is necessary to carefully study how the output is influenced by sink and how this varies during the course of development. The efficiency of individual plant parts, such as the leaves, stems, roots, and flowers, is a measure of how successfully they compete to suck in assimilates for potential growth rate (Marcelis, 1996). The amount of minerals, sugar, and amino acids available for the growth of other plant parts decreases as a result of developing blooms acting as strong sinks for these nutrients (Mossa et al., 2018). Leguminous plants have blooms that are designed to miscarry because reproductive organs compete for nutrients. Due to the mungbean's indeterminacy before it reached physiological maturity in the first flash, the second flash from fresh racemes develops from upper branches. The second flash from new racemes emerges from upper branches due to the indeterminacy of mungbean earlier than the physiological maturity of the first flash. Naturally, the mungbean crop exhibits low-high- high and low frequencies in pod formation with the first-second-third and later flash of the flower. It's interesting to note that mungbean crops, which have already completed their juvenile period, start to generate new blooms and pods after receiving new management. Hence one common method for limiting the plant's ability to reproduce and produce pod is to sink this opposition by eliminating flower buds (Kokubun et al., 2009). The mungbean's consistent blooming and fruiting, which displays a weekly and erratic cycle for pod development, causes problems for farmers. In the current study, BARI Mung-6, a typical flowering and bearing kind of mungbean variety were selected, causing farmers to deal with the bother of pod selection and incur significant costs. To Growth and yield in mungbean by sink manipulation 49 reduce the pod-picking event, an experiment was done in which the flowers buds−1 were removed on separate days following seeding while just keeping the pod. Materials and Methods An experiment was conducted in the pot-house of the Plant Physiology Division, BARI, during consecutive two Kharif-I (Mid-March to Mid-June) seasons, 2021 and 2022, to observe sink manipulation impacts on growth, yield, and the pod-picking episode of mungbean. Geographically the study area was located between 23°53' and 24°21' N latitudes and in between 90°09' and 92°39' E longitudes and 25 km north of the capital city of Bangladesh. This study was done following the randomized complete block design (RCBD) with 10 replications and each pot represented one replication. Mother seeds of trial var. BARI Mung-6 were collected from Pulse Research Centre of Bangladesh Agricultural Research Institute (BARI), Ishurdi, Pabna-6600. Five deflowering strategies were employed viz. (i) control (no deflowering) (NDF); (ii) Deflowering started at 40 days after sowing (DAS) (DF40); (iii) Deflowering started at 45 DAS (DF45); (iv) Deflowering started at 50 DAS (DF50), (v) Deflowering started at 55 DAS (DF55). A total of 50 plastic pots (26 cm top diameter, 20 cm base diameter, and 25 cm height) were organized in the pot-house of the plant physiology division of BARI, with 10 pots placed in each replicate blocks. Soil and fully decomposed farmyard manure were appropriately blended in a 4:1 volume ratio and sieved through a 2 mm sieve. The sieved soil samples were weighed and placed in pots, each holding around 12 kg of soil. Fertilizers @ 18-18-24-12-2.0-1.2 kg ha−1 of N-P-K-S-Zn-B were applied in the form of urea, triple super phosphate, muriate of potash, zypsum, zinc sulfate, and Boron respectively (Ahmmed et al., 2018). The pots had enough perforation system at the bottom for the drainage of water. Seven to ten healthy, bigger, and equal-sized mungbean seeds were chosen and treated with Provax 200 EC @ 2.5 g kg−1 seeds and sown on 05 March 2021 and 01 March 2022. Finally, following uniform emergence two seedlings in each pot were maintained. For growth data, randomly selected three pots were sampled for dry matter measurement at 35 DAS (Just before treatment application), 55 DAS, and 70 DAS (after final harvest). Sampled plants were separated into leaves, stems, and roots based on plant growth stages. Plants were dried in an oven for 72 hours at 80° C ± 2 and calculated total dry matter weight (g plant−1) from the summation of leaves, stem, and roots weights were taken in an electronic balance. Besides these, the relative yield, percent yield reduction; absolute growth rate and relative growth rate were calculated by using the following formula: Relative yield = Yield of deflowered (treated) plants Yield of control (non deflowered)plants × 100 Percent yield reduction = Yield of control pot − Yield of deflowering pot Yield of control pot × 100 𝐴bsolute Growth Rate (AGR) = ∆W ∆T = (W2−W1) (T2−T1) (García et al., 2006) Relative Growth Rate (RGR) = (ln 𝑊2̅̅ ̅̅ ̅̅ ̅̅ −ln 𝑊1̅̅ ̅̅ ̅̅ ̅̅ ) (T2−T1) (Hoffmann and Poorter, 2002) Where, W and T represent weight (g) and time (day), respectively. ln 𝑊2 ̅̅ ̅̅ ̅̅ ̅ and ln 𝑊1 ̅̅ ̅̅ ̅̅ ̅ are the means of the natural logarithm-transformed dry weights. At harvest, yield and yield components data were collected from three pots and analyzed using ANOVA technique Least Significant different values were calculated at 0.05 probability level wherever the F-test was significant. Data analysis was performed with the software environment R 4.2.3 using ‘agricolae’ package (R core team, 2023). 50 Talukder et al. Results and Discussion In the present study, mungbean crops growth and yield showed variable responses due to deflowering at different dates after sowing. The obtained response due to deflowering response and their relevant discussion has been described in this chapter. Total dry matter This study evaluated sink manipulation effect on total dry matter (summation of leaf, stem and root) production of mungbean. Dry matter at 3 stages of growth was collected viz. 30 DAS (before imposing deflowering treatment), 55 DAS and 70 DAS (just before harvest). In both 2021 and 2022, there were no significant differences in total dry matter production among the treatments at 35 DAS (Figure 1). Fig. 1. Effect of deflowering treatments viz. no deflowering (NDF), deflowering at 40 days after sowing (DF40), deflowering at 45 days after sowing (DF45), deflowering at 50 days after sowing (DF50) and deflowering at 55 days after sowing (DF55) on total dry weight in mungbean during kharif 2021 and 2022. Data were collected at 35 days after sowing (DAS), 55 DAS and 70 DAS in 2021. Treatments with same letter did not vary significantly. At 35 DAS, the ranges of total dry matter were 5.19 to 5.39 g plant−1 and 6.70 to 6.92 g plant−1 in 2021 and 2022, respectively. In 2021, at 55 DAS, total dry matter was recorded highest from DF40 (9.42 g plant−1), whereas the lowest but statistically identical total dry weight was found from NDF (7.55 g plant−1) and DF55 (7.58 g plant−1). At 70 DAS, dry matter production in DF40 (13.03 g plant−1) was, which was statistically identical with DF45 (12.80 g plant−1) and DF55 (12.80 g plant−1). Similarly in 2022, at 55 DAS, maximum total dry weight was recorded from DF40 (11.41 g plant-1). However, at 70 DAS, DF45 produced maximum dry weight plant−1 (22.07 g plant−1), which was again statistically identical to DF50 (21.80 g plant−1) and DF55 (21.60 g plant−1) (Figure 1). Over the growing seasons, total dry weight (g plant−1) was much greater in 2022 than 2021 due to sufficient rainfall during the growth period; however, treatment effects showed almost similar pattern of response (Figure 1). In the both 2021 and 2022, there was no discernible difference in total dry weight among treatments when samples were taken at 35 days following sowing. Deflowering effects on total dry weight were noticeable when sampling was 55 DAS and 70 DAS. Overall, it appeared that deflowering at later stage increased total dry weight in all deflowering treatments in both the years and followed increasing pattern as 35 DAS< 55 DAS< 70 DAS. Deflowered sunflower plants had a larger stem and leaf dry weight, according to previous research of Ho and Below (1989). In accordance with their Growth and yield in mungbean by sink manipulation 51 findings, deflowering effect in the present study showed increased total dry weight in comparison to control (NDF) (Figure 1). On an average, plant dry weight (summation of leaf, stem and root) was increased by 21.1 and 31.0%, 9.85 and 35.2%, 7.75 and 32.6%, and 2.79 and 34.6% at 55 DAS and 70 DAS sampling, respectively over the control. This could mainly be attributed to the production of new leaves and absence of potential sink in deflowered treatments. Previous study conducted by Mitra and Ghildhyal (1988) found that deflowered mungbean plants significantly increased in dry weight of leaf, stem, roots and nodules. Absolute growth rate and relative growth rate The Figure 2 showed the variation in absolute and relative growth rate at 35 DAS, 55 DAS and 70 DAS in different deflowering treatments. In 2021, AGR decreased from 35 DAS to 55 DAS in all treatments except DF40. Those treatments showed rapid rise in AGR after 55 DAS up to 70 DAS. DF40, however, demonstrated a continuous increase in AGR from 35 to 70 DAS. In case of RGR, all treatments dropped in RGR from 35 DAS to 55 DAS. However, RGR increased in DF45, DF50 and DF55 from 55 DAS to 70 DAS. RGR, however, did not rise any further in NDF, and DF40 continued to decline. During 2022, all treatments except DF40 showed slightly downward trend for RGR from 35 DAS to 55 DAS, however, all treatments showed sharp increase up to 70 DAS. Where, RGR were higher in DF45 and DF55. Fig. 2. Absolute growth rate and relative growth rate of mungbean as influenced by deflowering treatments during 2021 and 2022. 0 0.01 0.02 0.03 0.04 0.05 0.06 35 DAS 55 DAS 70 DAS R el at iv e G ro w th R at e 2021 NDF DF40 DF45 DF50 DF55 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 35 DAS 55 DAS 70 DAS A b so lu te G ro w th R at e 2021 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 35 DAS 55 DAS 70 DAS A b so lu te G ro w th R at e 2022 0 0.02 0.04 0.06 0.08 0.1 35 DAS 55 DAS 70 DAS R el at iv e G ro w th R at e 2022 52 Talukder et al. Effect of deflowering on plant height Deflowering treatments showed variable response in plant height in both years. However, overall plant height was found taller in 2022 than 2021 (Figure 3). In 2021, the range of plant height was between 20.4 ± 0.83 in NDF to 22.9 ± 0.58 in DF40, which was statistically identical to DF45 (22.6 ± 0.37). In 2022, the highest plant height was recorded from DF40 (33.0 ± 0.87 cm) and DF45 (33.0 ± 1.15 cm). Whereas, NDF produced lowest plant height 26.2 ± 0.58 cm. Fig. 3. Deflowering treatments effect on plant height (cm), number of pods plant−1, pod length (cm), number of seeds pod−1, 100-seeds weight (g) and yield plant−1 (g) in mungbean during kharif 2021 and 2022. Effect of deflowering on yield components and seed yield Over the growing seasons, the deflowering strategies effects were noticeable in the production of the number of pod plant−1 which was gradually increased with the prolongation of the deflowering period, and control (NDF) treatment produced significantly maximum number of pods plant−1 (23.0 ± 1.15 and 24.0 ± 1.15 in 2021 and 2022, respectively). Number of pods Growth and yield in mungbean by sink manipulation 53 plant−1 increased gradually when deflowering was delayed i.e., DF40