Influence of Sowing Date on Phenology, Biometric, and Yield of Mungbean ( Vigna radiata ) Cultivars in Chitwan, Nepal

,


Introduction
Mungbean (Vigna radiata (L.) Wilczek var. radiata), also known as Green gram or moong, is a commercially promising legume in the Terai region of Nepal [1]. Te majority of the mungbean area-more than 75%-is situated in the eastern and central Terai, where irrigation is possible, and the other 25% is in the west Terai and foothills [2]. Te estimated area under mungbean is about 12,000 ha with a production of 6,500 metric tons and productivity of 500 kg·ha −1 [3]. Te share of mungbeans in the area of grain legumes is approximately 4% [4][5][6]. Te potential yield of mungbean can be achieved through the optimum use of inputs and agronomic practices [7]. High-yielding varieties and suitable sowing times are the most important factors afecting yield. One of the most crucial agronomic variables for maximizing the yield potential of improved cultivars is choosing the right time to sow the crop because it facilitates total harmony between the vegetative and reproductive stages of the plant [8]. Terefore, sowing the crop at the optimum time plays a key role in obtaining high seed yields [9]. Te optimum sowing time is mainly dependent on the prevailing agroclimatic conditions of an area beside the cultivar grown [10]. Planting during an optimum period with suitable highly adapted cultivars ensures better harmony between the plant and the weather which ultimately results in a higher yield [11]. Early sowing may result in poor germination and poor plant stands, whereas yield from very late sown crops may be low due to unfavorable agroclimatic conditions for the growth and development of mungbean in subtropical areas characterized by high temperatures and heavy rainfall during the summer season (April to September) [12]. Delayed sowing after March may cause rain damage during maturity [13]. Terefore, there must be specifc sowing dates, especially in the summer season for diferent cultivars to obtain the maximum yield [14].
Cultivars play an important role in determining crop yield potential [8,10]. Te potential yield of cultivars within their genetic limit is determined by their environment [15]. Varieties difer in their yield potential depending on many physiological processes that are controlled by both genetic makeup and the environment [16]. Mungbean productivity can be achieved efciently with the selection of superior genotypes which is a prerequisite, possessing better heritability and genetic advance for various traits [17]. If highyielding varieties are chosen and planted at the right time of year, yield can be boosted more [18].
Tere are very few or negligible studies on the varietal development of mungbean in Nepal [18]. Only, 4 varieties of mungbean have been released to date viz. Pusha Baisakhi, Kalyan, Pratikshya, and Pratigya (Hum-16) [2]. Kalyan, Pratikshya, and Pratigya were given to the superior genotypes brought from IVRDC [19]. Tese lines are suitable for rice-based and maize-based systems, resistant to MYMV and CLS (Cercospora leaf spot) and have semisynchronous maturity (85% of the pod is harvested after two pickings) [20]. A few promising genotypes, including VC 6173(B-10), VC 6368 (46-40-4), NIMB101, Bari mung, and VC 6153B-20G, had up to 50% larger seeds and a yield that was around 25% greater than Saptari Local (maturity was about 65 days) [21]. Bari mung and NIMB 101 are resistant to MYMV [18]. So cultivation of these Cultivars from March 15 to March 30 might also have better yield because they are resistant to mungbean yellow mosaic virus (MYMV) and CLS.
Hence, there is a need to enhance the productivity of mungbean by adopting proper agronomic practices like dates of sowing and nutrient management apart from evolving new high-yielding cultivars [22,23]. Te introduction of such high-yielding cultivars has provided the scope for improving the overall productivity of the mungbean [8,24].
Tis experiment aims to determine the relation of planting time and varieties with phenological, biometric, yield attributing traits, and yield of mungbeans to guide the best planting time. Tis study hypothesized that variable sowing dates and cultivars can have diferential responses in terms of growth and seed production. Keeping these factors in view, the present study was designed to fnd out the proper date of sowing for the high gain yield of diferent mungbean cultivars.

Materials and Method
Te experimental feld, AFU, was located in the inner Terai of central Nepal has subtropical humid weather and climate from the 2nd week of February to the 3rd week of June ( Figure 1).

Climatic Conditions During Experimentation.
Te mean data of diferent weather parameters i.e., average relative humidity, maximum and minimum temperature, and the total rainfall during the growing season of mungbean at NMRP are presented at a monthly interval in Figure 2. Two irrigations were done during the critical stage of crop.

Experimental Design.
Te experiment was laid out in split-plot design (SPD) with three replications having 16 treatment combinations. Te main plot factor consisted of four sowing dates at 15 days intervals (13 th Figure 3. Spacing, experimental plot to plot distance, and replications distance were (40 × 10) cm 2 , 0.5 m, and 1.0 m, respectively. Te individual plot contained 10 rows and the outer two rows were used as border rows. Inner adjacent two rows from one border were used for destructive or sampling rows and after two sampling rows next were also used as the inner border. Sampling was done by excluding the peripheral efect for the next sampling. Te fve rows (4 m 2 ) from the other border row were harvested as net plot rows. Six plants were tagged from net plot rows and were used to take biometric data.
After the frst plowing, well-rotten farm yard manure (FYM) was applied@ at 10 tons·ha −1 and mixed them in the soil thoroughly. After the fnal preparation of the feld, the experiment was laid out as per Figure 2. All recommended doses of chemical fertilizers (20 : 40 : 20 kg NPK ha −1 ) were crossed wise broadcasted and incorporated as basal doses at the time of sowing. Te source of nitrogen was urea (46% N) and phosphorus through DAP (18 : 46 : 0%-N 2 : P 2 O : K 2 O), and the source of potassium was murate of potash (60% K 2 O). Pods were sun dried on the threshing foor for a week. Net plot areas were harvested manually by picking when 75% of plants showed brown color pods (physiological maturity). Second and subsequent picking and harvesting were done at seven to ten days intervals Treshing was manually done by beating the pods with a stick and trampling by feet. Grain was cleaned by winnowing and dried to reduce the seed moisture content by up to 11%.    International Journal of Agronomy calculated by dividing economic yield by biological yield (kg·ha −1 ) and expressed in percentage. Te shelling percentage was calculated from the pods' weight. It is the ratio of the weight of grain to the weight of pods.

Characteristics of Treated Cultivars
Shelling percentage(kg ha − 1) � Weight of grains Weight of pods × 100.
(1)   Table 1. 75% of pod formation, physiological, and harvest maturity signifcantly difered due to diferent planting dates shown in Table 2. Cultivars do not infuence the physiological maturity and harvest maturity at 75% of the phenological stage in these climatic conditions.

Biometric Traits.
Studied biometric traits were found to be signifcantly diferent in terms of sowing date however no diference in the case of the cultivar used. As compared to Feb 13, March 30 planting yielded a greater number of leaves, the highest plant height, and the highest above-ground dry matter. A study reported signifcant diferences in plant height due to various planting dates and cultivars used [13].  reported Feb 20 resulted in the lowest plant height. Several leaves, plant height, and above-ground dry matter% are highly signifcant with the date of planting. Te superior trait is found on March 30 plantation Table 3.

Yield Attributing Characters.
All studied yield attributing traits signifcantly difered except for several plants ha −1 . Te efect of sowing dates on plant population was nonsignifcant. Te efect of cultivars on the number of plant populations per hectare at harvest of mungbean was also nonsignifcant. Te number of clusters per plant was signifcantly afected by sowing dates. Te mean number of clusters per plant for total picking was found at 8.93 and it ranged from 7.05 on the 13th of February sowing to 9.69 on the 30th of March sowing of mungbean. Te number of clusters per plant during total plucking was shown to be unafected by cultivars. Similarly, the interaction efect of the date of sowing and cultivars was found nonsignifcant to the number of clusters per plant for total picking. Te number of pods per plant was signifcantly afected by sowing dates.
Te mean number of pods per plant for total picking was found 19.4 and it ranged from 18.72 on the 13th of February sowing to 20.11 on the 30th of March sowing of mungbeans. Te efect of cultivars on several pods per plant for total picking was found nonsignifcant. Similarly, the interaction efect of the date of sowing and cultivars was found nonsignifcant to several pods per plant for total picking. Maturity decreased with delay in sowing time pods per plant also decrease in delay sowing [7]. Pod length was signifcantly afected by both sowing dates and varieties. Te mean pod length was 9.06 cm and it ranged from 8.82 cm to 9.54 cm. Te pod length of mungbeans was signifcantly infuenced by planting time [8]. Singh   number of seeds per pod was 9.66 and it ranged from 9.33 to 10.04 (   International Journal of Agronomy 5 11 [26], which was according to our fndings. Te highest seed yield obtained from the 2 March sowing might be due to suitable temperature prevailing accompanied by higher soil moisture content due to sufcient rainfall in April, which enhanced the vegetative as well as reproductive growth of the crop. Pant-5 gave the highest yield due to its genetic potential. Te efect of sowing dates on biological yield was nonsignifcant but the efect of cultivars on biological yield was signifcant. Te mean biological yield of mungbean was 5830 kg ha −1 and it ranged from 5620 kg·ha −1 to 6032 kg·ha −1 ( Table 5). Te harvest index was signifcantly afected by sowing dates. Te mean harvest index was 34.36 and it ranged from 31.11 on the 13 th of February sowing to 37.17 on the 15 th of March sowing of mungbeans [27]. Seijoon et al.

Discussion
Te environment has a signifcant impact on the growth and development of crops. In each yield improvement program, breeders select superior genotypes under stress conditions. Planting time is the single most crucial element for maximizing mungbean production. So it is critical to choose the best time to grow mungbean because the expression of genetic potential varies with diferent environmental interactions.
Tis study shows that phenological traits like emergence, trifoliate, fowering, physiological pod formation, and harvest maturity have a signifcant relationship with days of sowing. Varieties do not show any signifcant relation with physiological and harvest maturity. Biometric traits like plant height and above-ground dry matter have a signifcant association with the sowing date, with the highest value on March 30. Statistically, biometric traits are not infuenced by treated varieties, as shown in Table 3. Yield-attributing characters like clusters per plant and seed per plant have a signifcant association with planting date but no relation with plant population (Table 4). Grain yield has a signifcant association with the planting date on March 15-30 with 2.223 tons/ha with Pratigya, Pant-5 cultivars followed by Pratikshya and Kalyan. Te harvesting index shows that plantations on March 15-30 had a higher index value of 37.17 for all cultivars. However, it is important to note that this study's fndings are limited to Chitwan and may only be useful for similar microclimatic conditions. Terefore, further research is needed to understand the level of interaction to genotype performance through the environment, fertility evaluation of diferent pipeline genotypes through application of phytohormones using different analyses such as principle component analysis and cluster analysis. Additionally, it is important to consider that salinity-afected regions might have contradictory performances at optimum sowing time. Te utilization of molecular concepts such as QTL (Quantitative Traits Loci) markers and the multiplication of the frequency of genes of interest through advanced technologies like CRISPR are essential for expediting the development of climate-resilient and biofortifed crop varieties in various environments. Tis approach has signifcant potential for enhancing crop yield and quality [28].

Conclusion
Te results indicate that early and late planting of mungbean cultivars considerably afected grain yield, yield characteristics, and phenology. Te optimum yield of mungbean can be achieved through high-yielding varieties planted at a suitable time. Too early sowing in sowing of spring mungbeans in February delay the germination, poor emergence due to a low temperature of soil takes more time to maturity and less yielder; however, planting on March 15-March 30 is suitable for overall growth and production for mungbean due to favorable agroclimatic condition during this period. Cultivar Pant-5 yielded more grain yield which is statistically at par with Partigya and Partikshya might be its superior genetic makeup.

Data Availability
Te data supporting this study are available from the corresponding author upon request. Treatment mean followed by common letters within the same column are not signifcantly diferent from each other based on DMRT at a 5% level of signifcance.