Effect of Seed Treatment and Nutrient Schedule on the Productivity of Blackgram (Vigna mungo L.)

Blackgram (Vigna mungo L.) is an important short duration crop which is grown throughout India. It accounts for 13% of total pulse area and 10% of total pulse production in India. It contains about 24% protein which is almost twice as cereals, 60% carbohydrates, 1.3% fat, 0.194% Ca, 0.192% Mg, 0.526% K, 0.44% P, 0.09% Fe, 0.0241 mg of vitamin C 100 g^-1. It is also rich in essential amino acids viz., 0.43% lysine and 0.07% tryptophan where cereals are normally deficient and it is also rich in phosphoric acid.
       
Though blackgram is used as source of human food, animal feed and also for enhancing soil fertility, the yield potential is very low as it is mainly grown in rainfed areas with poor management practices. Poor productivity may be due to various physiological, biochemical and inherent factors associated with this crop. The physiological factors viz., poor pod setting due to the flower abscission, insufficient partitioning of assimilates and lack of essential nutrients during critical stages of crop growth play a major role in declined blackgram production coupled with a number of diseases and pests (Mahala et al., 2001). The lower production and productivity may also be due to several problems with the blackgram growing farmer’s particularly improper knowledge on package of practices (Islam et al., 2011).
       
Seed treatment can improve seedling establishment and better crop stand; it also improves plants ability to tolerate stress at early growth stages. Seed treatment also helps to reduce the environmental impact on production process; it helps in decreasing number of spray applications of agrochemicals thus reducing exposure to non-target species. Micronutrients when applied as seed treatment enhance the performance of fertilizer, also supplies nutrients to soil and improves plant growth. Boron plays an important role in sugar translocation, nitrogen fixation, protein synthesis, sucrose synthesis, cell wall composition, membrane stability and K+ transportation. Molybdenum is associated with ammonia reduction and nitrogen fixation and its deficiency adversely affects plant growth and yield. Seed treatment with these micronutrients is a cost effective practice for enhancement of productivity of pulses.

Foliar application has the advantage of quick and efficient utilization of nutrients, elimination of nutrient losses through leaching and fixation in soil and also helps in regulating the uptake of nutrients by plants (Manonmani and Srimathi, 2009). Foliar spray is effective in correcting the midseason discrepancies in the crop growth which may be either due to intensive growth or inappropriate supply of nutrients from the soil under abiotic stress conditions. Foliar application of major nutrients using water soluble fertilizer is one of the possible ways to enhance productivity of blackgram.

A field experiment on ‘Seed treatment and foliar nutrition for enhanced productivity of blackgram (Vigna mungo L.)’ was conducted in block 4 of Instructional farm, College of Agriculture, Vellayani, Thiruvananthapuram during rabi, 2018. Co-6, released from Tamil Nadu Agricultural University, Coimbatore was used for the trial. The soil of the experimental field was red sandy clay loam in texture, acidic in reaction with pH 5.44. The soil was low in available N (225.79 kg ha^-1), high in available P (25.16 kg ha^-1) and available K (347.12 kg ha^-1) and medium in available B (0.732 mg kg^-1).
       
The experiment was laid out in randomized block design with six levels of seed treatments and two levels of nutrient schedule in three replications. The levels of seed treatment were s₀ - without seed treatment, s₁ - seed treatment with borax @ 1g kg^-1 seed, s₂ - seed treatment with borax @ 2 g kg^-1 seed, s₃ - seed treatment with sodium molybdate @ 1 g kg^-1 seed, s₄ - seed treatment with sodium molybdate @ 1.5 g kg^-1 seed and s₅- seed treatment with borax @ 1 g kg^-1 seed and sodium molybdate @ 1 g kg^-1. Two levels of nutrient schedule were n₁- ½ N + full P + full K as basal application + ½ N as foliar spray of urea at 15 and 35 DAS and n₂- ½ N + full P + ½ K as basal application + ½ N and ½ K as foliar spray of 13:0:45 at 15, 30, 45 and 60 DAS. Recommended dose of 20: 30: 30 kg NPK ha^-1 was adopted (KAU, 2016). Seed treatment with borax and sodium molybdate at rates as per experimental schedule were mixed thoroughly with rice gruel as sticking agent and shade dried on the day before sowing. On the day of sowing the seeds are treated with Rhizobium culture, common to all treatments, shade dried and dibbled into soil at spacing 25 cm × 15 cm.
       
The growth characters, yield attributes viz. number of pods per plant, seeds per pod, length of pod, 100 seed weight, grain yield and haulm yield were recorded at harvest stage. The harvest index was also worked out.

The results on yield attributes and yield are presented in Table 1a, 1b and 2a, 2b were favorably influenced by treatments.
 
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Plant height, number of leaves and branches per plant
 
All the growth attributes were significantly influenced by different levels of seed treatments. s₅ recorded significantly the tallest plants of 135.84 cm, higher number of trifoliate leaves (7.61) and higher number of branches per plant (6.39) at harvest respectively. Nutrient schedule also has significant influence on growth characters and maximum plant height (99.69 cm) and number of trifoliate leaves (6.68) at harvest were observed with n₂. Whereas, maximum number of branches (5.89 plant^-1) were registered with n₁. Treatment combination s₅n₁ registered the tallest plants (140.35 cm) and maximum number of branches per plant (6.78) at harvest, whereas; s₅n₂ documented maximum trifoliate leaves per plant (7.89) and was on par with s₅n₁.
       
This increase might be due to application of micronutrients which enhanced cell division and translocation of nutrients in combination with urea as foliar spray which had positive effect on legume plants in enhancing growth of plants. These results are in agreement with Venkatesh et al., (2012), Das and Jana (2016) and Shinde et al., (2018).
 
Nodules, effective nodules and weight of nodules per plant
 
Seed treatment with s₃ has significantly increased number of nodules, effective nodules and weight of nodules per plant. The data also showed that nutrient schedule with n₂ has significant influence on nodule characters. There were 17.93, 11.48 and 4.9 per cent increase in number of nodules, effective and weight of nodules per plant respectively. The treatment combination s₃n₂ registered maximum number of nodules (50.33), effective nodules (42.33) and weight of nodules (64.67 mg) per plant at flowering. The Mo seed treatment might have enhanced nodule formation and promoted N fixation by Rhizobium as it is an important component of enzyme nitrogenase and also foliar spray of KNO₃ promoted better translocation of nutrients and improved nodulation. Similar results are also supported by Tahir et al., (2014) and Sanjeev (2015) in soyabean.
 
Number of pods per plant
 
Seed treatment with borax @ 1 g kg^-1 seed and sodium molybdate @ 1 g kg^-1 seed significantly increased number of pods per plant and recorded maximum number of pods per plant (24.16). The interaction effect of seed treatment and nutrient schedule on number of pods per plant was found significant. Maximum number of pods per plant (24.99) was recorded with the treatment combination s₅n₁ which was on par with s₅n₂ and s₃n₂.
 
Number of seeds per pod
 
Seed treatment has significant influence on number of seeds per pod. Borax @ 1 g kg^-1 seed produced significantly the highest number of seeds per pod (7.33) and was statistically on par with s₃, s₄ and s₅. The treatment combination s₅n₂ recorded maximum number of seeds per pod (7.45) and was on par with s₁n₁, s₁n₂, s₂n₁, s₃n₁, s₃n₂, s₄n₁ and s₄n₂. This might be due to the role of boron in better sugar translocation, similar results were also reported by Masuthi et al., (2009) in cowpea, El-Dahsourie et al., (2017) in common bean and Mahadhule et al., (2019) in French bean.
 
Length of pod
 
Seed treatment with borax @ 1 g kg^-1 seed has significantly increased length of pod (5.23 cm) and was on par with s₁, s₃, s₄ and s₅. Maximum length of pod (5.59 cm) was recorded with treatment combination s₅n₂ whereas, minimum length of pod (4.61 cm) was observed in s₀ (without seed treatment).
 
100 seed weight
 
Seed treatment and nutrient schedule had significantly influenced 100 seed weight. Seed treatment with borax @ 1 g kg^-1 seed and sodium molybdate @ 1 g kg^-1 seed recorded maximum 100 seed weight (6.74 g). Scheduling the nutrients as ½ N + full P + ½ K as basal followed by ½ N and ½ K as foliar spray of 13:0:45 at 15, 30, 45 and 60 DAS recorded the highest 100 seed weight (6.52 g). The increased hundred seed weight might be due to enhanced photosynthetic activity, efficient transfer and accumulation of metabolites in the seed with the resultant increase in the size and weight of individual seed. These results were in accordance with Rahman et al., (2014) and Shinde et al., (2018) in chickpea.

Grain yield
 
Seed treatment with borax @ 1 g kg^-1 seed and sodium molybdate @ 1 g kg^-1 seed recorded the highest grain yield (1005 kg ha^-1), which was statistically on par with s₁. Nutrient schedule also had significant influence on grain yield. The basal application of ½ N + full P + ½ K and ½ N and ½ K as foliar spray of 13:0:45 at 15, 30, 45 and 60 DAS registered the highest grain yield (872 kg ha^-1). Interaction effect also significantly influenced grain yield, among different treatment combinations s₅n₂ produced maximum grain yield (1130 kg ha^-1) and was on par with s₁n₁. The main contributing factor for yield increase was due to increased dry matter production and efficient translocation of assimilates to developing reproductive parts thus leading to increased number of pods and higher grain yield. This might also be due to enhanced chlorophyll formation resulting in higher photosynthetic rates leading to an increase in plant attributes contributing to better seed yield. Dixit and Elamathi (2007), Manonmani and Srimathi (2009), Rahman et al., (2014) and Janaki et al., (2018) also reported similar findings.
 
Haulm yield
 
Significantly the highest haulm yield was registered with s2 (seed treatment with sodium molybdate @ 1 g kg^-1 seed) and was on par with s₂. Nutrient schedule of ½ N + full P + ½ K and ½ N and ½ K as foliar spray of 13:0:45 at 15, 30, 45 and 60 DAS produced the highest haulm yield of (1750 kg ha^-1). Among different treatment combinations s₃n₂ recorded the highest haulm yield (1899 kg ha^-1) and was on par with s₀n₂, s₁n₁, s₂n₁, s₂n₂, s₃n₁ and s₅n₂. This might be due to improved germination and balanced growth pattern of plants. These results were also in accordance with Tahir et al. 2014 in blackgram.
 
Harvest index
 
Seed treatment had significant influence on harvest index. Maximum harvest index of 0.38 was registered with s₅ (seed treatment with borax @ 1 g kg^-1 seed and sodium molybdate @ 1 g kg^-1 seed) and was on par with s₄.

The results revealed that, in blackgram, seed treatment with borax and sodium molybdate @ 1g kg^-1 seed each and scheduling nutrient application at 20: 30: 30 kg NPK ha^-1 as ½ N + full P + ½ K as basal followed by ½ N and ½ K as foliar spray of 13:0:45 at 15, 30, 45 and 60 DAS could be recommended for realizing higher growth and yield; whereas, treatment combination s₃n₂ found to be superior in increasing nodule characters.