Effect of seaweed saps on growth and yield improvement of green gram

A field experiment was conducted during the pre-kharif season at Uttar Chandamari village in 2012 to study the effects of seaweed saps on growth, yield and quality improvement of green gram in new alluvial soil of West Bengal. The foliar spray was applied twice at different concentrations (0, 2.5, 5.0, 7.5, 10.0 and 15.0% v/v) of seaweed extracts (namely Kappaphycus and Gracilaria). Foliar applications of seaweed extract significantly enhanced the growth, yield and quality parameters. The highest grain yield was recorded with applications of 15% Kappaphykus sap + recommended dose of fertilizer (RDF), followed by 15% Gracilaria sap + RDF extract resulting in an increase by 38.97 and 33.58% grain yield, respectively compared to the control. The maximum straw yield was also achieved with the application of 15% seaweed extract. Improved crop quality and nutrient uptake [nitrogen (N), phosphorus (P) and potassium (K)] was also observed with seaweed extract applications.


INTRODUCTION
Any improvement in agricultural system that results in higher production should reduce the negative environmental impact and enhance the sustainability of the system.One such approach is the use of biostimulants, which can enhance the effectiveness of conventional mineral fertilizers.Long-term indiscriminate use of them invites the crucial problem of soil health disorder vis-à-vis reduced input use efficiency, more precisely, fertilizer use efficiency.Due to these reasons the farmers are being compelled gradually day by day to turn towards various options like organic manures, biostimulants, growth regulators etc.One of such options is the use of seaweed extracts as plant nutrient bearing fertilizer.Marine bioactive substances extracted from marine algae are used in agricultural and horticultural crops, and many beneficial effects may be achieved in terms of enhancement of yield and quality.Liquid extracts obtained from seaweeds have recently gained importance as foliar sprays for many crops including various cereals, pulses and different vegetable species.Seaweed extracts contain major and minor nutrients, amino acids, vitamins, cytokinins, auxin and abscisic acid like growth promoting substances and have been reported to stimulate the growth and yield of plants, develop tolerance to environmental stress (Zhang et al., 2003), increase nutrient uptake from soil (Turan and Kose, 2004) and enhance antioxidant properties (Verkleij, 1992).Liquid extracts obtained from seaweeds have recently gained importance as foliar sprays for many crops including various grasses, cereals flowers andvegetable species (Crouch and Van Staden, 1994).In recent years, the use of seaweed extracts have gained in popularity due to their potential use in organic and sustainable agriculture (Russo and Beryln, 1990), especially in rainfed crops, as a means to avoid excessive fertilizer applications and to improve mineral absorption.Unlike chemical fertilizers, extracts derived from seaweeds are biodegradable, nontoxic, non-polluting and non-hazardous to humans, animals and birds (Dhargalkar and Pereira, 2005).
With the advancement of modern agricultural technologies, we somehow achieved food security for our country to feed its ever escalating population.But till date, unfortunately, we could not achieve nutritional security for our people.In West Bengal India, the growing of pulses in the cropping system is nowadays not a common practice, but it is well known that inclusion of any pulse crop in the sequence has all-round advantages.So, if we are to achieve nutritional security we must have to go for crop diversification in cropping pattern introducing crops like pulses for example, green gram, black gram etc. in Zaid (Summer) season and lentil, chickpea, garden pea etc. in Rabi (Winter) season.On the other hand, to nourish the protein energy malnourished (PEM) people and to maintain soil health properly pulse crops should be included in the cropping system.Green gram or mung bean (Vigna radiata L.) is the third most important food legumes grown and consumed in India and is a good source of proteins and minerals and its protein quality is similar to or better than other legumes like chickpea, black gram, peas, pigeon pea etc. (Kataria et al., 1989;Jood et al., 1998a).
Considering each and every corner of the above discussion, an experiment was conducted to study the effect of different seaweed saps on growth and yield of green gram and assess the nutrient removal by seed and stover of this pulse crop.

Experimental site and soil information
The field experiment was conducted during the pre-kharif season of 2012 on inceptisol at Uttar Chandamari village of Nadia district of West Bengal in India.The soil of the site was sandy clay loam with pH 6.45, organic carbon 0.57%, total nitrogen 0.055%, available P2O5 26.29 kg ha -1 and available K2O 148.72 kg ha -1 .The climate of the region is humid subtropical.The experimental site is located at 22° 57' N latitude, 88° 20' E longitude and altitude is 7.8 m.

Experimental designs and treatments
The experiment comprised of ten treatments, the details of the treatments are mentioned Table 1.
Two sprays of Kappaphycus and Gracilaria extract were applied; one at the seedling stage [20 days after sowing (DAS)] and the other at the pre-flowering stage (40 (DAS).For proper adherence, extracts were mixed with proper surfactant (Active 80 at 0.5 ml L -1 of water) at the time of spraying.The total spray volume was 650 L ha -1 in each application.The treatments were distributed in a randomized block design with three replications.The plot size was 5 × 6 m.The recommended dose of fertilizer (RDF) for green gram was 20:40:40 kg ha -1 N, P2O5 and K2O, respectively and all fertilizers were applied as basal.Date of sowing was 25 th of February, 2012 and the crop was harvested on 5 th May, 2012.

Preparation and chemical composition of liquid sea weed extract
The seaweed extract used in this study was obtained from Kappaphycus sp. and Gracilaria sp.The algae were handpicked from the coastal area of Rameswaram, T. N., India during September, 2011.It was washed with seawater to remove unwanted impurities and transported to the field station at Mandapum, Rameswaram.Here, samples were thoroughly washed using tap water.After that, fresh seaweed samples were homogenized by grinder with stainless steel blades at ambient temperature, filtered and stored (Eswaran et al., 2005).The liquid filtrate was taken as 100% concentration of the seaweed extract and further diluted as per the treatments.The nitrogen (N) content of seaweed extract (100% concentrate) was determined by taking 20 ml of filtrate which was oxidized and decomposed by concentrate sulphuric acid (10 ml) with digestion mixture (K2SO4 : CuSO4 = 5:1) heated at 400°C temperature for 2½ h as described in the semi-micro Kjeldahl method [AOAC International, 1995, method No. Ba 4b-87(90)], and other nutrient elements were analyzed by inductively coupled plasma-optical emission spectroscopy (ICP-OES), after wet digestion of filtrate (20 ml) with HNO3-HClO4 (10:4) di-acid mixture (20 ml) and heated at 100°C for 1 h and then raise the temperature to about 150°C (Richards, 1954)   (Tables 2 and 3).

Plant sampling
Data were taken through random sampling at 21 DAS, 42 DAS and 63 DAS to measure plant height, dry matter accumulation, crop growth rate (CGR) and leaf area index (LAI).CGR was computed with the help of the formula: [(W2 -W1)/ (t2 -t1)] where, W1= dry weight per unit area at t1, W2 = dry weight per unit area at t2, t1 = first sampling and t2 = second sampling.LAI was computed by the ratio of leaf area to the area of ground cover.For measuring nodule number per plant, data were taken at 21 and 42 DAS.Data on yield attributes were taken randomly before harvesting.At maturity, green gram seeds and stover samples were collected from each plot, oven dried at 70°C to constant weight and ground to pass through a 0.5 mm sieve for chemical analysis.The N content was determined by the semi-micro Kjeldahl method [AOAC International, 1995, method No. Ba 4b-87(90)].Phosphorus (P) content was determined by the Vanado-Molybdate yellow method (Jackson, 1973) and Potassium (K) content by flame photometry (Jackson, 1973).

Statistical analysis
Data were analyzed using analysis of variance (ANOVA) following randomized block design (Gomez and Gomez, 1984).Differences were considered significant at 5% level of probability.

Effect of treatments on growth of green gram
Foliar application of different sea weed saps along with RDF increased growth attributes of greengram significantly over control (Table 4).In general, a gradual increase in plant height, dry matter accumulation and LAI was observed with increasing seaweed extract application.Though these parameter are not significantly affected by foliar applications of seaweed extracts up to 5% concentration.Maximum plant height, dry matter accumulation, number of nodules per plant was recorded with 15% Kappaphycus-sap + RDF and was statistically at par with 15% Gracilaria -sap + RDF treated plot regarding all the observations taken at different DAS.In case of CGR during 21 to 42 DAS, the best result (7.75 g m -2 day -1 ) was recorded with the treatment T 8 which was closely followed by T 4 .Highest value of LAI was recorded with T 4 for all the observations.

Effect of treatments on yield attributes and yields of green gram
As per the data depicted in Table 5 the maximum numbers of branches per plant, pods per plant and seeds per pod were observed under the treatment T 4 (highest dose, that is, foliar application of 15% Kappaphycus sap along with RDF) which was closely followed by 15% Gracilaria -sap + RDF (T 8 ).The treatment T 4 (15% Kappaphycus-sap + RDF) showed the maximum increase in yield over control to the extent of 38.97% and this treatment was followed by the treatments T 8 (15% Gracilaria -sap + RDF), T 3 (10% Kappaphycus-sap + RDF), T 7 (10% Gracilaria -sap + RDF), T 2 (5% Kappaphycus-sap + RDF) and T 6 (5% Gracilaria -sap + RDF) recording 33.58, 27.28, 21.17, 19.77 and 13.86% yield increase, respectively over control.Similar kind of results reported for Phaseolus aureus (Bai et al., 2008).Increase in yield of several other crops like Capsicum annuum (Arthur et al., 2003), black gram (Venkataraman and Mohan, 1997) and canola plants (Brassica napus) (Ferreira and Lourens, 2002) are reported with the foliar application of seaweed extract.

Effect of treatments on the uptake of nutrients by greengram
The use of the seaweed extracts significantly increased N, P and K uptake by grains at higher concentrations (10% and above) and reached maximum at 15% seaweed extract compared with control (Table 6).The highest N and K uptake by grain was recorded with the treatment T 4 (15% Kappaphycus-sap + RDF) which was statistically at par with 15% Gracilaria-sap + RDF (T 8 ), 10% Kappaphycus-sap + RDF (T 3 ) and 7.5% Kappaphycus-sap + 50% RDF (T 10 ).15% Kappaphycussap + RDF showed the maximum uptake of P by grain.In case of nutrient uptake by stover, 15% Kappaphycussap + RDF was observed to be the best and it was closely followed by 15% Gracilaria -sap + RDF and 10% Kappaphycus -sap + RDF.Our results confirm those findings previously reported by Crouch et al. (1990) who noted an increased uptake of magnesium (mg), K and calcium (Ca) in lettuce with seaweed concentrate application.Turan and Köse (2004), Nelson and Van Staden (1984), and Mancuso et al. (2006) also observed  increased uptake of N, P, K and Mg in grape vines and cucumber with the application of seaweed extract.The presence of marine bioactive substances in seaweed extract improves stomata uptake efficiency in treated plants compared to non-treated ones (Mancuso et al., 2006).

DISCUSSION
Seaweed extract a the rich source of several primary nutrients like Although vitamin A is not present, the presences of its precursor carotene and another possible precursor fucoxanthin have been found.Apart from the above organic and inorganic constituents, there is an evidence of existence of different other stimulatory and antibiotic substances.These findings are in agreement with Jeannin et al. (1991), Vernieri et al. (2005), Kowalski et al. (1999), Zhang and Ervin (2008), Mancuso et al. (2006), Norrie and Keathley (2006) and Rayorath et al. (2008).Thus, being a wealthy source of versatile plant nutrients, phytohormones, amino acids, vitamins, stimulatory and antibiotic substances, the liquid sea weed extract enhances root volume and proliferation, bio-mass accumulation, plant growth, flowering, distribution of photosynthates from vegetative parts to the developing fruits and promotes fruit development, reduces chlorophyll degradation, disease occurrence etc. resulting Pramanick et al. 1185 in improved nutrient uptake, water and nutrient use efficiency causing sound general plant growth and vigor ultimately reflecting higher yield and superior quality of agricultural products.

Conclusion
Thus, it can be concluded that the seaweed extracts are effective in increasing the growth parameters, yield attributes, yield vis-à-vis quality of green gram.The saps also enhance nutrient uptake by this grain legume crop.Presence of micro-elements and plant growth regulators, especially cytokinins (Zodape et al., 2009;Zang et al., 2008) in Kappaphycus and Gracilaria extracts is responsible for the increased yield and improved nutrition of green gram receiving foliar application of the aforesaid two saps.

Table 1 .
Details of experimental treatment.
Data courtesy: National Institute of Nutrition, Hyderabad, India (except growth hormone data generated by CSMCRI using quantitative MS-MS and LC-MS techniques).

Table 3 .
Chemical composition of Gracilaria sap.

Table 4 .
Effect of treatments on plant height (cm), dry matter accumulation (g m -2 ), CGR (g m -2 day -1 ), no. of nodule per plant and LAI of green gram.

Table 5 .
Effect of treatments on yield components and seed and stover yield of green gram.

Table 6 .
Effect of treatments on nutrient removal by seed and stover of green gram.
Seaweeds also contain a wide range of vitamins which might be utilized by the crops.Vitamins C, B, (thiamine), B 2 (riboflavin), B 12 , D 3 , E, K, niacin, pantothenic, folic and folinic acids occur in algae.