Biofortification of Zn and Fe in Chickpea through Agronomic Intervention in Medium Black Soils of Karnataka

Chickpea (Cicer arietinum L.) is an important rabi pulse crop of India occupying 9.67 Mha area, producing 10.09 mt with the average productivity of 1043 kg ha^-1 (Anonymous, 2019). It plays important role in the diet of Indian population and agricultural economy. It is high in protein, low in fat and sodium, free of cholesterol and is an excellent source of fiber, CHO, vitamins and minerals. At present, there are many problems in chickpea production in India like deficiency of both major and micronutrients since the crop is often grown in marginal land with conserved moisture during post rainy season, diseases, insects and moisture stress.
       
Among the pulses, chickpea is highly sensitive to Zn deficiency which is common in the major chickpea growing regions of the country. Zn helps to increase water use efficiency, nodulation and nitrogen fixation in pulses (Roy et al., 2013). Iron deficiency is widespread in chickpea growing region of the world and is most prevalent among the micronutrients. Iron deficiency limits oxygen delivery to cells, leading to fatigue, poor work performance, decreased immunity and death (Jones et al., 1996). Large proportions of the population in developing countries consume less than the recommended dietary iron and are believed to be anemic. Consuming bio-fortified crops can help to address micronutrient deficiencies by increasing the daily adequacy of micronutrient intake among individuals throughout life cycle (Bouis et al., 2011). Bio-fortified pulses are best remedies to nourish malnourished population. Therefore keeping these in view an investigation was carried out to study effect of foliar and soil application of Zn and Fe on growth, yield and their concentration in the grains of chickpea under rainfed conditions of Karnataka State.

Field experiment was conducted during rabi seasons of 2015-16 and 2016-17 and 2017-18 at Zonal Agricultural Research Station, Gulbarga, Karnataka, India. The main objective of the investigation was to know the response of chickpea genotypes to soil and foliar application of Zn and Fe. The soil (pH 8.80) of the experimental field was clay loam in texture, low inorganic carbon (0.50%), available nitrogen (180 kg ha^-1), in organic medium in available phosphorus (25 kg ha^-1) and high in available potassium (350 kg ha^-1). The experiment was laidout in split plot design with three replications. The main plot consisted of two chickpea genotypes (Annigeri 1 and JG 11) and sub plot six biofortification treatments (Recommended dose of NPK, RDF + 0.5% Zn foliar application, RDF + 0.1% Fe foliar application, RDF + 0.5% Zn + 0.1% Fe foliar application, RDF + seed treatment of Zn @ 2 g kg^-1 seeds and RDF + soil application of ZnSO4 @ 15 kg ha^-1). The chickpea varieties Annigeri 1 and JG-11 (90-100 days) was sown at 30 × 10 cm during first week of October and harvested during second week of January during all the three years of experimentation. The recommended fertilizer dose (25:50:0 kg ha^-1 as N: P₂O₅ and K₂O) was applied at the time of sowing through urea and single super phosphate. Gap filling and thinning operations were carried out wherever necessary to maintain required plant population. Treatment imposition was done as per standard methods. Soil application of ZnSO₄ was done at 30 DAS. Foliar application of 0.5% Zn and 0.1% Fe was done through ZnSO₄.7H₂O (23% Z) and FeSO₄.H₂O (20% Fe) at flowering stage using 500 litres of water per hectare as per treatments. Weeds were controlled by applying pendimethalin @ 3.33 ml per litre of water as pre emergent spray followed by one hand weeding at 35-40 DAS. Regarding agronomic characters, ten competitive plants were randomly selected from each plot and observations were recorded for growth and yield attributes. Whereas, seed yield obtained from the net plot area was recorded and expressed in kg ha^-1. At harvest plant samples were collected from each plot for chemical analysis of Zn and Fe by using di-acid (HClO₄ + HNO₃ in 3:10 ratio) digestion in Atomic Absorption Spectrophotometer (Prasad et al., 2006). Economics was calculated on the basis of market price of chickpea and cost of cultivation. The data were statistically analyzed as per the procedure given by Gomez and Gomez (1984) for split plot design.

Growth and yield attributes of chickpea
 
Chickpea varieties differed significantly in-terms of their growth and yield parameters like plant height, number of branches plant^-1, pods plant^-1, pod weight plant^-1, seed yield plant^-1 and 100 seed weight (Table 1, 2 and 3).  The pooled data of three years indicated that, the genotype JG 11 recorded significantly higher plant height (37.42 cm) and number of branches (6.13 plant^-1), pods plant^-1 (37.08), pod weight plant^-1 (15.50 g), seed yield plant^-1 (13.02 g), 100 seed weight (22.10 g) when compared to Annigeri 1. This was mainly because of differences in varietal characters.
 

 

 

       
Biofortification of Zn and Fe either to soil or foliar sprays significantly improved the growth and yield attributes of chickpea. Among the different treatments, RDF + 0.5% Zn + 0.1% Fe had resulted in significantly higher plant height (26.20 cm), number of branches (6.70 plant^-1), pods plant^-1 (41.55), pod weight plant^-1 (16.80 g), seed yield plant^-1 (13.35 g), 100 seed weight (20.93 g) as compared to their individual application either to soil or foliar sprays. It could be due to the fact that application of Zn and Fe with RDF responded better in terms of growth and yield attributes due to balanced availability of micronutrients (Zn and Fe) and moisture throughout growing period and also application of zinc increased activity of meristematic cells and cell elongation, favorable effect on metabolic process. Zinc involved directly and indirectly as coenzyme in photosynthetic process which provide substrate for growth and development. Application of Fe might helped in better photosynthesis and photosynthete partitioning to yield attributing parameters which resulted in better source sink relationship. Similar kind of results were also found by Sharma et al., (2010) in pigeonpea, Der et al., (2015) and Goutami and Ananda (2015) in groundnut, Jha et al., (2015) in blackgram, Handiganoor et al., (2016) and Rathod et al., (2016) in pigeonpea.
       
The interaction effect between genotypes and biofortification of Zn and Fe on growth and yield attributes of chickpea was found significant. The treatment combination of JG 11 with RDF + 0.5% Zn + 0.1% Fe foliar application recorded significantly higher plant height (38.50 cm), number of branches (7.20 plant^-1), pods plant^-1 (45.60), pod weight plant^-1 (18.10 g), seed yield plant^-1 (15.00 g),100 seed weight (22.40 g) when compared to the rest of the treatment combinations.
 
Grain yield of chickpea
 
In the present investigation, a significant difference was noticed in yield of chickpea due to different genotypes (Table 5). Among the two genotypes tested, JG 11 recorded significantly higher grain yield (1309 kg ha^-1) with yield superiority of 25.74% compared with Annigeri 1 (1041 kg ha^-1).
       
Significant differences were observed in yield and yield components of chickpea as a consequence of biofortification of micronutrients involving different methods of application. All the biofortified treatments produced significantly higher grain yield (1096-1321 kg ha^-1) compared with control (1008 kg ha^-1). Control treatment registered 23.69% lower grain yield as compared to the best treatment RDF + 0.5% Zn + 0.1% Fe foliar application. Higher grain yield obtained in this treatment may be attributed to higher dry matter accumulation, better nutrient uptake (N, P, K, Zn and Fe) and translocation to reproductive parts and involvement of Zn and Fe in various enzymatic processes which helps in catalyzing reaction for growth finally leading to development of more yield attributing characters like number of pods per plant, pod weight, 100 seed weight and seed yield. Significantly lower grain yield (1008 kg ha^-1) obtained with recommended dose of NPK may be due to reduced availability of major and micronutrient in soil, less nutrient uptake, reduced photosynthates production which causes lower yield attributing characters and resulted decrease in yield. Similar results were obtained by Gupta and Sahu (2012) in chickpea, Shrikanthbabu et al., (2012) in pigeonpea, Debroy et al., (2013) in greengram, Goutami and Ananda (2015) in groundnut and Jha et al., (2015) in blackgram.
       
The interaction effect between genotypes and biofortification of Zn and Fe on grain yield of chickpea was found significant. Significantly higher grain yield was registered in the treatment combination of JG 11 with RDF + 0.5% Zn + 0.1% Fe (1416 kgha^-1) when compared to rest of the treatment combinations.
 
Influence of soil and foliar application of Zn ad Fe on Zn concentration of chickpea grains
 
Varieties of chickpea did not differ significantly in Zn content in grains (Table 4). However, Fe content differed significantly among the varieties;  Annigeri 1 registered significantly higher Fe content in grains (43.33 ppm) when compared with JG 11 (39.45 ppm). 
 

       
Among the different methods of soil and foliar application of Zn and Fe, significantly  higher Zinc content (33.29 ppm) was recorded  in the treatment of RDF + 0.5% Zn + 0.1% Fe foliar application  followed by RDF + soil application of  ZnSO₄ @ 15 kg ha^-1 (31.36 ppm). Increase in zinc content in seed in the above mentioned treatment may be due to high nutrient uptake with more availability of zinc in root zone, better nutrient absorption and beneficial role of zinc in increasing cation exchange capacity of roots and stimulatory effect on most of the physiological and metabolic processes of plant. Significantly lower zinc content in seed was recorded with treatment recommend dose of NPK only (26.12 ppm). This might be partly due to poor zinc concentration in root zone, lower nutrient uptake by crop which might have resulted in lower zinc content.
       
The interaction effect between genotypes and biofortification of Zn and Fe on Zn content of chickpea grain was found significant.  Annigeri 1 with RDF + 0.5% Zn + 0.1% Fe (33.67 ppm) recorded significantly higher concentration of Zn in chickpea grains when compared to rest of the treatment combinations, but it was on par with JG 11 with RDF + 0.5% Zn + 0.1% Fe foliar application  and JG 11 with RDF + soil application of ZnSO₄ @ 15 kg ha^-1.
 
Influence of soil and foliar application of Zn ad Fe on Fe concentration of chickpea grains
 
Concentration of Fe in seeds of chickpea varieties differed significantly due to soil and foliar application of Zn and Fe (Table 4). In the present study, Annigeri 1 registered significantly higher Fe content (43.33 ppm) in chickpea grains as compared to JG 11 (39.45 ppm).
       
Among the biofortification treatments, RDF + 0.5% Zn + 0.1% Fe foliar application recorded significantly higher Fe content in the seeds of chickpea (48.13 ppm) followed by RDF + 0.1% Fe foliar application. The higher Fe concentration in seeds in this treatment might be due to increased supply of iron through soil and foliar application, development of Fe pool in soil and also foliar spraying of Fe easily penetrates through leaves either by transportation or via stomatal pathway. Significantly lower Fe content in seeds of chickpea under control plot may be due poor nutrient status in soil, which might be resulted in lower nutrient uptake. Similar esults were also obtained by Bashrat et al., (2014), Goutami and Ananda (2015) in groundnut and Hanumantappa et al., (2018) in pigeonpea.
       
The interaction effect between genotypes and biofortification of Zn and Fe on iron content of chickpea grain was found significant. Annigeri 1 with RDF + 0.5% Zn + 0.1% Fe (53.42 ppm) recorded significantly higher concentration of Fe in chickpea grains when compared to rest of the treatment combinations, but it was on par with Annigeri 1 with RDF + 0.1% Fe  foliar application.
 
Effect of biofortification on economics
 
Gross returns (GR), net returns (NR) and benefit cost ratio (B:C ratio) differed significantly due to both soil and foliar application of Zn and Fe (Table 5).
 

       
Chickpea genotype JG 11 registered significantly higher gross returns, net returns and B: C ratio as compared to Annigeri 1 due to higher grain yield.
       
Among the biofortification treatments, significantly higher gross return (₹ 52829 ha^-1), net return (₹ 31179 ha^-1) and benefit cost ratio (2.44) were recorded with RDF + 0.5% Zn + 0.1% Fe foliar application when compared to rest of the treatments. The higher yields under this treatment may be due to soil application of fertilizers which might be resulted in higher nutrient concentration in root zone and direct foliar spraying of fertilizers leads to more absorption of nutrients, better photosynthetic activity and its distribution to various parts, increase in growth and yield attributing characters and finally resulted in higher yields, gross returns, net return and B:C ratio.
       
The interaction effect between genotypes and biofortification of Zn and Fe on gross returns, net returns and B: C ratio of chickpea was found significant.  Among the different treatment combinations, the genotype JG 11 with RDF + 0.5% Zn + 0.1% Fe foliar application registered significantly superior gross returns (₹ 56650 ha^-1), net returns (₹ 35000 ha^-1) and B:C ratio (2.62) when compared to rest of the treatments.

It was concluded from the 3 years study that application of recommended dose of fertilizers (RDF) along with 0.5% Zn and 0.1% Fe foliar spray was best option for enhancing nutrient concentration in chickpea grains and also for getting higher chickpea yield, net returns and B:C ratio.