Enhancement of finger millet productivity through STCR approach under climate change scenario

Introduction

Finger millet (Eleusine coracana L.) is an important food crop of India particularly cultivated in arid and semi-arid regions of Asia and Africa. It has gained importance due to its nutritional superiority and climate resilience nature in the era of changing climate. It is a rich source of minerals like calcium and iron along with essential amino acids, makes it a valuable crop to address malnutrition problem. Therefore, crop plays a significant role in food security and livelihood sustainability especially for small farmers. In spite of its importance, the productivity levels of finger millet in the country are below its potential, largely due to poor nutrient management practices, cultivation on low fertile soils and poor weed management practices. However, increasing population pressure has made it mandatory to enhance the productivity of crop so as to meet the growing demand for finger millet. Efficient nutrient management is crucial for maximizing crop yields and maintenance of soil health while enhancing nutrient use efficiency. But the traditional, fertilizer application methods based on the blanket recommendations doesn't take into account the soil fertility and thus results in imbalanced nutrient application and reduced yields and even some times end up in environmental issues. Hence, soil test-based fertilizer application is one such alternative to improve the productivity. Soil test-based fertilizer recommendations, based application is an approach in nutrient management which considers the initial soil nutrient status based on which the fertilizer application is done. The Soil Test Crop Response is yet another more advanced approach in nutrient management which integrates soil test values, the crop response data to articulate fertilizer recommendations tailored to achieve targeted yield. This approach aims to afford precise nutrient doses while maximizing economic returns. Bio-fertilizers Azospirillium which is known for its nitrogen-fixing capabilities, and Phosphorus Solubilizing Bacteria (PSB) which plays a crucial role in solubilizing insoluble soil phosphorus, making it accessible to plants are helpful in enhancing the nutrient availability and uptake. The combined effect of using chemical fertilizers and bio-fertilizers can lead to improvement of soil fertility, reducing reliance on synthetic fertilizers and enhancing crop productivity. In spite of the proven benefits of integration of the STCR approach and bio-fertilizers, comprehensive studies assessing their combined effect on finger millet are limited. Therefore, this study was formulated with the objective of investigating the effect of the STCR approach of nutrient management, both alone and in combination with Azospirillium and PSB, on the yield, nutrient uptake and economics of finger millet. The findings of this research are expected to provide valuable insights for developing sustainable and efficient nutrient management strategies for finger millet cultivation.

Materials and Methods

Field experiments were conducted at the Zonal Agricultural Research Station V.C. Farm, Mandya with the objective to evaluate the effect of the STCR approach of nutrient management on the yield and nutrient uptake of finger millet. Composite soil samples were drawn from a depth of 0-15 cm and subjected to soil analysis to determine the nutrient status. The results of soil analysis revealed that soil was neutral in pH (6.162) with electrical conductivity of 182.0 hs ppm -1 and organic carbon content of 0.55 per cent. The available nitrogen content was 238.00 kg ha -1 , available phosphorus was 18.75 kg P2O5 ha -1 and available potassium was 164.10 kg K2O ha -1 . The finger millet variety KMR-301 was used for sowing. The sowing of first crop was done during Rabi 2018 and second crop on Rabi 2019. Fertilizer adjustment equation developed by AICRP on STCR, UAS, Bangalore Centre for Zone-6 and validated for Zone-5 was used for calculating fertiliser to be applied for STCR treatments. The STCR equations are as follows FN = 3.29 T -71.17 SN (O.C%) -0.00281 OM FP2O5 = 1.798 T -0.189 SP2O5 (Bray's P2O5) -0.00173 OM FK2O = 1.775 T -0.15 SK2O (Amm.Acetate -K2O) -0.0015 OM where, T: Targeted yield (q ha -1 ) FN, FP2O5 and FK2O: N, P2O5 and K2O to be supplied through fertilizer (kg ha -1 ), respectively. SN, SP2O5 and SK2O: initial soil test values for organic carbon (%), available P and Ammonium acetate K2O (kg ha -1 ) OM: Nutrient content (kg t -1 ) in FYM × FYM to be applied (t ha - 1) . Based on the soil test values and the targeted yield, nutrients were applied as per the details presented in the Table 1. After the layout of experiment, calculated quantities of FYM were applied @ 10 t ha -1 as per the treatment details 15 days before the transplanting of the crop. At the time of transplanting, 50 per cent of nitrogen (through urea) and entire quantity of phosphorus (through SSP) and potassium (through MOP) were supplied as a basal dose to each plot and remaining 50 per cent of nitrogen was applied at 30 days after transplanting. Biofertilizer cultures of Azospirillium and PSB were obtained from Department of Agricultural Microbiology, University of Agricultural Sciences, GKVK, Bangalore. The seedlings were treated using the microbial culture and treated seedlings were then transplanted in the main field as per the treatment details.

The observations were recorded on the growth attributes and yield attributes and finally after the harvest of the crop, the grain yield and straw yield per plot were recorded and further subjected to statistical analysis.

Results and Discussion

Growth attributes

The data regarding the plant height and number of tillers plant -1 as influenced by application of nutrients based on different approach are presented in the Table 2. It is evident from the results that application of STCR based NPK to achieve a targeted yield of 55 q ha -1 along with application of Azospirillium and PSB recorded significantly higher plant height (98.3 cm and 98.9 cm), number of tillers plant -1 (3.6 and 3.9) over control (72.9 cm and 79.5 cm), (2.2 and 2.6) during 2018 and 2019, respectively, followed by T7 (application of NPK based on STCR equation for 50 q ha -1 targeted yield along with Azospirillium and PSB) (94.0 and 96.1cm), (3.4 and 3.5) and T4 (Application of NPK based on STCR equation for 55 q ha -1 targeted yield). The mean data over two years also revealed that application of STCR based NPK to achieve a targeted yield of 55 q ha -1 along with application of Azospirillium and phosphorus solubilising bacteria has recorded significantly higher plant height and number of tillers plant -1 over the absolute control treatment. Higher growth in STCR based fertilisation over the RDF, soil test based fertilisation and control might be due to the efficient supply of nutrients as per crop's needs along with contribution from soil and organic manure. The results aligning with Apoorva et al. (2010) [10] , Satalagaon et al. (2014) [4] and Sandhya rani et al. (2017) [3] . The improvement in growth parameters due to application of fertilizers on STCR basis and application of both fertilizers and organic manures may be attributed due to the increased supply of nutrients (Duryodhana et al., 2004) [2] .

Yield attributes

The data on yield attributes viz., number of fingers plant and finger length as influenced by application of nutrients based on nutrient management practices are presented in the Table 3.

Significant differences were observed with respect to number of fingers ear -1 and finger length of finger millet when compared to absolute control. Application of STCR based NPK to achieve a targeted yield of 55 q ha -1 along with application of Azospirillium and phosphorus solubilising bacteria recorded significantly higher number of fingers ear -1 (8.25 and 8.32), and finger length (8.96 and 9.52 cm) over control (5.33 and 5.80), (6.33 and 6.45) during 2018 and 2019 respectively. However, it was on par with T7 (application of NPK based on STCR equation for 50 q ha -1 targeted yield along with Azospirillium and phosphorus solubilising bacteria) and T4 (application of NPK based on STCR equation for 55 q ha -1 targeted yield).

Pooled mean of two years also revealed similar results with respect to number of finger plant and finger length of finger millet. Satalagaon et al. (2014) [4] reported that the enhanced nutrient uptake and increased nutrient use efficiency under STCR approach would have resulted in positive effect on growth and yield attributes that has enabled higher yield. also, there might be favourable complementary influence of organics and inorganics on soil properties under STCR integrated approach would have resulted in higher yield.

Grain yield and straw yield

The impact of application of nutrients based on different nutrient management practices are illustrated in Table 4. Significant differences were observed with grain yield and straw yield of finger millet when compared to no application of fertilizers that is absolute control. Grain yield and straw yield of finger millet differed significantly over the control treatment. Significantly higher grain yield (5763 and 5896 kg ha -1 ) and straw yield (7893 and 8212 kg ha -1 ) was recorded with application of STCR based NPK to achieve a targeted yield of 55 q ha -1 along with application of Azospirillium and phosphorus solubilising over control (2342 and 2034 kg ha -1 grain yield and 3562 and 3452 kg ha -1 of straw yield during 2018 and 2019 respectively. However, it was on par with T7 (application of NPK based on STCR equation for 50 q ha -1 targeted yield along with Azospirillium and phosphorus solubilising bacteria) (5012 and 5213 kg ha -1 grain yield and 7563 and 7741 kg ha -1 straw yield) and T4 (application of NPK based on STCR equation for 55 quintal ha -1 targeted yield) (5412 and5789 kg ha -1 grain yield and 8569 and 8563 kg ha -1 straw yield). Similarly, pooled mean of two years also revealed that application of STCR based NPK to achieve a targeted yield of 55 quintal ha -1 along with application of Azospirillium and phosphorus solubilising recorded significantly higher grain yield (5830 kg ha -1 ) and straw yield (8053 kg ha -1 ) over control (2188 and 3507 kg ha ha -1 , respectively). The improvement in the yield due to application of fertilizers based on STCR approach was attributed to the increase in growth attributes as a consequent of improved nutrient supply and efficiency of applied nutrients in the soil. The higher grain yield in STCR treatments could also be attributed to the ability of targeted yield approach to supply the nutrient demand of crop more efficiently as it considers the nutrient requirement of the crop and contribution of nutrients from soil, fertilizers (Regar and Singh, 2014) [6] and organic manures and it discourages lop sized application of nutrient or over fertiliation (Manish et al., 2014) [5] . The results are also in conformity with Manish et al.

(2017) [5] , Saraswathi et al. (2018) [9] and Sandhya rani et al., (2017) [3] who reported that the higher productivity of finger millet may be attributed to improved root growth, nutrient uptake, simulation of many different enzymes related to photosynthesis, improved soil properties and increased nutrient use efficiency of applied nutrients under integrated STCR based fertilisation treatment.

Nutrient Uptake

Uptake of nitrogen, phosphorus and potassium by finger millet differed significantly when compared to absolute control treatment (Figure 1). The Pooled data of two years revealed that significantly higher uptake of nitrogen (165.6 kg N ha -1 ), phosphorus (45.53 kg P ha -1 ) and potassium (152.01 kg ha -1 ) was observed in the treatments receiving nutrients based on STCR equation for 55q/ha targeted yield along with application of Azospirillium and phosphorus solubilizing bacteria over control. The next best treatment was nutrient application based on STCR equation for 55q ha -1 targeted yield. Application of fertilizers as per STCR treatments using both organic and inorganic nutrient sources increases the NPK content in plant parts because of balanced fertilization that might have improved nutrient status in the soil and hence improved uptake by the crop. Similar findings were obtained by Bhavya (2018) [7] that, increased NPK concentration were obtained in the root and shoot of carrot in treatment receiving nutrients as per STCR NPK + FYM approach. The findings of the experiment are also in line with Jagathjothi et al. (2010) [12] and Basavaraja et al. (2017) [8] .

Available nutrient status after harvest of the crop

The effect of different nutrient management practices on availability of major nutrients in soil after the harvest of finger millet variety KMR 301 is presented in Figure 2. Significant differences were observed with respect to available nitrogen, phosphorus and potassium in the soil as influenced by different treatments. Significantly higher available nitrogen values were observed during both the years (278.9 and 281.9 kg Nha -1 during 2018 and 2019 respectively) when the nutrients were applied based on STCR equation for 55 q ha -1 targeted yield along with Azospirillium and Phosphorus solubilizing bacteria when compared to absolute control (165.3 and 185.3 kg N ha -1 respectively). Significantly higher soil available phosphorus values were registered with the same treatment during both the years (59.78 and 51.81 kg P2O5 ha -1 during 2018 and 2019 respectively). Similarly, the available soil potassium values were significantly higher in the T8 treatment. The Pooled data of two years revealed that significantly higher available nitrogen (175.3 kg N ha -1 ), phosphorus (28.2 kg P2O5 ha -1 ) and potassium (121.4 kg K2O ha -1 ) was observed in the treatments receiving nutrients based on STCR equation for 55 q ha -1 targeted yield along with Azospirillium and phosphorus solubilizing bacteria over control. The next best treatment was nutrient application based on STCR equation for 55 q ha -1 targeted yield. Similar results are observed by Basavaraja et al. (2017) [8] .

Economics

Table 5 presents impact of different nutrient management approaches on the economic performance of the finger millet variety KMR 301. Economic analysis revealed that a gross return of 70256 Rs. ha -1 and 61026 Rs. ha -1 was realized from absolute control during the year 2018 and 2019 respectively. Among the different nutrient management practices, higher gross returns (172890 Rs. ha -1 , 176880 Rs. ha -1 ), net returns (126345 Rs. ha -1 , 130335 Rs. ha -1 ) and BC ratio (3.71, 3.80) was recorded with application of NPK based on STCR approach to achieve a target yield of 55 q ha -1 along with application of Azospirillium and PSB during the year 2018 and 2019 respectively and also pooled mean also followed similar trend. The next best treatment was application of NPK based on STCR equation for 50 q ha -1 targeted yield along with Azospirillium and PSB. Improvement in growth parameters such as plant height and number of tillers per plant might be due to application of fertilizers based on STCR approach along with application of Azospirillium and phosphorus solubilising bacteria which might have led to the increased supply of nutrients both by fixation of atmospheric Nitrogen by Azospirillium and also by solubilization of available phosphorus in the soil. Results are backed by Apoorva e al. (2010) [10] , Rai et al. (2016) [13] and Shetty et al. (2016) [11] . STCR is a fertiliser recommendation method that helps farmers apply the right amount of fertiliser to achieve the targeted yields with improved efficiency. The study revealed that application of NPK based on STCR approach to achieve a target yield of 55 q ha -1 along with application of Azospirillium and PSB shown superior growth, yield and nutrient uptake and also improved the soil nutrient status when compared RDF, soil test based fertilisation and control. The same treatment has also recorded higher gross returns, net returns and BC ratio. The next best treatment was application of NPK based on STCR approach to achieve a target yield of 50 q ha -1 along with application of Azospirillium and PSB.

Acknowledgement

AcknowledgementsThe authors are highly thankful to the Director of Research, University of Agricultural Sciences, GKVK, Bangalore for providing necessary facilities as well as rendering financial support for conducting the entire research work.

References

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