Effect of coated fertilizers on yield, nutrient use efficiency, and economic returns in Bt cotton

Introduction

Cotton (Gossypium hirsutum L.) is one of the most important commercial cash crop and important fiber crop of global significance cultivated in more than seventy countries. popularly known as "White gold or friendly fiber". The cotton plant belongs to the genus Gossypium of the family Malvaceae. It is grown for fiber and seed. Cotton is a multipurpose crop that supplies five basic products such as lint, oil, meal, seed and hulls and is popularly known as "King of Fiber". India rank first in area and second in production of cotton after China. In India, cotton is grown in ten states, out of which nine states grow both bt as well as non-bt cotton and Odisha is the state which grows only non-bt cotton. Maharashtra, Gujarat and Telangana occupy 70% of the total cotton area in India and 60% of overall cotton production in the country. These three states cultivate cotton in different agroclimatic conditions. Maharashtra state is the largest area and production under cotton cultivation in the country, but per hectare productivity is far below as compare to cotton growing states. In Maharashtra, cotton is the major crop cultivated in large extent besides soybean, maize, rice, wheat, pulses and other oilseeds. In general, Bt cotton hybrids are suitable for irrigated condition and it has been proved from production and productivity levels of Gujarat, Punjab and Haryana. In modern agriculture, chemical fertilizers play a crucial role in meeting the nutrient demands of crops and achieving high yields. However, conventional fertilizers often release nutrients rapidly, leading to losses through various pathways and a mismatch between nutrient availability and plant uptake. To address these challenges, slow-release and controlled-release fertilizers have been developed. These innovative fertilizers offer a means of improving nutrient use efficiency, reducing environmental pollution, and promoting sustainable agricultural practices by synchronizing nutrient release with plant requirements. The efficient use of fertilizers is critical for sustainable crop production. Controlled-release it was discovered that phosphate fertilizers produced by covering phosphatic fertilizers with wax, conditioner, asphalt, sulphur, wax, and sulphur were useless. This may be because the rate of release of phosphorus from these fertilizer products was much slower than the rate required by crops. However, this suggestion has recently been proven through testing the hypothesis without using specialised P fertilizer products. Therefore, it appears that using controlled-release phosphatic fertilizers could improve crop yields and phosphorous efficiency (Pauly et al., 2001) [10] . When urea is applied in the field, it is hydrolyzed by urease enzyme to ammonia (NH 4 ) and then further converted to nitrates (NO - 3 ) which are susceptible to volatilization, denitrification and leaching losses, respectively. The arrest of nitrogen loss can help to increase nitrogen utilization per unit area. It will help in lowering the cost of cultivation and increase in benefit to farmers and minimizing nitrate pollution. Recently several techniques have been evolved to coat the fertilizer material, which will help to reduce the losses and ensure their sustained release. Later on many slow release urea fertilizers like sulphur coated urea (SCU), neem oil coated urea (NOCU), isobutylidienediurea (IBDU) and lac coated urea (LCU) etc. have been developed. If urea fertilizers are modified with indigenously available material like neemcake, then they are economical to the farmers for farm use (Bharathi and Sekar, 2016) [1] .

Materials and Methods

A field trial was conducted during the Kharif season of 2020-21 at the Experimental Research Farm, Department of Soil Science and Agricultural Chemistry, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani. The experiments on cotton were conducted to study the "Studies on Efficacy of Coated Fertilizer on Soil Properties, Yield and Quality of Bt Cotton". The soil of experimental site was black soil dominant in Montmorillonite mineral which is inherently rich in lime, iron and magnesium (Gajbe et al., 1976) [2] . The soil was alkaline in reaction (pH 8.28), low in salt content (0.20 dS m -1 ) with high calcium carbonate content (10 g kg -1 ). The organic carbon status of the soil was medium (6.6 g ha -1 ). The soil available nitrogen was low (172.48 kg ha -1 ), available phosphorus was medium (9.11 kg ha -1 ), available potassium was very high (705.6 kg ha -1 ) and available sulphur was medium (20.55 mg kg -1 ). The experiment was carried out in Randomized Block Design (RBD) with ten treatments and three replications. A set of nine treatments viz.T 1 -Absolute control, T 2 -Recommended dose of fertilizer (Through straight fertilizer)T 3 -RDF through coated fertilizer grade (N:P 2 O 5 :K 2 O:S:Mg:Zn:B 11:23:10:4:1.9:0.4:0.2), T 4 -RDF through non coated fertilizer grade (N: P 2 O 5 :K2O:S:Mg:Zn:B 11:23:10:4:1.9:0.4:0.2), T 5 -25% reduction to RDF with coated fertilizer grade, T 6 -25% reduction to RDF with noncoated fertilizer, T 7 -50% reduction to RDF with coated fertilizer, T 8 -50% reduction to RDF with non-coated fertilizer, T 9 -RDF through straight/complete fertilizers + individual secondary and Micronutrients as per treatment second for basal dose only. Certified seed of cotton (Ajeet 155 BG II) were sown in Kharif by dibbling two seeds per hill. The total numbers of balls per plant from five observational plants were counted at 60, 90 and 120 days after sowing. At time of second picking seed cotton from five well opened representative bolls from each plant were picked and average bolls weight in (g) were recorded on each plant, seed cotton yield from each plot were recorded, Cost of cultivation was calculated by addition of all the cost incurred towards purchasing of inputs. And also Gross monetary returns, Net monetary returns, Benefit cost ratio were calculated. The nutrient use efficiency was calculated by using different nutrient use efficiency measures viz., partial factor productivity, agronomic efficiency and apparent nutrient recovery. The data were analyzed by statistical method as suggested by Panse and Sukhatme (1985) [9] .

Results and Discussion

Yield parameter of Bt cotton enhanced on application of coated fertilizer

The number of bolls per plant is a critical yield-determining parameter in cotton production, as it provides an estimation of the probable yield. The results from the study, as presented in Table 1, indicate significant variations in the number of bolls per plant across different fertilizer treatments at various growth stages. The data show that the number of bolls per plant increased progressively from 30 DAS to 90 DAS across all treatments. The highest number of bolls per plant was consistently recorded in Treatment T 3 , which received the recommended dose of fertilizer (RDF) through a coated fertilizer grade (N:P 2 O 5 :K 2 O:S:Mg:Zn:B-11:23:10:4:1.9:0.4:0.2). Specifically, T 3 recorded 24.30, 30.03, and 33.84 bolls per plant at 30, 60, and 90 DAS, respectively. This could be attributed to the controlled release of nutrients, ensuring a sustained supply of essential elements throughout the plant's growth stages. Treatments T 4 and T 5 , which received RDF through non-coated fertilizer and a 25% reduction to RDF with coated fertilizer, respectively, also exhibited a high number of bolls per plant. The results suggest that even with a 25% reduction in RDF, the use of coated fertilizers (T 5 ) maintained boll production close to that of the full RDF application, indicating efficient nutrient utilization. The absolute control treatment (T 1 ) recorded the lowest number of bolls per plant across all growth stages, with values of 18.10, 23.37, and 26.73 at 30, 60, and 90 DAS, respectively. This suggests that nutrient deficiency significantly limits boll formation, leading to lower productivity. The findings align with previous research by Hosamani et al. (2013) [5] , who reported that an increased seed cotton yield was associated with a higher RDF application, likely due to enhanced nutrient availability and uptake, leading to better boll retention and formation. The results emphasize the effectiveness of coated fertilizers in improving nutrient efficiency and sustaining cotton yield. The data on effect of coated fertilizer on dry matter yield of cotton, mean boll weight of cotton, seed cotton yield (q ha -1 ) are presented in Table 1. Significantly maximum mean boll weight of cotton i.e., 3.62 g was recorded in treatment (T 3 ), receiving RDF (120:60:60 Kg NPK ha -1 ) through coated fertilizer grade (N:P 2 O 5 :K 2 O:S:Mg:Zn:B 11:23:10:4:1.9:0.4:0.2) followed by (T 5 ), receiving 25% reduction to RDF (120:60:60 Kg NPK ha -1 ) with coated fertilizer grade 3.22 g, (T 7 ), receiving 50% reduction to RDF(120:60:60 Kg NPK ha -1 ) with coated fertilizer 3.16 g. However, minimum number of bolls per plant was recorded in (T 1 ) i.e., Absolute control 2.70 g. Significantly maximum dry matter yield of cotton i.e., 2887.73 kg/ha was recorded in treatment (T 3 ), followed by (T 5 ), (T 7 ). However, minimum dry matter yield of cotton was recorded in (T 1 ) i.e., Absolute control 2407.40.The result revealed that the seed cotton yield varied in the range of 532.00 to 1667.00 (Kg ha -1 ). Significantly seed cotton yield (q ha -1 ) of cotton i.e., 1667.00 kg/ha was recorded in treatment (T 3 ), receiving RDF (120:60:60 Kg NPK ha 1 ) through coated fertilizer grade (N: P 2 O 5 :K 2 O: S: Mg: Zn: B 11:23:10:4:1.9:0.4:0.2) followed by (T 5 ), T 7 . Depicted in fig. 2. However, minimum seed cotton yield (q ha -1 ) of cotton was recorded in (T 1 ) i.e., Absolute control 532.00 kg/ha. Hosamani et al. (2013) [5] reported that increased in seed cotton yield with 125 percent RDF might be due to significantly higher number of good opened boll per plant, total number of bolls harvested per plant, mean boll weight, amount of dry matter accumulation in reproductive parts of and leaf area upto harvest.

Optimizing Bt Cotton Economics through Coated Fertilizer Application

The economic evaluation of coated fertilizers in cotton cultivation is crucial for understanding their costeffectiveness and profitability. Effect of coated fertilizer on economics of cotton presented in Table 2. Data showed that the highest gross return (GMR), net monetary returns (NMR), and benefit-cost ratio (B:C) noticed with treatment (T 3 ) receiving RDF through coated fertilizer grade (N:P 2 O 5 :K 2 O:S:Mg:Zn:B 11:23:10:4:1.9:0.4:0.2) followed by T 5 >T 7 . The benefit cost ratio varied from Rs 1.19 to 2.20.

the highest benefit cost ratio observed in treatment (T 3 ), receiving RDF (120:60:60 Kg NPK ha -1 ) through coated fertilizer grade (N:P 2 O 5 :K 2 O:S:Mg:Zn:B 11:23:10:4:1.9:0.4:0.2) depicted in fig. 1 followed by T 5 >T 7 . Our results are corresponds with Niranjan et al. (2017) [7] , who reported that neem-coated urea significantly improved economic returns in soybean compared to conventional fertilizers. Similar result were found by Sharma and Singh 2011. [12] , Sanders et al., 2012. [11] , Shivay et al., 2016. [13] , Hatano et al., 2019 [4] .

Effect of Coated Fertilizers on Nutrient Use Efficiency in Bt Cotton

Nutrient use efficiency is a crucial parameter in assessing the effectiveness of fertilizer application in crop production.

The study evaluated partial factor productivity (PFP), agronomic efficiency (AE), and apparent nutrient recovery (ANR) to determine the impact of coated fertilizers on nutrient utilization efficiency in Bt cotton (Table 3). Partial factor productivity, which measures nutrient use efficiency based on economic and biological yield per unit of nutrient applied, was highest in T 7 (50% reduction to RDF with coated fertilizer), followed by T 8 , T 3 , and T 5 . This indicates that even with reduced RDF, the use of coated fertilizers significantly enhanced nutrient use efficiency. Our results are related to findings of Ghafoor et al. (2021) [3] the results show that, the positive effect of coated fertilizers was found on growth, development, physiological, yield and PFP in wheat crop. Gromor bentonite S pastille at 20 kg S ha -1 showed higher sulfur recovery than gypsum or SSP, likely due to its higher concentration, reduced leaching, and gradual release (Jena and Kabi, 2012) [6] . Agronomic efficiency, calculated as the yield difference between fertilized and control plots per unit of nutrient applied, followed a similar trend. The highest AE was observed in T 7 , followed by T 8 , T 3 , and T 5 . These findings similar with the study of Tesfay and Girmay (2019) [14] , who reported that combined agronomic efficiency was lower than individual nutrient agronomic efficiency, highlighting the importance of balanced fertilization. Apparent nutrient recovery, another measure of nutrient use efficiency, was highest in T 7 , followed by T 8 , T 3 , and T 5 . These results support the findings of Noor et al. (2017), who observed a positive effect of coated fertilizers on nutrient uptake and recovery efficiency. Study indicates that coated fertilizers enhance nutrient use efficiency, particularly under reduced RDF conditions. The findings suggest that adopting coated fertilizers can optimize nutrient utilization, improve cotton yield, and contribute to sustainable agricultural practices. Result were similar to Hatano et al., 2019 [14] .

Conclusion

From above study we can conclude that the application of coated fertilizers significantly enhanced Bt cotton yield, nutrient use efficiency, and economic returns. Among the different treatments, the recommended dose of fertilizer (RDF) applied through coated fertilizer (T 3 ) exhibited the highest seed cotton yield, dry matter yield, and mean boll weight. This treatment also achieved the highest nutrient use efficiency and economic benefits, with the highest gross monetary returns, net monetary returns, and benefit-cost ratio. Even with a 25% reduction in RDF (T 5 ), coated fertilizers maintained higher productivity and economic viability than non-coated alternatives. These findings highlight that coated fertilizers provide a sustainable and cost-effective approach to optimizing Bt cotton production by reducing nutrient losses, enhancing crop performance, and improving profitability. Thus, the application of coated fertilizers is recommended for maximizing yield and economic benefits in Bt cotton cultivation.

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