Effect of Nano DAP on nutrient content and uptake by Bt. cotton (Gossypium hirsutum L.)

Introduction

Cotton (Gossypium hirsutum L.) is an important commercial crop grown in various environments for its high quality fiber and oil. It is a kharif (monsoon) crop in India, predominantly grown in warm climates with moderate rainfall and well drained black cotton soils rich in calcium and organic matter. Cotton is primarily cultivated for its fiber (lint) which is spun into yarn and fabric but its by-products such as cottonseed oil, meal and hulls are also economically valuable in agriculture and industry. Among the four cultivated species G. hirsutum (Bt. cotton) occupies over 90% of the cotton growing area in India due to its higher yield potential and resistance to bollworms (Kranthi, 2016) [6] . It is known as the American cotton and most popular varieties and hybrids now under cultivation. Nitrogen is a fundamental element of protein production and is very important for healthy growth of cotton and its physiological development. It is also a key component in chlorophyll production and therefore influences the plant's ability to produce carbohydrates. Simultaneously, Phosphorus (P) is crucial regarding energy transfer, root development and promoting flowering and fruiting. The ideal balance between nitrogen and phosphorus is crucial for supporting plant growth at various stages of development. The application of Nanotechnology in fertilizer is the best alternative to increase nutrient use efficiency. Nanotechnology has provided the feasibility of exploiting nanoscale or nanostructured materials as fertilizer carriers or controlled release of nutrients so called "smart fertilizer" as new facilities to enhance nutrient use efficiency and reduce costs of environmental protection (Veronica et al., 2015) [11] . Nano fertilizer increases fertilizer use efficiency by targeted release of nutrient in adequate proportion without any harmful effect on soil in addition to plant (Rameshaiah et al., 2015) [7] . One such breakthrough application is the use of Nano-diammonium phosphate (Nano DAP) in cotton crops. The incorporation of Nano DAP in cotton crop management brings forth significant improvements in plant growth and development. This ensures that the plants receive the required nutrients at the right time resulting in enhanced overall growth, increased biomass production and improved resistance to biotic and abiotic stresses. Use of Nano DAP can lead to a significant increase in cotton yield by promoting higher flower retention, boll formation and improved fiber quality.

Materials and Methods

A field experiment was conducted during during the Kharif season of 2023 and 2024 at the Instructional Farm, Polytechnic in Agriculture, Junagadh Agricultural University, Halvad. The soil of the field was sandy loam in texture and slightly alkaline in reaction and which was found low in available N (215 and 225 kg ha -1 ), medium in OC (0.58 and 0.61%), available P 2 O 5 (28 and 31 kg ha -1 ), S (18.20 and 19.80 ppm), Fe (6.95 and 7.15 ppm) and Zn (0.72 and 0.76 ppm) while, high in available K 2 O (455 and 425 kg ha -1 ), Mn (19.50 & 20.36 ppm) and Cu (1.10 & 1.16 ppm) during year 2023 and 2024, respectively. Three times replicated experiment in randomized block design (RBD) consisted of treatment T 1 served as an absolute control. Treatment T 2 received the full RDF comprising 180 kg N, 37.5 kg P 2 O 5 and 112.5 kg K 2 O ha -1 . Treatments T 3 and T 4 involved application of 75% and 50% RDF, respectively combined with seed treatment using Nano DAP 7.5 mL per kg of seed. Treatments T 5 and T 6 received 75% and 50% RDF respectively, with seed treatment of Nano DAP 7.5 mL kg -1 seed along with foliar sprays of Nano DAP 3 mL L -1 of water at 30, 45 and 60 days after sowing (DAS). Similarly, treatments T 7 and T 8 received 75% and 50% RDF respectively, seed treatment with Nano DAP 7.5 mL kg -1 seed and foliar sprays of Nano DAP 6 mL L -1 of water at 30, 45, and 60 DAS. In treatments T 9 and T 10 75% and 50% RDF were applied respectively, along with foliar applications of Nano DAP 3 mL L - 1 of water at 30, 45, 60 and 75 DAS. Treatments T 11 and T 12 included 75% and 50% RDF respectively, with foliar application of Nano DAP 6 mL L -1 of water at 30, 45, 60 and 75 DAS. These treatment combinations were carefully designed to evaluate the synergistic effects of reduced chemical fertilizer doses with Nano DAP through seed treatment and/or foliar applications on growth, yield and nutrient accumulation in Bt. cotton. The nutrients of N, P and K were applied through source of urea, DAP and MOP, respectively and Bt. cotton hybrid (G.Cot.Hy.24 BG II) was sown with seed rate of 3.0 kg ha -1 at inter row spacing of 120 cm and intra raw spacing of 45 cm in order to obtain uniform plant stand.

Results and Discussion 1. Effect of Nano DAP on nitrogen content and uptake by seed and stalk

The finding expressed in Table 1 and 2 revealed that N content in seed and stalk of Bt. cotton significantly exhibited marked variation by different Nano DAP treatments during both the years and in pooled analysis. The application of 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 + foliar spray of Nano DAP 6 mL L -1 at 30, 45 and 60 DAS (T 7 ) evidently recorded the highest N content in seed (3.88, 3.84 and 3.86%) and stalk (0.912, 0.925 and 0.918%) and also it remained at par with treatments T 2 , T 5 and T 11 during both the year and pooled, respectively. The observed increase of nitrogen content in seed and stalk is consistent with the conclusions drawn by Attia et al. (2016) [2] , who suggested that nitrogen content in plant parts significantly increased by each increment of Nano fertilizer. The treatment with Nano N at 2.5 times reduced recommended dose recorded the highest N content in grain and straw of sorghum as also reported by Rani et al. (2019) [8] . Table 3 and 4 presents the effect of Nano DAP on nitrogen uptake (kg ha -1 ) by seed and stalk of Bt. cotton at harvest during both the years and pooled results. The highest uptake of N by seed (96.85 kg ha -1 and 93.53 kg ha -1 ) observed with application of 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 + foliar spray of Nano DAP 6 mL L -1 at 30, 45 and 60 DAS (T 7 ) and it was statistically comparable with treatments T 5 (87.67 kg ha -1 and 84.86 kg ha -1 ) and T 2 (87.02 kg ha -1 and 84.54 kg ha -1 ) during both years. The pooled data also revealed that T 7 performed better with highest N uptake (95.19 kg ha -1 ) by seed among all treatments and it was found on par with T 5 (86.27 kg ha -1 ). In both the year and pooled analysis least uptake of N by seed was noted under T 1 with 49.27, 44.07 and 46.67 kg ha -1 , respectively. N uptake by cotton stalk at harvest was exhibited lowest (22.97, 24.07 and 23.52 kg ha -1 ) under absolute control (T 1 ) to highest (44.52, 42.79 and 43.66 kg ha -1 ) under treatment T 7 in both year and pooled, respectively. During first season and second season, treatment T 7 was observed statistically at par with treatments T 2 (38.81 and 38.91 kg ha -1 ) and T 5 (38.45 and 40.29 kg ha -1 ), respectively. Similar trend was observed by Hemdan et al. (2020) [5] , who showed maximum uptake of nitrogen in plant with nano fertilizer application. Abouyuoseff et al. (2022) [1] reported that application of NPK nano fertilizers led to increase in nutrient uptake in plant.

Effect of Nano DAP on phosphorus content and uptake by seed and stalk

A perusal of data furnished in Table 1 exibits that P content in seed was significantly influenced by different treatments involving reduced RDF with Nano DAP application through seed treatment and foliar spray at different periods. Among all treatments, Treatment T 7 comprising 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 + foliar spray of Nano DAP 6 mL L - 1 at 30, 45 and 60 DAS recorded the significantly highest phosphorus content in seed as 0.573, 0.567 and 0.570% during 2023, 2024 and pooled, respectively. Treatments T 2 (0.525 and 0.523%) and T 11 (0.524 and 0.523%) was found at par with T 7 (in 2023 and 2024). While, treatment T 5 (0.534, 0.566 and 0.550%) noticed at par with T 7 in both years as well as in pooled data, respectively. The least P content (0.438, 0.463 and 0.451% in 2023, 2024 and pooled, respectively) was detected in T 1 as absolute control. The data presented in Table 2 indicated that phosphorus content in stalk of Bt. cotton at harvest was significantly influenced by different evaluated treatments. During 2023, the maximum P content (0.290%) in cotton stalk was examined under T 7 with application of 75% RDF + seed treatment with Nano DAP 7.5 mL/kg seed + foliar spray of Nano DAP 6 mL/L at 30, 45 and 60 DAS which was significantly superior over most of the treatments but remained at par with T 2 (0.264%), T 5 (0.276%) and T 11 (0.267%). In 2024, a parallel trend was noticed where T 7 further recorded the highest phosphorus content (0.287%) in stalk, succeeded by T 11 (0.259%), T 2 (0.265%) and T 5 (0.267%). In pooled data, T 7 maintained its superiority with 0.289% P content in stalk, which was at par with T 5 (0.272%). The minimal P content in stalk was examined under plot as absolute control (T 1 ) with value of 0.234% in 2023, 0.226% in 2024 and 0.230% in pooled year data. In aggrement with the current findings Chinnappa et al. (2023) [3] and Veeramallu et al. (2024) [10] demonstrated that nano fertilizer foliar application enhanced NUE and nutrient accumulation in crops. The results presented in Table 3 indicated that in seed of Bt. cotton the phosphorus uptake was reported greater through application of 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 seed + foliar spray of Nano DAP 6 mL L -1 at 30, 45 and 60 DAS (T 7 ) during 2023 (14.32 kg ha -1 ), 2024 (13.79 kg ha -1 ) and pooled (14.06 kg ha -1 ) among all treatments evaluated. The lowest seed phosphorus uptake was noted under T 1: absolue control as 6.40, 6.17 and 6.28 kg ha -1 in the year 2023, 2024 and pooled, respectively. Treatments T 5 (12.73 kg ha -1 ) and T 2 (11.84 kg ha -1 ) both expressed equivalent with T 7 during 2024 in respect to P uptake by seed. The data reported in Table 4 revealed that phosphorus uptake by stalk was significantly highest as 14.18, 13.31 and 13.75 kg ha -1 during 2023, 2024 and pooled, respectively with the application of 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 seed + foliar spray of Nano DAP 6 mL L -1 at 30, 45 and 60 DAS (T 7 ). It was remained at par with T 5 (12.12 kg ha -1 in 2023 and 12.16 kg ha -1 in 2024) and T 2 (11.77 kg ha -1 in 2024). The lowest P uptake by stalk was registered with T 1: absolute control (7.40, 6.97 and 7.18 kg ha -1 in first year, second year and pooled, respectively). The increased phosphorus uptake under integrated treatments may be ascribed to enhanced phosphorus mobility, improved root proliferation and greater nutrient assimilation efficiency facilitated by nano sized particles (Tomar et al., 2024) [9] .

Effect of Nano DAP on potassium content and uptake by seed and stalk

The summary of data accessible in Table 1 revealed that during 2023, K content in seed ranged from minimal 1.47% (T 1: Absolute control) to largest 1.71% (T 7: 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 seed + foliar spray of Nano DAP 6 mL L -1 at 30, 45 and 60 DAS) while in 2024 it varied from minimum 1.45% (T 1 ) to maximum 1.70% (T 7 ). Treatment T 7 also found statistically comparable with treatments T 2 (1.66 and 1.63%), T 5 (1.65 and 1.63%) and T 11 (1.65 and 1.64%) in respective both the years. On a pooled basis, treatment T 7 had the highest potassium content (1.70%) in seed, which was considerably better than the other treatments and statistically comparable to T 2 (1.65%), T 5 (1.64%), and T 11 (1.64%). The seed K content under T 1 (absolute control) found the lowest (1.46% pooled). The maximum potassium content (0.909%) in cotton stalk (Table 2) during 2023 was found by application of 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 seed + foliar spray of Nano DAP 6 mL L at 30, 45 and 60 DAS (T 7 ) and it was statistically on par with T 2 (0.866%), T 5 (0.852%) and T 11 (0.856%). During 2024, K content (0.891%) in stalk was observed maximum through treatment T 7 and it remained on par with T 11 (0.859%), T 2 (0.849%) and T 5 (0.844%). The pooled data expreseed highest K content (0.900%) in stalk through treatment T 7 , which was superior over all treatments but statistically at par with T 2 (0.858%), T 11 (0.857%) and T 5 (0.848%). The lowest potassium content in stalk during 2023 (0.735%), 2024 (0.730%) and pooled (0.733%) was observed with absolute control (T 1 ). Data presented in Table 3 revealed that during 2023, significantly maximum K uptake of 42.54 kg ha -1 by seed was recorded under application of 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 seed + foliar spray of Nano DAP 6 mL L -1 at 30, 45 and 60 DAS (T 7 ), which remained at par with T 2: 100% RDF and T 5: 75% RDF + seed treatment with Nano DAP 7.5 mL/kg + foliar spray of Nano DAP 3 mL/L at 30, 45 and 60 DAS. A trend was registered similar in 2024, wherein K uptake by seed was registered highest (41.09 kg ha -1 ) under treatment T 7 followed by T 5 (36.73 kg ha -1 ) and T 2 (36.57 kg ha -1 ). In pooled analysis, T 7 remained maximum with K uptake of 41.81 kg ha -1 which was superior over remaining treatments (Table 3). The uptake of potassium by seed was observed lowest in treatment T 1: absolute control during 2023, 2024 and pooled year (21.60, 19.00 and 20.30 kg ha -1 , respectively). The data allocated in Table 4 declared that potassium uptake by stalk was significantly influenced by different treatments in both the years and in pooled results. Among all treatments, treatment T 7 (75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 seed + foliar spray of Nano DAP 6 mL L -1 at 30, 45 and 60 DAS) recorded the highest K uptake by stalk (44.41 and 41.15 kg ha -1 during 2023 and 2024, respectively) with a pooled mean of 42.78 kg ha -1 , which was statistically at par with T 2 (37.61 kg ha -1 ) and T 5 (38.45 kg ha -1 ) in 2024. The absolute control (T 1 ) registered the minimum K uptake (22.67 kg ha -1 pooled). Adequate N and P from Nano DAP improves the functionality of K⁺ transport proteins and membrane permeability facilitating efficient K uptake and its redistribution within plant tissues (Chinnappa et al., 2023) [3] . The nano formulation further increases NUE by minimizing fixation and improving nutrient availability at the cellular level (Gousia et al., 2023) [4] .

Conclusion

On the basis of two years experimentation, the integrated use of 75% RDF + seed treatment with Nano DAP 7.5 mL kg -1 seed + foliar spray 6 mL L -1 at 30, 45 and 60 DAS exhibited its superiority in respect of major nutrient accumulation and their uptake by Bt. Cotton. Overall, the application of Nano DAP and reduced RDF level in integration plays a frontline role in greater nutrient content and uptake by Bt. cotton.

References

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