Agro- techniques for sesame (Sesamum indicum L.) under partial shade of coconut in southern laterites

Abstract

The study entitled ‘Agro-techniques for sesame (Sesamum indicum L.) under partial shade of coconut in Southern Laterites’ was undertaken at College of Agriculture, Vellayani during 2021-24, with the objectives to standardize the nutrient levels for sesame under partial shade of coconut in Southern Laterites, assess the response of promising sesame varieties to the identified optimum nutrient levels and evaluate the allelopathic effect of sesame on selected weeds and crops. Field experiments were conducted at Coconut Research Station (CRS), Balaramapuram, to identify the optimum nutrient levels for sesame in Southern Laterites during Rabi 2021-22 and 2022-23, using variety Thilak. The experiments were conducted in the inter row spaces of coconut palms aged more than 60 years planted at a spacing of 7.6 m × 7.6 m. It was laid out in central composite design (CCD), with 20 runs viz., T1:31:20:16 kg NPK ha-1, T2:64:20:16 kg NPK ha-1, T3:31:50:16 kg NPK ha-1, T4:64:50:16 kg NPK ha-1,T5:31:20:34 kg NPK ha-1, T6:64:20:34 kg NPK ha-1, T7:31:50:34 kg NPK ha-1, T8:64:50:34 kg NPK ha-1, T9:20:35:25 kg NPK ha- 1, T10:75:35:25 kg NPK ha-1, T11:48:10:25 kg NPK ha-1, T12:48:60:25 kg NPK ha-1, T13:48:35:10 kg NPK ha-1,T14:48:35:40 kg NPK ha-1 and T15 to T20 (represented the central points of CCD): 48:35:25 kg NPK ha-1, replicated thrice. The nutrient level for sesame in Southern Laterites was standardized by plotting response surface curves using the seed yield of sesame during both years. Remaining observations were statistically analysed using randomized block design (RBD) with fifteen treatments (T1-T14, same as that of CCD, T15: was taken as the average of treatments T15-T20 in CCD). The growth parameters viz., plant height, number of leaves per plant, number of branches per plant and dry matter production were significantly influenced by different nutrient levels. Results on growth attributes at harvest revealed that, T1 produced taller plants during 2021-22 and 2022-23. However, T1 was on par with T2 during 2021-22 and with T2 and T4 during 2022-23. During both years, the highest number of leaves per plant was observed in T1 at 60 DAS. However, T1 resulted in more number of branches per plant at harvest during 2021- 22 and was on par with T2. While, during 2022-23, T2 produced more number of branches per plant and was on par with T1. During both years, DMP was significantly higher in T1 at all stages of observation. Physiological parameters were also significantly influenced by nutrient levels. During both years at 60 DAS, T1 resulted in higher LAI. However, it was on par with T2 and T4, during 2021-22 and with T2 during 2022-23. Chlorophyll content at 60 DAS was significant only during 2021-22 and T2 resulted in higher chlorophyll content which was on par with T1 and T4. Crop growth rate varied significantly with nutrient levels. At 40 DAS-60 DAS, T1 resulted in higher CGR which was on par with T2, T4 and T7 during both years. Similarly, higher RGR was noted in T1 which was on par with T2, T4, T7 and T11 at 40 DAS-60 DAS. Greater number of seeds per capsule was observed in T1 which was on par with T2 during 2021-22 and with T2 and T4 during 2022-23. During both years, the highest number of capsules per plant (57.7 and 74.7, respectively) and seed yield (503.5 kg ha-1 and 554.7 kg ha-1, respectively) were observed in T1. Pooled analysis of seed yield also revealed the highest value in T1 (529.1 kg ha-1). Whereas, the haulm yield and harvest index in T1 and T2 were comparable during both years. The optimum NPK levels identified by plotting the response surface curves during 2021-22 were 35:26:7 kg NPK ha-1 and 34:21:3 kg NPK ha-1 and during 2022-23 was 34:35:3 kg NPK ha-1. Oil content in seed varied significantly only during 2021-22 with the treatment T1 resulting in significantly higher oil content. During 2021-22, higher crude protein content was observed in T1 which was on par with T2. While during 2022-23, T2 resulted in higher crude protein content which was on par with T1 and T4. Higher P, Mg and Fe content in the seeds were observed in T2 during both years. Calcium content in the seeds was significant only during 2022-23 and was higher in T1. Similarly, Zinc content in the seeds was significant only during 2021-22 and was higher in T1. Post experiment soil analysis revealed that T1 resulted in higher organic carbon content, available N and P in the soil during both years. Available K was higher in T1 during 2021-22 and in T2 during 2022-23. The N, P and K uptake by the crop were also significantly influenced by nutrient levels and were higher in T1. The results on economics of cultivation revealed the highest gross return, net return and B:C ratio in T1 during both years. Field experiment to validate the response of promising sesame varieties to the identified optimum nutrient levels was laid out in split plot design during 2023- 24 at CRS Balaramapuram. The main plot treatments included five nutrient levels viz., 35:26:7 kg NPK ha-1 (n1), 34:21:3 kg NPK ha-1 (n2), 34:35:3 kg NPK ha-1 (n3), 31:20:16 kg NPK ha-1 (n4) and 30:15:30 kg NPK ha-1 (n5) and the sub plot treatments comprised of six sesame varieties viz., Kayamkulam 1(v1), Thilathara (v2), Thilarani (v3), Thilak (v4), GT 10 (v5) and TMV 7(v6). The nutrient levels had significant influence on growth parameters. Among the nutrient levels, n2 produced the tallest plants at harvest. Similarly at 60 DAS, number of leaves and branches per plant were higher in n2. At harvest significantly higher DMP was observed in n2. Similarly at 60 DAS, n2 resulted in higher LAI and chlorophyll content which was on par with n1. At 60 DAS-harvest, n2 resulted in the highest CGR and RGR. Significantly more number of capsules per plant, seeds per capsule and higher seed yield were observed in n2. Higher haulm yield was also observed in n2 which was on par with n1. Among the quality parameters, higher P, Ca, Mg, Fe and Zn content in the seeds were observed in n2. Similarly, higher N, P and K uptake and available N, P and K in the soil were observed in n2. The results on economics of cultivation revealed that the highest gross return, net return and B:C ratio were observed in n2. Adoption of optimum nutrient level (34:21:3 kg NPK ha-1) reduced the consumption of K by 90 per cent, compared to KAU POP recommendation, which could be attributed to medium to high K status in the soil of Southern Laterites. The growth parameters varied among the tested sesame varieties. Among the varieties, the tallest plants were observed in v5 at harvest. At 60 DAS, greater number of leaves and branches per plant were recorded in v5 which was on par with v4. At harvest, the highest DMP was observed in v5 (19.71 g per plant). Similarly, at 60 DAS, v5 had higher LAI which was on par with v4. The chlorophyll content was the highest in v5 at 60 DAS. Significantly more number of capsules per plant (84.0), higher seed yield (1066.0 kg ha-1) and haulm yield (2502 kg ha-1) were recorded in v5. The variety v5 recorded higher P, Ca, Mg and Fe content in the seeds. Results on nutrient uptake and availability revealed that higher soil available N, P and K in the post-harvest soil and N, P and K uptake by the crop were observed in v5.The variety GT 10 resulted in the highest gross return, net return and B:C ratio. Interaction effect of nutrient levels over varieties revealed that at 60 DAS and harvest, taller plants were observed in n2v5. The treatment, n2v5 also recorded more number of leaves per plant at 60 DAS. At harvest, the highest DMP was observed in n2v5. Higher LAI and chlorophyll content at 60 DAS were observed in n2v5. Similarly, n2v5 produced greater number of capsules per plant, higher seed yield ha-1and haulm yield ha-1. The results on nutrient uptake revealed that n2v5 resulted in higher N and P uptake. The treatment n2v5 also resulted in the highest gross return, net return and B:C ratio. The interaction effect of varieties over nutrient levels revealed that at harvest, all varieties except v3 produced taller plants at nutrient level n2. While v3 produced taller plants at n3. At 60 DAS, all varieties except v3, produced greater number of leaves per plant at n2. While, v3 produced higher number of leaves per plant at n3. At 60 DAS and harvest, all varieties produced higher DMP, LAI and chlorophyll content at n2. Similarly, all varieties produced the highest number of capsules per plant and seed yield ha-1 at n2. All varieties except v3 produced higher haulm yield ha-1 at n2. However, v3 produced higher haulm yield ha-1 at n1. The results on post experiment soil analysis revealed that all varieties except v1 recorded higher available N at n2. While, v1 recorded higher available N at n1. All varieties recorded the highest N and P uptake at nutrient level n2. The results on economics of cultivation revealed that all varieties recorded the highest gross return, net return and B:C ratio at n2. The leachates of different sesame varieties had significant impact on germination and seedling growth of weeds viz., Alternanthera sessilis, Setaria barbata and Cyperus rotundus. Leachate of variety GT10 had significant inhibitory effect on the germination, seedling shoot length, root length, dry weight, SVI I and SVI II of all tested weeds. Similarly, the leachates of different sesame varieties had significant impact on germination and seedling growth of tested crops viz., cowpea and okra. Application of leachate of variety GT 10 resulted in the lowest germination percentage, seedling shoot length, root length, fresh weight, dry weight, SVI I and SVI II of cowpea and okra. While leachates had no significant effect on the germination and seedling growth of amaranthus. From the results of the study, it could be concluded that the optimum nutrient level for sesame under partial shade of coconut in Southern Laterites was 34:21:3 kg NPK ha-1. Among the tested sesame varieties, GT 10 was identified as the best variety for Southern Laterites. The variety GT 10 raised under partial shade of coconut gardens manured with 5 t ha-1 of FYM + 34:21:3 kg NPK ha-1 (full dose of P, K and 75 per cent N as basal application and 25 per cent N as foliar spray at 3 per cent concentration, 30 DAS) realized the highest seed yield, net return and B:C ratio. Application of leachate of variety GT 10 had significant inhibitory effect on the germination and growth of test weeds (Alternanthera sessilis, Setaria barbata and Cyperus rotundus) and test crops (cowpea and okra).