Dragon fruit (Hylocereus spp.), an important tropical fruit belonging to the family Cactaceae, is rich in essential nutrients such as vitamins, minerals, complex carbohydrates, dietary fibres and antioxidants. This study aims to distinguish three dragon fruit species well adapted to Andaman and Nicobar Island through morphological (34 quantitative and 26 qualitative traits), biochemical (5 traits) and molecular (14 ISSR primers) characterization. Morphological characterization revealed that presence of considerable amount of genetic variations among them especially for fruit characters viz., colour of peel and pulp. Cladode characters such as number of spines (3–5), length of areoles (mm) as 1–4, margin ribs of cladode (convex or concave) and its waxiness (weak or strong white waxy or light waxy) could be used for identification of three Hylocereus spp. under present study. Highest co-efficient of variation (%) obtained for pulp weight (88.7), whereas, lowest in distance of anthers belowstigma (3.3). Fruit and pulp weight (g) ranged from 26.5–419.3 and 10.3–258.8 with mean value of 204.8 and 125.3, respectively. Comparatively, high phenol (71.3–161.3) and flavonoid (26.6–508.2) content observed in peels than pulp (32.5–130.0 and 45.0–258.2) of fruit indicating higher antioxidant potential. Highest total carotenoids (µg 100 g−1), β-carotene (µg 100 g−1) and xanthophyll (µg g−1) content obtained in pulp on DGF3 (33.8), DGF4 (55.9) and DGF3 (32.7), whereas, in peel on DGF2 (24.3), DGF4 (18.5) and DGF2 (24.1), respectively. DPPH-based scavenging activity (%) revealed higher scavenging activity of peels (55.6–81.2) than pulp (36.0–75.3) extracts. Comparatively, ABTS-based scavenging activity (%) was found more than DPPH-based one. Sixteen ISSR primers screened, 14 were produced 178 reproducible amplified bands. Number of amplified bands varied from 5 in UBC887 to 19 in UBC811 with an average of 12.71 bands per primer. Range of polymorphic bands and % polymorphism observed were 1–13 and 20.0–92.8, respectively. The polymorphic information content value of ISSR marker ranged from 0.42 (UBC895) to 0.91 (UBC 856). Cluster analysis distinguished three different Hylocereus species on the basis of geographic origin and pulp colour by forming separate groups and two genotypes each showed 52% (DGF1 and DGF3) and 76% (DGF2 and DGF4) genetic similarity. Key traits identified for distinguishing three different Hylocereus species were: Pulp/ peel colour of fruits, number of spines and length of areoles in cladode. Genotypes with high carotenoid and xanthophylls content (DGF4 and DGF2) identified under present study may be of industrial importance for development of nutraceutical products to meet out the vitamin-A deficiency among humans in tropical regions needed future focus.

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A field experiment was conducted in farmer’s field during Kharif season at Badmaspahar village of South Andaman under National Innovation on Climate Resilient Agriculture (NICRA) to find out the influence of planting methods, seedling age on growth, productivity, profitability, nutrient uptake of rice under higher rainfall areas of Bay Islands. Among the method of planting and age of seedlings, square planting with 14 days old seedlings recorded the highest dry matter production of 63.2% higher dry matter production as compared to random planting with 28 days old seedlings. Maximum grain and straw yield of 4855 and 9460 kg/ha respectively was recorded square planting (20 x 20 cm) with 14 days old seedling which was 64.6, 45.6 and 71.7, 59.9% higher grain and straw yield as compared to random planting with 28 days old seedlings and same age of seedlings with line planting respectively. Higher gross return of Rs. 50920/ ha and net return of Rs. 32170/ ha with B: C ratio of 2.72 was recorded in square planting (20 x 20 cm) with 14 days old seedling. The higher N, P and K uptake of rice (78.7, 25.1 and 114.8 kg/ha, respectively) was recorded in square planting (20 x 20 cm) with 14 days old seedlings was comparable with line planting (20 x 15 cm) with 14 days old seedlings. Hence, it can be concluded that square planting (20 x 20 cm) with 14 days old seedlings with stand lodging, produced more economic yield and net return for realizing efficient use of resources and productivity.

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Aim: To study the effect of season-long weed management using encapsulated herbicides on weed control, productivity and nutrient uptake of rice. Methodology: Field experiment was carried out with oxadiargyl encapsulated / loaded in zeolite, biochar, starch, water soluble polymer. It was compared with commercial formulation of oxadiargyl, butachlor, weed free check and weedy check. The experiments were laid out in randomized complete block design and replicated thrice. The physico-chemical properties of the experimental sites was sandy clay loam to clay loam in texture with pH ranging from 6.9 to 7.3, low organic carbon content, low available nitrogen, medium available phosphorus and potassium. Results: The lowest weed density and weed dry matter production of 47.3, 28.0 m-2 and 96.2, 32.8 kg ha-1 was observed in 2016 and 2017 respectively with the application of oxadiargyl loaded with zeolite at 20 DAT. Application of butachlor at 1.25 kg ha-1 fb hand weeding on 40 DAT and application of oxadiargyl loaded with zeolite recorded 86.7, 76.9 and 81.3, 72.8 percent higher grain yield in 2016 and 2017, respectively, as compared to weedy check. Higher N, P, K uptake was observed with application of butachlor at 1.25 kg ha-1 fb hand weeding on 40 DAT, which was comparable with oxadiargyl loaded with zeolite and oxadiargyl loaded with biochar during both the year. Interpretation: It can be concluded that oxadiargyl loaded with zeolite was more efficient in controlling weeds coupled with maximum growth and productivity under the constrained situation of manual weeding. Key words: Biochar, Encapsulation, Herbicides, Rice, Water soluble polymer, Zeolite

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Field experiments were carried out during summer seasons of 2017 and 2018 to study the effect of preceding (Rice-Okra) crops herbicide residue on weed, growth, yield and economics of succeeding blackgram. Residual effect of butachlor at 1.25 kg/ha on 3 days after transplanting (DAT) fb hand weeding (HW) on 40 DAT imposed in the first season rice crop and followed by hand weeding (HW) twice at 20 and 40 days after sowing (DAS) (T6) in okra and blackgram significantly influenced the reduction of weed dry weight accumulation by 8.75 and 7.44 times in mainland and island ecosystem, respectively at 20 DAS. The same treatment recorded the highest weed control efficiency (WCE) of 88.6, 86.5 and 86.2, 80.7 % observed at 20 and 40 DAS under mainland and island ecosystem, respectively. Among, the weed control treatments, residual effect of butachlor at 1.25 kg/ha on 3 DAT fb HW on 40 DAT to rice and HW twice at 20 and 40 DAS (T6) to okra and blackgram has recorded 64.8 and 65.0% higher seed yield of blackgram under main and island ecosystem, respectively.