MSc

An investigation entitled ‘Integrating weed management with nano nitrogen in okra (Abelmoschus esculentus (L.) Moench)’ was conducted at College of Agriculture, Vellayani during 2020-2022. The major objective was to formulate an integrated weed management strategy based on nitrogen management using nano nitrogen to reduce crop weed competition in okra.
The field experiment was undertaken at Instructional Farm, Vellayani during January 2022- April 2022, laid out in randomised block design with 2 x 6 treatments replicated thrice. The treatments included combinations of nitrogen management [n1 – 50 per cent recommended dose of nitrogen (RDN) as urea in soil (basal dose) + nano N as 0.2 per cent nanourea spray at 20 and 40 days after sowing (DAS), n2 – 100 per cent N as urea as per KAU POP] and weed management practices [w1- pre emergence (PE) application of pendimethalin at 1 kg ha-1, w2- PE application of oxyfluorfen at 0.15 kg ha-1, w3- PE application of pendimethalin at 1 kg ha-1 followed by (fb) hand weeding (HW) at 30 DAS, w4- PE application of oxyfluorfen at 0.15 kg ha-1 fb HW at 30 DAS, w5- HW at 15 and 30 DAS, w6- weedy check].
The results of the study indicated significant influence for nitrogen management on all the growth attributes of okra. Half of the nitrogen applied as urea in soil and remaining as foliar application of nanourea at 20 and 40 DAS (n1) resulted in taller plants (97.81 cm) with more number of branches (3.74) and leaves (15.23) compared to n2. Among the weed management practices, w5 produced superior growth attributes followed by w3 with taller plants (103.39 cm), higher leaf area index (1.061) and dry matter production per plant (112.13g) while w2 and weedy check had the lowest for all growth attributes. The treatment combination n1w5 resulted in significantly higher dry matter production (120.96 g per plant) which was on par with n1w3 (117.16 g per plant) at harvest.
The yield attributes of okra were significantly influenced by nitrogen management, weed management, and their interaction. However, no significant impact was observed on the days to 50 per cent flowering. Nitrogen management with nanourea (n1) resulted in more number of fruits per plant (26.51), fruit length (15.13 cm), fruit weight (18.31g), fruit yield per plant (614.28 g), haulm yield per plant (50.07



g) and harvest index (0.52) compared to n2. Hand weeding at 15 and 30 DAS (w5) produced more number of fruits per plant (32.43), fruit yield per plant (856.09 g), haulm yield per plant (56.13 g) followed by PE pendimethalin 1 kg ha-1 fb HW at 30 DAS (w3). Fruit yield per plant and harvest index were the lowest with PE oxyfluorfen at
0.15 kg ha-1 (w2). The treatment combination n1w5 resulted in higher number of fruits per plant (37.30), fruit yield (3920 kg ha-1) and haulm yield (2263 kg ha-1) followed by n1w3 (33.11, 3301 kg ha-1 and 2153 kg ha-1 respectively).
The experimental field exhibited the dominance of grasses as the primary weed flora, with broader diversity of broadleaf weeds; however, the diversity of sedges was limited to Cyperus rotundus L. The density of grass weeds was notably influenced by nitrogen management with nanourea application resulting in the lowest density of grass weeds at 45 DAS (8.89 m-2). The lowest dry weight of weeds at 45 DAS was observed in n1 (8.77 g m-2), compared to n2 (15.43 g m-2). Oxyfluorfen (w2 and w4) resulted in the lowest density of grasses and BLW at 15 DAS and w4 resulted in the lowest weed dry weight at 45 DAS (2.92 g m-2) which was on par with w3 (3.57 g m-2) and w5 (5.22 g m-2). At 30 and 45 DAS, n1 resulted in higher weed control efficiency (WCE) (60.92 and 63.76 % respectively) than n2 (54.95 and 49.42%, respectively). The treatment w2 exhibited the highest WCE at 15 DAS (94.08%) while at 45 DAS, w3 achieved the highest WCE (89.35%) and which was comparable with w5 (88.77). Yield reduction in okra due to uncontrolled weed growth in both n1 and n2 were estimated to be 69.88 and
70.36 per cent respectively.

Between the two practices, nitrogen management n1 resulted in higher chlorophyll content (2.15 mg g-1), crude fibre (33.36 %) on dry weight basis, ascorbic acid (22 mg 100g-1) on fresh weight basis, and agronomic efficiency (20.32 kg kg-1). However, the crude protein content was higher in n2. The highest dehydrogenase (165.0,
128.8 and 99.4 μg TPF g-1soil day-1 respectively) and urease enzyme activity in soil at 15, 30 and 45 DAS (78.05, 109.27 and 57.14 μg urea hydrolysed g-1soil 4h-1 respectively) were noticed in n1w5. Total NPK uptake of okra was higher in n1 (56.45, 17.72, 70.99 kg ha-1) than n2. The treatment combination n1w3 could be adjudged as the most economic weed management practice with a higher B:C ratio of 2.16.



Application of 50 per cent recommended dose of nitrogen as urea in soil + nano N as 0.2 per cent nanourea spray at 20 and 40 DAS (n1) along with two hand weeding at 15 and 30 DAS (w5) turned out to be the most effective practice with respect to growth, yield and nutrient uptake. Considering the economics, n1 with pre-emergence application of pendimethalin at 1 kg ha-1 followed by hand weeding at 30 DAS (w3) could be adjudged as the most effective nitrogen based integrated weed management practice in okra.