Yield maximization of rice varieties under varying fertility levels in northern Himalayas

A field experiment was conducted during kharif 2018 at CSKHPKV, Rice and Wheat Research Centre (RWRC), Malan with the objective of fine-tuning fertility levels for maximizing yield of rice varieties in Northern Himalayas. The experiment consisted of 5 main-plot treatments comprising different fertility levels {50% recommended dose of fertilizer (RDF), 100% RDF (90:40:40), 150% RDF, 50% RDF + Azolla and 100% RDF + Azolla} and 4 varieties as sub-plot treatments {Vivekdhan 65, HPR 2143, HPR 2720 (red rice) and AZ 6508 (hybrid)}. The soil of the experimental site was silty clay loam in texture, acidic in reaction, medium in available nitrogen, phosphorus and potassium. Azolla was applied @ 20–25 g m⁻² at 10 DAT, which was allowed to multiply in-situ for about 2–3 weeks and subsequently trampled twice. The increase in fertility level and Azolla application increased the growth, yield attributes and yield of rice. Application of Azolla increased the rice productivity significantly both at 50 and 100% RDF by 399 and 481 kg ha⁻¹, respectively. Application of 100% RDF + Azolla recorded productivity (5319 kg ha⁻¹) and profitability (INR 79,490 ha⁻¹) which was at par with productivity and profitability achieved with 150% RDF (5192 kg ha⁻¹, INR 75,738 ha⁻¹). Similarly, 50% RDF + Azolla recorded productivity and profitability which was at par with 100% RDF thus revealing a saving of 50% RDF with the use of Azolla. Hybrid ‘AZ 6508’ recorded maximum grain yield of 6924 kg ha⁻¹ followed by Vivekdhan 65 (4822 kg ha⁻¹), red rice ‘HPR 2720’ (3924 kg ha⁻¹) and HPR 2143 (3740 kg ha⁻¹). The maximum net return (INR 93,924 ha⁻¹) and benefit cost (BC) ratio (2.13) were recorded by the hybrid AZ 6508. Though the productivity of Vivekdhan 65 was more than red rice ‘HPR 2720’, but due to higher price of red rice it fetched more net return (INR 76,248 ha⁻¹) and B:C ratio (1.94). Interaction effect revealed that the application of 100% RDF + Azolla to the hybrid AZ 6508 produced grain yield of7430 kg ha⁻¹ with net return of INR 101,630 ha⁻¹ and BC ratio of 2.23. Thus, farmers of mid-hills of Himachal Pradesh can maximize the rice productivity by growing hybrid AZ 6508 and applying 100% RDF + Azolla @ 20–25 g m⁻² 10 DAT. Next to hybrid, red rice HPR 2720 is the most profitable choice.