Efficient nutrient recycling strategy through integrated nutrient management in hybrid napier within a coconut (Cocos nucifera)-based system

The present field experiment was conducted to investigate the impact of various combinations of organic inputs on the growth of fodder grass in a coconut [Cocos nucifera (L.)]-based mixed farming during 2013-17 at ICAR-Central Plantation Crops Research Institute, Regional Station, Kayamkulam, Kerala and refined in farmer's field during 2018-21. The experiment was conducted in randomized block design with seven treatments and three replications with one control [chemical fertilizer (CF) alone] and six organic recycling options with combination of a native strain of Azospirillum sp. [L8(3)] isolated from the coconut rhizosphere, [100% RDN through cow dung slurry (CDS), 100% RDN through coconut leaf vermicompost (CLVC), 100% RDN through CDS + CLVC (1:1), 100% RDN through CDS + CLVC (1:1) + Azospirillum sp., 75% RDN through CDS + CLVC (1:1) + Azospirillum sp. and 50% RDN through CDS + CLVC (1:1) +Azospirillum sp.]. Basal application of 15 tonnes of dried cow dung, 400 kg lime and 90:30:24 kg NPK/ha were supplied irrespective of the treatments. The plants supplied with 100% RDN through CF and CDS + CLVC + Azospirillum sp. recorded the higher yield during the first year, followed by a yield decline in subsequent years which may be due to the nitrogen-induced reduction in soil pH as evident from the soil analysis. The significantly higher fresh fodder yield (126.9 tonnes/ha/year), dry matter yield (22.7 tonnes/ha/year), neutral and acid detergent fibres, crude protein and plant nutrient uptake were recorded by plants supplied with 75% RDN through CDS + CLVC + Azospirillum sp. Technological refinement by adding additional lime (400 kg/ha) during second and third years resulted in 24.59% higher yield. This system of recycling resulted 50% reduction in external physical inputs during the first year and 90% reduction in subsequent two years.