PhD

An investigation entitled “Vetiver based organic mediculture technologies for the sustainable development of watersheds” was carried out during 2016 to 2019 at the Instructional farm, College of Agriculture, Vellayani. The investigation comprised of three field experiments and one pot culture study. The objectives were to standardise nursery management practices for quality planting material production, develop vetiver based biological systems for soil and water conservation and to explore the phytoremediation potential of vetiver for waste water and degradable solid waste utilization. The vetiver variety “ODV-3”, turmeric variety “Varna”, cowpea variety “Bhagyalakshmi” and a local variety of greater galangal were used for the study.
The techniques for quality planting material production were standardised by testing planting materials (a1- slips; a2- clumps), planting systems (b1- planting strips; b2- shallow basins), rooting medium (c1- coirpith compost: soil: cowdung (2:1:1) + inoculation with Azospirillum and AM Fungi); c2- c1 + cowdung slurry at monthly interval) and moisture regimes (d1- irrigation at 8 mm CPE; d2- irrigation at 16 mm CPE) in a 24 factorial Randomised Block Design with three replications. Conclusions were drawn after two and four months of planting. Inoculation of vetiver clumps with biofertilizers and planting in shallow basins filled with enriched rooting medium and application of cowdung slurry at monthly interval with irrigation scheduling at 16 mm CPE resulted in the production of higher number of planting materials (10.67 tillers per plant) and the highest benefit cost ratio (2.83) after two months of planting. Considering the dual benefit of planting material production and root yield, inoculation of vetiver slips with biofertilizers and planting in polythene mulched trenches, filled with enriched rooting medium followed by application of cowdung slurry at monthly interval and irrigation scheduling at 8 mm CPE resulted in the highest net income (₹.5.84 lakhs ha-1) and benefit cost ratio (2.96) after four months of planting.
The study on “Vetiver based alley cropping systems for soil and water conservation” was undertaken in 32 factorial Randomised Block Design with three replications.
Combinations of vetiver vegetative barriers were developed in three different planting geometries, i.e., a1- normal row planting (50 cm x 50 cm), a2- paired row planting (25/75 cm x 50 cm); a3- high density planting (25/75 cm x 25 cm) with three different sequential intercropping systems, i.e., b1- turmeric- cowpea- turmeric, b2- greater galangal and b3- control (without intercropping). High density planting of vetiver followed by continuous alley cropping of greater galangal (a3b2) resulted in the highest vetiver equivalent yield (14.44 t ha-1), net income (₹.4.05 lakhs ha-1) and benefit cost ratio (2.27). Substantial reduction in runoff (95 %), soil loss (166 %) and nutrient erosion (76 %) could be achieved through a3b2 within a period of 18 months, extending from June 2017 to December 2018. Considerable improvement in soil health with respect to physical properties of soil, viz., bulk density (33 %), porosity (28 %), water holding capacity (47 %) and infiltration rate (72 %) and build-up of soil organic carbon (43 %) were also observed in a3b2 compared to initial soil status.
To develop vetiver systems for waste water utilization in agriculture, an experiment was laid out in Completely Randomised Block Design with seven types of waste water in three replications. The treatments were, a1- waste water from coconut husk retting yards, a2- kitchen waste water, a3- waste water from fish market, a4- coirpith leachate, a5-sewage water, a6- Vellayani lake water and a7- nutrient solution. Vetiver was proved as a good phytoremediator with respect to decontamination and water purification properties (nutrient and heavy metal uptake). In general, the morphological characters (number of leaves and tillers) and root characters (root weight, spread, volume and drymatter) were significantly improved by growing vetiver in fish-waste water.
To explore the phytoremediation potential of vetiver for degradable solid waste utilization, a study was conducted in 4 x 2 x 2 factorial Randomised Block Design with three replications. Four ratios of degradable land fill materials (sewage sludge) and virgin soil (a1- 1:0; a2- 1:1; a3- 1:3; a4- 1:5), two crop establishment techniques (nursery grown rooted slips with enriched rooting medium (b1) and without enriched rooting medium (b2)); foliar nutrition (c1-sequential application of cow‟s urine, vermiwash and fermented plant juice; c2- sequential application of NPK fertilizer grade of 19:19:19, KNO3 and Ca(NO3)2 at monthly interval) were tested in this study. It could be concluded that, production of vetiver slips inoculated with Azospirillum and AM Fungi in enriched rooting medium and transplanting in the main
field with sewage sludge and virgin soil (1:5) followed by sequential application of foliar fertilizers @ 0.50 per cent (19:19:19, KNO3 and Ca(NO3)2 ) resulted in the highest root yield (4.11 t ha-1), net income (₹.1.01 lakhs ha-1) and benefit cost ratio (1.97).
Vetiver based mediculture technologies in relation to cost effective quality planting material production, alley cropping systems for soil and water conservation and phytoremediation techniques for waste water and biosolid utilization were developed for the sustainable development of watersheds.