MSc

A study entitled “Rhizosphere dynamics of thermochemical organic
fertiliser fortified with nitrogen biosources in amaranthus” was conducted from
December 2020 to August 2021 at the Department of Soil Science and Agricultural
Chemistry, College of Agriculture, Vellayani with the objectives of studying the
dynamics of physicochemical and biological soil health parameters of the
rhizosphere against root free soil consequent to the application of thermochemical
organic fertiliser fortified with various organic nitrogen sources with and without
arbuscular mycorrhizal fungi (AMF) and evaluation of its influence on the growth
and yield of amaranthus.
Characterization of farm yard manure (FYM), poultry manure (PM), neem cake
(NC), vermicompost (VC), coir pith compost (CPC), organic nano NPK (nano NPK), and
thermochemical organic fertiliser (TOF) were carried out. The pH of manures was slightly
acidic to neutral, and the EC was within safe ranges. TOF had the highest TOC. PM recorded
the highest N and nano NPK recorded significantly higher P and K. Zn, Cu and B were also
the highest in nano NPK. TOF had higher Ca, Mg, S, Fe, Mn. Heavy metals (Pb, Cd) were
below detectable limits.
A pot culture trial of Amaranthus (var. Arun) was done to study the dynamics
of the physicochemical and biological soil health parameters of the rhizosphere as
against root free soil. Potting mixture was prepared with soil, coir pith (CP) and TOF
fortified with nitrogen bio sources so as to provide 1 per cent nitrogen and also
fortified with organic nano NPK at 0.1 per cent N in the ratio 1:1:1 on volume basis.
TOF was fortified with different organic nitrogen sources for a pot culture study for
30 days in a CRD experiment. The pH of the growing media decreased slightly at
harvest, whereas EC increased. Carbon fractions and nitrogen fractions were highest
in TOF+PM +AMF while there was a general decrease in both the parameters in all
the treatments at the harvest stage compared to the initial. P, K, Ca, S, Zn, B content
were higher in TOF+NPK +AMF whereas Mg and Cu were higher in TOF+PM
+AMF. Fe and Mn remained significantly different at rhizosphere zone only. In all the
treatments rhizosphere soil observed lower soil nutrient content than the bulk soil.
Biological properties such as dehydrogenase activity, microbial biomass carbon,
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indole acetic acid, total organic acids were higher in TOF+PM +AMF. The shoot and
root nutrient contents of TOF+NPK+AMF were higher than other treatments.
TOF+NPK+AMF was also superior in number of primary branches, shoot weight and
shoot dry matter content. Plant height was higher in TOF+FYM+AMF whereas stem
girth was higher in TOF+NC. TOF+VC+AMF recorded highest root weight (104.07g
plant-1
), root dry weight (13.01plant-1
) whereas root volume (63.33cm3
), total root
length (31.66 cm) was highest with TOF+CPC+AMF.
Three best treatments from the pot culture study were subjected to field testing in
micro plots to evaluate the influence of the fortified TOF on the soil health and growth and
yield of amaranthus (var. Arun) for two seasons (C1, C2) in RBD. Field soil had strongly
acidic pH, safe EC, medium OC, low N, K, high P, inadequate Ca, Mg, S and B. After the
harvest of each crop, the soil pH progressively decreased whereas EC and OC increased. Soil
available nitrogen was higher in TOF+NPK+AMF@OPOP100 %. P, K, S, Fe, Cu and B
contents were highest in TOF+NPK+AMF@OPOP100 %. Soil available Ca and Mg was on
par with TOF+VC@OPOP100 % in C2. Mn and Zn in C2 was higher in
TOF+NPK+AMF@OPOP100 %. Plant shoot N, P, K, Ca, Mg, S and micronutrients were the
highest in TOF+NPK+AMF@OPOP100 %. At C2 shoot Ca was on par with
TOF+VC@OPOP100 %. Root N, P, K, Ca, Mg, S and micronutrients were highest in
TOF+NPK+AMF@OPOP100 %. TOF+NC+AMF@OPOP100 % recorded highest root N in C2.
TOF+VC@OPOP100 % recorded the highest earthworm number in C1 and C2. Micro
arthropod counts were the highest in TOF+NPK+AMF@OPOP100 %. Dehydrogenase activity
and microbial biomass carbon (MBC) of TOF+NPK+AMF@OPOP100 % in C1and C2 were
significantly higher than other treatments. B:C ratio was highest for
TOF+NPK+AMF@OPOP100 % (1.57).
TOF fortified with various nitrogen bio-sources enhanced soil organic carbon and
possessed comparable fertility value as conventional organic manures and is environmentally
safe since heavy metal content is below detectable levels. Fortification of thermochemical
organic fertilizer facilitated efficient root dynamic characters coupled with proliferation of
rhizospheric microorganisms, which favoured enhanced mineralisation of soil available
nutrients and root nutrient acquisition. TOF fortified with nano NPK is an effective and
efficient substitute for conventional organic manures and help in realising higher productivity
and profitability in amaranthus.