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The study entitled “Carrier based slow release fertilizer formulations for
sustained nutrient release and enhanced crop production” was conducted at the
Department of Soil Science, College of Agriculture, Vellayani during the year 2022. In
this study slow release fertilizer formulations were prepared, characterized and
investigated for its nutrient release characteristics through leaching experiment with
soil column and incubation study. Based on the stability and sustained release of
nutrients throughout the leaching and incubation study, best formulations were selected
and evaluated. A pot culture experiment was conducted in a completely randomized
design replicated thrice using chilli variety Vellayani Athulya as test crop and
evaluated the effect of slow release fertilizer formulations on nutrient availability,
uptake, use efficiency, yield and quality of chilli.
Carrier based slow release fertilizer formulations containing major, secondary
and micro nutrients were prepared using compatible fertilizer sources (urea, rajphos,
muriate of potash, phosphogypsum, magnesium sulphate, zinc sulphate and borax),
carrier materials (zeolite, humic acid, charcoal, chitosan and nano zeolite) and
binding/stabilizing agent carboxy methyl cellulose (CMC). The slow release fertilizer
pellets prepared were, T1 - Fertilizer mix: Zeolite+ CMC (1:1), T2 - Fertilizer mix:
Zeolite+ CMC (1:0.5), T3 - Fertilizer mix: humic acid+ CMC (1:1), T4 - Fertilizer mix:
humic acid+ CMC (1:0.5), T5 - Fertilizer mix: charcoal+ CMC (1:1), T6 - Fertilizer
mix: charcoal+ CMC (1:0.5), T7 - Fertilizer mix: chitosan+ CMC (1:1), T8 - Fertilizer
mix: chitosan+ CMC (1:0.5), T9 - Fertilizer mix: nano zeolite+ CMC (1:1), T10-
Fertilizer mix: nano zeolite+ CMC (1:0.5). The pellets prepared were found to be
stable, disintegration time 9-13 hours, moisture 5.75- 8.68 %, pH 6.37- 6.90, EC
17.25- 23.17 dSm-1
, bulk density 0.5-0.58 Mg m-3
and weight 4.0- 4.5 g.
They contained 8.21 to 9.02 % nitrogen, 5.36 to 5.76 % phosphorus, 3.0 to
3.50% potassium, 5.40 to 5.68 % calcium, 2.01 to 2.86 % magnesium, 4.10 to
5.30 % sulphur , 1.2 to 1.6 % zinc and 0.17 to 0.23 % boron.
A soil column experiment was conducted for two weeks to study the nutrient
leaching and to confirm the slow release tendency of formulations. The results showed
a gradual increase in the release of nutrients from 2 to 14 days of leachate collected
from slow release formulations while, fertilizer mix alone showed increasing trend
initially and later decreased.
A laboratory incubation study was carried out to investigate the nutrient release
patterns of the formulations after addition to soil. The results revealed that the pH of
soil remained acidic (5.30- 6.17) throughout the incubation period and the EC was
found to be increasing from 0.11- 1.45 dSm-1
. The release of nutrients in soil was
found to be increasing gradually from 0 to 90 days of incubation with maximum
concentration was observed on 90th day for all the nutrients.
Based on the stability of pellets and the release of nutrients throughout the
leaching and incubation experiment three promising formulations were selected for the
pot culture experiment. They were, T2 (FM: Z+CMC 1:0.5), T4 (FM:HA+CMC 1:0.5)
and T5 (FM: CC+CMC 1:1) . The treatments of pot culture experiment were T1 -100%
RDF as SRF 1 (FM: Z+ CMC -1:0.5) applied as basal,T2 -100% RDF as SRF 1 (FM:
Z+ CMC -1:0.5) applied in two splits (basal & 1 MAP), T3 -75% RDF as SRF 1 (FM:
Z+ CMC -1:0.5) applied as basal, T4 -75% RDF as SRF 1 (FM: Z+ CMC -1:0.5) applied
in two splits (basal & 1 MAP), T5 -100% RDF as SRF 2 (FM: HA+ CMC -1:0.5)
appliedas basal, T6 -100% RDF as SRF 2 (FM: HA+ CMC -1:0.5) applied in two splits
(basal & 1 MAP), T7-75% RDF as SRF 2 (FM: HA+ CMC -1:0.5) applied as basal,
T8 -75% RDF as SRF 2 (FM: HA+ CMC -1:0.5) applied in two splits (basal & 1 MAP),
T9-100%
RDF as SRF 3 (FM: CHAR+ CMC -1:1) applied as basal, T10-100% RDF as SRF 3
(FM: CHAR+ CMC -1:1) applied in two splits (basal & 1 MAP), T11-75% RDF as SRF
3 (FM: CHAR+ CMC -1:1) applied as basal, T12-75% RDF as SRF 3 (FM: CHAR+
CMC -1:1) applied in two splits (basal & 1 MAP), T13-Soil test based POP
recommendation, T14- Control (No fertilizers).
The analysis of post harvest soil showed the highest content of available N
(320.8 kgha-1
), P (87.15 kgha-1
), K (214.3 kgha-1
), Ca (351.1 mg kg-1
), Mg (106.5 mg
kg-1
), S (9.32 mg kg-1
), Zn (4.25 mg kg-1
) and B (0.46 mg kg-1
) in T8 receiving 75%
RDF as SRF 2 (FM: HA+ CMC -1:0.5) applied in two splits (basal & 1 MAP).
With regard to nutrient content and uptake, the treatment T8 registered the highest
value. The growth and yield parameters like plant height (56.52 cm), number of
branches per plant (9.5), number of fruits per plant (56.70), fruit length (13.44 cm), fruit
girth (6.89 cm), fruit weight (11.03), fruit yield (581.2g plant -1
) and total dry matter
production (89.07 g) were found to be the highest in T8. Quality parameters of chilli
such as ascorbic acid and capsaicin content were also found to be the highest in T8.The
fertilizer use efficiency, agronomic efficiency, apparent recovery of major nutrients and
partial factor productivity were found to be the highest recorded in treatment T8.The
highest B:C ratio of 2.41 was recorded by treatment T8.
Slow release fertilizer formulations containing macro and micro nutrients can be
prepared using compatible fertilizer materials (urea, rajphos, MOP, phosphogypsum,
magnesium sulphate, zinc sulphate and borax), carrier agents(zeolite, humic acid,
charcoal, chitosan and nanozeolite) and binding agent (CMC). The slow release
fertilizer pellets were found to be superior with respect to stability, disintegration time,
nutrient content and release of nutrients. From the results it can be concluded that the
slow release fertilizer formulations containing fertilizer mix: humic acid+ CMC in the
ratio of 1:0.5 applied at 75% RDF in two splits as basal & 1 MAP was able to
significantly increase the yield, uptake of nutrients, NUE, B:C ratio and quality of
chilli