MSc

The research work entitled “Carbon dioxide evolution and yield responses in tomato
(Solanum lycopersicum L.) under organic nutrition” was conducted at College of Agriculture,
Vellayani during 2020 to 2022 with the objectives, to assess the carbon dioxide (CO2) evolution
from different organic sources and to evaluate the response of tomato to CO2 evolved under
organic nutrition. The study was conducted as two experiments, i) laboratory incubation and
ii) field experiment in trenches (elevated CO2) and under open field condition (ambient CO2).
The incubation experiment was carried out in Department of Agronomy, College of
Agriculture, Vellayani during January to March 2022 in Completely Randomized Design
(CRD) with twelve treatments in three replications. The treatments included were T1 : farmyard
manure (FYM), T2 : vermicompost, T3 : poultry manure, T4 : glyricidia leaves, T5 : coir pith
compost, T6 : goat manure, T7 : groundnut cake, T8 : neem cake, T9 : rice husk biochar, T10 :
rice straw, T11 : chemical fertilizer (3:1.6:1 ratio of N, P2O5, K2O respectively) and T12 : soil.
The data recorded were subjected to statistical analysis using GRAPES software.
Characterisation of the organic manures revealed that groundnut cake had superior N, P
and K contents and rice straw had the lowest contents. The narrowest C : N ratio (11.63:1) was
recorded in FYM and the widest, in rice straw (90.90:1) and rice husk biochar (68.25:1).
Microbial counts were significantly higher in poultry manure and glyricidia leaves and lower
in coir pith compost (bacteria) and rice husk biochar (fungi and actinomycetes).
Assessment of CO2 evolution showed a gradual increase in the initial stages with the
peak at the eighth week of incubation, and later,declined. The highest evolution (344.43 mg of
CO2 100 g-1
soil) was recorded in poultry manure treatment followed by glyricidia leaves and
significantly lower in chemical fertilizer and soil alone. Carbon dioxide evolution from the
media declined in the order, poultry manure > glyricidia leaves > rice straw > vermicompost >
goat manure > FYM > groundnut cake > coir pith compost > neem cake > rice husk biochar >
soil alone > chemical fertilizer. The release from organic sources was 14.40 to 47.30 per cent
more than that from chemical fertilizers and the highest was from poultry manure, 40.90 per
cent higher than from soil. The C degradation rate constant (0.062) was the highest in rice husk
biochar and the lowest in vermicompost (0.031).
The field experiment was laid out in CRD with six treatments replicated thrice during
November 2021 to March 2022 at the Instructional Farm, College of Agriculture, Vellayani.
The treatments comprised T1: FYM, T2: vermicompost, T3 : poultry manure, T4 : FYM +
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glyricidia leaves, T5 : vermicompost + poultry manure and T6 : integrated nutrient management
(INM). Tomato variety Manuprabha was raised at 60 cm x 60 cm spacing in the open and in
trenches. The NPK recommendation followed was 75:40:25 kg ha-1
and all cultural practices
followed were as per the package recommendations (KAU, 2016). The data recorded were
subjected to statistical analysis using GRAPES software and the treatments with no values were
excluded from statistical analysis.
In the open condition, plants were taller with superior number of branches, leaf area and
rooting depth and the highest photosynthetic rate in INM (T6) and the lowest in the combination
of vermicompost + poultry manure (T5). Flowering was early in INM (26.7 days) with more
number of fruits per plant (32.3), fruit weight (63.49 g) and fruit yield (2215 g plant
-1
). Among
the organic sources, FYM was found to be superior. Fruits contributed maximum (73.46 – 84.18
%) to total biomass. Quality attributes viz., sucrose, ascorbic acid and lycopene content were
significantly the highest in INM and the lowest in T5, whereas, catalase activity and nutrient
uptake were significantly higher in T5 treatment.
Post experiment soil analysis elicited non significant variations in soil pH, but organic
C was significantly the highest in FYM treatment . Available NPK status and microbial counts
revealed the high fertility status in vermicompost + poultry manure application. Carbon dioxide
evolution increased up to the 4
th and 5th week and decreased thereafter. The total CO2 release
was the highest in T5 (37,124 mg kg-1
soil) and the least in T1 (35,004 mg kg-1
soil). The trend
in CO2 release was T5>T4>T3>T6>T2>T1. Integrated nutrient management was found to be the
most profitable practice with a net return of ₹ 9396.82 per 40 m2
and B:C of 3.15 ratio.
Growth attributes viz., plant height and number of branches were significantly higher in
the treatment FYM + glyricidia leaves in trenches, while leaf area and root parameters were
higher in INM, on par with FYM + glyricidia leaves and sole application of FYM. Chlorophyll
content and photosynthetic rate recorded were the highest in INM.
Tomato plants in trenches showed poor fruit set and yields. Among the nutrient
management treatments, flowering was the earliest in sole FYM application and INM (31.3 and
31.7 days respectively). Stigma protrusion and severe flower drop caused poor fruit set in
trenches and hence hand pollination was carried out. However, the treatments T3, T4 and T5
failed to set fruits. The average fruit numbers recorded were 2.7 in T1, 1.7 in T2 and 2.00 in T6.
The largest fruits (12.85 g) and per plant yield (63.03 g) were recorded in T1. Vegetative
biomass contributed the maximum (85.68 – 100 %) to total biomass. Among the treatments,
INM recorded superior fruit quality and plant nutrient uptake. Soil analysis after the experiment
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revealed significantly higher organic C in FYM application and combination of vermicompost
and poultry manure, higher soil NPK status and microbial population.
The total CO2 release was the highest in vermicompost + poultry manure treatment
(71,247 mg kg-1
soil) and the lowest in FYM (60,895 mg kg-1
soil). The trend in CO2 release
was T5>T4>T3>T6>T2>T1. Air and soil temperatures were comparatively higher in T5 and
relative humidity was 100 per cent in all treatments throughout the experiment. Economic
analysis revealed negative net returns and very negligible B:C ratios.
Comparing the effect of nutrient sources on tomato grown in open field and elevated
CO2 condition (t test), it was unveiled that the tomato plants grown in trenches recorded taller
plants and higher leaf area and improved physiological attributes except stomatal conductance.
Fruit and vegetative biomass were the major drivers for the total biomass production in open
and trenches respectively. Fruit set and yield were higher in open but, quality attributes were
higher in fruits set in trenches than in open.
Based on the results of the study it could be concluded that addition of organic sources
in soil increased the CO2 evolution and it was the highest from poultry manure. Carbon
degradation declined in the order, FYM > vermicompost > poultry manure > soil alone > coir
pith compost > goat manure > rice straw > glyricidia leaves > neem cake > chemical fertilizer
> groundnut cake > rice husk biochar. In the open, the influence of the nutrient sources was
more prominent and high economic yields in tomato were realized in INM (75:40:25 kg NPK
ha-1
along with FYM @ 20 t ha-1
). Among the organic nutrition treatments, T1, FYM (@ 2.65 t
ha-1 along with alternative application of vermicompost @ 1 t ha-1
and supernatant solution of
fermented neem cake @1 kg 10 L-1
at 10 days interval up to 2 MAP) was superior in terms of
yield and B:C ratio. In the trenches, CO2 evolution significantly influenced the vegetative
growth and fruit setting. Fruit setting was poor and yields were realized with artificial
pollination in FYM, vermicompost and INM, and the yield per plant was comparatively higher
in organic nutrient management with FYM.