MSc

An exploratory research work titled "Developing compositional nutrient diagnostic
norms for coconut (Cocos nucifera L.) in Southern Laterites of Kerala" was performed
to develop compositional nutrient diagnosis norms for identifying nutrient imbalance
in coconut trees of the west coast tall variety. The fundamental objective of the research
is to establish CND norms for coconut and evaluate nutrient imbalance in southern
laterite soils of Kerala (AEU 8). The research was conducted in two parts. The first part
involves collection of soil and plant samples along with assessment of nutrient content
in coconut leaves and soil. The second part focused on the development of CND norms.
A preliminary survey was conducted in the panchayats of AEU 8, encompassing a
total of 24 panchayats, viz. Parassala, Karode, Chenkal, Kulathoor, Thirupuram,
Poovar,
Perumkadavila,
Kollayil,
Kunnathukal,
Athiyanoor,
Aryancode,
Kanjiramkulam, Kottukal, Vizhinjam, Venganoor, Pallichal, Vilappil, Malayinkeezh,
Maranalloor, Kalliyoor, Balaramapuram, Vilavoorkal, Kattakada and Karakulam. The
collection of representative samples from the index leaves of mature palm trees (WCT).
From January to March 2023, a total of 240 soil samples were gathered from specified
locations, with each sampling site providing samples from two different depths (0-15
and 15-30 cm) and 120 samples obtained from the index leaves of five selected plants
in each location.
Considering the chemical properties of the soil samples, the pH varied between
5.35 and 7.09 in the surface soil exhibiting an average value of 6.31 and that of
subsurface varied from 5.21 to 7.03. The recorded results for EC ranged from 0.01 to
0.98 dS m-1 for surface soil and from 0.01 to 0.95 dS m-1 for subsurface soil. In terms
of organic carbon content, the subsurface soil exhibited values ranging from 0.16 to
2.40 per cent, while the surface soil exhibited higher levels, varying between 0.12 and
2.71 per cent. The available nitrogen (N) ranges from 200.7 to 602.1 kg ha-1 in surface
and in subsurface soil N fluctuates between 163.1 and 526.9 kg ha-1. The availability
phosphorus (P) in the surface soil varies between 8.2 and 233.9 kg ha-1 and in
subsurface soil falls within the range of 4.11 to 148.4 kg ha-1. The available potassium
in the surface soil has an average value of 309.4 kg ha-1, with a range of availability
between 80.6 and 660.8 kg ha-1. In the case of subsurface soil, the available potassium
was in the range of 33.6 to 537.6 kg ha-1. The calcium content in the surface soil varies
from 130 to 580 mg kg-1 and in subsurface soil the Ca availability ranges between 110
and 530 mg kg-1. In the surface soil, Mg ranges from 12 to 150 mg kg-1 and in
subsurface soil Mg ranges from 6 to 144 mg kg-1. The S content in the surface soil
varies from 5.5 to 49.5 mg kg-1 and in subsurface soil S ranges from 4.0 to 44.0 mg kg
1
. The Fe content in the surface soil varies from 6.83 to 57.26 mg kg-1 and in subsurface
soil mean value obtained is 16.63 mg kg-1. As for Mn ranges from 7.93 to 33.52 mg
kg-1 in the surface soil and in subsurface soil Mn varies from 6.59 to 32.67 mg kg-1.
Zinc is found in the surface soil within the range of 0.94 to 18.37 mg kg-1 and in surface
soil varies between 0.94 and 18.37 mg kg-1 and in subsurface soil Zn ranges from 0.86
to 15.44 mg kg-1, with a mean value of 4.78 mg kg-1. In terms available Cu in subsurface
soil ranges between 1.05 and 8.65 mg kg-1. The available B varies between 0.048 and
2.05 mg kg-1 and in subsurface soil ranges from 0.016 to 1.78 mg kg-1.
The nutrient content of coconut leaves of AEU 8 was examined, the N content
ranged from 1.34 to 3.12 per cent and P varied between 0.12 and 0.25 per cent. The K
content varied from 0.12 to 2.12 per cent and the Ca content ranged from 0.12 to 1.64
per cent. Regarding Mg content indicated a variability from 0.01 to 0.4 per cent and
the range of S content in the samples varies from 0.54 to 0.77 per cent. Iron ranges
from 64 to 1087.2 mg kg-1 and Mn ranges from 56 to 688 mg kg-1. The Zn varies from
4 to 294.8 mg kg-1 and the Cu ranges from 20.4 to 90.8 mg kg-1. The B levels exhibit a
range of 0.8 to 120 mg kg-1. Additionally, the yield of coconut fluctuates between 34
and 118 nuts palm-1 year-1, with an average of 75.67 nuts palm-1 year-1.
The CND norms as per the recommendations of Parent and Dafir (1992), the
computed nutrient content in coconut leaves was converted to percentage, afterwards
calculated nutrient concentrations, residue value, simplex and row centered log ratio.
The database is divided into two sub-populations using the Cate-Nelson procedure,
based on ranked yield values. The cumulative variance ratio is the combination of
variance ratios at each iteration. The cumulative variance ratio function [FiC(VX)] has
been computed as a proportion of the total sum of variance ratios across all iterations.
The FiC(VX) for yield Y follows a cubic pattern, with the inflection point representing
the point at which the model changes concavity, as determined by the second
derivation. The yield cutoff value is calculated at inflection point. To classify a high
yield subpopulation, the highest yield cutoff value derived from nutrient expressions
can be selected. The maximum yield cut-off value was obtained for Mg, resulting in a
yield of 81.1 nuts palm-1 year-1. CND norms are determined by computing the means
and standard deviations of row-centered log ratios VX corresponding to various
nutrients found in high-yield groups, namely V∗N, ..,V∗Rd, as well as SD∗N, ..., SD∗Rd,
respectively. The computed CND norms are as follows: V*N= 3.03±0.20, V*P=
0.61±0.17, V*K= 1.96± 0.61, V*Ca= 2.11± 0.45, V*Mg= 0.81± 0.29, V*S= 1.66± 0.19,
V*Fe= -1.58± 0.55, V*Mn= -1.87± 0.46, V*Zn= -3.56± 0.53, V*Cu= -3.08± 0.26, V*B=
4.41± 1.03, and V*Rd= 6.71± 0.17. The CND indices (IX) have been computed using
VX, V*X, and SD*X. The CND indices may have positive or negative values. Nutrient
indices close to zero should provide the ideal nutrient balance. The negative value of
CND indices indicates deficiency of that particular nutrient, lower the value, greater
the deficiency.