PhD

An investigative analysis was undertaken during 1993-96 to work out an
objective and effective technology for nutritional management of black pepper
based on cause and effect relationship. A critical and comparative evaluation of
the available methods in this connection, viz. critical level concept, DRIS concept
and management based on soil test data, soil analysis was envisaged.
Approved standard procedures m estimating soil available and plant
contents of nine elements, viz. N P K Ca Mg S Fe Zn and Mn and standard
statistical methods were used in the study. A total of 1200 plants aged 14 years
maintained at RARS, Ambalavayal were used as the test material in the study.
A non-genic variability in yield ranging from 0.16 to 13.8 kg plant-1 was
manifested by tile crop which indicated that variability shall be bridged upwards
through managerial techniques.
The range of available status of the elements in the soil analysis was very
high. The lowest range of 0.9 to 4.5 ppm and the highest range of 144 to 1324
ppm were recorded by Zn and Ca, respectively. Soil pH ranged from 4.3 to 6.8.
These were at the individual plant level. Foliar content as well as the range of the
elements were much less and did not exactly related to soil available contents.
Results also indicated that elements showed significant and specific interactions
among themselves which varied with the elements. The pattern and magnitude
of interactions at soil and plant level were different.


Evaluation of soil test data of the study against approved soil test 0 - 9
scale classification showed that rhizosphere environments belonged to medium
rich to very rich class and that it could not explain the yield variability and hence
could not be a reliable basis of nutritional management in fertile soil.
Examination of the foliar content of elements and their comparison with
critical levels and ranges fixed by De Waard (1969) and Nybe (1986) respectively,
showed that foliar content of all the elements in the study were above the critical
levels which suggested that the critical level concept cannot be an adequate
guiding principle in nutritional management of black pepper. It may be adequate
only in situations where any element becomes specifically critical. Its inadequacy
may also be due to the positive and negative interactions of elements in the plant
system as well as due to the fact that yield is the resultant of a process involving
several elements simultaneously. Negative relationship of P in the early stages
and yield level of 6.5 and <1 kg berries at 2.33 and 2.35 per cent level and similar
observations confirmed the above contention.
DRIS concept was found to be more adaptable to explain the yield
variability as it takes into account the content as well as interaction represented
by ratios of every element with the others of the high yielding plants and tries to
simulate them in low yielding plants. Results of the present study showed that by
employing the DRIS concept and nutrient ratios, the content of every element can
be identified at any time as absolutely deficient, relatively deficient, relatively
sufficient, relatively excess and absolutely excess. This classification enabled to
define the nature of recommendation as additive, deletive or ameliorative/
corrective. Testing of the classification of the population into discriminative low
and high - yielding sub-populations employing mean ± one SD showed that the
system may be perfect when the magnitude of yield limiting factors in the entire
range of low yield is the same. Possibility of variability in yield limiting factors

could be accommodated by sub-dividing the lower yield group into smaller groups
as was done in deciles in the study. The results appeared to show that the per plant
variability can be accommodated with reasonable accuracy in such a system of
micro level yield group identification and application of DRIS norms to them. The
unique advantage of the DRIS system to reach the maximum realizable yield
through progressive diagnosis based on progressive experimentation shall be
substituted by the decile classification proposed in the study to a very good extent.
Results of the present study showed that yield and quality factors are
largely independent of each other and both can be improved by integrating the
respective components even at the higher yield levels obtained in the present
study. Analysis of inter-correlation matrix among elements at soil and plant level
revealed the possibility of making specific recommendations to achieve
progressive yield increases by working out quantity, intensity and rate of release
characteristics. of elements in the soil in relation to absorption.
Results in the present study showed that scientifically speaking the captions
of DRIS indices or index values as " order of requirement" be modified as
"order of limiting influences" - the former part of which is relative to metabolic
deficiencies and the latter part to the metabolic excess.
Imbalance indices have to be viewed as qualitative and not quantitative
indices as they are relative, primarily based on the relative deficiencies and
excesses which in turn are dependent upon the relative contents and valencies of
the ions.
The results of the study also revealed that with progressive increase in
yield, causing .higher nutrient removal, will make the soil not only more deficient
but also increase the frequency of application of nutrients more.



The progressive increase in the number of limiting factors with yield
improvement caused by higher rate of removal calls for more frequent monitoring
and not treating the norm as static for a long period. The results of the experiment
have brought to light a graded pattern of nutritional management for black pepper.
The primary limiting factors were found to be high native content of Fe and
Mn which will have to be ameliorated. Secondly, at the low yield level the yield
is limited by a relative deficiency of Zn caused by high P calling for a temporary
skipping of P; supplemented with N and K which can take the yield up to
5 kg plant-1. Excess S through the incidental application of prophylactic sprays
of Bordeaux mixture and shortage of Ca and Mg appear to be the limiting factors
at the higher yield class. Amelioration of acidity by supplying Ca + Mg carbonate,
substitution of S containing fungicides and application of N and K shall
constitute the recommendation, beyond which P may have to be applied.