PhD

A comprehensive approach has to be adopted for efficient fertilizer use,
incorporating soil test, field research and economic evaluation of the results for
providing a scientific basis for the process of enhancing and sustaining food
production as well as soil productivity with minimum environmental degradation, it
needs more. Soil testing is one of the best scientific means for quick and reliable
determination of soil fertility status. Soil test crop response study in the field provides
soil test calibration between the level of soil nutrients as determined in the laboratory
and the crop response to fertilizers as observed in the field for predicting the fertilizer
requirements of the crop. In Kerala, many studies have been conducted to get a
fertilizer prescription equation for targeted yield in various crops like rice, banana etc.
A programme was formulated to investigate the nutrient interaction in
soil test crop response studies on cucumber (Cucumis sativus L.) in the laterite soils of
Kerala. In this, the field works were conducted as per the pattern of soil test crop
response correlation studies.
A gradient crop experiment was conducted in the experimental field of
AICRP on STCR using maize. The purpose is to create a fertility gradient in the field
by applying different doses of fertilizers. The area was divided into three strips and the
doses of nutrients were applied as per STCR pattern of fertilization for maize. The
crop was harvested and the plant samples were taken for analysis. The pre and post
experimental soil samples were analysed. It was found that fertility gradients were
developed in the field. Using the data on dry matter production in various strips, the
nutrient uptake was also determined.
A test crop experiment was designed in the same field where the
gradient crop was raised. There were 24 treatments with three control plots. The
treatments included four levels of nutrients and three levels of farm yard manure. The
crop, cucumber (Var.: AAUC-2), popularly known as salad cucumber, was raised and
managed as per package of practices of KAU. The soil samples were collected before,

at flowering and harvest stages during the experiment. The plant samples were
collected at flowering and harvesting stages. The total dry matter production and yield
were taken treatment wise at the harvest. The soil samples were analysed for various
chemical parameters.
The data on yield, uptake of nutrients, nutrient status, nutrient
requirement, quantity of farm yard manure applied were used for formulating the
fertilizer prescription equations for cucumber. Using these equations, the quantity of
fertilizers to be used to get a target of yield can be calculated if the available nutrient
status is known.
The equations thus developed were verified in farmers' field at four
locations; Pallikandam, Maraikkal, Ayiloor and Vithanassery. The fields were laid out
with five treatments and four replications. The treatments were (i) farmers' practice,
(ii) KAU package, (iii) soil testing laboratory method, (iv) STCR method with a target
of 30 t ha-I and (v) STCR method with a target of 35 t ha-I. The soil samples were
analysed before raising the crop and the quantities of fertilizers to be applied were
computed for various treatments. The plant and soil samples at flowering and harvest
stages were analysed for pH, EC, CEC, Organic Carbon, available N, P, K, Ca, Mg,
and micronutrients such as Fe, Mn, Cu and Zn. The total dry matter production and
yield were taken treatment wise at the harvest.
The data were used for- statistical analysis for assessmg direct and
indirect effect of nutrients on yield and nutrient interactions. A positive correlation was
observed between organic carbon' and soil parameters at flowering stage. At the
harvesting stage, there was a positive correlation was found between yield and major
nutrients. The interaction between available P in the soil and Nand K in the plant was
observed. The availability ofP in plant was negatively correlated with Fe in the soil.
The targeted yield equations for cucumber could produce the yields of
30 and 35 t ha-I from the verification experiments conducted at the different locations.
The B:C ratio also was higher in the STCR methods over the farmers' practices,

blanket recommendations and STL recommendations. The information generated in
the project will help in making the soil testing programme scientifically sound in terms
of achieving predicted yields, maintaining soil fertility and helping the extension
agencies in ensuring balanced fertilizer use according to the soil fertility status and
crop requirement.