nutrient needs for yield potentiality of crop plants

1. Determination of Nutrient Needs
for Yield Potentiality of Crop Plants
Preeetam Kumar
Deptt. of Agronomy
CCSHAU Hisar

2. Nutrient
Essentiality of Elements in Plant Nutrition
A mineral element is considered essential to plant growth and
development if the element is involved in plant metabolic functions and
the plant cannot complete its life cycle without the element. Usually the
plant exhibits a visual symptom indicating a deficiency in a specific
nutrient, which normally can be corrected or prevented by supplying the
nutrient. Terms commonly used to describe levels of nutrients in plants:
• Deficient: When the concentration of an essential element is low enough
to limit yield severely and distinct deficiency symptoms are visible.
Extreme deficiencies can result in plant death. With moderate or slight
deficiencies, symptoms may not be visible, but yields will still be reduced
• Sufficient: The nutrient concentration range in which added nutrient will
not increase yield but can increase nutrient concentration. The
term luxury consumption is often used to describe nutrient absorption by
the plant that does not influence yield.

3. Forms of Uptake of Nutrients
Nutrient Chemical Symbol
Principal forms for
uptake
Carbon C CO2
Hydrogen H H2O
Oxygen O H2O, O2
Nitrogen N NH+4, NO-3
Phosphorus P H2PO-4, HPO2-4
Potassium K K+
Calcium Ca Ca2+
Magnesium Mg Mg2+
Sulfur S SO2-4, SO2
Iron Fe Fe2+, Fe3+
Manganese Mn Mn2+
Boron B H3BO3
Zinc Zn Zn2+
Copper Cu Cu2+
Molybdenum Mo MoO2-4
Chlorine Cl Cl-
Plant Nutrient Average
Concentration*
H 6.0%
O 45.0%
C 45.0%
N 1.5%
K 1.0%
Ca 0.5%
Mg 0.2%
P 0.1%
S 0.1%
Cl 100 ppm
(0.01%)
Fe 100 ppm
B 20 ppm
Mn 50 ppm
Zn 20 ppm
Cu 6 ppm
Mo 0.1 ppm

5. Determination
• To achieve their potential yield, crop nutrient
requirements cannot be met by soil supply alone.
• Yield potential of crop plants therefore, can be
achieved by external supply of nutrients through
organic and inorganic fertilizers.
• The soil contribution is estimated by soil tests.
Although soil testing is generally accepted as a
workable practice, there are some differences in
interpreting the tests. This results in radically
different fertilizer recommendations to the
farmers.

6. There are three major concepts for
making fertilizer recommendations:
Maintenance
Cation saturation ratio
Sufficiency level

7. • Maintenance concept implies that whatever may be the
soil supplying capacity, a quantity of nutrient has to be
applied to replace that amount removed by the crop.
Even though the soil supplying capacity of a given
nutrient is adequate for top yields, still fertilizers are
recommended based on the maintenance concept.
• As per the cation ratio concept, a soil is considered as
an ideal one with the following distribution of
exchangeable cations: 65 per cent Ca, 10 per cent Mg, 5
per cent K and 20 per cent H so as to have ratios of Ca:
Mg as 6.5: 1; Ca: K as 13: 1, and Mg: K as 2 : 1.
Fertilizers are recommended to maintain this ratio.
• In sufficiency level concept, crop response to applied
nutrients is considered.

8. Blanket recommendation
• Based on the fertilizer experiments conducted in
different regions with improved varieties,
fertilizer dose is recommended for each
environment.
• This approach does not consider soil
contribution.
• However, it is suitable for recommendation of
nitrogen since residual effect of fertilizer N
applied to previous crop is negligible and soils are
generally low in N content.

9. Nutrient Deficiency System
Careful inspection of the growing plant can help identify a specific nutrient
stress. if a plant is lacking in a particular nutrient, characteristic symptoms
may appear. Deficiency of a nutrient does not directly produce symptoms.
Rather, the normal plant processes are thrown out of balance, with an
accumulation of certain intermediate organic compounds and a shortage of
others. This leads to the abnormal conditions recognized as symptoms.
Visual evaluation of nutrient stress should be used only as a supplement to
other diagnostic techniques (i.e., soil and plant analysis). Nutrient
deficiency symptoms may be classified as follows:
• Complete crop failure at the seedling stage.
• Severe stunting of plants.
• Specific leaf symptoms appearing at varying times during the season.
• Internal abnormalities such as clogged conductive tissues.
• Delayed or abnormal maturity.
• Obvious yield differences, with or without leaf symptoms.
• Poor quality of crops, including differences in protein, oil, or starch content,
and storage quality.
• Yield differences detected only by careful experimental work.

12. Hidden Hunger
• Hidden hunger refers to a situation in which a crop
needs more of a given nutrient yet has shown no
deficiency symptoms. The nutrient content is above
the deficiency symptom zone but still considerably
needed for optimum crop production. With most
nutrients on most crops, significant responses can be
obtained even though no recognizable symptoms
have appeared.

14. Soil Test Crop Response (STCR)
Approach
• This approach takes into account the soil contribution and yield
level for recommending fertilizer dose for a particular crop.
• This approach is also called as rationalized fertilizer prescription or
prescription based fertilizer recommendations.
• It is specific to a given type of soil, crop and climatic situation.
• The requirement of nutrients is different for different crops.
• The efficiency of soil available nutrients and those added through
fertilizers is also different for different type of soils under a
particular set of climatic conditions.
• Therefore, following three basic parameters are worked out for the
specific crop and area for the development of prescription based
fertilizer recommendations:

15. After calculating these three basic parameters from the yield and uptake data
from the well conducted test crop experiment, these basic parameters, in turn,
are transformed into workable fertilizer adjust equations as below:

16. Total Plant Analysis
• In this process whole plant is dried, grind, nutrient analysis is
done by various laboratory tests. Precise results are possible
only when carefully selected plant material is submitted for
analysis. Accurate sampling requires that definite parts of a
plant be selected at certain stages of plant development.
Plant Tissue test, Biological test are also
helpful in analysing of nutreient requirement.

18. Precision tools
Global Information System (GIS)
• GIS technology can be used to prepare maps that
show the variability of specific nutrient
parameters within certain areas of land, which
helps manage variable-rate applications. A GIS
can compile the data from soils analysis and crop
yield to predict the nutrient/lime requirement of
a specific area. Using GPS coordinates, GIS maps
can be very useful in determining the variability
of any farmer’s field without even leaving the
office. GIS maps are generally prepared by the
remote sensing industry.

20. • Ground-based active optical sensors can measure plant
biomass and give readings in the form of Normalized
Difference Vegetative Index (NDVI). The development
of an algorithm is required to use these sensors. They
have been successfully used in wheat and corn for yield
prediction and in real-time N rate application.
University researchers with access to at least three
years of data can develop the necessary algorithms.
• Satellite imagery is another tool that uses NDVI data to
manage nitrogen (N) requirements, but it has the
disadvantage that images cannot be obtained during
cloudy weather. Its precision is inferior to ground-
based active optical sensors.

22. Information about the field can be gathered by using sampling
techniques, or with various types of sensors. Use of sensors is very
common these days, but there is some information — such as
nutrient analysis for pre-planting fertilizer application — that is best
determined by soil sampling. However, active optical sensor and
tissue sampling could be used for in-season nutrient applications.
On a commercial scale, sensors for the following applications are
readily available:
• Real-time ground-based active optical sensors for in-season
applications, remote imagery, unmanned avionics systems (UAV),
and satellite images
• Yield monitors
• Soil electrical conductivity sensors
• Sensors for measuring soil compaction
• Real-time soil pH sensors

23. Crop Sensor

24. Variable-rate controllers
• Variable-rate controllers are available for need-basis input
application. All kinds of fertilizers (liquid, granular, etc.)
could be varied depending on crop need. Existing
equipment can be modified for site-specific input
applications. Variable-rate equipment could range from a
full-sized commercial fertilizer applicator to a personal
seeder. Most controller consoles have compatibility with
many input/planting application devices, but checking with
the manufacturer to determine which one will work best
with your situation is a wise choice. The data-controlling
device could be more like a small computer. Most
companies have trained staff to help growers in the
selection of appropriate tools for site-specific farming.

27. Response Equation
• Field experiments are conducted with different levels of
fertilizers. The yield responses to different levels of
fertilizers are fitted into a mathematical equation based
on the shape of the curve. From the equation, economic
optimum dose is calculated and recommended to the
farmer. Curve Fitting. Generally, the response to
fertilizers is quadratic i.e. yield increases at increasing
rate with increase in fertilizer dose upto a certain level
and at a decreasing rate with subsequent doses of
fertilizers. At a particular level, yield approaches a
plateau and further increase in fertilizer dose decreases
the yield.

29. • From Fig. above, it can be seen that even with no
fertilizer application, one t/ha of grain yield can be
obtained due to inherent soil fertility. There is linear
increase in yield upto 60 kg N/ha (from A to B).
Subsequently, the response line is curvilinear (from B
to C) i.e. for every increase in fertilizer dose, the yield
increased at a decreasing rate.
• Beyond 100 kg N/ha, the grain yield does not increase
with increase in fertilizers which is called as plateau (C
to D). Further increase in fertilizer dose beyond 140 kg
N/ha, yield decreases and is considered as toxic level.

30. • This curve can be expressed as a mathematical equation.
Y= a + bN + cN2
Where
 Y is grain yield (kg/ha),
 N, nitrogen dose (kg/ha) and
 a, b and c are constants.
 Constant a is known as intercept which indicates the yield level
without fertilizers.
 Constant b, otherwise known as slope, provides the response rate (kg
grain obtained per kg N applied).
 Constant c represents the curvature of the response line which
indirectly indicates the adverse effect of excess dose of nitrogen.
Generally, constant c has a negative sign.
• The drawbacks in the responses equation approach are:
1. soil contribution is not considered,
2. the level of production, which is low with the farmer, is not taken
into account, and
3. response equations have to be different for each variety tested.

31. SPAD
• The Chlorophyll Meter SPAD-502Plus is an
instrument which measures the amount of
chlorophyll (an important factor for understanding
the nutritional condition of the plant) in a plant leaf,
and displays the results as SPAD values*1.
Measurements can be taken instantly on site without
the need to cut off leaf samples by simply projecting
light through a leaf, and can be used for agricultural
products such as rice, corn, wheat, cotton, and other
fruits and vegetables as well as ornamental or foliage
plants.

33. Green Seeker
• GreenSeeker® optical sensor technology enables you to
measure, in real time, a crop’s variability, and variably apply
the “prescribed” fertiliser or chemical requirements.
GreenSeeker® also predicts yield potential for the crop
using the agronomic vegetative index (NDVI).
• GreenSeeker® permits you to have better control of input
use, allowing you to apply the right amount in the right
place at the right time – improving your yields, decreasing
your nitrogen cost and increasing your bottom line!
• GreenSeeker® enables you to also collect data during
existing farming operations such as spraying, cultivation
and mowing.

34. Applications:
• In-season crop mapping for targeted agronomy
• Biomass and plant canopy measurements
• Variable Rate plant growth regulator (PGR)
• Variable Rate nitrogen
• Variable Rate insecticide (mapping grass grub and slug
pressure)
• Variable Rate fungicide
• Variable Rate desiccant
• Variable Rate herbicide
• Weed mapping

35. • The Trimble® GreenSeeker handheld crop sensor is an
affordable, easy-to-use measurement device that can
be used to assess the health – or vigour – of a pasture
or crop in order to make better nutrient management
decisions on your farm.
• The GreenSeeker handheld instantly takes a reading of
your crop’s health. Readings can be used to make non-
subjective decisions regarding the amount of fertiliser
to be applied to your crop, resulting in more efficient
use of fertiliser – a benefit to your bottom line and the
environment.

37. How it works:
• The sensor emits a brief burst of red and infrared light, and then
measures the amount of each type of light that is reflected back from
the plant.
• The sensor continues to sample the scanned area as long as the trigger
remains engaged
• The sensor displays the measurement in terms of an NDVI reading
(ranging from 0.00 to 0.99) on its LCD display screen
• The strength of the detected light is a direct indicator of the health of
the crop; the higher the reading the healthier the plant.
• Use the Connected Farm™ app on a smartphone or tablet to calculate
fertiliser application rates from crop readings taken with the
GreenSeeker handheld.

38. LCC
• The leaf color chart (LCC) is an innovative cost effective tool
for real-time or crop-need-based N management in Rice,
Maize and Wheat. LCC is a visual and subjective indicator of
plant nitrogen deficiency.It measures leaf color intensity that
is related to leaf N status. LCC is an ideal tool to optimize N
use in Rice/Maize/Wheat at high yield levels, irrespective of
the source of N applied, viz.,organic manure, biologically fixed
N, or chemical fertilizers. Thus, it is an eco-friendly tool in the
hands of farmers.

39. Indicator Plants

40. DRIS Approach
• Recently Diagnosis and Recommendation Integration
System (DRIS) approach is suggested for fertilizer
recommendation. In this approach, plant samples are
analyzed for nutrient content and they are expressed as
ratios of nutrients with others. Suitable ratios of
nutrients are established for higher yields from
experiments and plant samples collected from farmer's
fields. The nutrients whose ratios are not optimum for
high yields are supplemented by top dressing.
• This approach is generally suitable for long duration
crops, but it is being tested for short duration crops like
soybean, wheat etc.

41. Fluorimeter
• Fluorimeter laboratory instrument is, fluoresence pa
rameters used to measure: intensity and emission-
spectrum wavelength distribution of the light
spectrum excited then.
• Fluorimeter designed to measure the fluorescence
of chlorophyll plants.

43. Nutrient Management Based on
Previous Crop
• Crops of previous season are taken in account
for the fertilizer recommendations eg
• If previous crop is sorghum and next crop is
sunflower increase 25% N with respect to
normal recommendation.