This document discusses using growth potential (GP) as an index to estimate nitrogen requirements for turfgrass. GP is calculated using temperature data and assigns a numerical value from 0-1 to represent the effect of temperature on turfgrass growth. The document provides GP values for C4 turfgrass in Ahmedabad each month. It then estimates the nitrogen requirement in grams per square meter each month based on the GP values, and compares this to typical nitrogen application rates. The goal is to use GP to determine nitrogen needs more accurately based on temperature effects on growth, rather than relying solely on soil tests.

1. Using Turf Grass
Growth Potential to
estimate nitrogen
use
Yadvendra Shah
Assistant Superintendent,
Belvedere Golf and Country
Club Pvt. Ltd. Ahmedabad

2. Nitrogen
 Major Macro nutrient for plants
 Major component of Chlorophyll
 Component of Amino acids
 Component of energy transfer compounds
 Significant component of nucleic acid
 Limiting factor in crop productivity
 Strongest growth response of any mineral element
 Translocation within 10-24 hours of application
 Most abundantly available in the atmosphere ?

3. Nitrogen Cycle

4.  Deficiency :
 Slow growth
 Decreased density
 Weed encroachment
 Increased disease susceptibility
 Excess :
 Leaf burn
 Thatch accumulation
 Reduced root, rhizome and tiller growth
 Increase in operation costs
 Reduced stress tolerance
 Ground water contamination

5. Approach for estimating N
requirement for your Turf
1. Soil Tests
 Indicates concentration of nutrients
 High mobility of N makes the value volatile
 No established correlation between
analytical soil N and turf grass response
2. Plant tissue tests
 Accurate judgment of nutrient requirement
 Catch -22

6. Growth potential*
 An index which assigns a numerical value to the
effect of temperature on growth of turf Grass.
GP = e -0.5 (
𝒕
−
𝒕𝒐
𝒗𝒂𝒓 ) 2
GP = growth potential, on scale of 0 to 1
e = 2.718, a mathematical constant
t =average temperature for a location in degree Celsius
to = optimum temperature
var = adjusts the change in GP as temperature moves away from to ,
5.5 for C3 and 8.5 for C4 grasses
*Wendy Gelernter and Larry Stowell. Improved overseeding programs 1. the role of weather. Golf Course
Management, pages 108-113, March 2005

7. Temperature chart Ahmedabad
period 2000 to 20012 http://www.worldweatheronline.com/Ahmedabad-weather-
averages/Gujarat/IN.aspx

8. Growth Potential of C4 Turf grass in
Ahmedabad
period 2000 to 20012 http://www.worldweatheronline.com/Ahmedabad-weather-
averages/Gujarat/IN.aspx
0.43
0.61
0.92
0.99
0.92
0.98 0.98
0.96
0.98
0.96
0.78
0.54
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Growth Potential
Growth Potential

9. N required m-2 for Paspalum in
Ahmedabad
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
N g m-2
as per GP requirement
N g m-2
applied