Soil Organic Matter Impact on Extending Soil Water Availability in Crop Production

1. Presenters:
Seymour A. Webster, Ph.D.
Adrian Spence ,Ph.D.

2. INTRODUCTION
Regional and sub-regional climatology
Jamaica’s vulnerability and sensitivity to hydro-
meteorological conditions is a function of its location,
topography, size and geographical outlay.
Generally speaking, the climate in Jamaica is somewhat
similar to that of the Caribbean– wet summers and dry
winters
Socio-economic activities and every-day activities are to
a large extent determined by exogenous climatic
variability and to a lesser extent by endogenous factors,
which are themselves influenced by exogenous forces.

3. The strong influence of exogenous
climatic events are responsible
for the variability in climatology
Jamaica
 These events—ENSO—general
result in volatile and erratic
weather systems, which may have
devastating effects on climate-
sensitive sectors; such as:
 Agriculture and fisheries
 Tourism
 Water & natural environment
 Health and wellness sector
Historically, the rainy season in
Jamaica is characterized by a
bimodal distribution due to an
intervening drought in July (mid-
summer drought).
NAH moves
closer to
equator
Stronger trades
Low SST
Mid-lat fronts
NAH starts
Northward
migration
Weaker trades
SST begins to
increase
NAH
temporarily
retreats
Southward
‘Mid-
Summer
Drought’
NAH return
Northward
High SST
Easterly
waves
ITCZ North
Jamaica
Climatology (Bar graph – precip, line graph –temp)
Air Temp
follows the sun
Chen and Taylor,2008

4. SOCIO-ECONOMIC IMPACT OF DROUGHT
EVENTS ON JAMAICA
During the decade of the90s and from 2010 to 2015
Jamaica has experienced some of the worst droughts
in terms of intensity and socio-economic impact on
the agriculture sector.
In 1996 into 1998 losses due to drought was estimated
at US$ 8 M(Agriculture impacted the worst)
Between October 1999 to March 2000, crop losses due
to drought was estimated at US$ 6 Million.


5. In 2012/2013 the Jamaican economy was denied an
estimated 1.0 percent of GDP.
In 2014, an estimated 21900 hectares of crops—food,
ornamental, and pastures—at a value of 953.5 million,
were affected by the drought (Jamaica Information
Service, August 29, 2014).

6. Need for developing drought-Need for developing drought-
tolerant soilstolerant soils
Rainwater harvesting &
inventory
Irrigated VS rain-fed
dependent agriculture
75 to 80 per cent of harvested
or abstracted used in
agriculture
High consumptive use
FC is transient and has to be
replenished
FC variable with soil structure
and texture
Rainwater harvesting &
storage systems for
agriculture, developing at a
slow pace
Only 10 per cent of irrigable
cultivated lands is irrigated
Possibility of salt intrusion
Topography limiting factor
Production and productivity
largely dependent on
prevailing weather condition
Sector is vulnerable to the
impact of agricultural droughts
Food and nutrition insecurity

7. SPATIAL MAPPING OF MAJOR SOIL
ORDERS AND CROP SUITABILITY OF
JAMAICA
M is c e lla n e o u s
S o il O r d e r
H is t o s o l
I n c e p t is o l
V e r t is o l
M o llis o l
O x is o l
E n t is o l
U lt is o l
N
1 8 °
1 8 ° 3 0 '
7 8 ° 7 7 °
0 5 0
K i l o m e t r e s

8. PRACTICAL STRATEGIES FOR CSA
Monitoring systems and Early warning signs
Crop diversification
Protected agriculture
Increase use of irrigation
Drought-tolerant soil
 SOI and SOM
 Synthetic Soil Polymers

9. CHARACTERISTICS OF SOM
Globally, SOM contains ~4 x more carbon than is present in
all the world’s vegetation and 3 x more than the atmosphere.
SOM plays a critical role in global carbon balance – major
factor affecting global warming(greenhouse effect) Influences
the physical, chemical and biological properties of the soil
SOM is a complex and varied mixture of organic substances
Responsible for much of the CEC and WHC of surface soils
 Stabilization of soil aggregates
Contains large quantities of plant nutrients – esp. N.
Supplies energy and body building substances to many soil
microorganisms

10. Lehmann & Kleber, 2016

11. STABILIZATION OF SOI

12. SOM: LIFE-BLOOD OF MINERAL SOILS
Encourages aggregation and pore space
differentiation
Increases WHC & PAWC of soils
For every one per cent increase in SOM, PAW
increases by 0.44, 0.36, and 0.26 inch per foot soil
depth for : loam, silty clay-loam, and sandy soil,
respectively.
 Reduce frequency of irrigation– cost implication
Reduce soil erosion
Encourages proliferation of beneficial soil
microbes(soil health)

13. Relationship between water potential and water
availability to plants

14. WAY FORWARD
Education and training on sustaining and restoring
drought-tolerant soils
Increasing drought monitoring systems and early
warning signs
Encourage greater use of organic matter inputs
Improving carbon sequestration through smart land-
use practices
 Improve water harvesting systems
Soil conservation and watershed management

15. Thank You!