What Soil Science can Offer, for a Society Demanding more Food with less Water and Energy, Reducing Environmental

Impacts, while our Climate is Changing ?

SIAGRO 2014

Sao Carlos, Brazil

November 20-22, 2014

Jan W Hopmans

• Nexus of Soil & Water Science in Society

- Food – Water – Land – Energy - Climate

• Opportunities for Soil Science

- Irrigation Water Management

- Root/Soil Interactions

- Nitrogen Management in Irrigated Soils

• Research Challenges

What will be covered ?

- for both agriculture & natural ecosystems,

- and mediates most of the life-sustaining interactions among land, surface water and the atmosphere

Soil & Human Health

Soils Sustain Life:

ADVOCATE

SOILS are integral toFOOD-WATER-ENERGY NEXUS

of global society, but varies regionally

WaterEnergy

Food

LAND USE &

CLIMATE CHANGE

Climate change will affect theseinter-relationships, while suitable land

available for agriculture is becoming limited

FACTS: Water for food Water for lifeA comprehensive Assessment of Water Management and Agriculture

(David Molden, Ed. IWMI, 2007)

Is there enough water to produce food for a growing population over the next 40 years?

It takes about 1L of water per calorie of food (daily dietary needs is about 2-3 m3/day, or 600-800 gallons/day;

Global agricultural crop production takes about 70% of developed freshwater, of which about 30% is groundwater;

Whereas currently about 15% of agriculture is irrigated, it produces about 45 % of global food production;

About 1/3 of irrigated land is salt-affected;

PEAK SOIL (data from World Resources Institute)

Annual expansion rate of new farm land is about 0.27 % / year;

Over the past 40 years, about 2 billion ha of soil (15% earths land surface and 30% of the world’s cropland) has been degraded and has become unproductive.

Between 1982-2007, close to 10 Mha of US ag land has been converted for development (1 ha/2 minutes), USDA

As more marginal land is turning into agricultural production, worlds agricultural acreage is running out

The Global Challenge

In past 50 years, population more than doubled, irrigated area doubled, and water withdrawals increased by about 250%.

(Wada and Bierkens, 2014)

(Burney et al, PNAS, 2010)

Global Food Production Challenges

From 1950-2000, global population doubled, while per capita food production increased by 25 % (green revolution).

Future population growth will require about doubling of food production in the coming 50 years, and must use less water per unit of output produced, otherwise it will require double the water requirements of today.

In part, because of dietary changes, and shift away from cereals towards live-stock/fish, and high-value crops

Historical Crop Production TrendsGrassini, Eskridge and Cassman (Nature communcations, 2013)

•Incredible achievement •Evidence of plateaus in world’s

most intensive cropping systems

(biophysical/photosynthetic

yield ceiling);

• Yield stagnation at low-yield

levels (lack of agricultural inputs,

infrastructure, & capital)

• These regions have highest

potential for yield intensification

(no need for cropland expansion)

Rethinking Agriculture

• Based on a 2500 cal/day diet water demand under business as usual will increase to approximately 13,000 km3 by 2050 (double of that of 2000 year)

Total Population of the Continents

• Current trends indicate that population growth is outpacing food production in many parts of the world, and in 64 of 105 developing countries;

Where might the water come from?Blue Water

• Increase water use efficiency of irrigated agricultural systems – but salinity impacts

• Increased use of more marginal quality water• Expand land area for irrigated agriculture:

Water scarcity is a major threat to agriculture and food security in developing countries .

(1/5 of world population faces physical water scarcity and 1/4 suffers from economic water scarcity).

Global Water Scarcity – Imbalance between fresh water demand and availability

When annual water supplies drop below 1,000 m3 per person, the population faces water scarcity (3,000 L/day);

Food for Thought Green Water• Rainfed agriculture occupies about 85% cropland, yet irrigation

provides 46% of the gross value of world’s agricultural production.

Green water: ~65%

GOAL: Doubling of food production with no significant increase in land area, water use or environmental degradation

SECOND GREEN REVOLUTION

• Increase of land & water productivity of rain-fed agricultural systems will be critical, producing more food per unit water (e.g. crop genetics)

A Bigger Rice Bowl(Economist, May 2014)

• Demand for rice is rising in Asia and Africa

• Rule of thumb: every additional 1 billion of people requires 100 million

ton of rice; Yet, rice yields are stabilizing/falling• Rice is among the largest water users in agriculture – • Now requires yield boosting for rainfed rice (drought and flood

resistant varieties)

Water ProductivityUnbelievably low, for yields < 3 t/ha for cereal crops (essential all in developing countries)

Evaporation losses

Significant water savings can be gained

Increase T/ET ratio

Relationship between water productivity and yield for cereal crops in tropical/temperate farming systems (Rockstrom et al., PNAS, 2007)

Impacts of Limited Water Supply for Crop Production can be partly mitigated using

Technological Solutions . . . .

• Agricultural Biotechnology (plant breeding & molecular genetics) – improved drought & salinity tolerance

• Water Resources Engineering (water transfers?)

• Irrigation Technologies and Improved Irrigation Scheduling

• Fresh water Generation (e.g. ,reverse osmosis)

• Improved soil, water management, and agronomic practices, including improved water use efficiency and conservation

FUTURE AGRICULTURE MUST BECOME

BOTH MORE PRODUCTIVE AND SUSTAINABLE

Requires better understanding of how plants take up water and nutrients, so we can do more with less;

Need to improve water use efficiencies, and nitrate

use efficiencies

Requires Innovative Soil Research,

in combination with plant science and engineering technologies

Conservation TillageCentral Valley, CA

No-till cotton and tomatoes

Reduced till & Direct Seeding

Reduces Energy Footprint

CASI, Jeff Mitchell , UC CE Specialist

Thermal Neutron CT - MNRC

Gadolinium control rods

Non-invasive Neutron Tomography

Nuclear Research Reactor

•Neutron beam

Plant’s Response to Differential Soil Water Content ( Moradi, Oswald, Menon, Carminati, Lehmann & Hopmans, Special Publication, SSSA)

Moradi et al. 2012, New Phytologist

Climate – Water – Food Nexus

Increasing atmospheric CO2 causes increasing earth surfacetemperatures, affecting food production and water availability

WaterClimate

Food

Estimated net impact of climate trends for 1980-2008 on crop yields by country, divided by the overall yield trend per year for the same period.

Climate Trends and Global Crop Production Since 1980(Lobell et all., 2011, Science)

Maps of 1980-2008 linear trends in temperature (A) and precipitation (B) For the growing season of the Predominant crops (maize, wheat, rice, and soybean).

Temperature trends

Precipitation trends

Yield Trends largely Determined by Temperature rather than Precipitation Trends

Climate change BrazilClimate Change and extreme events in Brazil (FBDS, 2012 – H. Silveira Pinto)

• Longer dry spells in eastern Amazon;• Reduction in precipitation;• Increase in frequency of daily and seasonal extremes of

temperature and rainfall;

Impacts: • Hydropower generation

• Agricultural economy is

expected to by most

vulnerable to climate change

(30% of Gross Domestic Product)

Agricultural impacts of climate change in Brazil

• If predicted temperature increases for 2050 would happen today, all main crops (soybeans, rice, corn, beans, cassava, sunflower, cotton, coffee) would lose around 15% of their production areas.

• Only sugar cane would

increase its potential

area for cultivation.

• Longer drought periods

can be partly compensated

for by supplemental irrigation

CALIFORNIA

• Largely (semi) arid climate• 12th largest economy in the world

• Grows 50% fruits and vegetables and is number 1 dairy state in the US • ~25 million acres agricultural lands (10 million ha)• 52% is pasture/rangeland and 37% is irrigated crop land (10 million acres or 4 million ha)

• Irrigated agriculture requires about 27 MAF (27 BCM) of developed water (surface plus groundwater)

• State with most endangered ecological communities in the US

• Significant climate warming is forecasted, which will negatively impact available water supplies and mandate change/regulate state-wide water management practices/policies.

Climate Change Impacts on CA Water Resources

• More rain than snow• Earlier snow melt • Higher probability of flooding

• Less reliable water supply from reservoirs in the Valley for irrigation

California Drought 2011-14• About 1 million acres

is expected to be

fallowed;

• 2013-14 water year

Is driest year on record

• Precipitation is about

1/3 of normal year

The Palmer Drought Severity Index was devised in 1965, to assess moisture

status comprehensively. It uses temperature and precipitation data to

calculate water supply and demand, incorporates soil moisture.

Continued expansion of tree crops/vines in CAAs water becomes less available

California groundwater depletion and nitrate concentration

Groundwater pumping increased from about 1/3 to 2/3 oftotal irrigation water use in CA

Gg N /yr

Sources and Sinks of Nitrate

Agriculture and EnergyAbout 10 calories of energy is required

to produce 1 calorie of edible food

(35 calories for beef production);

• Roughly about 50% of this required energy goes towards production of synthetic fertilizers and pesticides;

• Fertilizer manufacturing uses about 3-5 % of the world’s annual natural gas production, and is equivalent to 1-2 % of the world’s annual energy supply;

• Specifically, it takes nearly 1,000 m3 of natural gas to produce one ton of ammonia,

with annual fertilizer production

of 178 million tons)

Nitrate use efficiency by crops

• Typically, half or more of the applied nitrate fertilizer is not taken up by the crop;

• The rest ends up in the natural environment: soil – surface/groundwater – atmosphere

CHALLENGE: How would one monitor

nitrate leaching???

Efficient irrigation and fertigation practices

Across CaliforniaObjectives: •Develop water & nitrate measurement techniques

•Recommend guidelines for improved irrigation

and nitrate management practices

Wireless Sensor Networks

Instruments list and functions:

1. Tensiometers: measures soil matric potential, range: 850 - 0 mbar, individually-calibrated pressure transducers

2. Decagon 5TE sensors: measures soil water content, electrical conductivity, temperature

3. Decagon MPS-2 sensors: measures soil matric potentials, range -4000 mbar – 0

4. Neutron Probe: measures soil water content, large representative soil volume

5. Suction lysimeters : is used to collect soil solution for nitrate analysis

6. Equilibrium-Tension Lysimeters: measures drainage below the root zone and collect soil solution samples for nitrate analysis

Multiple sensors at various depths and locations for each treatment plot

40cm

200cm

140cm

A B

Leaching measurement: Tensiometers below

root zone – Darcy Flow

q

( )BA

ABBA z

HHKq

−− ∆

−−= θ

Improved DeepTensiometer

Enormous depth variation in soil texture/layering, soil water retention,with corresponding

unsaturated hydraulic conductivity functions

Darcy Flow approach

Soil hydraulic properties

Laboratory methods

e.g. multi-step outflow experiments

Modelling based on measured parameters

e.g. soil moisture monitoring

Russell Ranch Sustainable Agriculture Facility

Summer Winter Fallow Bell Bean Triticale

Photo: R. Ford Denison

Tomato/Corn

•3 replicates of each treatment

Two soil types:Rincon silty clay loamYolo silt loam

Treatments:Winter fallowTriticaleBell beans

Russell Ranch –Tomatoes

Daily leaching rates of water and nitrate in Bell Bean treatment

Tomato Cover Crop Corn Cover Crop

1st graph: Average water potential in soil profile (0 is soil saturation, the more negative the dryer the soil) 2nd graph: Soil water gradients (driving force for water movement) across a soil layer at 90-150 cm deep3rd graph: Soil nitrate concentrations measured in soil solution in the 90-150 cm soil layer4th graph: Daily vertical downward /upward fluxes of water (blue line on left Y axes) and nitrate (green line on the right axes). Negative fluxes are downward and positive fluxes are upward. Most of the leaching of water and nitrate seem to happen in the fall and early corn season.

Tomato Cover Crop Corn Cover Crop

Cumulative nitrate leaching in all three treatments Vertical downward leaching of nitrate (negative values) throughout the crop rotations. Triticale showed to be the most efficient in reducing the nitrate leaching below the root zone (150 cm deep). Note the difference in nitrate leaching rate during different seasons in different treatments. While nitrate continuously leached below the root zone of winter fallow in fall through corn season, it slowed down in the two cover crop treatments.

Citrus sites: Orange Cove and Strathmore, CA• Collecting water and nitrate movement data in the root zone and below the root zone to capture seasonal variations in leaching and following irrigation and fertigation events• Where the tree roots are taking up water? Excavating and imaging root distribution in depth and lateral distances from the trunk and irrigation sprinklers

Wireless Sensor Networks

•Results - Mandarin

•43

Summary Water and Nitrate Leaching/Monitoring

• Only relevant if deep surface is wet

• Deploy wireless sensor network at the field scale• Develop deep tensiometers for accurate

gradient measurements

•Still need in situ soil nitrate sensor

Tuli, A., J.-B. Wei, B. D. Shaw, and J.W. Hopmans. 2009. In situ monitoring of soil solution nitrate: Proof of concept. Soil Science Society Journal. 73(2). Doi: 10.2136/sssaj2008.0160 .

Required Research Needs to meet food security challenge

• Develop improved water and nutrient use efficiency methods for both rainfed and irrigated crop production systems;

Field Research:

• Development of soil sensors using new technologies (wireless, multi-functional, noninvasive, big data);

• Study impacts of soil environmental stresses (water, nutrients, salinity, temperature) for both rainfed and irrigated production systems.

Collaborate with plant & soil scientists, agronomists, climate scientists, hydrologists, and others

Changes in CA Water Use, Irrigated Area (by crop type), and Agricultural Income

0

200

400

600

800

1,000

1,200

1,400

1960 1972 1980 1985 1992 2000 2005

Year-2005 inflation adjusted dollars per acre foot applied

water

1 acrefoot ~ 1ML1 MAF ~ 1 BCM~1 km3

CA agriculture has shown to be innovative and flexible, and seek ways to increase income (yield) with less water :

Sustaining CA agriculture in an uncertain future, Pacific Institute, 2009;

Managing CA’s water - From conflict to reconciliationPublic Policy Institute of CA, 2011

Agricultural issues Center, DANR, 2012

Total Developed Water Use in CAIrrigated Area in CA

Adjusted Income/AF applied water

30-40% is groundwater

CA population