The impact of wood biochar as a soil

amendment in aerobic rice systems of the

Brazilian Savannah

Wageningen, 2 February 2015.

The Brazilian tropical Savannah

42% of overall crop production in Brazil is coming from the Central West Region

Rice systems

Brazilian Savannah:Non-flooded (aerobic/rainfed)50% area - 30% productivity

South Brazil:Flooded

50% area – 70% productivity

Sandy Plinthosol Clayey Ferralsol

Large yield gap

• Actual yield ≤ 1 t/ha attainable yield ≥ 5 t/ha

• Causes:

• Biotic stress

• Rice blast (disease) and weed infestations

• Weathered soils

• Acidic

• Low soil organic matter content

• Poor nutrient availability

• Water stress (deficit) due to erratic rainfall:

critical period between panicle initiation and

flowering

Critical period

Optimal:220 to 250 mm

30-33ºC

Growing period of Aerobic rice650 – 750 mm / 20 – 35ºC

Sowing HarvestingFloweringPanicle initiation

End of Tillering

Sterile spikelets -> unfilled grains

Wood biochar

Forest Plantation ---- Slow carbonization-- Wood charcoal

(Eucalyptus sp.) (low concentration of

Oxygen)

Pieces ≤ 8 mm is a BY

PRODUCT and can be

used as BIOCHAR

Biochar as a soil amendment

Decrease acidity (liming effect)

Increase soil nutrients availability

Increase water retention

Potential increase in crop yields ~ 10%

Positive effects mainly from:

● Artificially controlled conditions (pot experiments)

● Rates of biochar higher than 2% w/w

● Short term experiments (1-2 years)

● Other crops than rice

Objectives

Quantify the effect of wood biochar amendment and its combination with mineral N fertilizer on aerobic rice crop performance on a sandy (non-irrigated) and clay soil (irrigated) of the Brazilian tropical Savannah

Analyse the effect of wood biochar amendment on soil physical and chemical properties throughout 4 rice seasons after biochar application

Monitor the effect of wood biochar amendment on N2O-N fluxes throughout crop seasons

Research design

• BIOCHAR: 4 levels (0, 8, 16 and 32 t/ha) incorporated once to

a depth of up to 15 cm

• NITROGEN: 4 levels (0,30, 60 and 90 kg/ha) applied annually

• SOIL TYPE (2 sites): Sandy soil in Mato Grosso (rainfed) and

Clay soil in Goias (rainfed + irrigation)

• 4 Blocks with 4 repetitions = 64 plots of 40 m2 in each site

• TIMESPAN, years after biochar application in soil:

Clay soil: 5 seasons S0.0, S0.5, S1.5, S2.5, S3.5

Sandy soil: 4 seasons S0, S1, S2, S3

Preparation of field experiments

The soil water retention

In the sandy soil: biochar increased the rice available water in 5-10 cm at 2 and 3 years after application

In the clay soil: biochar decreased soil bulk density and rice available water in 5-10 cm at 1.5 and 2.5 years after application

The soil acidity

In both soil types: biochar decreased soil acidity (measured as the increased soil pH)

The effect lasted up to 3 years in the sandy soil and up to 1.5 years in the clay soil

a) Sandy soil

b) Clay soil

The soil organic matter

In the sandy soil: biochar hardly (or not) affected the soil organic matter content

In the clay soil: biochar increased the soil organic matter content with time, at 2.5 and 3.5 years after application

a) Sandy soil

b) Clay soil

The rice performance

Varies according to soil type and season

In the sandy soil: very positive or no effect on grain yield

In the clay soil: no effect, negative or a positive effect depending on the N fertilizer applied

*Adapted from Petter et al. (2012)

a) Sandy soil

b) Clay soil

Greenhouse gas emission measurement:

static chambers to measure N2O-N fluxes

The effect of biochar on GHG emission

(Nitrous oxide: N2O-N fluxes)

Biochar would reduce N2O-N fluxes:

1) first, due to a decrease in soil N availability

2) with time, due to increased capacity of soil to retain mineral N

The effect of biochar on soil water could trigger N2O-N fluxes due to aerobic/anaerobic conditions

No interaction effect of biochar and the N fertilizer

Contribution to sustainable intensification

of farming systems in a tropical Savannah

The type of wood biochar used in this study:

• Can be used as an alternative to soil liming and supplementary mineral fertilization

• Can be used as an strategy to increase water retention in sandy soils

• Can be used as an amendment to enhance the soil organic matter content in clay soils with time

• Rate up to 32 t/ha was not sufficient to guarantee an increase in aerobic rice yield, and complementary mineral N fertilization is likely to be needed.

Funding

Obrigada!

Thanks!

Bedankt!

“Life isn’t a game, friend. Life is the art of the encounter.

Even though there might be so much discord (dis-encounter) in this life.”

(Samba da Bênção, 1967)