Conservation Agriculture:Prospects and

Problems In Semi-Arid Tropics

Dina KhadijaAnd

Dr. P. K. Mani

Department of Agril. Chemsitry and Soil Science Bidhan Chandra Krishi Viswavidyalaya

West Bengal, India

What is Conservation Agriculture?

An array of technologies such as residue retention, zero- and reduced tillage, crop rotations, green manure cover crops, controlled traffic and raised beds. When used in combination these, over time, reduce, and often revert, the degradation of soil and water resources. Residue retention distinguishes conservation agriculture from conventional agriculture, and all conservation systems include at least a certain level of surface residue cover.

Goals of CA FAO defined goals of CA as follows:

“CA aims to conserve, improve, and make more efficient use of

natural resources through integrated management of available soil,

water, and biological resources combined with external inputs. It

contributes to the environmental conservation as well as to the

enhanced and sustained agricultural production. Therefore, it can

also be referred to as resource efficient or resource effective

agriculture”.

WORLD SCENARIO

In India it is being practiced about 2-3 mha (WCCA Report 2009).

BASIC PRINCIPLES OF CA

Minimal Soil disturbances enable through No-till/reduced tillage

Maximum soil cover/ residues

Appropriate crop sequences/ rotations (Spatial and temporal crop sequencing).

Conservation Agriculture Means Dramatic Tillage Reductions Combined

with Adequate Surface Retention of Crop Residues

Conventional Till Systems CA Zero Till Systems

Zero Till (ZT) –Wheat Seeding

• Reduced costs (Rs 2000-2500/ha) due to savings in fuel and labor

• Timely planting of kharif and winter season crops, resulting in higher yields

• Lower density of herbicide resistance in comparison to traditional tillage.

• Significant irrigation water savings (up to 15-20%)

• Improved input use efficiency because of the right placement of seed and fertilizer nutrients

• Better plant stands• Less burning of crop resides

Advantages of Zero Tillage

Resource Conserving Technologies (RCTs)

1. No-tillage

2. Laser land leveling

3. Direct seeding of rice

4. Leaf colour chart for N

5. Crop diversification

Conventional

RCTs

CA based RCTs options for System sustainability

Zero tillage Paired row ZT Control traffic ZT Direct seeding Unpuddled transplanting Reduced tillage Bed planting Surface seeding

SEMI-ARID TROPICS

Characterized by:• variable and unpredictable rainfall

• structurally unstable soils

• low overall productivity

CONSERVATION AGRICULTURE IN SEMI –ARID TROPICS

protects the soil from the heating effect of the sun

protect soil against raindrop impact

allow improvement in soil aggregation

practices of minimum/ zero tillage and direct sowing techniques lead to minimum disturbance of soil.

Properly Managed CA Encourages Sustainable Soil

Management

Physical Soil Quality

ChemicalSoil Quality

BiologicalSoil Quality

Soil Organic Matter

Soil Chemical Quality: Higher soil cation exchange capacity (CEC) due to increased organic matter content.

Systems with pigeon peas (Cajanus cajan) resulted in a 70% increase in CEC compared to a fallow-maize system (FAO, 2001).

Combination of ZT with sufficient crop residue retention reduces evaporation from the topsoil and salt accumulation (Hobbs and Govaerts, 2010).

Contd.Table : Organic Carbon in Conventional & Minimum tilled fields

Tillage Treatments Organic C (g/kg)

0 – 5 cm 5-20 cm

Conventional Tillage

5.42 5.26

Minimum Tillage 6.16 6.00

Improves soil organic Carbon

Soil Physical Quality

Table:Tillage and Nitrogen level effect on infiltrability (cm/hr) Reduce soil

compactiondue to reduced traffic and application of crop residues.

Increase infiltration rate of water

Tillage

N50% N100%

N150%

Average

CT-CT 3.02 2.84 1.08 2.31

MB-RT 2.96 7.53 8.61 6.37

RT-RT 2.85 8.88 6.24 5.99

NT-NT 3.04 10.91 11.05 8.33

Average 2.97 7.54 6.74

Contd..

Increase soil moisture percentage

Conservation

Agriculture enhances biological

tillage instead of

mechanical tillage

Effect of Tillage on Soil Rhizobium Populations

0

10

20

30

40

50

60

Zero Tillage Conventional Tillage

Rhiz

obiu

m c

ells

Voss and Sidiras, 1985

Conservation Agriculture and C sequestration

Differences in soil organic carbon content (%) due to adoption of zero-tillage over conventional tillage.

Conservation and Water Use Efficiency

CA improve rain water infiltration (Shaxson et al., 2008)

Improve water holding capacity (Govaerts et al., 2009)

Reduce evaporative loss of water(Scopel et al., 2004)

Conservation Agriculture and Climate Change- Mitigation and Adaptation:

Adaptation to climate change mainly dueto enhanced water balance

Climate change mitigation through possible C sequestration and reduced emission of CO2 to the atmosphere

Conservation Agriculture and Climate Change- Mitigation and Adaptation

Figure : Mitigation and adaptation to climate change and variabilities through CA (Lal,2010)

Why CA is difficult to adopt?

Mindset/ attitudinal change

Strategies different from those we have adopted over past decades

Non-availability suitable farm equipment/ Farmers’ choice.

Constraints in Scaling Up Conservation Agriculture in SAT

Competitive Uses of Crop Residues

Weed Preponderance

New Implements and Operating Skills Required

Nutrient Immobilization

Carryover of Insect-Pests and Disease Pathogens

Monoculture leads to a build-up of pests and diseases. This is far more

marked in zero tillage than in conventional tillage

The key to controlling pests and diseases in zero tillage agriculture is crop

rotation. One should avoid seeding a crop into it’s own residues before these

are decomposed.

Up Scaling Conservation Agriculture in SAT

The obstacles in up scaling CA can be overcome through:

Interaction among associations of interested people

organization of promotional events such as field days

By providing credit to farmers to buy the equipment, machinery, and inputs through banks and credit agencies at reasonable interest rates.

Concluding Remarks: The SAT is characterized by highly variable and low rainfall, poorly developed infrastructure, degraded soils, and low socio-economic condition of the farmers.

CA has been reported as sustainable and eco-friendly crop production technique in the fragile eco-systems of SAT.

In the long-term CA has been found to render several benefits including

soil conservation with improved soil health higher rain water use efficiency climate change mitigation and adaptation improved biodiversity higher economic returns