Soil Intro Sp6-2010 c477

EDUARDO P. PANINGBATAN, JR. PhD Professor of Soil Physics

SOIL FORMATION Soil is formed from the weathering of rocks and minerals

Factor 1. Climate 2. Vegetation 3. Relief 4. Parent Material 5. Time

Pedogenic Processes Weathering Addition of Organic matter Leaching Soil Texture and Structure formation

Rock weathering

Continued weathering

Hypothetical Soil Profile showing the A, B and C Horizons.

Lowland Soil

Lowland Crops • Paddy Rice

Upland Soil Upland Crops •

Upland rice

•

Corn

•

peanut

•

vegetables

Plant need of a Soil The soil should be able to provide the plants: 

Adequate amount of available nutrients * 16 essential nutrient elements

•

Sufficient amount of water to satisfy enormous amount of evapotranspiration needs * Water requirement of most crops is 500 ml water / gm dry matter * 1 ha of corn will require about 5 million liter water per cropping.

•

Adequate amount air in the soil * O2 for root respiration

•

Favorable environment for root growth * favorable temperature, free from toxic materials and pathogens * firm but with low impedance to root growth

• Soil

is particulate and porous Soil Solid mineral matter and organic matter

Physical Component of a Soil

Pore Space (50 %)

Soil Solids (50%)

Fig. 1. Soil Composition showing the approximate volumetric proportion of the constituents.

Soil Structure - The pattern of arrangement of individual soil particles into aggregate and the aggregate into a soil mass.

• an indicator of soil structure

“Lower values of Bulk density is associated with higher porosity and good soil structure.

Some bulk density values and their interpretation

1.0 - 1.3 g/cm3

Normal soil

> 1.3 g/cm3

Compacted soil, poor soil structure

< 1.0 g/cm3

Very loose soil