Farm Diaries: Part 3

Soil aggregates and why they are important for the farm?

So I am back on farm after a long time!! Here's what I noticed on my first day back....

Soil aggregates!!! These are groups of soil particles that bind to each other more strongly than to adjacent particles essentially forming clumps. These clumps are held together by moist clay, organic matter, gums(from micro-organisms) and/or fungal hyphae. They vary in size from micrometres to millimetres or more.

They are responsible for soil pores which are the spaces between soil particles and soil aggregates. They can be full of air or they can have water in them. Soils with lots of aggregates are called "well-aggregated" and this condition is thought to be very desirable, for a number of reasons. Most important one is ofcourse the pores of many different sizes they create in the soil and these spaces are essential for storing air, water, microbes, nutrients and organic matter.

For almost all the crops the requirement is that the soil should not get water-logged except for rice. These aggregates have a major role in maintaining the drainage and aeration.

The fact that soil particles do not form a continuous and compact mass, but are arranged such that they create an interconnected pore space, makes possible the development of life in the soil. The volume formed by pores, channels, chambers and cracks allows the movement of air and water in the soil, providing a favorable environment for microbial activity and facilitating root growth of plants.

Granular Soil Aggregates: The Decievers

There are many types of soil aggregates. Granular aggregates are one kind that I came across today. They are spheroids, polyhedrons, curved or with irregular surfaces that are not casts of the faces of surrounding aggregates.

Many times people confuse it with gravel which is actually a rock aggregation and not soil aggregation. This can be simply resolved by pressing the aggregates in between finger tips if it becomes dust it's a soil aggregate and if doesn't then it's gravel.

Significance of Soil Aggregates For Farm Land

1.The surface of well-aggregated soils facilitates seedling emergence and water infiltration. 

2.A good aggregation prevents soil sealing and further formation of surface crusts.

3. In aggregated soils, enhanced water infiltration reduces runoff and water erosion, increasing the water available for plants. 

4.Also, aggregated soils allow a smooth flow of water, air and nutrients, promotes the development and activity of aerobic microorganisms, soil fauna and the penetration of roots. 

5. A well-structured soil is more resistant to erosion than the loose particles of sand, silt and clay and organic matter.

Dismantling of Soil Aggregates

This is the beginning of the end!!

Tillage methods and soil disturbance activities that breakdown plant organic matter, prevent accumulation of soil organic matter, and disrupt existing aggregates,

Cropping, grazing, or other production systems that leave soil bare and expose it to the physical impact of raindrops or wind-blown soil particles,

Removing sources of organic matter and surface roughness by burning, harvesting or otherwise removing crop residues,

Using pesticides harmful to beneficial soil microorganisms.

So make sure you don't till your soil to death!!

Refer to the following links for more information..

http://blogs.egu.eu/divisions/sss/tag/soil-aggregation/

http://soilquality.org/indicators/aggregate_stability.html

http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447039&topicorder=4&maxto=10