How do we quanitatively evaluate land degradation under rainfed agriculture?

Question

How do we quanitatively evaluate land degradation under rainfed agriculture?

Answer 1

http://ndrd.gsfc.nasa.gov/ndrdres/natura...

Answer 2

First you need to clarify about the land degradation definition.

If you want to mean erosion, then you can use revised GIS based universal soil loss equation [1]

If you focus on soil organic matter (SOM) loss/ change then situation is bit complex. you need to use some systems of differential equation integrating soil particles and environments.

For a holistic approach (actually for long term monitoring), you need to define system into different smaller module first. then use life cycle impact assessment (LCA)[2] with cradle to grave analysis for agricultural practice of your interest.

Answer 3

Water and irrigation sources, be they natural or not, is only one aspect of that which affects land and it's degradation. In the end, it matters little and one must utilize any and all material in the testing and evaluation process with record being a great place to start. All evaluation is the same with respect to that single event, where the land receives water. Look at soil structure and friability, composition with respect to nutrients, organics and parent material and note changes over time as has been recorded if that exists. One can discover quite a bit by comparisons of adjoining land and plots to include land that has not been farmed in the recent past, left to itself for whatever reason. Look also at harvest data and compare over time any changes and all amendments. Much of what you are looking for will be a comparison with the physical state of the land as it currently is with records of what it was.