The publication of this Handbook was supported by the Russian Federation

The general concept of soil 
monitoring
An evaluation of  the state of  cotton crops using remote sensing data and the analysis of  the spatial 
distribution, sizes and numbers of  cotton wilt patches using data collected in the late summer and 
early autumn serves as a basis for the estimation of  soil salinization dynamics. As demonstrated 
earlier [9, 19, 20], the main factor causing cotton wilt is the presence of  salts within the uppermost 
1 m of  soil. The larger and the more frequent the cotton-wilt patches, the stronger the salinization. 
Therefore, as a cotton-wilt patch by itself  is insufficient evidence of  strong salinization of  soils, 
it is necessary to analyse the general extent and distribution of  such patches. In cases when an 
image shows small areas (less than 20 m in diameter) and a sparse distribution of  cotton-wilt 
patches (<20% of  the total area), such patches have medium saline soils, while the rest of  the 
field has non-saline or weakly saline soils. In cases when an image shows large areas (50-100 m in 
diameter) and a dense distribution of  cotton-wilt patches (>50% of  the total area), such patches 
have strongly and very strongly saline soils, while the rest of  the field has medium and strongly 
saline soils with crops remaining unaffected (Table 2.1). Previous experience has shown that images 
from just two observation cycles fail to provide enough information for making a reliable judgment 
on salinization trends. It is necessary to organize regular annual observations on changes in soil 
salinity using remote sensing techniques and also to introduce mapping of  salinization dynamics 
into practice [15].