Land is the most important basic natural resource. It is a dynamic and complex combination of geology, topography, hydrology, soil and flora and fauna and influences every sphere of human activity. Different sectors including agriculture, industries, infrastructure, and power projects put forth competing demand for land. Subsistence farming practices, accelerated soil and water erosion, erratic rainfall, increasing population, and high density of livestock population have all contributed to unsustainable land use that has lead to degradation of this valuable resource, in Karnataka.
Land is classified into two categories, arable and non arable. Non arable land comprises of area under forests, permanent pasture land, current fallow, cultivable waste land and land put to non agricultural use. Arable land includes area sown with crops (net sown area), area sown more than once and gross sown area. The extent of non arable land is 60.50 lakh hectares.
Out of the total non-arable land in the state, 9.67 percent are rock lands. High proportion of rock lands occur in dry and coastal zones (about 15 percent each). Non-arable lands are strongly gravelly in about 79 percent in the state and a very high proportion (99.91 percent) is found in dry and transition zones (93.12 percent). About 27 percent of these lands have high slopes, high proportion of slopy land occurs in hill zone (50.85 percent) and coastal zone (35.32 percent). Soil with less than 25 cm depth occurs in dry (39.6 percent) and transition zones (47.60 percent). Erosion is a problem associated with nonarable land and 54.51 percent of the non-arable lands are severely eroded. Severe erosion of non-arable lands is a major problem particularly in dry zones (73.55 percent) and transition zones (97.05 percent).
The land and forest degradation has caused severe soil erosion in the maidan areas of Karnataka. The observed average rate of sedimentation is ranging between 2.19 to 23.59 hectare-meter/100 square kilometers, where as the threshold level is between 0.29 to 4.29 hectares. Most of the tanks have been silted up to more than 30 percent of their capacities reducing their command area by 35 percent.
The rate of silt deposition in irrigated tanks is estimated at 8.51 hectare-metre/100 square kilometers/year against the assumed siltation of 3.02 hectare-metres/100 square kilometers/year. As per the estimates of the State Government about half of arable land in the State needs protection. Out of 125.85 lakh hectares, 68 lakh hectares (57 percent) needs soil conservation. The salinization has become acute problem in the command areas of the State. It is reported that nearly 10 percent of the total irrigated area in the State is subjected to water logging, salinity and alkalinity.
Soil and water erosion has caused soil fertility loss, thus reducing its productive capacity. The soil structure, texture and moisture holding capacity are also affected due to soil erosion. Excessive chemical usage for agriculture is a problem in the cotton growing areas of the state. The average fertiliser used for growing paddy and sugarcane usually ranges between 80-150 kliograms/hectare. The arid regions of the state where rainfall is low are vulnerable to soil erosion. The type of land degradation for various districts is as follows: