Problematic Soils Point Wise Notes For Competitive exam

• More than 50% of net cultivated area falls in the category of problem soils.

• Wind erosion occurs in arid and semiarid areas devoid of vegetation where wind velocity is high.

Highly permeable coarse textured soils:

• Productivity of coarse textured sandy and loamy sand soils is low due to its exceptional permeability which permits percolation of water and nutrients and does not encourage high level of costly inputs.

• Occurs in larger areas of Rajasthan, Haryana and Gujarat.

• Soil compaction and clay mixing should be done to improve them.

Slowly permeable soils:

• These soils associated with black clay soil. Occurs in MP, Maharashtra, AP, Gujarat and TN.

• Problems of these soils are linked with topography and annual rainfall.

Crusting soils:

• Crusting of alluvial soils is serious problem all over country especially in Haryana, Punjab, Rajasthan, Bihar and West Bengal.

• Formation of soil crust involved breakdown of soil aggregates by the impact of raindrops, dispersion of soil water to form soil suspension and then sedimentation.

• Application of FYM or green manuring will improve them.

Red chalka soils:

• Red sandy loam soils chalka cover large area in Andhra Pradesh.

• Becomes very hard on drying, so crop growth adversely affected.

• Incorporation of slow decomposing crop residues and other inorganic materials such as powdered groundnut shell, paddy husk each at 50q/ha helps in favourable crop growth by reducing hardness of the soil.

Based on chemical nature:

Salt affected soils:

• Soils containing excess soluble salts in the root zone which adversely affect growth and yield of crop plants are called salt affected soils.

• In India salt affected soils covers 7 mha. UP-1.29 mha, Gujarat – 1.21 mha, West Bengal – 0.85 mha, Rajasthan – 0.72 mha, Punjab – 0.69 mha

• Salt affected soils are categorized into three groups

1. Saline soils

2. Alkali soils (sodic ) soils

3. Saline alkali soils

Saline soils:

EC> 4 dS/m, pH < 8.5, ESP < 15

• They have excessive salt concentration in soils which adversely affect the plant growth mainly due to increased osmotic pressure which causes physiological drought.

• Predominant salts are Cl- and SO42- of Na+, Mg2+

• There is imbalance of available plant nutrients leading to toxicity or deficiency.

• Excess soluble salts should be reduced upto moderate levels (6 dS/m in 0-30 cm depth) by leaching with good quality water.

• Leaching requirement calculated according to intensity of problem and quality of leaching water.

• Leaching is the process of displacing the saline soil solution from the root zone with water of lower salt concentration.

• Provision of drainage is of utmost importance in the case of saline soils resulting in lowering water table, reducing salt content and increasing crop yields.

• Mulching helps to reduce soil salinity. Mulching reduces upward movement of salt due to decline in evaporation losses.

• Addition of organic matter improves physical condition of the soil and more water holding capacity keeps salts in diluted form.

• Barley, cotton, sugarbeet – tolerant to salinity Wheat, rice, oats, maize, sorghum, potato – medium tolerance Legumes, Beans, groundnut – sensitive

Alkali soils:

• EC< 4 dS/m, pH > 8.5, ESP > 15

• Excessive exchangeable Na, high pH, lack of nutrients Ca, N, Zn and poor physical conditions, coupled with poor aeration are chief causes for low productivity.

• Soil colour becomes black due to dispersion of clay and organic matter

• Water infiltration rate becomes very low resulting in stagnation of water

• Soil becomes cloddy and hard at drying.

• Heavy irrigation is applied after the addition of gypsum to facilitate the leaching of soluble slats of Na.

• In order to replace excessive amount of Na, application of Ca is essential.

• Several amendments such as gypsum, S, H2SO4, CaCl2, FeSO4, iron pyrites, Al2(SO4)3 are available but gypsum is most popular.

Saline-alkali soils:

EC >4 dS/m, pH > 8.5, ESP >15

• These soils have mixture of characteristics of both saline and alkali soils.

• Soils showing high salinity and ESP should be reclaimed for both but first for salinity and later for excessive exchangeable Na.

• Tolerance of crops to exchangeable sodium Tolerant – Rice, Sugarbeet, Dhaincha Medium tolerant – Wheat, Barley, Oats, Millets Sensitive – Legumes, Maize, Groundnut

Acid soils:

• Blue litmus paper turns red in contact with moist acid soil.

• These soils high in exchangeable Al3+ and H+, with pH < 5.5 and responds to lime application.

• Exchangeable Al3+ derived from breakdown of soil clay minerals.

• Soils with organic matter more than 15% show acidic condition because of considerable exchangeable H+ in addition to exchangeable Al3+.

• The greatest inhibition effect of an increasing Al3+ concentration in soil solution is on the absorption of Ca2+ irrespective of plant type and absorption of Mg2+ and K+ is also inhibited.

• These soils normally belong to laterite and lateritic, red and yellow group rich in Kaolinitic clay minerals with low CEC.

• They have low organic matter, N, P and MgO.

• Acid soils cover a large area of about 4.5 mha in Assam, Tripura, Manipur, West Bengal, Bihar, Odisha, Karnataka, Tamil Nadu, Himachal Pradesh, Kerala.

• Principal factors which influence lime requirement are pH, amount and type of clay, CEC, buffering capacity of soil.

• Paddy, Potato, Tea, Millets – tolerant to acidity

Semi tolerant – Bengal gram, Maize, Sorghum, Peas, Wheat, Barley

Sensitive – Arhar, Soybean, Cotton, Oats