Problem soils possess undesirable physical properties like infiltration, water holding capacity, structure, texture, hydraulic conductivity and bulk density. These soils have soluble salts like chlorides and sulphates of Ca and Mg and Na in higher concentration. This leads to improper growth and development of crops resulting in low yield of crops.
The soils possessing various constraints and management strategies are described hereunder:
1. Chemical Constraints:
The problem soils possessing chemical constraints are grouped into three categories based on electrical conductivity (Ec), pH and exchangeable sodium percentage (ESP).
a. Acid Soils:
i. The pH of the soil is < 5.5
ii. Leaching of bases occurs due to rainfall as this type of soils is common in hilly regions
iii. Accumulation of H+ and Al3+ ions in higher concentration
iv. Deficiency of cations due to leaching
v. Fixation of P by Fe and Al oxides
vi. Toxicity of Al and Mn
vii. Reduction in microbial activity.
i. Application of lime (CaCo3) to neutralize the acidity which will improve the availability of nutrients to crops.
Ii. Growing of acid tolerant crops.
b. Saline Soils:
i. This soil is found in arid and semi-arid regions where the rainfall is not sufficient enough to leach out the salts.
ii. Accumulation of soluble salts like chlorides and sulphates of Na, Ca, Mg and K in the soil due to rise in ground water table and evaporation.
iii. Plants that are grown in this soil will not absorb water effectively due to higher salt concentration (Physiological wilting/ reverse osmosis).
iv. Reduction in yield of crops (20 – 30%).
i. Leaching of soluble salts with good quality water by intermittent pounding
ii. Drainage should be provided at the distance of 25 m with a depth of 1.75 m for reclamation
iii. Addition of organic manures like FYM, vermicompost, coir pith compost etc.
iv. Growing of salt tolerant crops:
(a) High tolerant – Sesbania, rice, sugarcane, oats and barley
(b) Medium tolerant – Castor, cotton, sorghum, cumbu, maize and mustard
(c) Sensitive – Pulses, sunhemp, linseed, Bengal gram and sesamum
v. Other management practices:
(a) Growing of crops in ridges and furrow method
(b) Adoption of micro irrigation (Drip irrigation/Sprinkler irrigation)
(c) Application of biofertilizer- Vesicular Arbuscular Mycorrhizae (VAM)
(d) Scrapping of salty patches, and
(e) Conjunctive use of saline and good quality water.
c. Sodic Soils:
i. Accumulation of Na in higher concentration
ii. Deflocculation of soil aggregates
iii. Water logging due to low infiltration and permeability
iv. Deficiency of macro and micronutrients
v. Sodic conditions cause dispersal of clay particles, and
vi. Hardening of surface soil.
i. Application of organics like FYM, vermicompost, pressmud etc.
ii. Application of biofertilizers
iii. Growing of green manure crops especially Sesbania aculeata (Daincha).The acids produced during decomposition will reduce the pH of soil
iv. Growing of Prosopis juliflora over the years will reclaim sodicity of soil
v. Application of green leaf manures
vi. Inclusion of pulses in crop rotation
vii. Growing of salt tolerant crops:
a. Tolerant crops – Rice, sugarbeet, ragi, amla, tamarind, date palm and grasses
b. Semi tolerant crops – Wheat, barley, oats, sugarcane and cotton
c. Sensitive crops – Cowpea, gram, groundnut, pea and maize
viii. Application of gypsum as per the soil analysis. Sulphate in the gypsum reacts with sodium forms sodium sulphate, which can be easily leachable with water.
ix. Application of iron pyrites and sulphur compounds help in reducing pH of soil
x. Scrapping of salt affected patches
xi. Profile inversion by using bulldozer, and
xii. Mixing healthy and sodic soil to reduce pH as soil breeding measure.
2. Physical Constraints:
Physical constraints include shallow soil, subsoil hardpan, slow and excessive permeability and fluffy soils. These constraints occur in the soil due to improper management of physical properties. To overcome these problems and to sustain the productivity of soil, the under mentioned strategies should be adopted.
a. Shallow Soils:
i. The depth of soil is less than 25 cm
ii. Parent rock is present immediately below the soil surface at 15-20 cm depth.
iii. Restricts growth and spread of roots leading to poor growth and development of crops.
iv. The fertility of soil is exhausted within 2-3 seasons thus reducing the yield of crops in subsequent seasons.
i. Higher and frequent application of organic and inorganic sources of nutrients helps to improve the physical, chemical and biological properties of soil.
ii. Judicious irrigation management.
b. Subsoil Hardpan:
i. Bulk density of soil is more than 1.8 g/cc
ii. Presence of subsoil hardpan below the soil surface which is formed due to illuviation of clay coupled with cementing action of iron and aluminium oxides and calcium carbonate.
iii. Reduction in infiltration and percolation rate of soil.
iv. Prevents proliferation of roots.
v. Reduction in mobility of air and nutrients.
i. Ploughing with chisel plough at 50 cm interval once in two years to break the hardpan of soil.
ii. Hardening of soil can be avoided through summer ploughing.
iii. Application of organic manures for improving the structure of soil which will prevent the movement of clay particles to lower layer of soil (preventing illuviation).
iv. Growing of deep rooted crops like cotton, mulberry, tapioca and jasmine.
c. Slow Permeable Soils:
i. The rate of infiltration is less than 6 cm per day.
ii. High clay content makes the soil less permeable to water and air.
iii. Erosion of surface soils.
iv. Reduced infiltration increases the rate of runoff, which removes more nutrients leading to decline in soil fertility.
v. Impeded drainage leads to water logging.
i. Application of organic manures to improve the physical properties of soil.
ii. Application of sand to reduce the clay content of soil and compaction should be done with 400 kg stone roller.
iii. Growing of crops in ridges and furrows and in raised beds to avoid water logging.
d. Excessively Permeable Soils:
i. This type of soil has more than 70 % of sand.
ii. Poor soil structure.
iii. High infiltration rate.
iv. Poor water and nutrient holding capacity.
v. Wilting symptoms in plants appear frequently.
i. Application of higher quantities of organic manures.
ii. Application of clay at 100 t/ha to improve the structure of soil and compaction should be done with 400 kg stone roller 8-10 times at optimum moisture content.
iii. Frequent irrigation should be given.
e. Fluffy Paddy Soils:
i. This type of soil has high clay content.
ii. Fluffiness of soil results due to break down of soil aggregates during intensive puddling.
iii. Animals or tractors may sink in the soil while working.
iv. The transplanting operation becomes difficult in these soils.
i. Compaction should be done with 400 kg stone roller 8-10 times at optimum moisture content. Sand can be applied to the soil if necessary.
ii. Growing of garden land or irrigated upland crops after rice – rice cropping system.
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