Sugarcane being a long duration C4 plant with high biomass yield utilizes matching quantity of water and nutrients. Its ratooning ability has enabled the growers to retain the crop for 3 to 6 years without replanting and the assured market through buyback arrangement by sugar factories encourages the farmers to cultivate the crop continuously. Improper soil management practices and lack of crop rotation practices has resulted in the overexploitation of the soil resources affecting the soil productivity as evidenced from the stagnating or even declining sugarcane productivity. A good soil should have the following characteristics.
- Optimum organic matter to support macro and micro fauna
- Optimum reaction and salt concentration in soil solution.
- Adequate supply of nutrients
- Good drainage and optimum moisture retention
- Small population of plant pathogens and insects/pests
- Large population of beneficial organisms
- Free of chemicals and toxins that may harm the crop
- Resistance to degradation
Sugarcane prefers well drained, well-structured and aerated loams to clay loams that are more than 1 m deep.Preferably the ground water table should be at a depth below 1.5 m from the surface.An available water content of the soil of >150 mm/m is optimal. Though sugarcane tolerates short spell of water logging (1 – 2 weeks) or flooding, these conditions may enhance the risk for fungal, viral and bacterial diseases.It can also withstand mild drought. Sugarcane can equally be grown on soils with textures other than loam or clay loam with appropriate management practices. Classification of soil constraints
Physical Constraints
- Slow permeability
- Excessively permeability
- Subsoil hardening
- Surface crusting
- Soil compaction
Chemical constraints
- Acid soils
- Saline and alkali soils
- Poor fertility
- Calcareous soils
Biological constraints
- Poor or low soil organic matter
Management of soil constraints
Physical constraints
Slow permeability
The permeability and drainage is an estimate of the pathway of rainfall/irrigation water movement when it contacts the soil surface.Slow preamble soils are those having infiltration rates <6 cm/day due to high clay content of the soil.Due to low infiltration rates, the amount of water entering the soil profile is reduced thus increasing the run-off. Further, it encourages erosion of surface soil leading to nutrient removal in the running water.Moreover, due to heavy clay content, the capillary porosity is relatively high resulting in impeded drainage and reduced soil conditions.This results in increase of some soil elements to the level of toxicity to the plants. It also induced nutrient fixation in the clay complex thereby making the nutrient becoming unavailable to the crop, eventually causing deficiency of nutrients.
Management
1. Provision of drainage facilities either through open or closed sub surface drains
2. Application of river sand or red soil of coarser texture
3. Application of liberal doses of organic manures like farm yard manure, compost, green manure, composted coir pith, sewage waste, press mud etc.
However, if water stagnation is due to high water table, which is the characteristic of the geographical location, growing varieties tolerant to water logging and adopting suitable planting methods along with improving the drainage facilities will help to overcome the yield loss or even total crop loss.
Excessively permeability
Excessively permeable soils are those having high amount of sand exceeding 70%.Due
to this, the soils are inert and unable to retain nutrients and water. These soils being devoid
of finer particles and organic matter, the aggregates are weakly formed and the non-capillary
pores dominating with very poor soil structure. Due to low retaining capacity of the soils, the
fertilizer nutrients are also lost in the drainage water.
Management
1. Compacting the field with 400 kg stone roller (tar drum filled with 400 kg of sand or stones can also be used) 8-10 times at optimum moisture conditions.
2. Application of clay soil up to a level 100 t ha-1 based on the severity of the problem and
availability of clay materials.
3. Application of organic materials like farm yard manure, compost, press mud, sugar factory slurry, composted coir pith, sewage sludge etc.
4. Crop rotation with green manure crops like sunhemp, sesbania, daincha, kolinchi etc
Subsoil hardening
The sub soil hard pan in red soils is due to illuviation of clay to the sub soil horizon coupled with cementing action of oxides of Fe, Al and calcium carbonate, which increases the soils bulk density to more than 1.8 Mg m-3. Hard pan can also develop due to continuous cultivation of crops using heavy develop due to continues cultivation of crops using heavy implements up to certain depth constantly. Besides, the higher exchangeable sodium content in black soils areas also results in compactness. All put together lowered the infiltration and percolation rates, nutrient movement and free air transport within the soils profile. It prevents root proliferation and limits the volume of soils available for nutrients uptake resulting in depleted, less fertile surface soil. Due to this, the contribution of sub soil fertility to crop growth is hampered.
Management
1. Chisel ploughing at 0.5m interval crisscross at 0.5m depth once in 2-3 years.
2. Application of organics to improve the aggregation and soil structure so as to prevent further movement of clay to the lower layers.3. Deep ploughing of the field during
3. Deep ploughing of the field during summer season to open up the sub soils.
4. Cultivating deep rooted crops like tapioca, cotton so as to encourage natural breaking of the hard pan in crop rotation
5. Raising deep rooted semi perennial crops to open up the sub surface hard pan
Surface crusting
Surface crusting is due to presence of colloidal oxides of iron and Aluminium in Alfisols which binds the soil particles under wet regimes. On drying it forms a hard mass on the surface. The ill effects of surface crusting are
1. Obstructs germination
2. Retards/inhibits root growth.
3. Results in poor infiltration.
4. Accelerates surface run off
5. Creates poor aeration in the rhizosphere
6. Affects nodule formation in leguminous crops
Management
1. Plough the soil at optimum moisture
2. Liming@ 2 t ha-1
3. Farm yard manure at 10 t ha-1 or composted coir pith at 12.5 t ha-1 or other organics
4. Scraping surface soil by tooth harrow
5. Sprinkling water at periodical intervals may be done whenever possible.
Soil compaction
Soil compaction is the reduction of soil volume due to external factors. The risk of soil
compaction is greater today than in the past due to an increase in the size of farm
equipment.Compaction is caused by wheel or foot traffic on the soil and by soil tillage. Soil
compaction reduces soil productivity.Besides reducing yields, soil compaction also reduces
soil health and environmental quality:
1. Compacted soil is dense and has low porosity. Large poreswhich are very important for water and air movement in the soil are compressed.Infiltration is reduced and erosion is increased
2. Compaction causes an increase in the soil’s penetration resistance and more energy is expended when tilling compacted soil
3. Compacted soil is a harsher environment for soil organisms, especially earthworms, to live in
4. Compaction affects nutrient uptake.Denitrification rates can increase in compacted soil due to limited aeration.Enhances ammonia volatilization loss and reduces P and K if root growth is inhibited.
An understanding of the causes of soil compaction is necessary to develop management strategies that either avoid or correct its effects. Compaction avoidance is much preferred over compaction alleviation after a problem has been caused because correction strategies can be costly and often may not correct the problem entirely. The aim of compaction management should be to avoid subsoil compaction altogether, and to limit surface compaction as much as possible.Soil compaction is not likely to cause much damage if traffic is limited to dry soil conditions.
Management
1. Reduce axle load to at least below 10 tonnes by reducing load; increasing number of axles
2. Reduce contact pressure by reducing tire pressures to minimal allowable pressures; using flotation tires, tracks or duals to replace singles, radial-ply instead of bias-ply tires; installing larger diameter tires to increase length of footprint; properly ballasting tractor for each field operation
3. Reduce the number of passes over the field and limit the area of the field that is impacted by traffic by increasing swath width of spreading and spraying equipment and reducing width of tracks.
4. To avoid plough pans, do not drive a tractor wheel in the furrow; use: no-tillage; a chisel instead of moldboard plough; a field cultivator instead of disk harrow.
Chemical Constraints
Acid soils
Sugarcane is also cultivated in acid soil in some areas of Kerala, Karnataka and Goa.Acid soils are characterised by low pH (less than 6.5), which leads to increased solubility of aluminium, iron and manganese often to levels that are toxic to the plants.Shoot elongation as well as tillering of cane is adversely affected. Application of lime (2.5 to 7.5 t/ha) is recommended to raise the pH to neutrality. The quantity of lime recommended depends on the pH, CEC and buffering capacity of the soil. The common liming materials are burnt lime,
pulverised limestone and dolomite. The caustic nature of the burnt lime causes handling difficulties and is also costly.However pulverised limestone and dolomite are cheaper and safe for handling.Liming materials are to be applied before ploughing.Red and laterite soils
benefit largely from regular and adequate liming.Among the phosphatic fertilizers, bone
meal and rock phosphates are well suited for acid soils.
Saline and alkali soils
The primary cause of accumulation of salts is weathering of parent materials in arid and semiarid regions where evaporation is greater than precipitation (low rainfall coupled with high temperature). The secondary causes of salt accumulation are continuous use of bad quality irrigation water, rise in groundwater table, impeded drainage, indiscriminate land use pattern and construction of dams, inundation of seawater etc. Due to excess salts in soil solution plant has to exert more energy to absorb water.Osmotic potential of soil moisture increases and results in physiological water stress.The excess of salt may have direct or indirect effect on plant metabolism.
The soluble salts contain important
cations namely calcium, magnesium, sodium and potassium and anions namely sulphate, chloride, carbonate, bicarbonate and borate.Excess of calcium will have only indirect effect rather than direct effect. It causes lime induced iron chlorosis and also zinc deficiency.It may also cause magnesium and potassium deficiency in extreme cases. Excess of magnesium interferes with the uptake of calcium and to some extend potassium.Excess potassium may result in calcium and magnesium deficiency. Excess of sodium may have either direct or indirect effect. pH of cell sap increased and most cells are inactivated. Enzyme activity also reduced and many of the metabolic activities stopped. Causes necrotic symptom and ultimately leads to death of plants.
Indirectly excess of sodium affects physical and chemical properties of soil. Humus dissolved, pore space blocked as a result of deflocculation and destruction of soil structure. Dues to water stagnation the root zone are deprived of oxygen. In sodic soil, pH will be more than 8.5 due to hydroxide, carbonate and bicarbonate of sodium. Plant roots are affected by high soil pH. Phosphorus is precipitated and availability reduced. Molybdenum and boron are highly soluble and have toxic effect. Due to anaerobic condition the nitrification is reduced
In alkaline condition ammonium is converted into gaseous ammonia and lost.Deficiency of calcium and magnesium are noticed. Chloride toxicity rarely occurs in small patches. It causes necrotic leaf spot and drying of leaf margin. Chlorine generally interferes with quality. Sulphate injury is common in acid soils than in salted soils. It induces the uptake of sodium and potassium and reduces calcium uptake. Carbonate and bicarbonate cause direct injury and are most deleterious anions.
They cause iron and zinc deficiency by precipitating them. They also interfere with nitrogen nutrition. Boron at high pH dissolves as borate and causes boron toxicity. Salinity/sodicity causes reduction and delay in germination in sugarcane. It causes burning of tips of young leaves and edges of older leaves.In extreme cases, the spindle dries up exhibiting a burnt appearance.It retards stem elongation, root development and tiller production resulting in poor yield and juice quality. The canes harvested from salted soils are withered and pithy.Normally sugarcane crop stand is poor in salt affected soils with slick or barren spots in the field.EC of 4 dS m-1 and ESP of 15 are considered as threshold levels.
Management
Saline soil
Saline soils are characterized by high soluble salts (ECe>4.0 dS/m). The reclamation process involves leaching of excess soluble salts and avoiding further accumulation of salts.The field should be leveled first and divided into small plots of about 1000 sq. m by providing bunds.Drainage channels of 75 cm depth are to be provided all-around the field.The field is to be irrigated copiously with the best available water and stagnated for two to three days so that the salts in the soil get dissolved.Then the salts are removed by draining the water through drainage channels (vertical drainage) so that the salts are removed from profile at least to a depth of 75 cm.This leaching process has to be repeated till the soil is free of harmful salts.Surface drainage has to be avoided.Leaching and drainage could be improved by applying huge quantities of organic manure and mechanical treatments like deep ploughing, sub-soiling, sanding and profile inversion.
Sodic soils
Sodic soils are characterized by high pHe (>8.5) and high exchangeable sodium percentage (ESP) (>15) without salinity (ECe<4.0). The saline sodic soils are characterized by high ECe (>4.0).The physical condition of sodic soils is to be improved by addition of large amount of organic matter in addition to chemical amendments to replace sodium by calcium in the exchange complex and to remove carbonate and bicarbonate with sulphate.Generally gypsum, phosphogypsum, pressmud, sulphur and pyrites are recommended as amendments.Gypsum is the most effective and cheap amendment.
The recommended quantity of powdered gypsum (2.5 to 12.5 t/ha depending upon soil pH, ESP and soil buffering capacity) is applied to the soil by broadcasting, irrigated with good quality water and ploughed thoroughly so that the reaction takes place effectively.Reclamation of saline-sodic soil involves the addition of amendments to replace excess of sodium present in exchange complex with calcium ion.Then the excess soluble salts and sodium salts formed are to be removed as in the case of saline soils.After reclamation, the following points are to be considered while cultivating alkaline soils.
1. Level the land
2. Apply huge quantity of organic manure
3. Use 25 per cent more N than recommended
4. Apply 25 kg FeSO4 and 12.5 kg ZnSO4 per hectare
5. Irrigate with less quantity of water at frequent intervals.
6. Improve drainage facilities
7. Grow resistant sugarcane varieties
8. Use physiologically acidic fertilizers
9. Mulching can be practiced.Enriched pressmud may also be applied to improve soil physical conditions
10. Monitor soil pH, EC and ESP and avoid salt accumulation Poor fertility
Poor fertility
Indian soils are in general poor in nitrogen and well supplied with phosphorus and potassium.Application of NPK fertilizers based on soil test results will help in improving sugarcane productivity. Iron chlorosis is common mainly due to high lime content in soil.This can be corrected by repeated foliar spray of ferrous sulphate (1.0 to 2.0%) with 0.1% citric acid at weekly intervals till the chlorosis vanishes.In normal soils, soil application of ferrous sulphate (@ 50 kg/ha) will alleviate this malady.Application of 150 kg of ferrous sulphate along with organics is recommended for calcareous soils.Zinc deficiency is also noticed in some soils.This can be corrected by foliar spray (0.5%) coupled with soil application (25 kg/ha) of zinc sulphate.
Calcareous soils
More than one-third of the world’s soils are calcareous.In India, sizable sugarcane growing area is occupied by calcareous soils.The calcareousness is a unique property of soil, which affects the physico-chemical properties, nutrient availability and plant growth. Calcareous soils may have CaCO3 content varying from a small amount in some part of the soil profile to an appreciable amount occurring throughout the profile.Availability of nutrients in the calcareous soils becomes even more complex phenomena due to presence of solid CaCO3. This is because (i) CaCO3 serves as a prominent sorbent of nutrition, (ii) its presence increases soil pH and (iii) it supplies Ca, which forms salts of various solubilities.
In such soils, the availability of nutrients like, iron, manganese, phosphorus, zinc and boron due to heavy fixation has been limiting and still posing a serious threat to successful crop production.The presence of CaCO3 also induces loss of nitrogen through volatilization. Application of ferrous sulphate (125 kg/ha) and zinc sulphate (25 kg/ha) fortified organic manure could be applied besides liberal use of organic manures.Soil pH should be corrected towards neutrality by using the amendment gypsum. Sulphur or pyrites could also be used.Foliar application of ferrous sulphate (0.5 – 2.0 %) with 0.1% citric acid and zinc sulphate (0.25 – 0.50 %) from 45th day after planting at weekly interval till the crop recovers is an effective method to alleviate deficiency of zinc and iron.
Biological constraints
Low soil organic matter
Soil organic matter content, measured during routine soil testing, is considered as one of the most important indicators of soil health.From an agronomic and environmental point of view, organic matter gives the largest benefits if it is found close to the soil surface.It improves soil aggregation, infiltration, resistance to erosion, workability, and leads to improved seed-to-soil contact when planting.
Soil becomes resistant to compaction and facilitates root development.Depleting SOM content in the agricultural soils within the past four decades has been evidenced by reduced soil organic carbon content to the tune of <0.5% from around 1.0% half a century ago. Especially in sugarcane based cropping system, where the bulk of the crop residue is burnt due to handling problems and even the stubbles are removed for fuel after the final harvest (of the ratoon crop) and the soil is tilled several times in a cropping cycle, the carbon input is lower and the loss of SOM through oxidation is also accelerated. SOM inputs can be increased leaving the crop residues in the field, growing cover crops during otherwise bare fallow periods and adding compost and manure.
Soil tillage reduces surface organic matter content, so minimizing tillage will help improve soil health.Recent research suggests that tillage, especially moldboard plough primarily redistributes organic matter to deeper soil layers.With moldboard plowing, soil organic matter content is uniform throughout the plough layer while the chisel plough and disc harrow cause smaller surface organic matter losses.In long-term no-tillage system, soil organic matter content will be high at the soil surface and decrease rapidly below 2 or 3 inches. Sugarcane based cropping system provides ample opportunities to enhance the SOM
and soil health. Some of them are as follows:
Pressmud compost
Fresh press mud has a wide C : N ratio and evolves a lot of heat during decomposition.Hence it should be applied only after proper decomposition.Fresh press mud composted using Pleurotus,Trichoderma viride (1 kg/t of press mud), urea (5 kg/t of press mud), cow dung as a starter (50 kg/t of press mud) and enriched with rock phosphate, ferrous sulphate, zinc sulphate etc. serves as good organic manure.Bio-earth is produced by nheaping fresh press mud in windrows sprayed with correct proportion of distillery effluent and mixed thoroughly by using Aero tillers mounted on tractors.Simultaneously the microbial culture is also sprayed and mixed.
A distinctive black, loamy, free flowing and dry baggable compost with pleasant earthy smell is produced.The experience with this compost in many countries has shown a reduction in fertilizer inputs by up to 50% with simultaneous rise in production of crops.This is the best way of restoring organic matter to soil and the most practical and profitable method of disposing distillery effluent.
Sugarcane trash compost
In sugarcane about 10 t of trash/ha is available and in most of the locations, it is burnt.By trash burning we not only lose valuable organic matter, but also kill the soil fauna ranging from microscopic bacteria to macroscopic earthworms and micro-arthropods.Trash contains about 0.35% N, 0.13% P2O5, 0.65% K2O, 0.27% CaO and also appreciable quantities of micronutrients, but with wider C:N ratio (60:1).The lingo-cellulosic nature of the trash combined with its silica content and spiny nature makes its handling a difficult task.
Decomposition also takes longer time. Its bulkiness also demands huge labour for transporting out of the field. Burning of trash results in 100% loss of N and a sizable quantity of P and S from it.The rapid trash composting technique similar to that of press mud composting technique using fungal cultures (Trichoderma viride and Pleurotus – one kg) 7.5 kg of urea + 50 – 75 kg of fresh cow dung for every tonne of trash can be adopted.Trash compost has a nutrient content of 0.8% N, 0.25% P2O5 and 0.7% K2O with C:N ratio of 22:1.Trash can also be composted along with press-mud.This may substitute about 20 – 30 % of the nutrient requirement also.
souce-
- sugarcane breeding institue
