Soil physical constraints


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Soil Physical Constraints and their Management

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Soil physical constraints

  1. 1. SOIL PHYSICAL CONSTRAINTS AND THEIR MANAGEMENT Tamil Nadu state with an area of 1,29,951 Sq.Km. lies at 8 0 5 and 130 40 Northlatitude and 760 15 and 800 70 East longitude, with a warm climate and located in the east of theWestern ghat and has a gradual slope to the east extending upto the low hills of the Eastern ghats.Physiographically it is divided into (i) The Coastal plain (ii) the Eastern ghat (iii) The plateau areaand (iv) The Western ghat. The coastal plain stretches about 992 Km. from Pulicate lake to Cape Comerin withthree sub regions viz., the Northern plain, the Cauvery delta zone and the Southern plain. It isabout 86 to 96 Km. wide with an average elevation of 80 m. The Northern plain comprises ofChingleput , a major part of South Arcot, the eastern part of North Arcot and Northern part ofTrichi districts. The Cauvery delta zone consists of Tanjore and part of Trichi, where as theSouthern Coastal plain is shared by Ramnad, Thirunelveli and Kanyakumari districts. The Eastern ghat area between the rivers of Palar and Cauvery and the Coastal plain isbalked by discontinuous lines of hills, the Javed, Sherveroys, Kalrayon, Pachaimalai and Kollimalai. North of the Palar river, smaller or even more broken hills are linked with the tails ofGuddapah in the Nagari hills. Across the Cauvery, further detached leads on to the longVarashanad, Audipatty range and then to Cardomam hills. This line of discontinuous hills areknown as The Eastern ghat. The area between the Eastern and Western ghat lies the Plateau area with elevationranging from 170 to 650 metres. Hence the topography is undulating. The Plateau is fringed onthe west by a group of hills known as Western ghats. On either side of the Palghat gap, thehighest mountains of the Peninsula dominates. They are the Nilgiris in the north and the Anamalai,Palani and Cardomam hills in the south.Soils of Tamil Nadu The soil of Tamil Nadu are highly heterogeneous having different parent materials ofmetamorphic, sedimentary, acid igneous rocks rich in soda lime feldspars, amphiboles andpyroxenes of gnessic rocks, chernochites and sand stones. Thus it endowed with the collection offive major soil order viz., Alfisol, Entisol, Vertisol, Inceptisol and Ultisol. Therefore it opensavenue to carry out diversified research on physico chemical properties and also biophysical 1
  2. 2. properties at greater length and breadth. The total geographical area of Tamil Nadu is about 13m.ha, out of which 8 m ha of the soils are of red in nature, 2 m.ha alluvial, 2 m.ha black and therest lateritic. Because of the diversified nature, characterised by their different origin, location andsoil forming processes, these soils are found to possess various types of soil constraints. The plant nutrient availability in soil is a measure of soil fertility, while the soil physicalenvironment is the kingpin which regulate the retention and movement of soil moisture, soilaeration, soil nutrient movement, soil temperature, seed germination, seedling establishment, rootpenetration and proliferation etc. Hence, soil physical environment directly and indirectly controlsall the other factors influencing the plant growth and in turn the production potential of the crop. Recently, under the fold of Integrated Nutrient Management technique, organic andIntegrated Farming System, an attempt has been made to increase the crop production underrationalised plant nutrient management, where the management of physical condition plays apivotal role. Besides by ameliorating certain physical constraints existing in the marginal andsubmarginal lands, it would be easier to enhance the production potential of the crop in an unitarea. Knowingly or unknowingly, the poor soil management, unexpected natural calamities oftenaffect the soil environment and arrest its productivity. By judicious application of all the requiredplant nutrients at times fail to yield good results. It might be due to unforeseen weather conditionslike heavy rain, stagnation of water, long dry spell or continuous cultivation which finally affectsthe physical environment like infiltration, moisture retention and transmission, soil compaction andaggregation leads to soil physical constraints constantly. The most frequently occurring soil physical constraints in the state of Tamil Nadu areexcessive permeable soils, sub soil hardpan soils, slow permeable soils, fluffy paddy soil, surfacecrusting and shallow soils. The nature and extent of the soil physical constraints in the soils ofTamil Nadu are not delineated by the staff of Soil Survey and Land Use Planning and hence, oneof the major objectives of the AICRP on "Tillage Requirements of Major Indian Soils underDifferent Cropping Systems" is to characterise the major soil series of Tamil Nadu for theirphysical constraints. In Tamil Nadu, so far six districts viz., Coimbatore, Salem, Dharmapuri,Trichi, Madurai and North Arcot were surveyed for identifying the areas having soil physicalconstraints and suitable technologies were developed and test verified in farmers holdingscontinuously for more than three years. The following are the major soil physical problemscommonly met with in Tamil Nadu. 2
  3. 3. Table 1 Delineation of physical constraints in the soils of Tamil Nadu stateSoil series Area in Problems Identified Per centCoimbatore districtPeelameduDasarapattyPerianaicken 739 Slow permeable 4.69palayam soilsIrugurPalladam 6,519 ExcessivelyVannapatty permeable soils 41.82Tulukkanur 1,320 High sub soilPichanur bulk density 8.46DharmapuriDharmapuriNattam Slow permeableHosur 526 soils 5.47Vannapatty 3,774 Excessively 39.24 permeable soilsTrichiIrugurTulukkanurPalladam 2,800 Excessively 32.00Vannapatty permeable soilsPeelameduKallakudiPoovalur 1,243 Slow permeable 14.20Mudukulam soils 3
  4. 4. Soil series Area in Problems Identified Per centMadurai districtAnaiyur SubsoilMadukkur 2,450 compaction 30.0Irugur 1,837 Excessively 22.5Palladam permeable soilsSalem districtIrugurMallasamudram ExcessivelyMallur 1,845 permeable soils 21.35Peelamedu 420 Slow permeable 4.85 soilsVellalur 209 Shallow soils 2.45North Arcot districtUdic Haplustalf 1,448 Sub soil 17.61Typic Rhodustalf hardpanTypic Ustifluent 524 Excessive 6.37 permeable soilsTypic Ustorthents 384 Shallow soils 4.67 4
  5. 5. The consolidated survey report of the Tamil Nadu is presented in Table 2.Table 2 Extent of soil physical constraints in Tamil NaduTotal Geographical Area = 130 lakh ha.Districts Area Excessive Slow Subsoil Shallow permeable permeable hardpan soils soils soils soilsCoimbatore 15.8 6.5 0.7 1.3 -Dharmapuri 9.6 3.8 0.5 - -Trichi 8.8 2.8 1.2 - -Madurai 8.2 1.8 - 2.5 -Salem 8.6 1.8 0.4 - 0.2North Arcot 8.2 0.5 - 1.5 0.4Total 59.2 17.2 2.8 5.3 0.6% surveyed 45.5% to surveyed area 29.3 5.0 8.8 1.0 The common soil physical constraints often encountered in Tamil Nadu are • Sub soil hard pan • Excessive permeability • Surface soil crusting • Fluffy paddy soils • Slow permeability Out of the total area of the state (130 lakh ha.) 45.5 per cent was surveyed out ofwhich, 29.3 percent of the surveyed area was found to possess excessive permeability, 5.0 per centslow permeability, 8.8 per cent sub soil hard pan and 1.0 per cent are shallow soils. The resultsalso indicated that the most of the soil physical constraints viz., the excessive permeability, subsoil hardpan and shallow soils, which are associated with red soils, are predominant in the soils ofTamil Nadu owing to the fact that about 60 per cent of the soils of Tamil Nadu belong to thiscategory. The characteristics of the soils possessing soil physical constraints, extent and their 5
  6. 6. management practices are briefly discussed here under:Excessive permeable soils Excessive permeable soils are those having high amount of sand exceeding 70 per cent.Due to this, the soil is inert and unable to retain water and nutrients. These soils being devoid offiner particles and organic matter, the aggregates are weakly formed, the non-capillary poresdominating with very poor soil structure. Due to low retention capacity of the soils, the fertilizernutrients are also lost in the drainage water. The excessive permeable soils are spread over 6,519 in Coimbatore, 3, in Dharmapuri, 2,800 in Trichi, 1,837 in Madurai, 1,845 in Salem and524 in North Arcot districts. The excessive permeable soils can be managed by adoptingthe techniques given below:• Compacting the field with 400 kg stone roller (tar drum filled with 400 kg of sand or stone can also be used) 8 - 10 times at optimum moisture conditions.• Application of clay soil (Soil Breeding) up to a level 100 t ha-1 based on the severity of the problem and availability of the clay material.• Application of organic materials like farm yard manure, compost, press mud, sugar factory slurry, composted coir pith, sewage sludge etc.• Providing asphalt sheet, polythene sheet etc., below the soil surface to reduce the infiltration rate.• Crop rotation with green manure crops like Sunnhemp, Sesbania, Daincha, Kolinchi etc.Sub soil hard pan The sub soil hard pan in red soil is due to the illuviation of clay to the sub soil horizoncoupled with cementing action of oxides of iron, aluminum and calcium carbonate, whichincreases the soil bulk density to more than 1.8 Mg m-3. Further, the hard pan can also developdue to continuous cultivation of crops using heavy implements upto certain depth constantly.Besides, the higher exchangeable sodium content of clay complex in black soil areas also resultedin compactness of the sub soil. All put together lowered the infiltration and percolation rates,nutrients movement and free air transport within the soil profile. It prevents the root proliferationand limits the volume of soil available for nutrient uptake resulting in depleted, less fertile surfacesoil. Due to this, the contribution of sub soil fertility to crop growth is hampered. 6
  7. 7. The sub soil hard pan areas are found in 1,320 in Coimbatore, 2,450 inMadurai and 1,448 in North Arcot districts. Depending upon the depth of occurrence ofhard pan, the management practices are to be adopted. Hence for soils having sub soil hard pan atshallow depth, the following technologies could be adopted.• Ploughing the soil with chisel plough at 0.5 m interval criss cross at 0.5 m depth once in 2-3 years.• Application of organics to improve the aggregation and soil structure so as to prevent further movement of clay to the lower layers.• Deep ploughing of the field during summer season to open up the sub soil.• Cultivating deep rooted crops like tapioca and Cotton so as to encourage natural breaking of the hard pan.• Raising deep rooted semi perennial crops like mulberry, jasmine match wood tree etc., can also help in opening up the sub soil hard pan.Slow permeable soils Slow permeable soils are those soils having infiltration rates ranging from less than 6 cmper day due to high clay content of the soil. Due to low infiltration rates, the amount of waterentering the soil profile is reduced thus increasing the run-off. Further, it encourages erosion ofsurface soil leading to nutrient removal in the running water. More over, due to heavy claycontent, the capillary porosity is relatively high resulting in impeded drainage and reduced soilconditions. This leads to increase of some soil elements to the level of toxicity to the plants. Italso induces nutrient fixation in the clay complex thereby making the nutrient becoming unavail-able to the crop, eventually causing deficiency of nutrients. The results of the work carried out in the scheme had indicated that the slow permeablesoils extended over an area of 739 in Coimbatore, 526 in Dharmapuri , 1243 inTrichi and 420 in Salem districts. The constraints in such soils can be managed by adoptingsuitable management practices like,• Provision of drainage facilities either through open drains or closed sub surface drains.• Forming contour bunding and compartmental bunding to increase the infiltration rates of the soils.• Application of huge quantities of river sand or red soils of coarser texture to dilute the heaviness of the soil. 7
  8. 8. • Application of liberal doses of organic manures like farm yard manure, compost, green manure, composted coir pith, sewage waste, press mud etc.• Adopting ridges and furrows, raised beds, broad bed and furrow systems of irrigation.• Application of soils conditioners like H-concentrate, vermiculite, Jalasakti etc., to reduce run- off and soil erosion.Shallow soils The shallow soils are characterised by the presence of the parent rock immediatelybelow the soil surface at about 15 - 20 cm depth. This restricts the root elongation and spreading.Hence the crops grown in these soils necessarily be a shallow rooted crops, which can exhaust thesoil within 2 - 3 seasons. There fore frequent renewal of soil fertility is a must in these soils. Among the six districts surveyed, the shallow soils are prevalent in a notable proportionof 209 and 384 in Salem and North Arcot districts respectively. These soils can bemanaged by growing crops which can with stand the hard rocky sub soils like Mango, Ber, Fig,Country goose berry, West Indian cherry, Anona, Cashew, Tamarind etc.Technologies for soil physical constraints, demonstrated to the farmers through fieldexperiments The various technologies like chisel technology for sub soil hard pan soils, compactiontechnology for the soils having excessive permeability and fluffyness, and other managementpractices to overcome the slow permeable soils, surface crusted soils in addition to thetechnologies developed are demonstrated to the farmers through field experiments and on farmtrials. The details of soil characteristics, extent, technologies and the results of experimentsconducted are detailed below. 8
  9. 9. Chisel technology for sub soil hard pans In Tamil Nadu, red soils (Alfisols) occupy 8 million hectares which constitutes 62 percent of the total geographical area. The occurrence of hard pan at shallow depths is the majorprevalent soil physical constraints in these soils. The agricultural crops are not able to enjoy thefull benefits of the soil fertility and nutrient use due to this major cause. The reasons for theformation of sub surface hard pan in red soils is due to the illuviation of clay to the sub soil hori-zons coupled with cementing action of oxides of iron, aluminium and calcium carbonate. The subsoil hard pan are characterised by high bulk density (>1.8 Mg m-3) which in turn lowers infil-tration rate, water holding capacity, available water and movement of air and nutrients withconcomitant adverse effect on the yield of crops.Technology to overcome sub soil hardpan To eradicate the problems of sub soil impervious layer in red soils, many trials wereconducted in farmers field / Tamil Nadu Agricultural University farms with chisel plough, whichproved effective than any other implements in successfully break opening of the hard pan, there byhelped to facilitate better root growth, nutrient and water movement with concomitant increasedproductivity.Methodology• The field is to be ploughed with chisel plough at 50 cm interval in both the directions.• Chiselling helps to break the hard pan in the sub soil besides it ploughs up to 45 cm depth.• The farm yard manure or press mud or composted coir pith at 12.5 t ha-1 is to be spread evenly on the surface.• The field should be ploughed with country plough twice for incorporating the added manures.• The broken hard pan and incorporation of manures make the soil to conserve more moisture 9
  10. 10. Experimental results Field experiments were conducted using chisel plough under rainfed and irrigatedconditions and the results are furnished hereunder. The results of the experiment conducted in farmers holding at Kande Kounden Chavadi(Pichanur soil series) with sorghum as the test crop indicated that chiselling at 0.5 m interval and 1m interval being on par recorded higher grain yield (Table 3).Table 3 Effect of chiselling on the grain yield of sorghum (Mg ha -1) and soil physical propertiesTreatments Bulk density Hydraulic conductivity Grain Yield (Mg m-3) (cm h-1) Mg ha-1Chiselling(0.5m apart) 1.42 11.9 4.72Chiselling(1.0m apart) 1.45 9.7 4.08Chiselling(1.5m apart) 1.58 9.1 3.71Unchiselled 1.65 5.2 3.42 The effect of chiselling was much realised in the residual crop than the first crop (Table4). The effect of chiselling at closer interval was spectacular as could be seen from the yield dataof second crop compared to chiselling at wider intervals. The experiments conducted on bothseasons clearly indicated the need for breaking the dense layer occurring at shallow depth withcloser intervals of chiselling for obtaining higher yield of sorghum crop.Table 4 Residual effect of chiselling on the grain and straw yield of sorghumTreatments Yield (Mg ha-1) Grain Strawchiselling (0.5 m apart) 4.48 20.37chiselling (1.0 m apart) 3.91 14.00chiselling (1.5 m apart) 2.51 11.22Unchiselled 1.37 9.22 10
  11. 11. In order to evaluate the efficacy of chisel plough with other tillage implementscommonly used by the farmers in soils having hardpan, a trial was conducted with tapioca as thetest crop and the results proved the superiority of chisel plough than the disc plough (Table 5)Table 5 Comparative efficacy of chiselling on the tuber yield of tapiocaTreatments Tuber yield Bulk density (Mg m-3) t ha-1 0-20cm 20-40cm 40-60cmChisel plough 53.79 1.527 1.666 1.635Disc plough 49.46 1.564 1.698 1.692Country plough 43.97 1.575 1.729 1.759Similar trend of results were also obtained when groundnut was raised as the test crop. Trials conducted with cotton as the test crop in farmers holding at Valukkuparai ofMadukkarai block where the actual problem of subsoil hard pan exists. The results revealed thatchiselling at 0.5 m interval with application of composted coir pith at 12.5 t ha 1- recorded 29 percent yield increase over unchiselled plots (Table 6).Table 6 Effect of chiselling and composted coir pith on bulk density and kapas yield of CottonTreatments Cotton kapas Bulk density (Mg m-3) Yield 0-15 15-30 30-45 (q ha-1) cm cm cmUnchiselled 7.8 1.552 1.714 1.745chiselled(0.5 m apart) 9.5 1.513 1.548 1.745chiselled + CCP 10.1 1.459 1.523 1.594CCP = Composted coir pith @ 12.5 t ha-1 After the harvest of cotton, maize Co 1 and sorghum Co 26 were raised as first andsecond residual crops. In both the crops, chiselling at 0.5 m apart with composted coir pith at12.5 t ha-1 recorded 21 and 15 per cent yield increase over the control respectively, revealing theadvantageous effect even for one or more residual crops. 11
  12. 12. The mobility of nitrogen and potassium ions was studied both in chiselled as well as inunchiselled plots (Table 7). The nitrogen and potassium mobility were observed up to 45 cmdepth due to chiselling, whereas in the unchiselled plot (control) the N and K mobility wasrestricted with the surface layer. Thus chiselling besides providing conducive physicalenvironment, helps in the nutrient mobility particularly N and K.Table 7 Mobility of nitrogen and potassium ions in chiselled and unchiselled plotsDepth (cm) chiselled Unchiselled KMnO4-N NH4OAc-K KMnO4-N NH4OAc-K kg ha-1 kg ha-1 kg ha-1 kg ha-10 - 15 217 213 224 34215 - 30 226 303 210 19030 - 45 236 118 172 6945 - 60 150 64 145 56 With a view to demonstrate and to disseminate the chiselling technology large scaledemonstrations were conducted in Pichanur soil series. Demonstration plots in an area of 8 acreswere laid out in Kande Koundan Chavadi in farmers field with rainfed sorghum Co.24 as the testcrop (Table 8) which proved the beneficial effect of chiselling to the farming community.Table 8 Effect of chiselling on the yield of rainfed SorghumTreatments Grain yield Straw yield t ha-1 t ha-1Country plough 0.54 2.19Chisel plough 0.82 2.69 The grain yield of sorghum was found to be higher in chiselled plot compared tocountry ploughing treatment. The residual effect of chiselling was also studied in the same plotswith Ganga 5 maize. The grain yield in chiselled plots was 3.27 t ha -1, while it was 2.69 t ha-1under the unchiselled plots, proving the superiority of chiselling. Demonstration trials for chiselling were also conducted with groundnut, blackgram, 12
  13. 13. maize tomato, samai as the test crops which again proved the beneficial effect of chisellingtechnology.Economics of chiselling The field experimentation and On Farm Trial (OFT) results showed that chiselling at 0.5m apart enhanced the yield of crops and improved the soil physical properties. However, anytechnology could be successful only if the return by adopting it is economical. Hence theeconomics of the chiselling technology was calculated for different crops. The economics worked out for sorghum Co 23 showed that a net profit of Rs 1125ha-1 could be obtained by adopting chiselling technology for loosening sub surface compact layers(Table 9). Table 9 Economics of chiselling in sorghum Treatments Yield (t ha-1) Grain Straw Value (Rs ha-1) Control 3.42 10.45 5,838 Chiselling 4.72 13.51 7,964 Increase over control 1.30 3.05 2,526 Cost of chiselling - - 1,000 Net profit - - 1,125 The economics of chiselling in tobacco crop is furnished in Table 10. Table 10 Economics of chiselling in tapioca Particulars Tuber yield (t ha-1) Value (Rs ha-1) Control 44.0 15,400 Chiselling 53.8 18,830 Increase over control 9.8 3,430 Cost of chiselling - 1,000 Net profit - 2,430 The results showed that chiselling in the hard pan soils improved the tapioca tuber yieldby 22 per cent and there by resulting in a net profit of Rs. 2,430 ha-1. The economics of chisellingwas worked out for groundnut, blackgram and maize are given in table 11.Table 11 Economics of chisel technology for groundnut, blackgram and maize 13
  14. 14. Crops Yield (t ha-1) Value of grain (Rs ha-1) Unchiselled Chiselled Unchiselled Chiselled Net profitGroundnut 1.34 2.18 4,704 7,642 2,240Blackgram 0.39 0.64 1,584 2,591 308Maize 2.10 3.27 4,620 7,190 1,870 The net profit ranged from Rs. 308 for blackgram to Rs. 2,240 ha -1 for groundnut crop.The chiselling was more beneficial for groundnut crop by breaking the sub soil hard pan in red soil,thus facilitates the peg formation.Conclusion drawn from the chiselling experiments• Reduces the bulk density by 0.2 to 0.4 Mg m-3.• The hydraulic conductivity was almost doubled in sub soil i.e. below 15 cm to 45 cm depth.• Conserves around 30 to 40 per cent more soil moisture.• Roots proliferation is improved by 40 to 45 per cent.• Nutrient mobility especially N and K increased by 20 to 30 per cent and 30 to 40 per cent respectively to sub surface layers.• Enhances the crop yield1. Sorghum : 25 - 30 per cent2. Tapioca : 20 - 25 per cent3. Groundnut : 15 - 20 per cent4. Cotton : 25 - 30 per cent• Residual effect can be realised for three seasons. 14
  15. 15. Technology developed for excessive permeable soils Sandy soils containing more than 80 per cent sand fractions occur in coastal areas, riverdelta and in the desert belts. Such soils do occur in Coimbatore, Trichi, Kanyakumari, Tanjore,Tirunelveli districts and in parts of coastal areas in Tamil Nadu. Delineation of areas for soilphysical constraints in Tamil Nadu focused that a total area of 14.93 lakh hectares were affectedby excessively permeable soils. The nature of excessive permeability of the sandy soil results in very poor waterretention capacity, very high hydraulic conductivity and infiltration rates. So whatever thenutrients and water added to these soils are not utilized by the crops and subjected to loss. Inaddition, it is not providing anchorage to the crops grown.Compaction Technology To correct the textural weakness of these sandy soils and to make them suitable forsound farming, various ameliorative measures have been devised by the scientists of Tamil NaduAgricultural University. Introduction of artificial barriers in the sub soil zone using asphalt,bitumin and cement dust have been found to arrest the higher rate of nutrient and water losses insandy soils. But the prohibitive cost of sub surface barriers make practically unavailable tofarmers. So, for such soils compaction technology developed by Tamil Nadu AgriculturalUniversity scientists proved to be very effective.Methodology• The soils should be ploughed uniformly.• Twenty four hours after a good rainfall or irrigation, the soil should be rolled 10 times with 400 kg stone roller of 1 m long or an empty tar drum filled with 400 kg sand.• Then, shallow ploughing should be given and crops can be raised.Other management practices• Use of minimum and frequent irrigations.• Form minimum plot size.• Adopt more number of splits for fertilizer application especially for nitrogen and potassium.Results from the field experiments 15
  16. 16. A field experiment was conducted initially in the sandy soils of Tindivanam (SouthArcot district, North eastern zone) with groundnut as test crop. The soil was compacted from thesurface at 10 per cent moisture level by making 10, 15 and 20 passes of stone roller weighing 400kg, after 24 hours and 48 hours of irrigation. The surface soil was then loosened by using acountry plough and groundnut was raised. The results revealed that there was an increase in pod yield of Groundnut by 11 per centdue to compaction of sandy soil with 15 passes of roller after 24 and 48 h of irrigation overcontrol. In addition, it increased the bulk density of the soil by 0.12 to 0.19 Mg m-3 and there byresulting in reduced infiltration rate and hydraulic conductivity. For groundnut crop, thecompaction with 15 passes of stone roller after 24/48 h of irrigation was helpful in enhancing thepod yields besides establishing good physical condition in soils. In an another field experiment in farmers field at Mankarai in Coimbatore district(Western zone) with maize as the test crop, the compaction technology proved its benefit over theexisting method of cultivation. The infiltration rate of the soil was significantly reduced bycompaction (Table 12). Table 12 Effect of compaction on Infiltration rate of the soil Treatments Infiltration rate (cm h-1) Control 14.88 10 passes 11.84 15 passes 10.40 20 passes 7.84 Compaction with stone roller in the field of high permeability was significantly effectivein increasing the bulk density (from 1.49 to 1.62 Mg m-3) and in reducing infiltration rate (from16.6 to 7.84 cm h-1), moisture retention from 7.71 to 10.62 per cent. As the number of passesincreased the bulk density also increased. However 10 passes of roller was significantly superiorin giving the highest grain and straw yields (36 and 39 per cent increase in yield respectively overcontrol). 16
  17. 17. In an another field trial conducted in farmers holding at Veerapandipudur (Coimbatore ,Western zone) to test the compaction technology with sorghum as test crop. The results showedthat as the number of rollings increased, the bulk density was increased from 1.51 to 1.71 Mg m -3in the surface layer of 0 - 15 cm depth and from 1.49 to 1.64 Mg m -3 in the sub soil layers. Theinfiltration rate decreased from 32.0 for control plots to 11.2 cm h-1 in the plots which received12 passes of stone roller However, the highest grain yield of Sorghum (20 and 25 per cent overcontrol) was obtained by passing of stone roller 9 times, after 24 h of irrigation and 6 times after48 h of irrigation respectively. The treatments with 9 passes of stone roller after 24 h of irrigationappeared optimum for higher grain yield of Sorghum by increasing the bulk density and loweringthe infiltration rate. Field experiments were conducted with groundnut (POL 2) crop in farmers holding atVeerapandipudur Coimbatore (Western zone) with 0, 5, and 10 passes of 400 kg stone roller after24 h of irrigation as treatments. Increase in the levels of compaction, increased the bulk density atall three depths with concomitant moisture retention from 5.85 to 7.39 per cent. Infiltration ratewas predominantly reduced to 59.79 cm h-1 from 70.66 cm h-1. Increased pod yield and haulmyields were recorded (18 and 13 per cent over control) by compacting the soil with 400 kg stoneroller 10 times. To test verify the compaction technology under rainfed conditions field experiment wasconducted with the test crop of groundnut followed by residual crop of tomato (Pusa ruby) andgroundnut (TMV 3) in the farmers holding at Coimbatore. Half of the area was left uncompactedand the other half was compacted with 400 kg stone roller 10 times, 24 hours after a rain fall(Table 13). 17
  18. 18. Table 13 Effect of compaction on crop yields (t ha-1)Treat Main crop First residual Second residualment Groundnut Tomato Groundnut Pod yield Fruit yield pod yieldCompacted 2.42 3.40 2.35Uncompacted 2.02 2.95 2.11 The results indicated that in the first crop of Groundnut, the compaction technologyhelped in enhancing the pod yield by 20 per cent over control (Table 13). The residual effect waswell reflected in the second and third crop of Tomato and Groundnut. Tomato - Pusa ruby, thefirst residual crop gave 15 per cent increased yield and the second residual crop recorded 11percent increased yield over the control. Thus it is very clear that compacting the soil by passing400 kg stone roller 10 times is more advantageous for improving the crop yields, that apart, theresidual effect can be realised for three years. Similar types of responses to compaction was alsoobserved in maize followed by groundnut crop in cultivators field at Veerapandy Pudur.Conclusions from the compaction technology experiments• Conserves more moisture (20 to 25 per cent).• Prevent nutrients from leaching and retains in the surface layer upto 20 to 25 %, 5 to 10 % and 25 to 30 % with respect to N,P and K)• Enables better seed soil contact• Enhances the yields of main and residual crops 1) Groundnut : 15 - 20 per cent 2) Maize : 25 - 30 per cent 3) Sorghum : 20 - 25 per cent 18
  19. 19. Compaction technology for fluffy paddy soils In Tamil Nadu fluffy rice soils are prevalent in Cauvery delta and in many parts of thestate due to the continuous rice - rice cropping sequence. The traditional method of preparing thesoil for transplanting rice consists of puddling, which results in substantial break down of soilaggregates into a uniform structureless mass. Under continuous flooding and submergence of thesoil for rice cultivation in a cropping sequence of rice - rice - rice, as in many parts of Tamil Nadu,the soil particles are always in a state of flux and the mechanical strength is lost leading to thefluffiness of the soils. This is further aggravated by in situ incorporation of rice stubbles andweeds during puddling. This causes sinking of draught animals and labourers during puddling.This has been thus, an invisible drain of finance for the farmers due to high pulling power neededfor the bullocks and slow movement of labourers during the puddling operations. Further thefluffiness of the soil lead to very low bulk density and thereby leading to very rapid hydraulicconductivity and in turn the soil does not provide a good anchorage to the roots and the potentialyield of crops is adversely affected.Technology In Tamil Nadu due to continuous and intensive cropping of rice. Puddling poses a bigproblem of sinking of draught animals and labourers to more than knee deep. Hitherto the onlyremedial measure adopted by the farmers was engaging very light animals like the Umbalacharibreeds. Now big and heavy Kangayam breeds are engaged for puddling operations which furtheraggravated the problem and hence to prevent the sinking, compaction technology was developedby the scientists of Tamil Nadu Agricultural University.Methodology• The irrigation should be stopped 10 days before the harvest of rice crop• After the harvest of Rice, when the soil is under semi - dry condition (proctor moisture level), compact the field by passing 400 kg stone roller or an empty tar drum filled with 400 kg of sand 8 times.• The usual preparatory cultivation is carried out after compaction.Results from the field experiments 19
  20. 20. To overcome the fluffiness in rice fields, a field trial was conducted with rice (Paiyur-1)in wet lands, Tamil Nadu Agricultural University farm, Coimbatore. The treatments imposed werepreparatory cultivation under dry condition after compacting the field with 400 kg stone roller bypassing 8 and 16 times. The results exhibited that 8 passes of roller was optimum for compactingthe soil, besides increasing the yield of rice grain by 35.5 per cent over control, where preparatorycultivation was done under dry condition, the increase was only 31.4 per cent under puddledcondition. Another field trial with rice (Ponmani) as test crop in wet land was carried out. Thetreatments imposed were compaction by passing 400 kg stone roller 8 times and application ofgypsum at 2 t ha-1. Compaction increased the grain yield of ponmani by 17.8 per cent over thecontrol. Second crop of rice (IR-50) was sown in the same plot to study the residual effect ofcompaction. Yield of rice in the compacted puddled field was enhanced by 10 per cent over thecontrol.Soil surface crusting In Tamil Nadu, soil moisture is a very serious constraint in dry belts, but even the smallamount of rainfall received is capable of developing the surface crusts. This problem is prevalentmostly in red soil areas (Alfisols) and is of greater magnitude in districts like Trichy, Pudukottai,Ramnad and Tirunelveli. Surface crusting is due to the presence of colloidal oxides of iron andaluminum in Alfisols which binds the soil particles under wet regimes. On drying it forms a hardmass on the surface. The surface crusting results in the prevention of germinating seeds,retardation of root growth, poor infiltration increased surface run off and poor aeration in therhizosphere.Results of the field Experiments A field trial with greenroom was conducted by applying different levels of farm yardmanure and lime at National Pulses Research Center, Vamban, Pudukottai District (Table 14).Table. 14 Effect of FYM and Lime on the physical properties of soil and yield of Green gramTreatments Grain yield Bulk density Total porosity 20
  21. 21. t ha-1 Mg m-3 Per centLime at 2 t ha-1 + 0.24 1.45 40.3FYM at 10 t ha-1Control 0.20 1.48 39.7 Combined application of lime and farm yard manure enhanced the yield by 20 per centover control besides improving the physical properties of the soil. In an another experiment with organics application to mitigate the surface crustingproblem, application of gypsum at 10 t ha-1 recorded the highest grain yield of cowpea (35 percent increase over control) closely followed by sheep manure application. The lowest yield wasrecorded in the control plots.Management of slow permeable soils Delineation work carried out in Tamil Nadu exposed that 14.32 lakh hectares of landare affected by slow permeable soils. Slow permeable soil is mainly due to very high clay contentand poor drainage conditions which results in poor aeration and water stagnation and ultimatelyleads to poor crop growth and in certain cases leads to complete death of crops.Results from the field experiments A field experiment was conducted with sorghum Co.24. employing different culturalmethods, the highest grain yield of sorghum was obtained from the raised bed plots, followed bysowing on the ridges, while the least yield was recorded from the flat beds. The second crop ofCotton MCU.9. raised in the same plots, the results showed that the flat bed system was superiorby registering the highest yield (1.02 t ha-1) Addition of organics namely FYM / Composted coir pith / press mud at 12.5t ha -1found to be optimum for the improvement of the physical properties besides, it facilitates watermovement to the root zone. For rainfed crops ridges are formed along the slopes for providing adequate aeration to 21
  22. 22. the root zone. Interception drainage channels should be provided to carry the excess water to ricefields located at lower end of the slope. The bulk density was found to be reduced due to increase in non-capillary pores inupper 10 cm layer of raised bed besides increase in yield of crops by forming raised and sunkenbeds. To reduce the amount of water retained in black clay soils during first 8 days of rainfall,broad beds of 3 - 9 m wide should be formed either along the slope or across the slope withdrainage furrows in between broad beds. 22
  23. 23. the root zone. Interception drainage channels should be provided to carry the excess water to ricefields located at lower end of the slope. The bulk density was found to be reduced due to increase in non-capillary pores inupper 10 cm layer of raised bed besides increase in yield of crops by forming raised and sunkenbeds. To reduce the amount of water retained in black clay soils during first 8 days of rainfall,broad beds of 3 - 9 m wide should be formed either along the slope or across the slope withdrainage furrows in between broad beds. 22
  24. 24. the root zone. Interception drainage channels should be provided to carry the excess water to ricefields located at lower end of the slope. The bulk density was found to be reduced due to increase in non-capillary pores inupper 10 cm layer of raised bed besides increase in yield of crops by forming raised and sunkenbeds. To reduce the amount of water retained in black clay soils during first 8 days of rainfall,broad beds of 3 - 9 m wide should be formed either along the slope or across the slope withdrainage furrows in between broad beds. 22