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PAGE 1 deep ripping fact sheet 2009 Deep ripping not appropriate for all soil types A comprehensive understanding of the cause and location of high soil strength is required before undertaking deep ripping as research has shown it is does not provide an economic solution in some soil types. PHOTO: BrAD COLLiS KeY pOints ■ deep ripping of compacted soils is most likely to improve grain yields on sandy soils and where compaction has occurred on upper parts of the soil profile through machinery traffic or livestock trampling. ■ deep ripping is less effective on heavy clay soils unless combined with gypsum on sodic soils prone to waterlogging. ■ deep ripping will provide little benefit if other subsoil constraints such as salinity, sodicity or acidity are also present. ■ recent advances in machinery, such as ‘slotting’ and deep placement equipment to simultaneously introduce ameliorants at depth with ripping, could increase the financial and agronomic effectiveness of this The greatest yield responses approach to managing subsoil following deep ripping have constraints. been recorded in sandy soils. Soils with high strength can occur By breaking up the soil, deep ripping of ameliorants. Nutrients can be naturally or due to compaction, but can free the way for roots to penetrate deep placed to ameliorate nutrient either way, left untreated, these soils can the soil and access water and deficiencies and toxic concentrations significantly limit on-farm profitability nutrients, leading to yield increases. of aluminium, deep placement of lime by reducing grain yields and quality. can ameliorate acidity and gypsum However, it is only effective on certain can ameliorate sodicity. Soil compaction can occur in many soil types and is only likely to be cropping soils of southern Australia financially viable when combined with and may be traffic or livestock- strategies to ameliorate other subsoil What is deep induced or naturally occurring. constraints such as nutrient deficiency By limiting the ability of crops to gain or toxicity, or sodicity (see Sodicity). ripping? access to water and nutrients, soil How the soil is managed after ripping Deep ripping, sometimes known as compaction can reduce crop growth, also affects the return from ripping. subsoiling, involves disturbing the soil grain yields and quality. Converting to stubble-controlled traffic below the normal cultivation layer, often farming can help retain the value of to 40cm, with strong, narrow tines Deep ripping involves disturbing the deep ripping. without inverting the soil. it is not the soil below the normal cultivation layer, same as delving, also called clay delving, often up to 40 centimetres, without Deep ripping also presents an where wide-bladed tines are used to mix inverting the soil. opportunity for deep placement deep clayey subsoil with sandy topsoil. Level 1, Tourism House | 40 Blackall Street, Barton ACT 2600 | PO Box 5367, Kingston ACT 2604 | t. +61 2 6166 4500 | f. +61 2 6166 4599 | e. firstname.lastname@example.org | w. www.grdc.com.au PAGE 2 Why deep rip? When to deep rip? Deep ripping breaks up traffic-induced Deep ripping is slow and costly. Timing often result in large soil clods being or naturally occurring layers with high of ripping is critical but the results brought to the surface. Conversely, soil strength. With deep ripping, roots can last for many years if appropriate if soils are too wet, smearing can can penetrate the soil faster and deeper management practices are used. result. A good rule of thumb to assess to absorb more soil moisture, capture appropriate soil moisture condition For maximum yield response, the is to roll the soil (at different depths more soil nutrients and improve yield. depth of ripping must be below where the ripping will occur) between These benefits vary with soil type and the traffic pan and this may mean your hands. if a long ribbon (>10cm) are more likely to be observed where penetration to at least 30cm. Moist forms easily then the soil is still too there are no other chemical constraints, soil throughout the ripping depth moist. if no ribbon can be formed or if such as sodicity, present. is necessary to reduce the power the soil is too hard to reform then the Care must be taken to avoid immediate requirement and wear of points and to soil is probably too dry. re-compaction by minimising wheel obtain efficient softening. traffic on newly-ripped paddocks. When suitable soil moisture conditions The main difficulty in accommodating exist, deep ripping should be done Some growers move to controlled deep ripping within the farming system prior to the cropping phase but traffic to reduce re-compaction. By is the availability of suitable soil sufficient time allowed for subsequent matching all implement widths and moisture conditions. seedbed preparation. in many tractor wheel spacing, controlled traffic ensures all vehicle traffic is confined to if soils are too dry, draft and environments/seasons this is not the same tracks, minimising the area of fuel consumption are increased always possible. re-compacted soil. significantly. ripping very dry soils can in Western Australia, in the areas where ripping has been adopted fastest, responsive soils are often cropped continuously with wheat and lupin rotations. ripping can be done after substantial summer rains, or at PHOTOS: KELLiE PENFOLD the break of the season before sowing wheat. ripping at the break conflicts with lupin seeding or with early sowing of wheat. Delaying wheat or lupin planting can reduce yields. However, this must be weighed against potential The block clods of the compacted layer following ripping (right) compared to the small yield advantages from ripping, friable aggregates in an uncompacted soil (left). including its residual value. high sOiL strength from deep ripping depend on soil type, FIGURE 1 AFFECT OF TYRE WIDTH Many of australia’s cropping soils are rainfall and crop species. ON THE SHAPE OF COMPACTION pre-disposed to compaction because the an audit of agricultural land in australia by IN UNDERLYING SOIL proportions of sand, silt and clay particles the national Land and Water resources in these sandy or loamy soils are ideal for audit (2001) suggested that once the bulk tight packing. also the types of clays in density exceeds 1.6 – 1.8g/cm3 in sandy these soils do not often promote strong soils and above 1.4g/cm3 in silty and clay swelling and shrinking, which helps break soils, root penetration, and consequently up compaction. plant growth, are affected. soil compaction can reduce crop growth compacted or hard layers can also and yield as it limits the ability of crops cause water logging within the root zone, to gain access to water and nutrients. often resulting in a perched watertable. compacted layers can occur naturally due if this occurs, the soil profile above the to the chemical and physical characteristics hard layer can become saturated, oxygen of the soil or may be induced by traffic (as can be excluded and plant roots can seen in figure 1) or livestock. eventually die. Topsoil these layers may be visible or indicated although no comprehensive surveys have by distorted root growth. When measured been undertaken to estimate the extent they will record a penetration resistance of and severity of compacted layers in at least 2 Mega pascals (Mpa). generally australian agricultural soils, the available a subsoil strength of 1.5Mpa is the evidence suggests compacted layers are a accepted threshold at which root growth major problem in some soils. is restricted. at a strength of 3Mpa root growth is significantly reduced. Tyre width can change the shape, position Compaction zone deep ripping is one method of reducing and degree of compaction beneath the SOURCE: Subsoil, kirby, et al, Soiil and Tillage Research, soil compaction, however yield responses tyre tracks but compaction still occurs. Elservier, Netherlands, 1991 PAGE 3 identifying high-strength or compacted soils When talking about high-strength capacity (usually in winter when the Soil and land type soils, the terms ‘high bulk density’ soil profile has wet-up to at least 50cm Sandy soils tend to have higher bulk and ‘compaction’ are often used depth) as soil water content can have densities compared to clay soils, so interchangeably. a bigger influence than compaction awareness of soil type will help in on penetration resistance. readings diagnosing high bulk density. Soil Bulk density is the weight of soil in a of more than 1.5MPa should be strength is generally independent of given volume. Many subsoils naturally investigated further. if the soil is not soil type and so provides a unifying have high bulk density and sandy soils wet, field capacity readings from the measure of compacted soil. are more prone to high bulk density. suspect compacted site should be compared with those from a known Subjective assessment of When soil compaction occurs the bulk soil structure density of the soil in the compacted uncompacted site. Both sites should have the same soil type and the same The presence of physical constraints layer increases. Compaction typically can be assessed visually by digging occurs to a depth of about 30 to soil water content. a shallow soil pit (see box below) 40cm due to traffic by machinery Plant symptoms to observe crop rooting depth, the and/or animals. The type of tyre, the identifying plant symptoms that are presence of compacted soil layer and air pressure in the tyre, the weight of directly caused by compacted subsoil fracture planes. The occurrence of wet the vehicle and, most importantly, soil horizons is difficult because other soil within the rooting zone at harvest moisture, all have a bearing on soil factors can cause similar symptoms. also indicates the presence of subsoil compaction by vehicles. Overall, compacted subsoils impede constraint/s. Compaction is typically measured by root growth, causing reduced plant vigour and poorer water-use efficiency Signs of compaction are large peds (or the amount of force (in megapascals) clods) with a platy (horizontal) shape required to penetrate a layer; bulk as roots have limited access to water and nutrients, especially in the subsoil. or massive (featureless) look. in poorly density is measured as the mass of soil structured cracking clays, ped faces per unit volume (g/cm3). Other symptoms include a lack of roots present below a certain depth (shallow are dull rather than shiny. The soil may root system) and, in some cases, feel puggy when wet and peds will tear Penetrometer apart like raw pastry. When dry, peds An accurate and rapid method for roots turning or branching to grow horizontally above the compacted are not friable; they break where you determining soil strength (to depths apply force rather than parting along of more than 45 centimetres) is layer. This horizontal growth can often be easily observed in pulse and oilseed natural fracture faces. to use a cone penetrometer. High penetration resistance may reveal a crops by carefully excavating a few compacted layer but the measurement plants with a shovel. Plant roots can is strongly affected by soil moisture. penetrate compacted layers through The measurements should ideally cracks and macropores in structured be taken when the soil is wet to field soils causing very little impact on yield. soil pits FIGURE 2 ROOT ZONE SOIL CONSTRAINTS in-crop soil pits allow the rooting depth – PHYSICAL, CHEMICAL AND BIOLOGICAL of a crop to be determined. they can help identify potentially limiting soil layers that negatively impact on root growth. these can include compacted Soil borne layers or hard pans, carbonate layers, pathogens ferricrete or calcrete. this method - Fungi Surface stubble Surface is useful in diagnosing the presence cultivation A Horizon - Nematodes of chemical and physical subsoil constraints. Once identified, detailed Deleterious Compaction bacteria Al toxicity Fe, Zn testing is required to determine the extent of any limitations and whether (low pH) deficiencies Acidity Sodicity B Horizon it is feasible to reduce or remove Ion toxicities Transient Low them. aerial photographs, eMi (Na, B, Al, HCO3) salinity permeability (electromagnetic induction) maps that Macro and indicate soil moisture, salt and clay micronutrient Alkalinity Reduced deficiencies (high pH) leaching content and maps of yield or biomass can be used to determine the best locations to dig soil pits and to take soil samples. PAGE 4 Where to deep rip The success of deep ripping in and high-pressure injection to to control (non-ripped) treatments improving crop growth and yield is simultaneously apply ameliorants on lighter textured soils. in 46 trials strongly dependent on the soil type at depth with deep ripping, could conducted between 1981 and 1989 and presence of other soil chemical/ increase the effectiveness of this in WA on yellow loamy sands, all but physical constraints to crops. approach. two demonstrated increased yield with ripping. Generally, ripping is most successful Once deep ripping and amelioration on sandy soils and least successful are completed, strategies such as in other areas and on different soil on heavy clay soils (see summary stubble retention and controlled traffic types deep ripping has been much less compiled by John Kirkegaard, CSirO, should be considered to maintain soil reliable and benefits persist for shorter Table 1). its effectiveness in improving structural improvements, otherwise re- periods. it is not clear whether this is subsoil structure is also strongly compaction will quickly occur in most due to the compacted layers having dependent on implement design, soil types. less impact on crop productivity or that soil water content and the depth of the deep ripping approaches have not ripping as well as the concurrent use Generally, sand-over-clay soils will not been fully effective. of amendments. The primary aim of respond to ripping unless the depth of deep ripping should be to maximise the sand is deeper than the depth of A review of crop responses to deep disturbance (loosening) in the subsoil ripping. Sand-over-gravel soils have ripping to 40cm in southern NSW whilst minimising the draft. responded to ripping if the gravel is not from 1980 to 2005 showed yield a completely restrictive layer. improvements in only five of the 15 Deep ripping appears to be more crops measured despite deep ripping successful where compacted layers in WA deep ripping has increased reducing soil strength to less than induced by tillage are present rather cereal yields in areas with more than 1MPa. ripping had no effect on yield than where the subsoil is sodic and 350 millimetres rainfall by more than at five sites and significantly reduced has inherently high soil-strength, 600 kilograms per hectare in deep crop yield/biomass at four sites. for example sodosols. Sodosols sandy soils that have a compacted are common in the cropping areas layer less than 40cm deep and where The current published evidence does of Victoria and South Australia. On the subsoil is not highly acidic. not support deep-ripping of soils in sodic soils, ripping is unlikely to south-eastern Australia, except in A study in the northern Mallee of combination with gypsum on sodic have significant long-term beneficial Victoria recorded yield responses in effects unless the structure of the soil clay soils, where winter water-logging wheat of up to 40 per cent by deep can cause significant yield reductions is simultaneously stabilised through ripping on non-sodic sandy loam soils. amelioration with gypsum (calcium in wet seasons. Studies in WA have also demonstrated sulphate) or organic matter (see Soil yield increases of 25 per cent in wheat pits, page 3). recent advances in and 30 per cent in chickpea compared machinery, such as slotting equipment TABLE 1 SUMMARY OF DEEP-RIPPING RESPONSES RELIABLE RESPONSES VARIABLE RESPONSES FEW RESPONSES Soil type and Deep acid Neutral/ Sodic clay Duplex- Duplex- Red loams Black depth sand alkaline sand (grey/brown vertosol) deep shallow (Kandosol) vertosols Cultivated 0cm Self zone 10cm Waterlogging mulching Compact layer Strength >1.5 – 2.0 MPa; Distorted roots 25cm Acid layer Waterlogging Acid layer Low nutrient Sodic clay Sodic clay Associated availability Sodic clay Anaerobic subsoil 100cm High density Salinity Anaerobic Anaerobic High density High density problems Low water Boron High density High density well structured Poor structure Salinity and N holding Poor structure Poor structure Salinity (Cl-) N leaching Salinity 200cm Mean crop WA 20–37% Vic/SA 23% NSW 33% (0-300) WA 22% 4% Few Few response (0–43) WA 47% NSW 0–20% range (wheat) Vic 25% Best bet Rip with lime if Rip with Rip with gypsum Rip if clay >30cm Do not rip Few responses Few responses management acid claying nutrition Avoid Possibly add Self repairing re-compaction gypsum/lime References Jarvis (2000) Sadras et al (2005) Chan et al (2003) Crabtree (1989) Crabtree (1989) Kirkegaard (W’shop) Dalal (W’shop) Davies et al (2006) Wilhelm (W’shop) Armstrong (2001) Davies (2006) Davies et al (2006) Hamza (2003) Armstrong (W’shop) McKenzie et al (1990) Jarvis (Various) Hall (W’shop) Hamza (W’shop) Ellington (1986) Kirkegaard (W’shop) PAGE 5 rainfall produce responses in crop growth, but Negative responses to ripping can On suitable soils, responses to ripping grain yield responses may be curtailed be observed in some seasons with a have been least reliable in areas with if there are poor finishing rains or soil ‘dry finish’ as crops growing on deep less than 325mm annual rainfall. moisture is restricted. ripped soils grow more vigorously. Plant roots only grow where there is They produce more biomass, and use subsoil moisture. With limited rainfall, if the season has had good rainfall up the available subsoil water more soil may not be wet deep down in the or significant amounts of soil water quickly, leaving insufficient soil water soil profile. ripping, therefore, will not have accumulated during the previous for grain filling. provide roots any additional access summer, there is more potential for to water. root growth, water and nutrient extraction from deeper in the soil On responsive soils in the medium profile when subsoil constraints have rainfall area, ripping will almost always been dealt with. Deep ripping impacts Following deep ripping, roots can so they are potentially groundwater penetrate the soil faster and deeper recharge areas. They are also likely to absorb more soil moisture, capture to be susceptible to soil acidification, more soil nutrients and improve yield. partly through leaching of nitrate. There are other impacts of deep ripping, both positive and negative. Apart from the productivity gains from deep tillage, the higher-yielding residual value of deep ripping wheat crops will use more water and The response to deep ripping can last nutrients. This will reduce the leaching for many years. in responsive soils the of nitrate, through deeper rooting and residual benefit of the ripping in the greater nitrogen uptake, and in the second year is about half the initial long-term will reduce flooding and response and declines further over salinity of lower landscapes. time due to: ■ re-compaction by traffic; Deep ripping downsides PHOTO: STEPHEN DAViES ■ natural soil settling and cementation; Although deep ripping can increase and water infiltration into the soil, it can also ■ the greater removal of nutrients and destroy the natural soil aggregation water by the previous year’s higher- and macropores of loamy or finer- yielding crop. textured soils, bring sodic subsoil to the surface (resulting in poor The use of controlled traffic after deep establishment of crops), and deplete ripping has been shown to help retain soil organic matter. it can also reduce Differences in root growth are clear the benefits of deep ripping for longer, soil water content in the surface layers between un-ripped soil (left) where very especially in heavier soils. by disturbing and exposing the soil to few roots penetrated below 30cm and evaporation, which can reduce crop Other benefits of deep ripping the rip line (right) where roots were still yield in dry seasons. The soils that are most likely to common at 40cm. respond to deep ripping are sandy, The economics of deep ripping sodicity Economics should be the overall long-term beneficial effects unless the deciding factor on whether an structure of the soil is simultaneously sodicity occurs naturally in amelioration strategy is implemented stabilised through amelioration with soils that contain a high level or not. The final strategy selected will, either calcium or organic matter. of sodium relative to calcium, in turn, depend on the capacity of the potassium and magnesium. landholder to afford these costs and A sensitivity analysis can be a useful it causes dispersion of soil their attitude to risk. method of assessing the change in particles, which leads to the crop yield by identifying a specific price collapse of soil structure and The benefit of deep ripping on crop required to return the cost of deep loss of pore spaces, which performance varies widely. Most ripping. in the example in Table 2 the limits seedling emergence, the studies indicate that deep ripping total amelioration cost for deep ripping growth and efficient function alone provides little or no long-term based on contract rates is $40/ha. of plant roots and increases impact on the physical condition of With an average production cost of waterlogging. gypsum clay subsoils. Yield benefits have been $165/ha the total cost of production (calcium sulphate) application recorded from deep ripping on non- equals $205/ha. The breakeven points is extensively used to counter sodic sandy loam soils in the northern for both wheat price and yield are sodicity. Mallee. On dispersive (sodic) soils, highlighted in yellow over the page. ripping is unlikely to have significant PAGE 6 TABLE 2 THE ECONOMiCS OF DEEP riPPiNG Price ($/tonne) Yield (t/ha) 100 150 200 250 300 350 0.5 50 75 100 125 150 175 1 100 150 200 250 300 350 1.5 150 225 300 375 450 525 2 200 300 400 500 600 700 2.5 250 375 500 625 750 875 an example of the impact of changes 3 300 450 600 750 900 1050 in price and yield to achieve payback 3.5 350 525 700 875 1050 1225 from deep ripping in the first year if the 4 400 600 800 1000 1200 1400 total cost of production including deep ripping is $205/ha. 4.5 450 675 900 1125 1350 1575 SOUrCE: Identifying, understanding and managing hostile subsoils for cropping - A reference manual for neutral-alkaline soils of south-eastern Australia. Deep ripping equipment Deep ripping can be achieved using a a dense subsoil, disturbance may variety of implements. need only be confined to relatively shallow depths (for example, 20cm). Various tine designs have been used Once deep ripping and amelioration successfully in deep ripping including are completed, strategies such as a ‘winged’ design (Spoor and Godwin stubble retention and controlled traffic 1978), shallow tines in front of the should be considered to maintain deep tines (Hamza et al. 2005), and any improvements in soil structure. the ‘Paraplough’, as well as more Otherwise, re-compaction will occur traditional tines with straight shanks. quickly on most soil types. Draft requirements increase rapidly recent advances in machinery, with the depth of soil disturbance such as ‘slotting’ equipment to so a good knowledge of where the simultaneously introduce ameliorants Where compaction is closer to the principal soil physical limitation is in at depth with ripping, could increase surface a deeper pass with narrow the soil profile is required. For example, the effectiveness of this approach to tillage points has been able to break up on soils with a shallow but fertile managing subsoil constraints. thin compacted layers. topsoil (for example, 10cm), overlying Useful resources: ■ A general description of various subsoil constraints and how to manage them for grain production (including deep ripping) can be found in Identifying, understanding and managing hostile subsoils for cropping - A reference manual for neutral-alkaline soils of south-eastern Australia, published by The Profitable Soils Group (2009) (ISBN 978-0-9806136- 0-5) which can be downloaded from www.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/soil_mgmt_subsoil ■ Roger Armstrong, DPI Victoria (03) 5362 2336, Email email@example.com ■ Stephen Davies, Department of Agriculture and Food, WA (08) 9956 8555, Email firstname.lastname@example.org ■ John Kirkegaard, CSIRO Plant Industry (02) 6246 5080, email@example.com ■ Western Australia www.agric.wa.gov.au/objtwr/imported_assets/content/lwe/land/ cult/fn088_1994.pdf Disclaimer Any recommendations, suggestions or opinions contained in this publication or arising by reason of any person using or relying on the information in this do not necessarily represent the policy or views of the Grains Research and www.coretext.com.au publication. Development Corporation. No person should act on the basis of the contents of caUTiON: researcH ON UNreGisTereD PesTiciDe Use this publication without first obtaining specific, independent professional advice. Any research with unregistered pesticides or of unregistered products reported The Corporation and contributors to this Fact Sheet may identify products by in this document does not constitute a recommendation for that particular use by proprietary or trade names to help readers identify particular types of products. the authors or the authors’ organisations. We do not endorse or recommend the products of any manufacturer referred to. Other products may perform as well as or better than those specifically referred All pesticide applications must accord with the currently registered label for that to. The GRDC will not be liable for any loss, damage, cost or expense incurred particular pesticide, crop, pest and region. produced by Acknowledgements: Roger Armstrong, DPI Victoria; John Kirkegaard, CSIRO; and Stephen Davies; Department of Agriculture and Food, WA.
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