Soils: the Last Agricultural Frontier? David Granatstein WSU-Center for Sustaining Agriculture and Natural Resources Wenatchee, WA

Transcription

1 Soils: the Last Agricultural Frontier? David Granatstein WSU-Center for Sustaining Agriculture and Natural Resources Wenatchee, WA The Dalles, OR April 18, 2014

2 Outline Introduction Soil quality concept Soil testing Management impacts on soils Soil biology Conclusions Questions and discussion Spray-on paper mulch

3 Orchard Research Investment Pest and disease management - hi Genetics, genomics - hi Training systems - hi Fruit quality, post-harvest - hi Labor reduction Soils probably the least research investment in this part of the orchard system We don t fully understand the role of soils in the orchard ecosystem.

4 Why Are Soils Important? Water intake and storage Nutrient supply Decomposition - litter, pesticides Gas exchange with roots Soil biology good, bad, indifferent Physical support - trees, equipment Micro-climate

5 Orchard Floor Management Functions Water intake/storage Physical support Gas exchange for roots Nutrient cycling/storage Habitat (micro, macro) Micro-climate Impacted by: Understory species Understory canopy Irrigation system Nutrient inputs Spray drip Organic inputs Issues change with the age of the orchard.

6 Orchard Floor Management Review Examples of well-documented effects Microclimate: soil temperature inverse to the amount of herbage or mulch plant mulch dampens extremes of daily soil temperature plant cover reduces minimum air temperature by o C bare, compacted wet soil raised minimum air temperature by as much as 2 o C dwarf rootstocks grow best at 14 o C vs. up to 27 o C for seedling rootstocks (Skroch & Shribbs, 1986)

7 Orchard Floor Management Review Soil quality: avoid cultivation favorable soil effects: legumes > grass > mulch > bare ground > cultivation Water: soil moisture availability: mulch > bare soil > minimal cultivation > grass > legumes > continuous cultivation mowing decreases water use (Skroch & Shribbs, 1986)) Research Knowledge and Needs for Orchard Floor Management in Organic Tree Fruit Systems. Granatstein & Sánchez, Intl. J. Fruit Science 9:

8 Two Soil Paradigms 1. Soil as inert physical medium to anchor trees, transfer water and nutrients to roots, support machine traffic. Fumigate Irrigate Fertigate Herbicide strip 2. Soil as an essential living part of the orchard ecosystem that can enhance tree performance and environmental stewardship. Soil health, soil biology, nutrient cycling, biocontrol, plant diversity (above and below ground)

9 Soil Health Chemical O.M. Biological Physical Dynamic interplay of these 3 aspects (chemical, physical, biological); Organic Matter affects all three Influenced by environment (climate, geology, plants), these changes happen over long times Influenced by human activity (erosion, fertilization, irrigation, plants), these changes can happen quickly Soil health and soil quality mean the same thing

10 Greatest single factor determining natural soil productivity = amount & depth of SOM L. Carpenter-Boggs

11 Mini Tatura Trellis on M.9 Washington Standard System Herbicide strip, grass alley

12 With the first paradigm, we can fine tune nutrient timing and rate to maximize efficient use, and tree response; use precision irrigation; allow no competition in the tree row; plant grass sod in the alley. This can provide the tree with its needs but essentially by-passes the soil. With the second paradigm, we would encourage the soil biology and nutrient cycling to play a role in plant nutrition; symbiotic relationships between soil organisms and roots (e.g. mycorrhizal fungi); carbon inputs to support the soil biology; improved soil structure from soil biology and more active root systems. So current orchard practice is well-designed for the first paradigm but is almost opposite what is needed for the second.

13 Nutrient Export by Tree Fruits One part of nutrient management is understanding the removal rate by fruit and ensuring those amounts are replenished. Generally, this is inadequate as the trees themselves need additional nutrients, there are system losses (e.g. leaching, leaves blowing away), and nutrient uptake is less than 100% efficient (maybe 40-80% depending on the system). Careful irrigation water management is needed to minimize leaching losses. Yield lb/acre N P K Ca Apple 50 bin Pear 30 ton Peach 12.5 ton Cherry 7 ton

14 lb/ac Nutrient Content and Distribution in Apple N P K Ca Mg S Fruit Roots Leaf Top wood Different nutrients are concentrated in different parts of the tree. Here is an example from a 14 yr old Golden Delicious, 200 trees/acre. (Neilsen and Neilsen, 2003)

15 Soil and Plant Testing Many growers do not see relationships between soil (or tissue) tests and orchard performance. The following soil tests can be done for nutrients in soil. The standard test is the potentially available with strong extractants. Total nutrient (mineral) Potentially available strong, weak extractants Water soluble Biologically mediated in microbial biomass; P solubilizing bacteria; N fixation; mycorrhizal transfer; nutrient cycling Crop responses are evaluated by applying different levels of a given nutrient and seeing how yield or tissue level responds. With each type of test, a separate study is needed.

16 Soil and Plant Testing Most tests were designed for annual crops, and disregarded the soil biology. Some newer tests attempt to include the biological component. For a perennial crop like cherries, there is a considerable amount of nutrition within the tree and it can be remobilized, which further confounds soil test results. Newer approaches: Water soluble available now; affected by irrigation management; WE organic C = food for microbes; WE organic N, has been missing from standard tests, can be half the total avail. N Organic acid extractant mimics plant root, microbe effects Biological tests respiration, microbial biomass, enzymes, soil food web, nematode community, etc. WE=water extractable

17 Soil and Plant Testing Plant monitoring can be done by several methods, some commercial, others more in development or research. Plant sap analysis is a newer approach with some history in Europe and just being explored in the US. Plant monitoring: Leaf tissue test Plant water stress Remote sensing, imaging Plant sap analysis Monitoring tree water stress with a pressure bomb.

18 Management Can Change Soil Soil chemical changes in five orchards (12 40 years old); sprinkler irrigation and ammonium based fertilizer Row Alley ph w Ca (ppm) Al (ppm) Bases (%) Normal orchard practice can thus lead to dramatic changes in the soil in relatively short periods of time. Often, organic matter decreases in the tree row while it increases under the grass in the alley.

19 Soil Organic Matter Change 0-20 cm depth after 5 yr, New York, apples (Merwin, 2003) Herbicide Living mulch Mowed grass Straw mulch

20 MI Tart Cherry Conventional Conventional + fertigation (Irr) Cover crop mix (Irr) Cover crop + fertigation (Irr) Mulch Compost Compost biosystem (Irr) Highest yields mulch Cover crops, compost improved soil quality Cover crop + fertigation was among most profitable Nitrate leaching most in season-long herbicide Fewest pest mites in cover crop; beneficial mites all year in red clover (Edson et al., 2003)

21 MI Tart Cherry (Edson et al., 2003)

22 Weed Fabric in Sweet Cherry OSU, Hood River, OR Fabric groundcover vs. bare ground in tree row fabric $2124/acre increased costs 2004 fabric trt net returns $2306/ac more than bare ground (1 st yr of production) $1633/ac more with fabric Fabric trees produced more fruit at an earlier age, maintained higher yields (Yin et al., 2007) Photo: H. Ostenson

23 Yield Effects - WA Fruit Yield (bins/acre) Gala apple a b b Fruit Yield (bins/acre) Anjou pear Mulch Herb/flame Tillage a ab b p= Commercial organic orchards, large-scale field plots yr cost/ac: Till $318 Mulch/flame $1,425/acre Mulch returned $4,776/ac more than Till

24 Wood Chip Mulch weed control for 1-3 yr can increase fruit yield, size and/or tree growth wood chips have not attracted voles

25 Effect of Orchard Mulching on Soil Moisture Depletion Soil Depth (cm) Moisture Depletion (mm) Mulch 20-25% reduction in irrigation water from mulching Unmulched

26 Treatment Soil Changes from Mulches in Tree Row Soil C (g/kg soil) Infiltration (L/hr) Herb. Strip (check) 10 d 5.5 cd Biosolids 19 a 14.6 ab Shredded Paper Mulch 13 cd 10.0 bc Alfalfa Mulch 15 bc 15.5 ab SPM + Biosolids 17 ab 16.0 ab Black Fabric Mulch 9 d 3.4 d 7-yr study, Summerland, BC; sandy loam soil, high density Spartan /M.9 Soil carbon (C) and water infiltration improved with the various mulches vs the Check and Fabric (Neilsen et al., 2003)

27 Orchard Mulching Trials Summerland, BC 5 th Leaf Spartan / M.9 TCSA Roots Yield (mm 2 ) (g/0.018m 3 ) (kg/tree) 1. Check (glyphosate) 1011 b 11.3 c 10.3 c 2. Biosolids (Vancouver) 1052 b 16.9 bc 11.2 bc 3. Paper mulch 1565 a 28.7 abc 13.0 ab a 41.8 a 13.9 a 5. Composted biosolids a 38.7 a 14.9 a 6. Alfalfa hay 1203 b 35.2 ab 14.0 a 7. Black fabric mulch 1125 b 19.1 bc 12.7 abc Tree responses to amendments parallel the changes in soil in the previous slide. TCSA=trunk cross sectional area. Trunks grew 40-50% more, roots increased 2-3 times, and fruit yield rose 30-40% over the Check. (Hogue et al., 2000)

28 Nematodes / 100ml soil Effect of Mulches on Nematodes in Orchard Soil - Summerland, BC Bactiv. (x10) Omni/Pred Pratylenchus Check VBio PM VBio+PM KBio+PM AlfM Geotex In addition, the mulches changed the nematode community in the soil, increasing omnivorous and predatory nematodes which likely resulted in the (Hogue et al., 1998) large decrease in root lesion nematode (Pratylenchus). (T. Forge)

29 Before sweeping After sweeping 2/18/10 2/18/10 Sweeping flailed prunings onto the tree row can be an internal source of mulch. Mulch on tree row 2/18/10 4/30/10

30 Mow and Blow Side Discharge/Mulching Mower Mowing alley grass and blowing onto the tree row is another internal source of mulch. Benefits include: Reduced passes with mower Reduced passes with weed sprayer Reduced irrigation (H. Huntley)

31 Mow & Blow Mulch Trial Quincy, WA Fuji/M.9 2 nd and 3 rd leaf Tall fescue forage grass mix, mowed weekly 1x rate = lb/ft 2 dry matter About 10% of clippings retained after 2 yr 2x rate led to significant increase in tree growth Clippings add lb K/ac; 50 bin/ac apple crop removes 56 lb

32 Mow & Blow Mulch Trial Quincy, WA % increase in trunk growth with 2x mow and blow p=0.025 % Increase TCSA a a b a a b a a b 0 1x 2x year

33 Orchard Alley Legumes Other plants can be grown in the alley for specific purposes, for example, legumes to supply nitrogen to the orchard. Alfalfa Trefoil Quincy, WA -- Direct seeded, May 2008 Year 3, 39 days after mowing

34 Legume Cover Crops for N 5 th year Mulch build-up Kura clover

35 Qunicy, WA Trial Cumulative Cover Crop Biomass Cover Crop Biomass, Add lb N/ac $0.65/ lb N Biomass DM (kg/ha) Alfalfa Grass Kura Ladino Trefoil Alfalfa Grass Kura Ladino Trefoil Spray No spray

36 Rebuilding Soil Sweet Cherry Wenatchee, WA Planted in old gravel pit; trees dying, poor growth, etc. Compost, mulching, mow and blow used to rebuild soil More uniform trees, less compost used More even soil moisture and less frequent irrigation Yields ton/ac (G. Johnson)

37 Checking mulch Checking Lbs Per Treated Acre Oct 27, quantity 10/27/ (G. Johnson)

38 Mulch Analysis Nov The mulch contains a wide range of nutrients, as well as a large carbon input. (G. Johnson)

39 Experiment Results 6,625 lb/ac of mulch! Total N in mulch was 170 lb. Estimate that 15-20% of that is plant available, mulch can provide lbs N/ac/yr Mulch has added 1,300 lb/ac Carbon! (G. Johnson)

40 Soil Quality Soil Biology The last frontier Three different relationships with microbes in soil: Microbe - Microbe Microbe - Macrofauna Microbe Plant (root)

41 Apple Replant Disease Gala/M26, Moxee, WA Growth after one year. Virgin row was 14 from replant row and had not had apple previously Same shovel Replant soil Virgin soil (M. Mazzola)

42 Many perennial crops experience what is known as a replant disease when they are planted back into soil where they were previously grown. Letting the land lie fallow for several years did not reduce replant disease for apple. Planting new trees in the former alleys did dramatically reduce disease. Soil fumigation is currently the standard practice and leads to clear economic benefits, but there may be some long-term impacts on the soil biology that are suboptimal. The disease appears to largely come from the shift in the original soil microbial community before apple (or other species) is grown, driven by the root exudates from apple. In the following slide, the effect of the length of time apple was grown on soil in which an apple seedling is replanted is shown, on the same site and soil type with a sequential series of apple plantings. By the third year, the soil biology has changed such that the apple roots of a replanted seedling are virtually destroyed by the plant pathogens that have become more prevalent.

43 Growth of Gala Apple Seedlings in Soil from Orchard Blocks of Varying Age (M. Mazzola)

44 Researchers have looked at various biological approaches to remediate replant disease. Dr. Mark Mazzola, USDA-ARS in Wenatchee, WA, tested the growing of short-succession wheat crops prior to replanting apple. The effect varied with the cultivar of wheat used. Penewawa wheat led to some of the best apple growth. The seedlings in the untreated control barely grew. The wheat technique was very successful in the greenhouse but did not perform as well in field trials and thus is not a recommended practice at this time. Current focus is on the use of brassica seed meals and anaerobic soil disinfestation.

45 Growth of Gala Apple Seedlings in CV Orchard Replant Soil Following Planting with Different Wheat Cultivars (M. Mazzola)

46 Cherry in Apple Soil Cherry planted after cherry, or after apple or other tree fruit, also experiences replant disease. The heat from pasteurization greatly reduces the replant disease. Gisela 5 Roots in Apple Soil Pasteurized Control Pasteurized Control Consistent and large improvement in growth of apple, cherry and pear when established in replant soils (irrespective of previous fruit tree species) in response to steaming the soil or applying chloropicrin.

47 Final Report Card Improved Tree Performance Dr. Gerry Neilsen, AgCanada, conducted a number of multi-year studies of mulches and soil amendments, using high density apple on dwarfing rootstock in randomized, replicated trials. He found that surface mulching led to measurable improvement in tree performance about 2/3 of the time, whereas incorporated amendments showed a benefit less than 1/3 of the time. Sites Success Batting average Surface Mulch Incorporated amendment Some summary observations he made: Mulch/amendment buffered against accidental water stress (reduced fruit size) Ineffective on fertile sites, strong fertigation programs, high frequency irrigation, excessive irrigation (N leaching) Ineffective when an important limitation was not addressed by treatment (replant disease, K deficiency) (G. Neilsen)

48 Knowledge Gaps Many questions remain regarding orchard soils including: Is there an ideal soil quality for our orchards? Does organic matter matter? Manipulation of rhizosphere vs. bulk soil for specific results Interaction of rootstock genetics with soil Enhancing beneficial soil biology e.g. mycorrhizae, plant growth promoting bacteria Pest / nutrition interactions In addition, growers are anxious for better tests of soil and plants that are predictive of future orchard performance.

49 More information can be found at the Orchard soils web page