Cover Crop Effects on Soil Health

Transcription

1 Managing & Monitoring Cover Crop Effects on Soil Health A root-centric perspective

2 Joel Gruver WIU AGRICULTURE

3 Big Hugh, how long will it take to win the war against soil erosion?

4 > $300 billion in technical & financial assistance Montgomery Cty, IA

5 > 70 years later (2008) We haven t won the war but there is growing recognition that soil improvement is a better goal than olerable degradation

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8 Major progress has been made in some areas Lookin real green in the neighborhood Home of the Tillage Radish but CCs are used by less than 20% of farmers in most counties

9 Farmers are at the forefront of Cover Crop Innovation

10 Is this really possible?

11 The classification of 60% or more of the sampled pedons differed from the original. Classification of 15-32% of the sampled pedons changed at the Order (or equivalent) level with 11 to 33% of the pedons originally classified as Black soils (i..e. Mollisols, Chernozems ) no longer classified as Black soils This is going in the wrong direction!

12 Soil Changes After Sixty Years of Land Use in Iowa Jessica Veenstra, Iowa State University, 1126 Agronomy Hall, Iowa State University, Ames, IA Soils form slowly, thus on human time scales, soil is essentially a nonrenewable resource. Therefore in order to maintain and manage our limited soil resources sustainably, we must try to document, monitor and understand human induced changes in soil properties. By comparing current soil properties to an archived database of soil properties, this study assesses some of the changes that have occurred over the last 60 years, and attempts to link those changes to natural and human induced processes. This study was conducted across Iowa where the primary land use has been row crop agriculture and pasture. We looked at changes in A horizon depth, color, texture, structure, organic carbon content and ph. Hill top and backslope landscape positions have been significantly degraded. Catchment areas have deeper topsoil. -> significant loss of productivity -> little gain in productivity

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17 This past fall, students in my Soil Properties class brought in paired (Crop field & Fence Row) soils from their family s farm. In most cases, the fence row soils had higher carbon dioxide and ammonia production.

18 What do the analytical results tell us? More informed decision making???

19 Informed decision making requires regional calibration! Consistent depth of sampling is important!

20 Sometimes the story changes with depth of sampling In essentially all cases where conservation tillage was found to sequester C, soils were only sampled to a depth of 30 cm or less

21 Slabaugh Farm Goshen, IN Hayfield ~ 5 yrs ago

22 Former hayfield Even more perplexing Uniform management for > 40 years Smith Family Farms - KS

23 Former hayfield Intensive soil sampling has not explained the consistent difference in productivity Smith Family Farms - KS

24 Farmers want to understand what yield maps are telling them about their soils

25 Some yield variability is easy to explain Pattern tiling The main factor driving yield variation in this field is BELOW the plow layer!

26 Maybe we need to take a deeper soil health

27 It is becoming clear that root traits are important drivers of many ecosystem processes such as C and nutrient cycling and the formation and stabilization of soil structure

28 Bardgett et al.(2014)

29 In this review, we propose the use of suitable plant species, termed primer-plants, for the primary purpose of preparing soil conditions for the benefit of following crops.

30 Proportions of roots of the current crop recolonizing root induced macropores (RIMs) of the previous crop averaged 18% for corn after corn, 22% for alfalfa after corn and 41% for corn after alfalfa

31 Our data suggest that surface mulch and deep root channels left by winter cover crops can be advantageous for summer crop growth, particularly when soils are highly compacted. Tap-rooted forage radish and rapeseed cover crops enhanced corn root access to subsurface soil water by providing deep root channels in compacted soils

32 soil penetration capabilities radish > rapeseed > rye

33 Within 2-4 weeks we began to see the ryegrass extract break down the fragipan not only does ryegrass have a deep root system that can penetrate the pan, but it also releases a chemical or chemicals that can help break it AD Karathanasis

34 Impact of preceding cover crops on cash crop root density Chen and Weil (2011)

35 Soil moisture sensors showed more rapid water use by corn roots (and more rapid recharge of soil moisture after rains) in the subsoil of plots previously growing forage radish compared to plots previously growing rye or no cover crop. In contrast, the rye cover provided more residue mulch than the radish and so conserved more water in the surface soil above the plow pan.

36 How should we target our management Soil/crop management systems impact the 1) movement of water, 2) storage of water, and 3) volume of soil from which crop roots acquire water and other resources. to most improve crop access to water?

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38 The calculator predicts soil hydrologic properties based on soil texture as well as modulating factors: OM, salinity, gravel content and compaction Predicted Soil Hydrologic Properties Based on data from ~ 2000 soil samples

39 + 10% + 150%

40 - 14% - 86%

41 Water movement (infiltration vs. run-off) and depth/volume of soil from which crop roots acquire water and other resources are much more sensitive to management than water holding capacity

42 A conceptual model of nutrient acquisition from the SUBSOIL Subsoil supplies more than water Kautz et al. (2012)

43 Compaction strongly impacts root growth and function Sub-soil water and nutrients Brady and Weil (2002)

44 Least Limiting Water Range LLWR for loose well-aggregated soil Soil too hard for roots to penetrate LLWR for compacted soil Not enough O 2 for root respiration Compacted soils are more easily penetrated when wet BUT only some CC species can tolerate wet soils dry Soil water content, cm 3 /cm 3 *100 wet Ray Weil

45 Annual ryegrass is very tolerant of wet soil conditions Brassicas are not!

46 Many of you are probably familiar with the extraordinary root illustrations by John E.Weaver

47 Soil particle size variation with depth at Dr. Weaver s research farm (Lincoln, NE) Depth (ft) %sand %silt %clay Deep rooting in this soil required excellent structure!

48 Ontario Ministry of Ag and Food Intensive tillage Long term no-till (w/ healthy soil biology) Plow pan Network of cracks and biopores

49 Different species of worms make different types of biopores! more roots + more worms more biopores

50 Soil/crop management strategies for optimum root growth and function Alleviate existing physical, chemical and/or biological barriers to root growth Prevent development of physical, chemical and/or biological barriers to root growth Plant crops on soils for which they are well adapted Treat seeds/roots with biological inoculants to enhance root-enhancing biological relationships Grow strategic sequences of crops/cover crops to maximize a positive cycle of root zone improvement

51 Green Lands = Blue Waters Winter cover crops Perennial-based rotation systems Conservation Cropping Systems Permanent pasture systems Tree crops

52 The best way to grow biopores!

53 D Go beyond T - Manage for C!

54 Go beyond T - Manage for C! DEPTH!

55 Effectiveness of conservation practices should be assessed with respect to impact on root growth and function NOT tons of soil loss.

56 I encourage all of you to think deeper New methods and new priorities can provide an invaluable ROOT S EYE VIEW of soil health

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