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Integrated IWM Field Handbook
Conservation Tillage and Crop Residue Management

PowerPoint Text (SQ8b)

 What is Residue Management/Conservation Tillage

•         Any tillage or planting system that maintains at least 30% crop residue cover on soil surface (leaves about a third of soil covered after planting).  

Residue Management, Mulch-Till

Residue Management,
No-Till & Strip-Till

•         No-till: Leaving the residue from last year’s crop undisturbed until planting

•         Strip-till: No more than a third of the row width is disturbed with a coulter or specialized shank that creates a strip.  If shanks used, nutrients injected at same time.

Why Use a Conservation
Tillage System? Environment:

1. Reduce sheet and rill erosion.

2. Reduce wind erosion.

3. Maintain or improve soil organic matter content and tilth.

•         Each tillage trip oxidizes some organic matter

•         Continuous no-till can increase organic matter in top 2 inches of soil about 0.1% each year.

4. Conserve soil moisture. (Improved infiltration and increased organic matter; tillage reduces available moisture by about 1/2” per trip)

Residue reduces evaporation:

Surface Cover %                Relative Potential Evaporation

                                    0                                  1.00

                                    10                                0.90

                                    20                               0.78

                                   30                                0.70

                                    40                                0.67

                                    80                                0.58

 

5. Manage snow to increase plant available moisture.

6. Improves water quality

7. Provide food and escape cover for wildlife.

Why Use a Conservation
Tillage System? Economic:

1. Yields - are as good, if not better

2. Saves time and labor: On a 1000-acre farm, an additional 100 hours needed for every pass (example based on 18' disk, 160 Hp FWD)

3. Reduces fuel consumption: No-till can reduce fuel use by 3.5 gal/ac

4. Reduces machinery wear: Less machinery means fewer pieces need to be replaced. Up to $14/acre cost reduction.

 

Differences in residue cover between Conservation Tillage practices 

•         No-till leaves the most surface residue

–        With high residue crops, e.g. corn, wheat , sorghum, 75 % +

–        With low  residue crops, e.g. soybeans, cotton, residue cover is   significantly less

•         a cover crop may be needed to meet residue  goals

•         In some climates, some residue cover may carry over from year to year

–        Winter annuals also add to surface residue

•         Mulch-till residue levels can be significantly less than no-till

•         With high residue crops, 30-50 % possible

•         With low residue crops, difficult to retain 30 percent

•         May need cover crop to achieve residue goals

 

Management of Residue 

•         Surface residue must be evenly distributed

•         Residue decomposes with time

•         If target is 40 percent cover after planting, will need more over winter

•         May need to control winter weeds in dryland areas to help conserve soil

            moisture in spring

•         Crop residue and moisture level impacts soil temperature - less variation

•         Under no-till, soil temperatures will be cooler

–        May be critical in cool, wet springs

–        May be justification for strip-till

•         Less extremes in soil temperature under no-till may result in increased root growth and improved soil biological activity

 

Residue Management - Irrigation

Surface residue

•         slows flow - especially with furrow

•         increases opportunity time, water holding capacity, random roughness (structure)

•         decreases surface evaporation

•         cools seedbed temperature

•         More difficult - small seeded vegetables

•         More requirements for incorporation of pesticides

•         Management techniques may need modification

•         especially with furrow irrigation.

 

Potential Problems from Residue

•         Residue may float off of field

•         Accumulate in fence rows and road ditches

•         If not evenly distributed can cause planting/weed problems

•         May have cool, wet soils at planting

 

Low Residue Crops (i.e., Vegetables)

•         Residue orientation and row orientation become more important

•         Leave as much residue standing as possible

•         Orient rows perpendicular to prevailing wind direction

 

Benefits of Increasing Organic Matter

•         Soil aggregate stability increases

•         Plant available water increases

•         Cation exchange capacity of soil increases

 

Crop Residue and Microorganisms

•         Provides an energy source for microorganisms

•         As surface residue increases, microorganisms increase

•         Through their life processes, they return humus to the soil

•         When residue is plowed under, residue is rapidly consumed and microorganism processes end

      •     Microorganisms utilize surface residue slowly, remain active for longer periods, and significantly improve soil humus

•         When soils are tilled, it is similar to stirring a fire.

•         Argentina cropping systems – “aggression” (years of tillage)  vs. “recuperation” (years of no-till)

•         C02 is one of the greenhouse gases

 

Microorganisms can tie-up Nitrogen, continued:

•         Microorganisms utilize N during decomposition process

•         N is temporally tied-up, but released during growing season

•         Under no-till systems, N release is more evenly distributed during growing season compared to conventional systems. 

•         No-till systems do not have typical flush of N released as in conventional systems

 

Soil Properties - Soil Structure

•         Surface soil becomes more granular and friable with continuous residue management systems 

•         Extent of change is dependent on the residue management practice used, climate, and soil

•         Changes apparent in about 3-5 years with no-till/strip-till and ridge-till

•         Type of soil and climate strongly influence the rate of this change

 

Expected Changes in Soil Structure with Residue Mgt.  Systems

•         Improved soil aggregate stability

•         Improved water holding capacity

•         Increased granular structure at the surface

•         Less surface ponding of rainfall

 

Soil Properties - Infiltration

•         Major benefit from Residue Mgt.

•         No-till/Strip-till and Ridge-Till

–        improved soil structure

–        slowed runoff

–        leaves old root and macropore structure undisturbed

–        fastest way to improve soil quality

•         Mulch-Till

–        full width tillage disturbs macropores

–        slows runoff due to increased surface roughness

–        chisel can break-up shallow compaction layers

 

Role of Macropores

•         Develop from decayed root channels and earthworms

•         If open to the surface infiltration may be significantly increased

•         May be direct conduit for contaminants

•         Full-width tillage disturbs macropores to depth of tillage

 

Soil Properties - Compaction

•         Compaction created by tillage and vehicle traffic can be corrected

•         Other compacted layers occur naturally and may or may not be correctable

 

Soil Properties - Crusting

•         Serious concern in soils low in organic matter, like NM

•         More prevalent on soils excessively tilled

•         Can interfere with crop emergence

•         May require operation to break crust

•         Residue mgt. Practices can reduce crusting - especially no-till

–        Surface residue absorbs impact of falling raindrops

–        Organic matter is increased

–        Improved aggregate stability

 

Water Quality - Sediment

•         Sediment is number 1 pollutant

•         Creates physical problems

•         Potential hazard to fish and wildlife

•         Residue mgt. practices can result in a major benefit through:

–        reduced soil erosion, improved aggregate stability, and increased organic matter 

•           Greater amount of surface residue, the greater the reduction in soil erosion

•           As erosion is reduced, sediment delivery is generally reduced

 

Water Quality - Nutrients

•         Phosphorus attached to soil is slow to move in the soil profile

•         But soil attached phosphorus can move with surface runoff

•         Residue mgt. practices reduce soil erosion, improve infiltration, and reduce runoff

•         Nutrients that are dissolved but not infiltrated the soil can move freely in surface runoff

•         Nitrate-nitrogen can move freely as water percolates through the soil

•         Residue mgt. practices often increase water infiltration - care must be taken when applying nitrogen

•         If nitrogen is fall applied, consider nitrification inhibitor

•         Apply nitrogen as close as possible when crop needs are greatest

•         Use caution when manure is surface applied

•         Avoid applying on frozen ground

•         Injecting manure reduces risk of surface runoff, but there are tradeoffs

•         With mulch-till, manure may be incorporated using one of the planned tillage trips

 

Water Quality - Pesticides

•         Pesticides can be soluble or attach quickly to soil particles

•         If soluble, can move with surface runoff

•         If attached to soil particles, can move offsite via erosion

•         Residue mgt. practices reduce erosion, surface runoff, and sediment delivery

•         Increase infiltration which may be detrimental where shallow groundwater exists

•         Extensive macropores, open to the surface raise some concern

 

Water Quality - Pesticides, Macropores and Solute Movement

•         Earthworm channels contain large   amounts of O.M.

•         This O.M. material can help absorb pesticides

•         Earthworm channels have increased microorganism activity

•         Timing and amount of precipitation important

•         With small rain pesticide moves into soil profile

•         If large storm occurs before pesticide enters soil, direct entry into macropore is possible

•         Avoid surface application of a pesticide, especially if highly soluble, just prior to an imminent storm if not immediately incorporated

•         Mulch-till provides opportunity to make a tillage pass to incorporate a pesticide or for row cultivation

 

Conservation Tillage –

Bottom Line

•         Helps keep topsoil, nutrients (P), and crop protection products on your fields and out of creeks, streams and lakes

•         If you properly manage crop rotation, soil conditions, irrigation, equipment selection and adjustments, plant nutrients, and weed control, it helps  improve yields and soil productivity