Conservation Tillage

= portion of previous crop residue left unincorporated on soil surface

Conservation Tillage = portion of previous crop residue left unincorporated on soil surface Opposite of conventional tillage (plowing) Plowing benefits: good root zone, weed management Not plowing benefits: erosion management

Tillage Options Tillage (turn in everything) Top mowed and removed (root stubble left) Top mowed, but left as mulch (root stubble left) Planting into dead crop residues (nothing removed)

Tillage and Crop Residue Management TILLAGE INTENSITY NONE FREQUENT0% 100% SURFACE RESIDUE

Tillage and Crop Residue Management TILLAGE INTENSITY NONE FREQUENT0% 100% SURFACE RESIDUE No tillage Minimum tillage Reduced tillage

Tillage and Crop Residue Management TILLAGE INTENSITY NONE FREQUENT0% 100% SURFACE RESIDUE No Tillage 90% 30% Minimum Tillage

Conservation Tillage = portion of previous crop residue left unincorporated on soil surface Many different terms: = Reduced Tillage = No Tillage = Minimum Tillage = Crop Residue Management

Conservation Tillage = Reduced Tillage = No Tillage = Minimum Tillage = Crop Residue Management Many different terms, depending on relative amounts of residues and varying degrees of incorporation (cover crop mowed and used as mulch, forage removed with stubble left in field, etc.)

Strip Tillage Crops planted into narrow tilled strip (4- 12”, cm) Residue on surface

Strip Tillage Planting into Crop Residue

Rye Cover Crop Killed by Herbicide, Use Strip Till Planter to Plant Crops

Crops Strip Planted into Green Cover Crop, Cover Killed Later with Herbicide

Strip Till Peanut in Rye Mulch (double row)

Strip Till Peanut in Rye Mulch (single row)

Strip Till Corn in Rye Mulch

Strip Till Cotton in Rye Mulch

Conservation tillage in US increased rapidly since 1980’s Schertz, 1994

Advantages and Reasons for using Minimum Tillage Reduced erosion Economics Moisture conservation Stabilizes soil temperature Improved soil fertility and accessibility Improved quality of surface water Government regulations and programs Improved yields

Relationship between Conservation Tillage (more surface residue) and Reduction in Erosion

Advantages and Reasons for using Minimum Tillage Reduced erosion Economics (reduced trips over field and fuel costs, but more herbicide) Moisture conservation (reduced evaporation rates) Stabilizes soil temperature Improved soil fertility and accessibility Improved quality of surface water Government regulations and programs Improved yields

Relationship between Conservation Tillage (more surface residue) and Moisture Conservation (less evaporation)

Advantages and Reasons for using Minimum Tillage Reduced erosion Economics Moisture conservation Stabilizes soil temperature Improved soil fertility and accessibility (preserves OM) Improved quality of surface water (reduced erosion and runoff) Government regulations and programs Improved yields

Advantages and Reasons for using Minimum Tillage Reduced erosion Economics Moisture conservation Stabilizes soil temperature Improved soil fertility and accessibility Improved quality of surface water Government regulations and programs (Food Security Act – 1985 – Minimum tillage considered part of soil conservation program to reduce erosion) Improved yields

Advantages and Reasons for using Minimum Tillage Reduced erosion Economics Moisture conservation Stabilizes soil temperature Improved soil fertility and accessibility Improved quality of surface water Government regulations and programs Improved yields ? --- Depends on soil types and conditions….

Soybean Yield (bu/A) Tillage systemFavorable soilsDroughty soils Conventional plowing No-till From Johnson, 1994 Benefit from no-till in poor soils

Improved Yields from Minimum Tillage? South US, dry soils greater yields North US lower yields (cooler temps., less DD in no-till)

Problems with Minimum Tillage Weeds Weed pressure often severe in min. tillage Increased herbicide usage for weed control and for killing crop residues Roundup-Ready cultivars New weed problems – K strategists, etc. Compaction -- varies

US Pesticide Sales following Increase in Conservation Tillage Johnson, 1994 Mostly herbicides

Effects of minimum tillage on physical and biological factors Soil moisture Soil temperature Soil fertility Soil acidity Pests

Effects of minimum tillage: Soil Moisture Decreased evaporation and water loss + + improved water holding capacity on soils that tend to dry - - may delay drying in water-logged soils

Effects of minimum tillage: Soil Temperature Lowers soil temperature, depending on amount of residue + + for South US, tropics - - for north (soil warming may be delayed in spring)

Effects of minimum tillage: Soil Fertility + + increased organic matter, reduced erosion - - N availability can be affected by residues and lead to deficiency: Fertilizer placement and degree of incorporation is important C:N ratio of residue is critical Placement important with other nutrients (P, K) too

Effects of minimum tillage: Soil Fertility + + increased organic matter, reduced erosion - - N availability can be affected by residues and lead to deficiency: Fertilizer placement and degree of incorporation is important C:N ratio of residue is critical Placement important with other nutrients (P, K) too Strip Tillage can help with these fertilizer placement problems !

Effects of minimum tillage: Soil Acidity Can increase with decomposition and organic acids Can affect nutrient availability Takes time to develop and may be confined in a relatively narrow vertical strip

Effects of minimum tillage: Pests Weeds --- can be major problem Diseases Insects

Effects of minimum tillage: Diseases Varies with specific situations and ecology of pathogens Crop rotation important to eliminate residues of the same crop (contaminated residues could be source of disease inoculum) Some seed pathogens worse with cooler soil temperatures

Effects of minimum tillage: Insects Varies --- may favor pests or beneficials Favorable habitat and hiding places for crop pests in residues (cutworms, snails, slugs) May provide habitat for predators

Tillage impacts larger organisms; No tillage benefits earthworms, predators Coleman and Crossley, 1996

Seedbed Problems in Min. Tillage Problem in cool, moist soils Increased seedling mortality from: Mulch layers Diseases (aggravated by cool temp. and moisture) Slow germination and establishment (lower DD if soil is cool)

References Text, Ch. 14, pp Altieri, Ch. 11. Coleman, D.C., and D.A. Crossley Fundamentals of Soil Ecology. Academic Press, San Diego. Johnson, R.R Pp in P.J. Bauer and W.J. Busscher, eds. Proc. of the 1994 Southern Conservation Tillage Conference for Sustainable Agriculture. USDA Coastal Plains Soil, Water, and Plant Research Center, Florence, SC. Schertz, D.L Pp. 1-5 in Bauer and Busscher.