**9. Conservation tillage**

Conservation tillage continues to grow in importance in crop production since its inception over 40 years ago. C.M. Woodruff in 1970 was conducting research on strip-planting corn into tall fescue sod on Missouri hillsides with the idea of producing a cash grain/feed crop along with a forage crop for livestock production while maximizing conservation of the soil and rain water (Anonymous, 1970). Anders et al., (2004) found that phosphorus (P) concentrations in run-off water were higher for no-till rice than conventional tilled paddies, most likely due to the P being surface applied. However, total-P concentrations in run-off were lower in no-till because of the reduced loss of soil in no-till and its bound P. Conservation tillage which includes both minimum tillage and no-till practices, are used to grow an array of crops from corn, soybean, cotton, grain sorghum, and several small grain species almost always in some rotation scheme. It is popular not only for the conservation of natural resources as just mentioned, but also for the savings in fuel, time, wear and tear on farm equipment, and the environmentally sustainable attributes of the various practices. Minimum tillage, by reduced soil disturbance, promotes a complex decomposition subsystem that enhances soil system stability and efficiency of nutrient cycling. Basically minimum tillage more closely mimics natural ecosystems than conventional cropping systems (Francis and Clegg, 1990). Tillage has been reported to reduce the diversity of bacteria in the soil by reducing both the substrate richness and evenness (Lupwayi et al., 1998). They found that the influence of tillage on microbial diversity in fields planted to wheat was more prominent at the flag-leaf stage of growth than at seeding and more prominent in bulk soil than in the rhizosphere at the flag-leaf stage.

Kladivko et al., (1986), studied the production of corn and soybean using an array of tillage systems ranging from conventional moldboard plowing and seedbed preparation to no-till on a range of soils differing in organic matter, texture, and slope for seven-year and six-year periods. At one location on a Chalmers silty clay loam (fine-silty, mixed, superactive, mesic *Typic Endoaquolls*) comparisons of a corn-soybean rotation to continuous crops of these two species using various tillage systems was conducted for 10 years (Table 7). Yields of rotated crops tended to be greater than those of the monocultures regardless of tillage. Kladivko et

could be harvested in the U.S. for ethanol production. Worldwide other crops that produce sufficient quantities of residue that could be used to produce ethanol include rice, barley, oat, wheat, sorghum, and sugar cane (*Saccharum officinarum* L.). The use of crop residues for lignocellulosic ethanol production has however run into opposition due to the negative impacts such removals have on C sequestration, soil properties, and nutrient availability for subsequent crops. Wilhelm et al., (2007) reported that between 5.25 and 12.50 Mg ha-1 of corn stover are required to maintain soil C at productive levels for subsequent crops. Lal (2004) states that even though the energy acquired from the world's crop residue would be equivalent to 7.5 billion barrels of diesel, a 30% to 40% removal of crop residue would increase soil erosion and its subsequent pollution hazards, deplete soil organic C, and increase CO2 and other greenhouse gas emissions from the soil. He suggests establishing biofuel plantations of adapted species on marginal lands rather than remove crop residues from land used to grow food and feed grains. Development of such plantations will require more aggressive research into developing crop rotation schemes specific for growing

Conservation tillage continues to grow in importance in crop production since its inception over 40 years ago. C.M. Woodruff in 1970 was conducting research on strip-planting corn into tall fescue sod on Missouri hillsides with the idea of producing a cash grain/feed crop along with a forage crop for livestock production while maximizing conservation of the soil and rain water (Anonymous, 1970). Anders et al., (2004) found that phosphorus (P) concentrations in run-off water were higher for no-till rice than conventional tilled paddies, most likely due to the P being surface applied. However, total-P concentrations in run-off were lower in no-till because of the reduced loss of soil in no-till and its bound P. Conservation tillage which includes both minimum tillage and no-till practices, are used to grow an array of crops from corn, soybean, cotton, grain sorghum, and several small grain species almost always in some rotation scheme. It is popular not only for the conservation of natural resources as just mentioned, but also for the savings in fuel, time, wear and tear on farm equipment, and the environmentally sustainable attributes of the various practices. Minimum tillage, by reduced soil disturbance, promotes a complex decomposition subsystem that enhances soil system stability and efficiency of nutrient cycling. Basically minimum tillage more closely mimics natural ecosystems than conventional cropping systems (Francis and Clegg, 1990). Tillage has been reported to reduce the diversity of bacteria in the soil by reducing both the substrate richness and evenness (Lupwayi et al., 1998). They found that the influence of tillage on microbial diversity in fields planted to wheat was more prominent at the flag-leaf stage of growth than at seeding and more

Kladivko et al., (1986), studied the production of corn and soybean using an array of tillage systems ranging from conventional moldboard plowing and seedbed preparation to no-till on a range of soils differing in organic matter, texture, and slope for seven-year and six-year periods. At one location on a Chalmers silty clay loam (fine-silty, mixed, superactive, mesic *Typic Endoaquolls*) comparisons of a corn-soybean rotation to continuous crops of these two species using various tillage systems was conducted for 10 years (Table 7). Yields of rotated crops tended to be greater than those of the monocultures regardless of tillage. Kladivko et

prominent in bulk soil than in the rhizosphere at the flag-leaf stage.

lignocellulosic crops for biofuel.

**9. Conservation tillage** 

al. (1986) also reported from this research at other locations that conservation tillage systems resulted in increased soil water contents, lower soil temperatures, increased soil organic matter, and more water-stable aggregates near the soil surface with higher bulk densities than conventional tillage. Corn yields were found to be equal to or better than conventional tillage practices when grown on the better drained soils using conservation tillage. Only on the poorly drained soils did corn yields on conservation tilled fields fail to exceed conventional tillage, most likely due to low temperatures and excess wetness in the spring as depicted with the Chalmers silty clay in Table 7.


Table 7. Mean corn and soybean yields (Mg ha-1) in response to tillage system and crop rotation on a Chalmers silty clay loam in Indiana in 1980-1984 (data is from 6th to 10th year of the study). (Kladivko et al., 1986).

Roth (1996) presents several crop rotation schemes to use in no-till farming on Pennsylvania dairy farms. One of the more popular is an alfalfa-grass sward for hay followed by no-till corn. This involves killing the sod in the fall with herbicides to control weeds and reduce residue by early spring to facilitate corn planting. This rotation seems to work best where hay production is limited to three years. Alfalfa is also successfully no-tilled into fields that have just been harvested for corn silage or following the harvest of a spring seeded sorghum sudangrass. Lafond et al., (1992), evaluated no-till, minimum till (one pre-seeding tillage operation) and conventional till (fall and spring pre-seeding tillage operations) on a fouryear crop rotation study. The rotations were fallow-spring wheat- spring wheat-winter wheat, spring wheat-spring wheat-flax (*Linum usitartissimum* L.)-winter wheat, and spring wheat-flax-winter wheat- field pea. Tillage systems did not affect the amount of water conserved during fallow. However, no-till and minimum till did result in an increase in soil water from the surface to 120 cm in depth over conventional till. All three crops in the study had greater yields in the no-till and minimum till treatments than in the conventional till. In an experiment using conservation tillage practices (strip-till or no-till) in combination with a corn-soybean rotation, both full-season soybean or double-crop soybean following wheat had the most consistent increase in seed yields (Edwards et al., 1987).

In recent years there has been considerable interest in various tillage practices and their influence on the sequestration of atmospheric CO2 as a partial means of mitigating its current increase and subsequent impact on climate change. Sampson and Scholes (2000), state that the optimization of crop management to facilitate accumulation of soil organic matter could help sequester atmospheric CO2 and lower the rate of its increase. West and Post (2002), found that, excluding a change to no-till in wheat-fallow rotations, a change from conventional tillage to no-till can sequester between 43 to 71 g C m-2 yr-1. These values are within the upper range (10 to 60 g C m2 yr-1) of those reported in a review by Follet (2001). West and Post (2002) also stated that enhanced crop rotation complexity can sequester an average of 8 to 32 g C m-2 yr-1 which is similar to an average of 20 g C m-2 yr-1

Anders, M., Olk, M.D., Harper, T., Daniel, T, & Holzauer, J. (2004). The effect of rotation,

Anonymous. (1970). Strip planting corn in fescue sod. *The Southeastern Missourian*, 10 Sept.,

Aref,S. and Wander, M.M. (1998). Long-term trends of corn yield and soil organic matter in

Ashton, T.S. (1948). *The Industrial Revolution*. (3rd printing 1965 ed.) Oxford University Press,

Baldwin, K.R. (2006). Crop rotations on organic farms. The Organic Production publication

Bowman, D.H. (1986). A history of the Delta Branch Experiment Station. *Mississippi Agric. & Forestry Exp. Sta., Special Bull. 86-2.* Mississippi State Univ., Mississippi State, MS. Brooks, S.A. (2011). Influences from long-term crop rotation, soil tillage, and fertility on the

Bruns, H.A., Pettigrew, W.T., Meredith, W.R., & Stetina, S.R.. (2007). Corn yields benefit in rotation with cotton. *Crop Management.* URL: doi:10.1094/CM-2007-0424-01-RS. Buhler, D.D.. (1995). Influence of tillage systems on weed population dynamics and management in corn and soybean in the central USA. *Crop Sci.* Vol.35:1247-1258. Butt, J.J. (2002). Daily life in the age of Charlemagne p. 82-83. *Greenwood Publishing Group*,

Capehart, T. (2004). Trends in U.S. tobacco farming. *Electronic outlook report from the Economic* 

http://www.ers.usda.gov/publications/tbs/nov04/tbs25702/tbs25702 . Cardina, J. Herms, C.P., & Doohan, D.J. (2002). Crop rotation and tillage systems effects on

Clark, M.S., Horwath, W.R., Shennan, C., & Scow. K.M. (1998). Changes in soil chemical

Croissant, R.L. Peterson, G.A., & Westfall. D.G. (2008). Dryland cropping systems. *Crop Production Series* no. 0.516. *Colorado State University Extension*. Fort Collins, CO. de Friature, C., Giordano, M., & Laio, Y. (2008). Biofuels and implications for agricultural

Delate, K. & Hartzler R. (2003). Weed management for organic farms. *Organic Agriculture* 

Duley, F. L., & Miller, M. F. (1923). Erosion and surface run-off under different soil

http://www.extension.iastate.edu/Publications/PM1883.pdf .

*Research Service. United States Department of Agriculture.* URL:

properties resulting from organic and low-input farming practices. *Agron. J.* Vol.

*Series. Iowa State Univ. Univ. Extension. Ames, IA.* PM 1883 URL:

severity of rice grain smuts. *Plant Disease* Vol.95:990-996.

weed seedbanks. *Weed Sci.*Vol. 50:448-460.

Carolina State University, Raleigh, NC. pp 26-33*.*

1970. Cape Girardeau, MO. p 14.

*Agron.* Vol.62:153-197.

New York, NY. p 21.

*Raleigh, NC*. URL:

Westport, CT., USA

90:662-671.

water use: blue impacts

of green energy. *Water Policy 10 Suppl*. Vol. 1:67-81.

conditions. *Mo. Agr. Exp. Sta*. Res. Bull. 63*.* 

an09.pdf .

tillage, and fertility on rice grain yields and nutrient flows. *Proceedings 26th Southern Conservation Tillage Conference for Sustainable Agriculture*. 8-9 June. North

different crop sequences and soil fertility treatments on the Morrow Pltots. *Adv.* 

series. *Center for Environmental Farming Systems. North Carolina Coop. Ext. Service,* 

http://www.cefs.ncsu.edu/resources/organicproductionguide/croprotationsfinalj

**11. References** 

estimated by Lal et al. (1998; 1999) resulting from an improvement in rotation management.

Conservation tillage can present pest control problems that are different from those found in conventional systems, particularly weeds. Weed species composition and abundance often change in response to crop and soil management practices (Cardina et al., 2002). Buhler (1995), wrote that most conservation tillage practices rely heavily on increased herbicide use and that reduced herbicide efficacy has slowed the adoption of conservation tillage practices. Weed populations have tended to shift more towards perennials, summer annual grasses, biennials and winter annual species in conservation tillage systems. Moyer et al.,(1994) stated that successful conservation tillage systems usually involve crop rotations of three or more species and several different herbicides. Legere et al., 1997 concluded that conservation tillage has the potential to produce sustained yields of spring barley in Quebec, provided attention is given to critical aspects such as crop establishment and weed management. With respect to plant diseases, Peters et al., (2003) determined that soil agroecosystems can be modified by crop rotation and conservation tillage to increase disease suppression by enhanced antibiosis abilities of endophytic and root zone bacteria in spring barley and potato (*Solanum tuberosum* L.).
