Regeneration of Our Soil: Conservation No-Till Agriculture

Fig.1 Tractor Cultivating Field At Autumn (Source: Shutterstock) 

Agriculture originated in the Fertile Cresent of the Near East, together with it tools to place and cover seeds in soil were produced. Since then, soil preparation through tillage has been an important component of traditional agriculture. However, this practice has come at a cost. It has lead to widespread soil erosion and land degradation. The Dust Bowl is one of the severe incidences happened through human-induced land degradation when more than 75% of the topsoil was blown away by the 1930s. 

The loss of soil can impact strongly on the environment and has high economic costs. It leads to the decline of soil organic carbon (SOC) and precious nutrients, effects water infiltration and storage and the breakdown of soil structure. Therefore, scientists revisited the scientific basis for ploughing as a seedbed preparation and the idea of no-till farming originate in the 1940s with Edward Faulker. However, it was not until after WW2 when researchers and farmers started to try out this idea (Lal et al., 2007). 

What is No-Till and How is it Done 

A No-till (NT) system usually refers to the combination of farming practices such as residue management that seek to use the natural organisms of the soil to obtain the best possible sustainable return from our soils. 

The main principles of a no-till system are as follows:

• no disturbance of the land through tillage
• retain surface residue once harvest
• plant cover crops during winters 
• crop rotation over years 

Fig.2 Cover crop growing in plant residue in a no-till agriculture field
(Source: No-Till Farmer) 

What are the Benefits 

These series of activities have a number of impacts on the physical and biological properties and have shown to improve the soil structure. 

Erosion control and moisture conservation

Research has shown that no-till management improves surface soil physical properties which dictate to the infiltration characteristics and potential of the soil. Shaver et al. (2001) found that no-till systems resulted in the decreased bulk density, increased soil porosity and increased macro-aggregations as crop intensity, crop residue and subsequent SOC production increased in no-till systems. This reduces in overall soil compaction, results in the significant increase of water infiltration into the no-till soil than into ploughed soil at similar water contents. With more water infiltrating and stored in the soil, less of the topsoil along with the precious nutrients would be washed out under the impact of rain and wind. Moreover, the plant residues and cover crops act as a shelter to the underlying soil,  other than slowing down the wind and water speed at ground level which reduces water run-off and soil erosion, it also conserves water moisture by reducing evaporation from the soil. Basche et al. (2016) found that cover crop treatment has increased soil water storage by 10-11%. 

For a more intuitive demonstration please look at the following video, which shows the interaction between rail and soil between conventionally tilled (left) VS. no-till with a cover crop (right). The comparison is stunning. 

Watch what happens when rain interacts with #soil that's been conventionally tilled (left) vs. no-till with a #covercrop (right) #EarthDay pic.twitter.com/2UElhFO8qI

— Indiana Dept of Ag (@ISDAgov) 21 April 2017 

(Source: Indiana Dept of Ag Twitter @ISDAgov)

Land management of reduced/no-till, plant residue retention and cover crop and other supporting practices such as contour farming have been included in policies of the Good Agricultural and Environmental Condition (GAEC) for several decades. It has reduced the soil loss rate by an average of 9.5% in Europe and by 20% for arable lands (Panagos et al. 2015). 

Organic matter content increase 

A good soil carbon management is vital for its role in maintaining soil fertility, physical properties and biological activities required for food production and environmental quality. Conventional farming system mined soils for nutrients and organic matter through repetitive harvesting, resulting in the dramatic decline in soil organic matter and gaseous carbon released to the atmosphere. Reicocksy and Lindstrom (1995) found that there's a major short-term loss of CO2 immediately after tillage which partially explained the long-term carbon loss into the atmosphere. Soil erosion caused by extensive tillage may lose 75-80% of its carbon content and have a consequence release of carbon into the atmosphere (Morgan, 2005). 

Allmaras et al. (2000) showed that conventional tillage system store less SOC than conservation systems. It is shown that surface plant residue results in the accumulation of SOC at the immediate soil surface (Novak et al., 2007), even though some studies report that measured carbon has not necessarily increased below the horizon of tilled soil. If combined with strategies such as adding animal manure to the soil, no-till management has shown to increase organic matter content compared to conventional tillage (Jiao et al., 2006). However, some studies argue that the increase in SOC stock is short-term and continuous resupply of fresh residue is needed. 

Other benefits include economic aspects such as reducing fuel, labour and machinery requirements. 

Some Disadvantages

Although many studies have reported an increase in yield after adopting no-till, numerous studies have shown no changes or a decrease in yield associated with the adoption of NT. 

No-till with residue management significantly increases rain-fed crop's productivity in dry areas, while yield decreases mostly in wet and cool climate conditions.The plant residue layer causes depression on soil temperature which would affect the yield by delaying the planting date 1-2 weeks, according to Gupta (1985). Moreover, Dwyer et al. (2010) suggested a slower crop growth in spring due to less warm soil caused by the surface plant residue layer. Other studies found that no-till cause crops to be more susceptible to disease and weed infestation, which may increase dependence on fungicides and herbicides.