Understanding Reduced Till and Zero Till Practices in Agriculture
What are reduced till or zero till practices?
Tillage is a common practice in agriculture and is applied in most fields. It involves disturbing the soil structure to prepare the seedbed, manage weeds, and facilitate crop establishment and growth. It normally necessitates using instruments such as plows to reverse the soil at a depth of up to 30 cm.
Zero-till agricultural practices focus on reducing the amount of tillage that occurs within a field. Depending on the level of soil disturbance, this can be applied as a reduced till or zero till. These 2 systems can help decrease soil degradation and facilitate regeneration (better soil health). They can help increase the moisture in the soil, reduce peak summer temperatures and runoff (of water and nutrients), increase topsoil retention, improve soil structure, and alleviate compaction. This practice could present a cost-effective option for farmers facing an increasingly challenging profession.
The history of the tillage practice
During the 17th century, tillage became a popular option for farmers in Britain, Germany, and America. This coincided with increased breakthroughs and innovations in agriculture, such as the iron plow and later the mouldboard plow. These inventions enabled more efficient preparation of the fields and were found to reduce weed presence and increase yield. Consequently, the practice of plowing quickly spread across the globe. This became a common practice during the Green Revolution, from the 1940s onwards when the world’s farmers sought solutions to feed a rapidly growing population.
Tillage also improves soil drainage for poorly draining soils such as clays and facilitates weed control. Additionally, the soil warms up faster in spring due to the reduced water level, increasing the seed germination rate.
The negative effects of excessive tilling?
One of the worst American agricultural disasters was the Dust Bowl, a series of severe dust storms in the Great Plains region during the 1930s that stripped vast sums of topsoil, up to 300 million tons in a day, from overplowed and drought-riddled cropland.
The overuse of tillage and farming on marginal lands removed the topsoil to such an extent that when drought arrived, aeolian processes removed most of the nutrient-rich zone of the soil. This disaster led to farming communities seeking new practices to deploy on their land. During the 1940s and especially into the 1950s, the modern zero-till practice was formulated. It encouraged farmers to reduce the amount of plowing conducted and choose less invasive options than moldboard plows.
The principles of zero-till
Zero-till practices promote soil structure by keeping crop residues in the field. Over the winter, the remaining plant roots help bind the soil together, reducing the amount that storms and strong winds can drift, a time when, traditionally, fields would be left bare. Furthermore, residues such as stems and leaves are left on the soil's moisture, creating better conditions for soil microbiome and reducing runoff of water and nutrients. These mechanisms were first cited in the 1940s as options to ensure that a second Dust Bowl would not occur.
Putting zero-till to the test
Since the early 1970s, Nigeria has been conducting research into the deployment and effectiveness of zero-till agricultural practices. Test fields have been used to compare traditional tilling methods to zero-till, minimum-till, and mulching. These comparisons have been reported in various and ongoing peer-reviewed papers. The findings support the continued uptake of zero-till and reduced-till agriculture across the planet.
The most noteworthy findings are that minimum till can reduce the annual soil loss from 17.3 tons to 2.1 tons per hectare. Over time, this reduces the loss of topsoil, increases the carbon stored in the soil, and increases the yield.
The importance of limiting soil erosion cannot be overstated. This was a key issue triggering the Dust Bowl and will be key to the battle against desertification in the Sahel region of Africa. Furthermore, the soil remains cooler, especially in the root zone. In one trial, in a conventionally plowed soil planted with maize, the temperature was recorded to reach 41.4 degrees Celsius. On the contrary, at the same time, in zero tillage soil, the temperature was 10 degrees lower (31.6 degrees Celsius). The reduced temperature provides better conditions for invertebrates and beneficial soil bacteria, which are critical for soil health. Due to the reduction in soil temperature, the soil moisture also increased from 9.7% to 13.3%. All of these changes mean that the field is farmed sustainably, limiting the amount of soil leaving the field will ensure that it is fit for agriculture for many generations. With unchecked topsoil loss, the field will continually decrease in productivity and eventually need to cease being farmed. In tropical climates, this will result in desertification of vast areas of land.
Zero till spotlight: India
India has been a "hot bed" of zero till agriculture. In the rice paddies of the south and corn fields of the north, zero-till practices have been adopted in order to increase yield, decrease labor and irrigation costs, and improve drought resistance. It is the most resource-preserving practice that farmers can deploy. Fields that are protected with such conservation methods can produce increased crop yields (e.g., wheat during the cool season). At the same time, the monsoon season (July to September) can be exploited to cultivate rice without losing any crop to flooding. As monsoons become more violent, this practice may prove vital for farmers and rural communities within India and the wider Indo-Gangetic plain.
Successful deployment of zero-till
To achieve the best result, gathering all the necessary information and planning in advance (e.g., the summer before we want to apply it) is essential. The first thing we need to do happens during crop harvest. It is important to leave as much plant residue on the soil as possible, including stalks, roots, and leaves. These residues will protect the topsoil layer, limiting the runoff in winter storms.
During the sowing of the next crop (under the no or reduced tillage system), we need to select planting techniques and machinery that limit the disturbance of the residue left on the field. Ensuring that during the spring growing season, the residue remains in the soil, acting as protection, and as it starts to decompose, it releases key nutrients back into the soil for the current crop to uptake.
Zero-till agriculture has become increasingly popular in recent years, and the reason for this has become apparent in what we discussed above.
References
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Erenstein, O., 2008. Zero tillage impacts in India's rice–wheat systems: A review. Soil and Tillage Research, 100(1), pp. 1-14.
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Further reading
Tillage can sometimes help but usually harm soil and water conservation
Soil and Water Conservation Strategies
Agricultural Machinery – Tractor Attachments for different Farming Operations
What is (Crop) Residue Management?
Enhancing Soil Health: Benefits of Cover Crops and Practical Examples
