Recent literature on no-till is reviewed with particular emphasis on research results and commercial uptake in northern, western and southwestern Europe. Increased interest in no-till, as well as minimum or reduced tillage, is the result of changes in the economic circumstances of crop production, the opportunity to increase the area of more profitable autumn-sown crops and increased concern about environmental damage associated with soil inversion by ploughing. Highly contrasting soil and climate types within and between these regions exert a strong influence on the success of no-till. While no-till may often result in crop yields which equal or exceed those obtained after ploughing, modest reductions in yield may be tolerated if production costs are appreciably lower than with ploughing. The relative costs of fuel and herbicides have changed appreciably in recent years making no-till more attractive commercially. While effective weed control is an essential aspect of no-till, current herbicide technology may not yet fully achieve this. No-till soils will usually have lower temperature and higher moisture content at the time of drilling, delaying drilling of spring-sown crops in northern regions. Their bulk density and bearing capacity are greater than for ploughed soils but the pronounced vertical orientation of macroporosity will allow encourage penetration of roots and water, especially in view of the increased population of deep-burrowing earthworms. Particular care must be taken to minimise soil damage at harvest and to ensure the even distribution of crop residues prior to drilling. Reduced erosion and runoff under no-till are widely observed and are of particular importance in southwestern Europe. No-till reduces losses of phosphorus in runoff and the loss of nitrate through leaching. Emissions of greenhouse gases CO2 and N2O from no-till soils are highly variable and depend on complex interactions of soil properties. Emission of CO2 from fuel during machinery usage is always appreciably reduced with no-till. Increased soil organic carbon in surface layers of no-till soils may not be associated with increased carbon sequestration throughout the profile. All relevant factors must be included in the evaluation of the relative overall climate forcing effects of no-till and ploughing. Adoption of no-till could be encouraged by government financial assistance in recognition of environmental benefits, although future restrictions on the use of herbicides may be a deterrent. Opportunities for further research on no-till are outlined.

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No-till in northern, western and south-western Europe: A review of problems and opportunities for crop production and the environment

Can no-tillage stimulate carbon sequestration in agricultural soils? A meta-analysis of paired experiments

Our 2000 paper Soil macroaggregate turnover and microaggregate formation: A mechanism for C sequestration under no-tillage agriculture had its genesis in attempts to identify and isolate soil organic matter (SOM) fractions that reflect the impacts of climate, soil physiochemical properties and physical disturbance on the soil organic carbon balance. A key prerequisite for the investigation was the development of a simple device to isolate the microaggregates (53–250 μm) contained within stable (i.e., resistant to slaking) macroaggregates (>250 μm) obtained by conventional wet-sieving. By comparing the abundance and C content of micro-within-macroaggregates, the size distribution of intra-aggregate particulate organic matter (iPOM) and isotopically-based estimates of the age of the organic matter in the different fractions, we were able to corroborate our hypothesis that the absence of tillage (i.e., in no-till and native soils) promotes greater longevity of newly-formed macroaggregates, resulting in greater SOM stabilization in microaggregates formed within stable macroaggregates. Follow-up research has indicated that the microaggregate-within-macroaggregate fraction is 1) potentially a robust indicator for management-induced SOC changes over decadal time scales, 2) of biological origin and therefore useful in interpreting impacts of soil biota on soil C and N dynamics, but not in-situ CO 2 and N 2 O fluxes, 3) useful in complimentary chemical and spectroscopic approaches to relate SOM dynamics to soil structure and attributes of the soil pore space, and 4) a good candidate for being incorporated into models as a measurable fraction.

Aggregate-associated soil organic matter as an ecosystem property and a measurement tool ☆

Fil: Alvarez, Roberto. Universidad de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario; Argentina

A review of the effects of tillage systems on some soil physical properties, water content, nitrate availability and crops yield in the Argentine Pampas

Application of crop residues to soil and reduced or no tillage are current management practices in order to achieve better water management, increase soil fertility, crop production and soil erosion control. This study was carried out to quantify the effect of wheat straw mulching in a no tilled Fluvisol under semi-arid conditions in SW Spain and to determine the optimum rate in terms of cost and soil protection. After a 3-years experiment, mulching application significantly improved physical and chemical properties of the studied soil with respect to control, and the intensity of changes was related to mulching rate. The organic matter content was generally increased, although no benefit was found beyond 10 Mg ha−1 year−1. Bulk density, porosity and aggregate stability were also improved with increasing mulching rates, which confirmed the interactions of these properties. Low mulching rates did not have a significant effect on water properties with respect to control, although the available water capacity increased greatly under high mulching rates. After simulated rainfall experiments (65 mm h−1 intensity), it was found that the mulch layer contributed to increase the roughness and the interception of raindrops, delaying runoff generation and enhancing the infiltration of rain water during storms. Mulching contributed to a reduction in runoff generation and soil losses compared to bare soil, and negligible runoff flow or sediment yield were determined under just 5 Mg ha−1 year−1 mulching rate. It was observed that during simulations, the erosive response quickly decreases with time after prolonged storms (30 min) due to the exhaustion of available erodible particles. These results suggest that the erosive consequences of intermediate intensity 5-years-recurrent storms in the studied area could be strongly diminished by using just 5 Mg ha−1 year−1 mulching rates.

Effects of mulching on soil physical properties and runoff under semi-arid conditions in southern Spain

Under semiarid conditions, soil quality and productivity can be improved by enhancing soil organic matter content by means of alternative management practices. In this study, we evaluated the feasibility of no-till (NT) and cropping intensification as alternative soil practices to increase soil organic C (SOC). At the same time, we studied the influence of these management practices on two SOC fractions (particulate organic matter C, POM-C, and the mineral-associated C, Min-C), in semiarid agroecosystems of the Ebro River valley. Soil samples were collected from five soil layers (0-5-, 5-10-, 10-20-, 20-30-, 30-40-cm depth) during July 2005 at three long-term tillage experiments located at different sites in the Ebro River valley (northeast Spain). Soil bulk density, SOC concentration and content, SOC stratification ratio, POM-C, and Min-C were measured. Higher soil bulk density was observed under NT than under reduced tillage (RT), subsoil tillage (ST), or conventional tillage (CT). At the soil surface (0-5-cm depth), the highest total SOC concentration, POM-C, and Min-C were measured under NT, followed by RT, ST, and CT, respectively. In the whole soil profile (0-40 cm), similarly, slightly greater SOC content was measured under NT than under CT with the exception of the Selvanera site, where deep subsoil tillage combined with moldboard plowing accumulated more SOC than NT. In semiarid Mediterranean agroecosystems where CT consists in moldboard plowing, NT is a viable management practice to increase SOC.

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Tillage Effects on Soil Organic Carbon Fractions in Mediterranean Dryland Agroecosystems

The co-ordinated European research project Wind Erosion and Loss of SOil Nutrients in semiarid Spain (WELSONS) was carried out from 1996 to 1999 to understand and predict the potential impacts of land-use change and management on soil degradation by wind erosion on agricultural land in Central Aragon, a semiarid desertification-threatened region in NE Spain. This paper gives a description of the project's experimental approach and an overview of the main results regarding the effects of agricultural practices (i.e. conventional, CT, versus reduced tillage, RT) on surface conditions affecting wind erosion, the mobilisation of soil particles in the saltation layer and the atmospheric emission of fine dust into the suspension layer. The characterisation of the soil surface showed that soil erodibility by wind under RT was lower than that under CT. Though strong Cierzo wind events occurred during the experimental period, only a limited amount of material was available for wind erosion mainly due to soil crusting, a common feature in the area. In spite of this, saltation transport flux was measured at CT plots for different erosion episodes. Also, significant vertical emission of dust was observed only in the CT plot. Finally, the sandblasting efficiency calculated in the present experiment could be interpreted as the result of a higher binding energy for the particles of the silt loam experimental soil compared to soils with a lighter texture.

https://digital.csic.es/bitstream/10261/10899/1/LopezMV_Catena2003.pdf

Wind erosion in a semiarid agricultural area of Spain: the WELSONS project

There is limited information on the effects of tillage practices on soil hydraulic properties, especially changes with time. The objective of this study was to evaluate on a long-term field experiment the influence of conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) on the dynamics of soil hydraulic properties over 3 consecutive 16-18 month fallow periods. Surface measurements of soil dry bulk density (ρb), soil hydraulic conductivity (K(ψ)) at -14, -4, -1 and 0 cm pressure heads using a tension disc infiltrometer, and derived hydraulic parameters (pore size, number of pores per unit of area and water-transmission porosity) calculated using the Poiseuille's Law were taken on four different dates over the fallow period, namely, before and immediately after primary tillage, after post-tillage rains and at the end of fallow. Under consolidated structured soil conditions, NT plots presented the most compacted topsoil layer when compared with CT and RT. Soil hydraulic conductivity under NT was, for the entire range of pressure head applied, significantly lower (P < 0.05) than that measured for CT and RT. However, NT showed the largest mean macropore size (0.99, 0.95 and 2.08 mm for CT, RT and NT, respectively; P < 0.05) but the significantly lowest number of water-conducting pores per unit area (74.1,118.5 and 1.4 macropores per m 2 for CT, RT and NT, respectively; P < 0.05). Overall, water flow was mainly regulated by macropores even though they represented a small fraction of total soil porosity. No significant differences in hydraulic properties were found between CT and RT. In the short term, tillage operations significantly increased K (P < 0.05) for the entire range of pressure head applied, which was likely a result of an increase in water-conducting mesopores despite a decrease in estimated mesopore diameter. Soil reconsolidation following post-tillage rains reduced K at a rate that increased with the intensity of the rainfall events.

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Dynamics of soil hydraulic properties during fallow as affected by tillage

In semi-arid Mediterranean areas, studies of the performance of conservation tillage systems have largely demonstrated advantages in crop yield, soil water storage and soil protection against wind and water erosion. However, little attention has been given to interactions between soil biochemical properties under different tillage practices. Biochemical properties are useful tools to assess changes caused by different soil tillage systems in long-term field experiments. This study deals with the effect of long-term tillage practices (reduced tillage and no-tillage vs. traditional tillage) on soil chemical properties and microbial functions in three different sites of Spain (two of them located in the Northeast and one in the Southwest) under semi-arid Mediterranean conditions. Soil biological status, as index of soil quality, was evaluated by measuring microbial biomass carbon (MBC) and dehydrogenase (an oxidoreductase) and protease (a hydrolase) activities at three soil depths (0–5, 5–10 and 10–25 cm). In the three experimental areas, increases in soil organic matter content, MBC and enzymatic activities were found at the superficial layers of soil under conservation tillage (reduced tillage and no-tillage) in comparison with traditional tillage. Values of the stratification ratio of some biochemical properties were significantly correlated with yield production in Northeast sites. Conservation tillage has proven to be an effective strategy to improve soil quality and fertility in Mediterranean areas of Spain.

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Effect of long-term conservation tillage on soil biochemical properties in Mediterranean Spanish areas

A study was carried out on the root distribution and root activity of the olive tree (Olea Europaea, L., var. manzanillo) as influenced by drip irrigation and by several soil characteristics such as texture and depth. The experiments were conducted in two plots within a drip-irrigated grove of 20-year-old trees planted at 7×7 m spacing. One soil was a sandy loam, the other a clay-loam. Both cylinder and trench methods were used to determine root distribution. Labelling with 32P was used to determine root activity. Under dryland conditions the adult tree adapted its rooting system, following the installation of a drip system, by concentrating the roots within the wet soil zones near the drippers. The highest root densities occur in those zones, down to a 0.6 m depth, the most abundant being the <0.5 mm diameter roots. The most intensive root activity was also found in that zone. For a given irrigation system, wet soil bulbs are more extensive and therefore root distribution expands to a larger soil volume when the soil is more clayey and with a hard calcareous pan present at about 0.8 m depth which prevents deep drainage.

J.L. Arrúe

Papers

Tillage Effects on Soil Organic Carbon Fractions in Mediterranean Dryland Agroecosystems

Wind erosion in a semiarid agricultural area of Spain: the WELSONS project

Dynamics of soil hydraulic properties during fallow as affected by tillage

Effect of long-term conservation tillage on soil biochemical properties in Mediterranean Spanish areas

Drip irrigation, soil characteristics and the root distribution and root activity of olive trees