Aggregate distribution and soil organic matter under different tillage systems for vegetable crops in a Red Latosol from Brazil (original) (raw)
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2021
The aim of this study was to evaluate i) the different cover crops contribution used in no-tillage system (NT) to biogenic aggregation; and ii) the influence of aggregate formation pathways on the compartmentalization and the soil organic carbon origin. Two areas managed under NT with different implementation times (6 and 18 years, NT06 and NT18, respectively) and cover crops were evaluated, totaling six sampling areas: NT06, millet (NT06MI); NT06, brachiaria (NT06BR); NT06, sunn hemp (NT06SH); NT18, millet (NT18MI); NT18, brachiaria (NT18BR); NT18, and sunn hemp (NT18SH). In each sampling area, five pseudo-replicates were collected in the 0.00-0.05 and 0.05-0.10 m layers. The samples were air-dried and sieved using sieves with 9.7 and 8.0 mm mesh, and the aggregates retained within this interval were selected. The percentage of each type of aggregate (physicogenic and biogenic) was quantified. Total organic carbon (TOC) and the natural abundance of δ13C (‰) were analyzed and the ph...
Agricultural Sciences, 2018
Vegetables productions systems are done normally with intense soil tillage causing a strong decline of soil quality. Use of conservation systems can be an alternative to recover this quality. In order to evaluate the effects of such systems on soil organic matter, an experiment has been conducted in randomized blocks design and factorial scheme 3 × 2: three soil management systems (no-tillage; reduced tillage and conventional tillage) and two cover crops (maize single; and intercropping maize with gray velvet bean-Stizolobium niveum); and repeated measures over time. Soil samples were collected before the implementation of the experiment and at the end of each crop cycle until the fifth crop cycle. Carbon associated with humic substances is also determined in 0-5 cm, 5-10 cm and 10-30 cm at the end of the last crop cycle. The SOM content was higher in RT (48.34 g•kg −1) than in the CT (39.48 g•kg −1) at the end of the fifth crop cycle. SOM content in NT (44.92 g•kg −1) was statistically equal to RT and CT, during the same period. In 0-5 cm, carbon contents associated to the humic substances present the same behavior of SOM contents in 0-10 cm. Probably these results are associated with the capacity of each system to improve superficial contents of SOM stable fractions. It follows that the conservation systems used are alternatives to the cultivation vegetables in order to improve soil organic matter contents.
Conservation Tillage Impact on Soil Aggregation, Organic Matter Turnover and Biodiversity
Sustainable Agriculture Reviews, 2012
Tillage is one of the oldest practices in agricultural production and offers many short term benefits in agro-ecosystem. These perceived benefits of tillage, however, have been gradually questioned because of its negative long-term consequences on soil and environment. With this realization, conservation tillage systems have become the subject of intensive research among scientific communities and common practices among farming communities. However, scientific information on beneficial effects of conservation tillage systems on soil and environment is scattered. Critical analysis and synthesis of such information is helpful for scientific communities, farmers, students, policy makers and so on.
Agriculture
Tillage is a significant type of soil intervention and should be conducted based on the specific soil type. The aim of this study was to determine the influence of different tillage intensities (RT: reduced tillage; CT: conventional tillage), which are correlated with carbon sequestration, on soil properties. The study areas included fields on real farms in Eutric Fluvisol (EF), Mollic Fluvisol (MF), Haplic Chernozem (HC), Haplic Luvisol (HL), Eutric Regosol (ER), Eutric Gleysol (EG), and Stagnic Planosol (SP). The effects of tillage systems depended on the soil type and were more evident in soil aggregates of more productive soils. Agronomically, the most valuable fractions of aggregates were dominant in more productive soils (EF, MF, HC) in the CT system and less dominant in less productive soils (HL, ER, EG, SP) in the RT system. Smaller aggregates (<0.5 mm), which indicate deterioration of soil properties, were negatively correlated with clay (r = −0.364, p < 0.01), total ...
Soil & Tillage Research, 2005
In Brazil, no tillage (NT) is a soil conservation practice now widely adopted by farmers, including smallholders. The effect of NT and conventional tillage (disc ploughing followed by two light disc harrowings, CT) was investigated on the aggregation properties of a clayey Rhodic Ferralsol from southern Brazil under different crop rotations. The same soil type under secondary forest was used as reference. Macro-and microaggregate classes were separated by wet sieving using a series of eight sieves (8, 4, 2, 1, 0.5, 0.25, 0.125, 0.053 mm) at four sampling layers (0-5, 5-10, 10-20, 20-30 cm). The soil in general had high structural stability. At 0-5 cm, meanweight diameter (MWD, 11.1 mm) and total organic C in macroaggregates (TOC, 39 g kg −1 soil) were highest for the forest soil. Soil under NT had a more similar distribution of aggregate size classes and TOC to the forest soil than CT. The most pronounced difference between tillage systems was observed in the surface soil layer (0-5 cm). In this layer, NT had higher aggregate stability (AS NT : 96%; AS CT : 89%), had higher values of aggregate size distribution (MWD NT : 7.9 mm, MWD CT : 4.3 mm), and had on average 28% greater TOC in all aggregate size classes than CT. Soil under NT had greater TOC in macroaggregates (NT: 22 g kg −1 ; CT: 13 g kg −1 ). Crop rotation did not have a significant effect on soil aggregate distribution and TOC. By increasing macroaggregation NT increased organic carbon accumulation in soil.
Journal of Soil and Water Conservation, 2020
Sustainability of agriculture with no-tillage (NT) production requires appropriate cover cropping and not a simple and random approach of any cover crop species. However, relatively little is known of the long-term soil surface impacts of different cover crops in rotation with soybean (Glycine max) under NT in the tropics. We evaluated the impacts of different cover crops on soil aggregation, soil organic carbon (C) and nitrogen (N) fractions, and soil microbial activity of a Typic Rhodudalf at the end of 12 years under NT in São Paulo state of Brazil. Treatments included main plots during the winter dry season (triticale [× Triticosecale] and sunflower [Helianthus annuus]) and subplots during the spring cover crop season (pearl millet [Pennisetum glaucum], sunn hemp [Crotolaria juncea], forage sorghum [Sorghum bicolor], and fallow with occasional chiseling). All eight of these treatments followed soybean in summer. Winter crop treatments had no effect on soil aggregation, but total organic C and N concentrations were greater (p < 0.05) with triticale than with sunflower. Across depths, soil aggregation and soil C and N fractions were generally enhanced when sunn hemp was cover crop than with fallow in the spring. Triticale followed by sunn hemp provided soil cover and fresh mineralizable residue for improving soil quality in this unfertilized (N) soybean-based cropping system. Our results suggest that maintaining soil cover is important to improve soil aggregation and soil C and N fractions, but also the quality of organic inputs determined by cover crop species is an important factor controlling the dynamics of these soil responses.
Tillage impacts on soil biological activity and aggregation in a Brazilian Cerrado Oxisol
Soil and Tillage Research, 2007
Mechanized agriculture is increasing rapidly in the Cerrado region of Brazil, causing concerns about water quality, off-site impacts, and sustainability. Our objective was to determine the impact of tillage on soil biological activity and aggregate stability in an Oxisol typical to the region. Three different tillage practices common to the Cerrado region (no-till, disk harrow, and disk plow) and an area under native vegetation were examined. Five different soil enzyme activities, C-and N-mineralization, organic C, total N, and aggregate distribution were determined. Total N, acid phosphatase, arylamidase, and C-and N-mineralization were the most sensitive to changes in tillage management. For each of these analyses, the no-till system had greater concentrations or activities (18-186%) than disk plow in the 0-5 cm layer. Significant differences observed in the 0-5 cm depth did not necessarily translate into total profile differences to a depth of 30 cm. No-till had significantly greater levels of total N, and C-and N-mineralization (20-127%) than the disk harrow system. Total N ranged from 1.8 to 2.2 kg m À3 ; C-and N-mineralization (24-day incubation) ranged from 2.8 to 6.8 and 0.04 to 0.10 kg m À3 , respectively, among tillage systems and soil depths. Enzyme activities in all treatments were more strongly correlated with total soil N than with soil organic C (SOC), contrary to the norm in temperate soils where the stronger correlation is with SOC. Mean weight diameter of water stable aggregates was related to SOC (r = 0.73) and total N (r = 0.92), indicating that soil organic matter does play a significant role in stabilizing aggregates in Oxisols. Results indicated the importance of reducing tillage as a means of increasing soil biological activity of the topsoil in the Cerrado region of Brazil. By understanding the effects of tillage on soil biological properties, management systems can be implemented that improve natural nutrient cycling processes and soil structure, resulting in increased agricultural sustainability of tropical ecosystems. Published by Elsevier B.V.
Soil and Tillage research , 2020
Agricultural management practices control soil organic carbon (SOC) content in croplands. Long-term cropping system experiments offer a great opportunity to understand the magnitude and direction of SOC change in response to management practices. Such information is very limited from the southeastern US, a region with warm and humid climatic conditions that typically favor SOC decomposition over accumulation. Therefore, this study was conducted to assess the effect of 39 years of chisel plow (CP), disc plow (DP), moldboard plow (MP), no-tillage (NT), NT with winter wheat (Triticum aestivum L.) cover crop (NTW), and NT with wheat-soybean (Glycine max L.) double crop (NTWD) on total SOC and SOC fractions including permanganate oxidizable C (POXC), water extractable C (WEC), resistant C (RC), and aggregate-associated SOC in a continuous soybean system. Additionally, aggregate size distribution, mean weight diameter (MWD), and wet aggregate stability (WAS) were determined. Results showed that NTW and NTWD significantly increased SOC and POXC compared to MP with mean SOC (g kg−1 soil) of 12.2 (NTW) ≥10.9 (NTWD) >7.2 (MP) and mean POXC (mg kg−1 soil) of 465 (NTWD) ≥418 (NTW) >252 (MP). The WEC and RC fractions did not differ among treatments. Across the treatments, the greatest aggregate-associated SOC concentration was found in microaggregates (0.053–0.25 mm) and the lowest in clay- and silt-size particles (<0.053 mm). Additionally, WAS under NT systems was significantly higher (45.5–52.3 %) than under tilled treatments (21.9–29.1 %). Total SOC correlated significantly with POXC (r = 0.68, p < 0.01), RC (r = 0.46, p < 0.05), WAS (r = 0.65, p < 0.01), and aggregate-associated SOC concentrations (r > 0.6, p < 0.01). Overall, this study revealed that NT enhanced SOC and POXC accumulation and macroaggregation compared to tilled treatments. Cover cropping and double cropping further improved SOC accumulation. In conclusion, long-term adoption of different tillage intensities can strongly alter SOC dynamics in bulk soil and aggregates under continuous soybean production systems of the southeastern US.