Reduced Tillage Research Articles

Tillage system and farmyard manure impact on soil physical properties, CO2 emissions, and crop yield in an organic farm located in a Mediterranean environment (Croatia)

A 2-year study was carried out in a Croatia to assess the impacts of tillage and fertilisation on soil bulk density (BD), penetration resistance (PR), CO2 emissions and grain yields. The tillage treatments were: conventional tillage (CT), minimum tillage (MT) and reduced tillage (RT). Inside these plots, subplots were fertilised with organic fertiliser, 600 kg ha−1 (CF), 15 t ha−1 (FYM15) and 30 t ha−1 (FYM30) of farmyard manure. In 2017, BD at 10–20 cm was significantly higher in MT than in RT and CT. The same was observed in 2018 at 0–10 cm and 10–20 cm. In 2017, RT had a significantly lower PR than MT and CT. In 2018, PR in RT was significantly lower than MT. In 2017 and 2018 FYM30 and FYM15 application decreased significantly BD in comparison to CF. In 2017, the highest dose of farmyard manure (FYM30 50, 5 kg ha−1 day−1) increased significantly CO2 fluxes comparing to CF (40.7 kg ha−1 day−1). Soil CO2 fluxes under CT (47.9 and 52.3 kg ha−1 day−1 in 2017 and 2018, respectively) were significantly higher than RT (39.1 kg ha−1 day−1) in 2017 and MT (41.7 kg ha−1 day−1) in 2018. Conventional tillage (2.26 t ha−1) had significant lower oat yields than RT (2.72 t ha−1) and MT (2.56 t ha−1). The opposite occurred in barley yields. Farmyard manure significantly increased oat yields in 2017 compared to CF. Overall, reduced tillage with addition of FYM30 can be considered a sustainable management practice, since improved soil physical properties, reduced CO2 fluxes and increased grain yield.

Effect of Tillage and Water Management on Aggregate Stability of a Gleyic Cambisols

The objective of this study was to determine the effect of tillage and water management on the physical stability of irrigated lowland rice field, in Kwalkwalawa, Sokoto State. The experiment was carried out in a farmer`s field, near the Usmanu Danfodiyo University Teaching and Research Farm, Kwalkwalawa, Sokoto State. The coordinates of the area were taken using global positioning system (GPS) model Garmin etrex 20.0, which shows that the area is located on (N13°05.963”E005°12.650” and at 252 m asl). The soils of the study area were classified as Aeric Endoaquepts at subgroup level in the USDA Soil Taxonomy System which correlated with Gleyic Cambisols in the World Reference Base. The treatments consisted of factorial combination of two tillage systems (conventional tillage (CT) and reduced tillage (RT), three irrigation water managements (Alternate one, two and three days irrigation intervals, which were carried out from one week after transplanting to hard dough stage) and three rice varieties (FARO 44, 60 and 61) all laid in a split-plot design and replicated three times. After harvest, disturbed soil samples were collected with the aid of soil auger, prepared and passed through 5 mm sieve for aggregate stability determination. Result reveals that a consistent trend in aggregate size fraction was observed between the two tillage systems in both years, were a significant decrease in values of aggregate fractions of both the CT and RT in 2019 compared to in 2018. Aggregate size fraction of 5-2 mm had a significantly high value of RT compared to CT, 2-0.25 mm fractions were at par (0.41) while a greater value of aggregate fractions for CT in both 0.25-0.005 mm and ˂0.005 mm were observed compared to RT. Alternate days to irrigation and sampling depths increase with a corresponding in all the aggregate size classes in the two years of this study. A significant difference in mean weight diameter (MWD) and geometric mean diameter (GMD) between the two tillage, water management and depth was noticed in both years of the trial where RT and alternate one day had high value while MWD and GMD increase with increasing depth.

Biological Nitrogen Fixation and Productivity of Soybean in Maize-Soybean Intercrop under Tillage and Bradyrhizobium Inoculation on Alfisols of Northern Guinea Savanna, Nigeria

A field study was conducted in the 2011 cropping season to investigate the effect of tillage and bradyrhizobium inoculation of soybean on biological nitrogen fixation (BNF) and yield components in maize-soybean intercropping systems. Treatments comprised of two tillage practices (conventional tillage (CT) and reduced tillage (RT)) as the main plot and bradyrhizobium inoculation at four levels (inoculated sole soybean, inoculated soybean/maize intercrop, uninoculated sole soybean, and uninoculated soybean/maize intercrop) as sub-plot. The treatments were laid in a split-plot under a randomized complete block design with three replications. Results showed that BNF and nitrogen derived from atmospheric (Ndfa) were significantly higher under RT than CT by 4.18 and 0.10 %, respectively. The BNF was consistently higher in the maize-soybean intercropping system with soybean inoculated with bradyrhizobium than in the uninoculated. BNF was 28.0 % higher in inoculated sole soybean and 80.2 % higher in inoculated maize-soybean intercrop than the uninoculated sole and intercropping system. Similarly, grain yield was 31.0 % higher in the inoculated sole soybean than the uninoculated sole and 33.7 % higher in inoculated maize/soybean intercrop than in the uninoculated intercrop. Biomass yields under inoculatedsole soybean and maize-soybean intercrop, respectively, were significantly higher than in uninoculated sole soybean and maize-soybean intercrop by 30.99and 33.66% for inoculated and uninoculated soybean sole and 34.44 and 30.40 % for inoculated and uninoculated intercrop. The results demonstrated that integrating bradyrhizobium inoculants and tillage will improve N fixation and productivity in maize-soybeanbased intercropping systems in Alfisols of Northern savannah.

Manejo y diversidad de las comunidades arvenses en las estepas cerealistas: propuestas para una gestión sostenible

Alarcon Villora, R., Sanchez, A.M., Hernandez-Plaza, E. 2019. Management and diversity of weed communities in Mediterranean cereal steplands: new proposals under the sustainability paradigm. Ecosistemas 28(3):36-45. Doi.: 10.7818/ECOS.1821 The word weed is used to define the herbaceous plants that inhabit the cultivated fields. In rainfed crops, weeds have been considered one of the main causes of yield loss. However, works on the relationship between management practices, crop yields and weed communities in cereal steplands, are still scarce. Nonetheless, some of these works challenge the prevailing negative view on weeds, while questioning the efficacy of a weed management solely based on herbicide use. In Spain, the large extension of cereal steplands (6.5Mha) made the management of its weed diversity a question of great relevance. In this study, we summarize the state of the art on the effects of management practices on weed communities of cereal steplands. We identify knowledge gaps, and point out new research to support the development of management strategies based on the recovery of traditional crop rotations, the reduction of soil tillage and the use of organic fertilization. These will serve as the basis for the design of management strategies that permit to maintain crop yields and biodiversity.

Temporal variations of the hydraulic conductivity characteristic under conventional and conservation tillage

Conservation agriculture promotes as one of its three key principles the reduction of tillage intensity to minimize soil physical disturbances. The choice of tillage system alters hydraulic conductivity at (Ks) and near saturation. Drier regions of the hydraulic conductivity characteristic (HCC) may be affected as well. Temporal variations of the HCC along with water retention characteristics of tilled soils have come into the focus of researchers in recent years. It was shown that it may be preferable to account for such variations in soil water modelling.Here, the effects of a conventional tillage (CT), reduced tillage (RT) and no tillage (NT) system on the HCC were investigated on an experimental field with a Haplic Luvisol in Eastern Germany throughout part of a winter wheat growing season. This included changes following agricultural management such as stubble breaking and seedbed preparation. Hood infiltrometer measurements were conducted in the field and transient evaporation experiments in the laboratory were performed on undisturbed soil cores to describe the HCC over a wide range of pressure heads (h) from saturation to −1000 cm (pF 3).On tilled plots, Ks and hydraulic conductivity at h = −2 cm (K−2 cm) were more variable with time than observed spatial variability. Overall, Ks was significantly (p < 0.05) higher under RT compared to NT while for CT they ranged in between. Correlation and multiple linear regression indicated a distinctly different soil structure between tilled and untilled treatments. While bulk density and macro-and mesoporosity could explain some variability in Ks and K−2 cm on CT and RT, it was meaningless for the untilled soil. A denser soil matrix on NT with few conducting macro-and biopores was attributed to those findings. Under tillage, the loosened soil matrix and decaying organic matter mixed into the topsoil likely govern water transport at and near saturation. Over the entire HCC, variability decreased with drier conditions on NT while this was less pronounced on tilled soil, especially RT, indicating that tillage may affect not only soil macroaggregates but also the soil matrix. In this specific case, variability of the HCC with time was shown to be large for tilled plots, and modeling of soil water may benefit from an explicit consideration of these changes. Contrasts in soil structure under tilled and untilled soil should also be reflected in the future development of pedotransfer functions for the prediction of (near-) saturated K. Different soil physical property predictors may be needed for a valid estimation.

Chemical Properties and Enzyme Activity of Soil as Affected by Tillage System and Previous Crop

The objective of this study was to evaluate the effect of tillage system and previously cultivated crop on the chemical properties and enzyme activity of soil. The first-order experimental factor was the tillage system, i.e., (1) conventional tillage (CT) and (2) reduced tillage (RT), whereas the second-order experimental factor was the previously cultivated crop, i.e., a) pea and b) durum wheat. Samples of soil were analyzed for the contents of organic C, total N, available forms of P, K, and Mg, as well as soil pH, total sorption capacity, and activity of soil enzymes (dehydrogenases, phosphatases, ureases, and proteases). The study demonstrated that the contents of organic C, total N, and available forms of K and Mg as well as soil pH were higher in soil subjected to RT than in that subjected to CT. In plots after pea cultivation, higher values were determined for the contents of total N and Mg, whereas in plots after durum wheat cultivation, the contents of organic C, P, and K and the soil pH were higher. Higher activities of dehydrogenases and phosphatases in soil were noted in soils subjected to the CT system than in those subjected to the RT system, whereas the activities of ureases and proteases were higher in soils subjected to RT. In addition, higher activities of dehydrogenases, phosphatases, and proteases were determined in the soil after pea cultivation than after durum wheat cultivation, whereas a higher activity of ureases was found in the soil after durum wheat cultivation. The C/N ratio was more beneficial after CT than after RT, as well as in the soil from plots after pea cultivation than after durum wheat cultivation.

Evaluation of wheat genotypes under tillage practices: application of technique for order preference by similarity to ideal solution method

Adoption of conservative agriculture at farm level is associated with reducing the production costs and leads to crop yield stability. The aim of this study was to prioritize experimental treatments based on different criteria by applying technique for order preference by similarity to ideal solution (TOPSIS).A filed experiment was carried out at Zarghan research station, Fars province, Iran, during 2014-2016 growing seasons. Experimental treatments were three tillage practices including conventional tillage (CT), reduced tillage (RT) and no tillage (NT) that were assigned to main plots and four spring wheat genotypes (Chamran, Sirvan, Picaflor#1 and M-89-10)were randomized in subplots using split-plot arrangements in randomized complete block design with three replications. Selected criteria including two groups of economic- i.e. water cost, weed control cost, production cost and gross margin- and agronomic –i.e. grain yield and soil bulk density criteria used to prioritize the treatments. The weights of bulk density (0.040), grain yield (0.180), gross margin (0.280), water cost (0.0270), weed control cost (0.150), and production cost (0.080) was calculated. Results showed, considering all criteria to prioritize wheat genotypes under different tillage practices, that Sirvan and Picaflor#1 genotypes under RT practice could be the first treatments in 2014-15 and 2015-16 growing seasons, respectively. Therefore, the multiple criteriamethodshould be used for selection of the best tillage practices and wheat genotypes under tillage practices rather than a criterion such as grain yield or production cost.

Long-term effectiveness of sustainable land management practices to control runoff, soil erosion, and nutrient loss and the role of rainfall intensity in Mediterranean rainfed agroecosystems

Mediterranean environments are especially susceptible to soil erosion and to inappropriate soil management, leading to accelerated soil loss. Sustainable Land Management (SLM) practices (such as reduced tillage, no-tillage, cover crops, etc.,) have the potential to reduce soil, organic carbon (OC), and nutrient losses by erosion. However, the effectivity of these practices is site-dependent and varies under different rainfall conditions. The objective of this paper was to evaluate the effects of SLM practices – in two rainfed systems (a wheat field and an almond orchard) representative of a large area of the driest Mediterranean regions - on runoff, soil erosion, particle size distribution, and OC and nutrient (N and P) contents in sediments. The influence of the rainfall characteristics on the effectiveness of the SLM practices was also evaluated. The SLM implemented were: reduced tillage (RT) in the wheat field and almond orchard and reduced tillage combined with green manure (RTG) in the almond orchard; these were compared to conventional tillage, the usual practice in the area. Open erosion plots were set up to monitor the effects of SLM on soil carbon and nutrients and on soil erosion after each rainfall event over six years (2010–2016). The results show that the SLM practices evaluated resulted in increased organic carbon (OC) and nutrients (N and P) contents in the soil, and reduced runoff, erosion, and mobilization of organic carbon and nutrients in sediments. Reductions in runoff of 30% and 65% and decreases in erosion of 65 and 85% were found in the wheat field and almond orchards, respectively. In addition, the total OC, N, and P losses in the wheat field were reduced by 56%, 45%, and 64%, respectively, while in the almond field the OC, N, and P losses were reduced by 90% under RT and by 85% under RTG.The beneficial effect of the SLM practices on soil erosion was observed within 18 months of their implementation and continued throughout the six years of the study. Furthermore, the effectiveness of tillage reduction with respect to erosion control and carbon and nutrients mobilization was highest during the most intense rainfall events, which are responsible for the highest erosion rates in Mediterranean areas. Our results support the key role of SLM practices under semiarid conditions as useful tools for climate change mitigation and adaptation, given the expected increase in high-intensity rainfall events in semiarid areas.

Climate and land use change effects on soil erosion in two small agricultural catchment systems Fugnitz – Austria, Can Revull – Spain

Soil erosion represents one of the most important processes of land degradation in the world and is considered a serious threat to the provision of food supply, to human health and to terrestrial ecosystems. In Europe, soil erosion by water and tillage is responsible for the loss of fertile topsoil and therefore productive land. Under Global Change scenarios climate and land use are expected to impact soil loss and sediment discharge rates distinctly in contrasting climatic regions, further influenced by tillage practices. Soil erosion modeling is a valuable tool to estimate future changes and elucidate opportunities to mitigate future threats to soil loss and crop yield, ultimately leading to the development of Best Management Practices (BMPs). In this study, future change of soil erosion processes under the IPCC Representative Concentration Pathways RCP2.6 and RCP6.0, as well as a conventional tillage (CT) and a reduced tillage (RT) practice are investigated in two small agricultural catchments in Europe under contrasting climate; Can Revull in Spain and Fugnitz in Austria. We applied GeoWEPP, the Geospatial Interface for the Water Erosion Prediction Project, to model these two agricultural catchments at a fine spatial resolution. We demonstrate that tillage practice, precipitation and runoff are driving factors for soil erosion at both locations. Furthermore, we illustrate that tillage practices have a greater effect on soil erosion than climate change scenarios. RT could reduce soil erosion by more than 75% compared to CT practices. Under RCP6.0, future changes in runoff, hillslope soil loss and sediment discharge would be greater compared to RCP2.6, with different responses depending on the investigated climatic region. Linking soil erosion models on a fine spatial scale and with different management practices to downscaled global circulation models, can provide valuable input for the development of future BMPs to reduce soil loss in agricultural landscapes.

Carbon emissions and economic assessment of farm operations under different tillage practices in organic rainfed almond orchards in semiarid Mediterranean conditions

Sustainable land management practices, such as reduced tillage or crop diversification, are potentially efficient measures to fight against soil degradation and desertification. The decision to approve these practices must be justified by both integrated environmental and economic assessment studies. In this work, we analysed the carbon emissions associated to farm operations and economic profitability for two organic rainfed almond (Prunus dulcis Mill.) farms under semiarid conditions. In the analysis, we considered the following soil management strategies: conventional tillage (CT); reduced tillage (RT); reduced tillage plus green manure (RTG); and no tillage (NT). A cradle-to-farm gate life cycle assessment (LCA) was applied based on long-term data from two farms. The results obtained showed that the NT strategy provided, as expected, the lowest greenhouse gas (GHG) emissions but that its yield was also the lowest, which negatively affects its economic viability even with the consideration of subsidies. The RT strategy reduced GHG emissions and improved the ratio of profit/GHG emissions, whilst the RTG strategy increased GHG emissions and reduced the ratio of profit/GHG emissions as a consequence of using seeds. In conclusion, it has been demonstrated that some level of reduced tillage leads to environmental and economic benefits with respect to conventional tillage in organic rainfed almond orchards under semiarid conditions.

Agronomic and Economic Benefits of Rotating Corn with Soybean and Spring Wheat under Different Tillage in Eastern Canada

Agronomic and economic performance of the corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation is well documented, but few studies have investigated the addition of spring wheat (Triticum aestivum L.) to this rotation, particularly at the northern limit of corn and soybean production in North America. A 6‐yr field study was initiated in 1999 on a clay soil in eastern Canada to identify the best crop rotation (continuous corn, continuous soybean, corn–soybean, corn–corn–soybean, corn–soybean–spring wheat, or corn–spring wheat–soybean) under moldboard plow (MP) and reduced tillage (RT) in terms of grain yield, soil aggregate distribution, and annual net returns. To isolate the effect of annual climatic conditions, all crop phases of each rotation were present each year for a total of 13 rotation sequences within each soil tillage practice. Corn grown in rotation had greater yield (+0.6 to +0.9 Mg ha−1) than continuous corn or second‐year corn regardless of soil tillage. Soybean grown once every 3 yr had consistently greater yields (+0.20 Mg ha−1) than continuous soybean. The addition of spring wheat in the rotation improved both corn and soybean yields compared with either continuously cropped. The RT management did not affect crop yield but increased the soil macro‐aggregation only when corn was present in the rotation. Economic analysis revealed that continuous soybean, the 3‐yr corn–soybean–spring wheat with wheat straw being sold, and the 2‐yr corn–soybean were the most profitable and most efficient rotations when averse risk is considered.Core Ideas Corn in rotation yielded 0.7 Mg ha−1 more than continuous corn, regardless of soil tillage. Soybean grown once every 3 yr had consistently higher yields than continuous soybean. Including spring wheat in the corn and soybean continuous cropping improved corn and soybean yields. Reduced tillage did not affect crop yield but improved soil macro‐aggregation when corn grown continuously or in rotation. Continuous soybean, corn–soybean, and 3‐yr rotation with corn, soybean, and spring wheat with wheat straw being sold were the most efficient economic rotations when considering the risk aversion.

Weed community structure and soybean yields in a long-term organic cropping systems experiment

AbstractWeed management is a major challenge in organic crop production, and organic farms generally harbor larger weed populations and more diverse communities compared with conventional farms. However, little research has been conducted on the effects of different organic management practices on weed communities and crop yields. In 2014 and 2015, we measured weed community structure and soybean [Glycine max(L.) Merr.] yield in a long-term experiment that compared four organic cropping systems that differed in nutrient inputs, tillage, and weed management intensity: (1) high fertility (HF), (2) low fertility (LF), (3) enhanced weed management (EWM), and (4) reduced tillage (RT). In addition, we created weed-free subplots within each system to assess the impact of weeds on soybean yield. Weed density was greater in the LF and RT systems compared with the EWM system, but weed biomass did not differ among systems. Weed species richness was greater in the RT system compared with the EWM system, and weed community composition differed between RT and other systems. Our results show that differences in weed community structure were primarily related to differences in tillage intensity, rather than nutrient inputs. Soybean yield was lower in the EWM system compared with the HF and RT systems. When averaged across all four cropping systems and both years, soybean yield in weed-free subplots was 10% greater than soybean yield in the ambient weed subplots that received standard management practices for the systems in which they were located. Although weed competition limited soybean yield across all systems, the EWM system, which had the lowest weed density, also had the lowest soybean yield. Future research should aim to overcome such trade-offs between weed control and yield potential, while conserving weed species richness and the ecosystem services associated with increased weed diversity.

Corn nitrogen management using NDVI and SPAD sensor-based data under conventional vs. reduced tillage systems

Present analyses to calculate nitrogen fertilizer recommendations are time consuming and costly. Therefore, a field study determining the efficiency of SPAD and NDVI meters to calculate soil N deficiency and guide fertilizer application timing and rate was completed. Reduced vs. conventional tillage at various N application rates was studied. Regardless of tillage system, both NDVI and SPAD were able to detect N deficiency at early growth stages, however, SPAD measurements better reflected plant N status regarding N application rates. A modified Michaelis-Menten model was used to illustrate the relationship between N rates and grain yield, as well as grain N content and leaf N content, and both showed acceptable goodness of fit. Grain yield under reduced tillage was significantly higher than that of conventional tillage. The combination of leaf nitrogen, SPAD, and NDVI data may become a tool to manage corn field nitrogen status and predict grain yield.

Influence of Long-Term Tillage and Residue Management on Soil Biota in Tropical Climate

A study was conducted during 2002–2018 to study the effects of conservation practice on soil biota properties in a sandy clay loam soil. Tillage treatments consisted of conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). Residue treatments consisted of 0 residue input (NR), 50% residue input (HR), 100% residue input (TR). Microbial biomass C (MBC), urease (UA), and dehydrogenase (DHA) obtained a mean of 29.7–41.2% higher in RT and NT than in CT. In comparison with NR, HR and TR increased the numbers of mesofauna and macrofauna, but decreased the number of microfauna. The residue addition soils favored soil moisture, total organic C and available K. Soil fauna community analysis indicates that residue systems provide a more diverse residue resource entry into soil food webs, and that NT system is beneficial for soil ecosystem stability and sustainability.

Soil C and N dynamics and hydrological processes in a maize-wheat rotation field subjected to different tillage and straw management practices

The impact of farmland nutrient losses on environment security is of serious concern. Conservation tillage led to reduced water and soil losses and increased grain yield, and is therefore one potential solution, but this approach requires an understanding of the complex adaptive traits for environment conditions. In this study, a 4-year field experiment was conducted to quantify the crop yield, runoff and soil water, organic C and N content dynamics in summer maize-winter wheat rations subjected to different tillage and straw management practices. Based on these, the effects of different tillage and straw management regimes on water, C and N balances of the soil-plant system was evaluated with a 11-year model prediction using the SPACSYS model. The treatments used in this study included conventional tillage (CT) with straw removal, conventional tillage with straw returning (CTSR), reduced tillage (RT) with straw removal and reduced tillage with straw returning (RTSR). The results showed that maize yield was remarkably affected by straw returning while there was no significant tillage effect. By contrast, wheat yield showed a high inter-annual variability, but was not significantly influenced by tillage and straw management practices. The soil water balance analysis demonstrated that the treatments with straw returning improved water use efficiency by increasing transpiration while reducing water losses through evaporation and runoff, compared to the straw-removal treatments. The simulations for all of the treatments showed that the soils acted as C and N sinks in the present study. Furthermore, plots that included straw returning amassed more C and N in the soil than the that with straw removal. Our work demonstrates that in maize-wheat rotation slopping land reduced tillage with straw returning is a win-win practice for the equilibrium between agricultural productivity and low soil water, C and N losses.

Effects of different long-term tillage systems on the composition of organic matter by 13C CP/TOSS NMR in physical fractions in the Loess Plateau of China

The adoption of conservation tillage is promising for soil management system in the Loess Plateau of China; however, how conservation tillage influences the molecular structure contributes and long-term stabilization of soil organic matter (SOM) is still not clear in this area. In this study, experimental plots were continually cultivated with winter wheat (Triticum aestivum L.) and soil samples were collected in September 2009 and September 2015, 10 and 16 years after the experiment was initiated, respectively. Four treatments were applied: reduced tillage (RT), no tillage (NT), sub-soiling (SS) and conventional tillage (CT). Soil samples were physically fractionated into five fractions: free light fraction (FLF), occluded light fraction (OLF), coarse sand particulate organic matter (c-POM), fine sand particulate organic matter (f-POM) and mineral associated organic matter + silt + clay (m-SOM). The soil organic carbon (SOC) stocks were analysed in SOM fractions and bulk soil (BS). Solid state 13C cross polarization/total sideband suppression nuclear magnetic resonance (13C CP/TOSS NMR) spectroscopy was applied to determine the abundance of different forms of carbon (C) (carboxyl C, O/N-alkyl C, aromatic C and alkyl C) in the soil physical fractions.The SOC stocks in the 0–30 cm layer were influenced by the tillage systems. Although there were no significant differences in SOC stocks among these four treatments in the 0–10 and 10–20 cm layers in first 10 years, after 16 years, the SOC stocks were highest in the SS and NT treatments in the 0–10 cm layer. As the duration of the experiment increased from 2009 to 2015, the SOC content of m-SOM-C fraction under RT and CT also increased. As determined by 13C NMR, in the light fractions (FLF to OLF), the abundance of aromatic C increased when the abundance of O/N-alkyl C declined and there was a higher aromatic C/O/N-alkyl C ratio. A gradual increase in the abundance of alkyl C of heavy fractions was accompanied by a decrease in aromatic C, which might be due to the microbial by-products deposited on mineral surface in the soils. In addition, a higher SOM preservation were shown in conservation tillage (NT and SS) by our NMR data. Particular interesting were the results of the light and c-POM fractions, in which conservation tillage showed a higher abundance of O/N-alkyl C and a lower aromatic C/O/N-alkyl C ratio in these two fractions compared with conventional tillage (RT and CT).However, these changes were not evident in the heavy fractions. The changes in the chemical structures of the light and c-POM fractions were possibly due to the retention of crop residues and low levels of soil disturbance. In conclusion, long-term conservation tillage affected the fractions and the chemical functional groups of SOM and could be ideal to preserve SOC in the Loess Plateau.

Straw mulching is more important than no tillage in yield improvement on the Chinese Loess Plateau

Conservation agriculture (CA) represents an efficient agro-ecosystems management for sustained crop production under the circumstances of global warming. However, the relative importance of three principles of CA has not been comprehensively assessed. Consequently, it has caused a controversy of whether no tillage (NT) is beneficial for crop yield improvement compared to conventional tillage, ranging from significant decrease to significant or insignificant increase. It remains unclear whether such a controversy is caused by statistical methodology or different acknowledge of the CA principles. This study aimed to clarify the relative importance of various tillage and straw mulching practices in crop yield, evapotraspiration (ET), and water use efficiency (WUE). Published data from experiments reporting the effects of CA on changes of crop yield and water use on the Chinese Loess Plateau were collected. A database of 49 sets of paired experiments was compiled, with tillage practices including conventional tillage without straw mulching (CT), conventional tillage with straw mulching (CTs), no tillage without straw mulching (NT), no tillage with straw mulching (NTs), reduced tillage without straw mulching (RT), reduced tillage with straw mulching (RTs), and subsoiling with straw mulching (Ss). Variable-controlling approach was used to divide these practices into reasonable groups. Paired t-tests were further conducted to systematically evaluate the relative importance of tillage reduction and straw mulching. The results showed the sole application of straw mulching as well as the combination of straw mulching and tillage reduction both resulted in a significant increase of crop yield. Tillage reduction itself including NT and RT caused a significant crop yield decline. The sole application of tillage reduction or straw mulching has neutral or negative impacts, whereas the combination of tillage reduction and straw mulching has neutral to positive on ET changes. WUE changes were similar to that of crop yield. The results illustrated that the increased crop yield reported on the Loess Plateau area is mainly due to the application of straw mulching, rather than the adoption of NT. The positive influences of CA practices on crop yield and water use tend to be higher under dry climate conditions compared to humid climate conditions. In addition, the adoption of paired t-test significantly improves the evaluation of the effects of CA compared to one way-ANOVA (LSD). Overall, the results help clarify the higher importance of straw mulching over tillage reduction and therefore challenge the centrality of NT in crop yield and WUE improvement.

Residue retention and minimum tillage improve physical environment of the soil in croplands: A global meta-analysis

Conservation tillage practices, here defined as no-tillage (NT) or reduced tillage (RT) with/without residue retention, have been widely used to alleviate the negative effects caused by intensive tillage practices. Implementing effective and sustainable agriculture requires a deeper understanding of the impacts of conservation tillage practices on soil physical properties. This study examined the effects of conservation tillage practices on soil physical properties, including soil bulk density, aggregate size and stability, hydraulic properties, and soil pH; based on data collected from 264 studies published worldwide since 1980. The results indicated that no-tillage (NT), NT with residue retention (NTS), and reduced tillage (RT) increased bulk density by 1.4, 2.6, and 2.1%, respectively, compared with conventional tillage (CT). Soil bulk density decreased by 2.9% in NTS compared with NT, and 3.9% in RT with residue retention (RTS) compared with RT. The effect size of bulk density significantly decreased with the increasing experimental duration under NT and NTS practices. Compared to CT, conservation tillage practices increased aggregate mean weight diameter (MWD), geometric mean weight diameter and water stable aggregate (WSA) regardless of the residue retention or minimum tillage systems. The largest effect size of MWD (51.9%) and WSA (54.9%) appeared under NTS as compared to the CT. The effect size of MWD and WSA increased under NT with the increasing experimental duration. NT increased saturated hydraulic conductivity by 24.6% compared to CT. All conservation tillage practices increased soil available water capacity (AWC) compared with CT and NTS with a 10.2% increase in AWC compared with NT. The effect size of AWC increased under RT and NT practices with the increasing experimental duration. Soil pH decreased by 1.7 and 1.0% under RTS compared with RT and CT, respectively; and NT led to a 2.8% reduction in soil pH compared with CT. The effect size of soil pH decreased under RT and NT treatments with the increasing experiment duration. Overall, conservation tillage practices positively affected many soil physical properties; and the extent of the effects varied with the duration of the experiment.

INFILTRATION CHARACTERISTICS OF A TYPIC HAPLUSTULT UNDER DIVERSE TILLAGE PRACTICES AND COVER CROPS IN NORTHERN GUINEA SAVANNA OF NIGERIA

&lt;p&gt;Soil tillage and vegetation cover impact a great deal on hydrological processes in soil. However, there exist a dearth of literature on the extent of these effects in semi-arid Nigeria. This study investigated the effect of tillage practices (no-till, (NT) reduced till (RT) and conventional tillage (CT)) and cover crops (&lt;em&gt;Centrosema pascuorum&lt;/em&gt; (CP)&lt;em&gt;, Macrotyloma uniflorum&lt;/em&gt; (MU)&lt;em&gt;, Glycine max &lt;/em&gt;(GM)&lt;em&gt;, Cucurbita maxima&lt;/em&gt; (CM)&lt;em&gt; &lt;/em&gt;and no cover crop (bare) as control) on soil water infiltration rate and characteristics. A double ring infiltrometer was used to carryout infiltration study of soils under the aforementioned tillage practices and cover crops. Data obtained were used to calculate infiltration rate and these were also fitted into the Philip and Kostiakov’s models. The quality of adjustment of the models was verified by a chi square and T test, coefficient of determination (r&lt;sup&gt;2&lt;/sup&gt;) and standard deviation. Result revealed higher infiltration rate in soil under conservation tillage (NT and RT) due to soil pores continuity, than in the CT where the pores had been disrupted by tillage implement. Similarly, the use of any of the evaluated cover crops improved water infiltration better than the bare soil with no cover crop. Conservation tillage system (RT and NT) favoured better soil infiltration rate by 41.25% and 29.53% respectively more than conventional tillage system. Plots with cover crops had 65.27%, 59.46%, 54.88% and 18.9% higher soil water infiltration rate in CP, MU, GM and CM treatments respectively than the bare (no cover crop) treatment. Both Kostiakov and Philip’s model were suitable for predicting the first one-minute infiltration rate. However, Kostiakov’s equation showed superior performance over Philip’s equation, in determining cumulative infiltration, this was evident from the lower standard deviation and CV values of Kostiakov’s parameters. In addition to the general non-significance differences obtained between measured and Kostiakov’s predicted infiltration values as revealed by Chi square test.&lt;/p&gt;

Tillage history and crop residue input enhanced native carbon mineralisation and nutrient supply in contrasting soils under long-term farming systems

Understanding the legacy effect of tillage-based farming systems on soil organic carbon (SOC) mineralisation and nutrient [nitrogen (N), phosphorus (P) and sulphur (S)] supply after crop residue input is critical to appropriately manage plant available nutrients at the farm scale. To enhance this understanding, crop residues [canola (Brassica napus: δ13C 124‰) or wheat (Triticum aestivum: δ13C 461‰)] were added to Luvisol and Vertisol from two long-term (16–46 years) field experiments and incubated under a controlled environment for 126 days. The practices in the Luvisol were conventional tillage (CT) and reduced tillage (RT) under mixed crop-pasture rotation, and no-till (NT) under continuous cereal-cover crop rotation. The practices in the Vertisol were CT and NT under wheat-wheat rotation. The residue input significantly stimulated SOC mineralisation via “positive priming”, which was greater (p < 0.05) in the CT than RT/NT in the Luvisol only. The SOC mineralised after 126 days was 3.1–4.2 and 1.6–2.5 times higher in the canola and wheat residue-amended soils, respectively, than the unamended soils. Although the CT or RT versus NT had higher net N availability in the Luvisol only, the residue input did not increase plant available N in both soils, possibly due to stronger residue-induced N immobilisation than mineralisation. The results showed a significant release of available P and S in both residue-amended soils (canola > wheat) after 26–50% of residue-C was mineralised over 126 days, and the Vertisol had greater net available P than Luvisol. Our results suggest that considerable quantities of available P and S may release from the soil reserves via SOC priming, and possibly via dissolution/desorption reactions in the soils, in addition to their direct release from the residues. In conclusion, crop residue input to historical farming systems enhanced the supply of available P and S, which varied with tillage, crop residue and soil type.