Reduced Tillage Research Articles

Effect of tillage, rhizobium inoculation in maize-soybean based cropping systems and nitrogen fertilizer application on chemical fertility status of savanna Alfisol, Nigeria

Field experiment was conducted at Research Farm of Institute for Agricultural Research, Ahmadu Bello University, Samaru, Nigeria, to investigate the effect of tillage, rhizobium inoculation in maize-soybeanbased cropping systems and nitrogen fertilizer application on chemical fertility status of a savanna Alfisol. The study was split-split plot design with three replications using improved soybean variety (TGX-1448-2E) and maize (SAMMAZ 14). The treatments were two tillage practices (reduced and conventional tillage) as main plot, four rhizobium inoculation in soybean-maize-based cropping systems (inoculated soybean-maize intercrop, uninoculated soybean-maize intercrop, inoculated soybean-maize rotation and uninoculated soybean-maize rotation) as sub-plot and four nitrogen fertilizer rates (0, 40, 80 and 120 kg N ha-1) as sub-sub plot. At harvest, soil samples were taken from each of the experimental plots and analyzed for selected soil chemical properties. Soil organic carbon, total nitrogen, soil pH, available phosphorus and exchangeable bases were consistently higher under reduced tillage (RT) than under conventional tillage (CT). Soil organic carbon, total nitrogen, soil pH, available phosphorus and exchangeable bases were significantly higher under rhizobium inoculated soybean-maize rotation compared to other cropping systems. A significant difference was found among the effect of nitrogen rates on soil organic carbon, total nitrogen, soil pH, available phosphorus and exchangeable potassium which were significantly lower under 0 kg N ha-1. The study demonstrated that integration of rhizobium inoculated soybean in soybean-maize-based cropping systems under tillage practices, especially RT would improves chemical fertility status of the soil and subsequently reduced N application rate from 120 to 80 kg N ha-1.Key words: tillage, rhizobium inoculation, cropping systems, Nitrogen fertilizer, chemical fertility, Alfisol

Carbon and nutrient mineralisation dynamics in aggregate-size classes from different tillage systems after input of canola and wheat residues

Aggregate-size classes may have different microbial accessibility and therefore different decomposability of aggregate-associated soil organic matter (SOM). However, processes and mechanisms of soil organic carbon (SOC) mineralisation and availability of nutrients [nitrogen (N), phosphorus (P) and sulphur (S)] in different aggregate-size classes, and particularly, the interaction of aggregates with tillage intensity and crop residue type in contrasting soils is poorly understood. Soil samples from conventional tillage (CT) and reduced tillage (RT) systems under mixed wheat–pasture farming, and no-till (NT) under continuous cereal–cover cropping in a Luvisol, and from CT and NT under continuous wheat cropping in a Vertisol, were separated into three dry aggregate classes of different sizes [mega-aggregates (>2–6.5 mm), macro-aggregates (0.25–2 mm) and micro-aggregates (<0.25 mm)]. Two residue types (canola and wheat stem; δ13C 124 and 460‰, respectively) were added into each of the three aggregate class samples from Luvisol (δ13C −24.7‰) and Vertisol (δ13C −18.5‰). Total CO2-C, δ13C in CO2-C, microbial biomass C (MBC), and plant available N, P and S were measured periodically during the 126-day incubation. The results showed that crop residue input increased native SOC mineralisation (via positive priming), MBC and microbial metabolic quotient in all three aggregate-size classes from different tillage systems in both soils. Native SOC mineralisation was 1.5–3.7 and 0.6–2.8 times higher in the canola and wheat residue-amended (cf. control, non-amended) aggregates, respectively. Native SOC mineralisatiion and MBC were higher in the macro- and micro- than mega-aggregates in both soils. However, priming of native SOC mineralisation, relative to the control, was similar across the aggregates, except for the CT in the Luvisol where priming was higher in the macro- than micro- and mega-aggregates. Native SOC mineralisation among the aggregate-size classes was 26–114% higher under CT or RT cf. NT in the Luvisol but was similar under CT and NT in the Vertisol. Net available N was significantly higher in the residue-amended than the control aggregates, particularly in the CT and/or RT versus the NT at day 30 only, and mainly in the Luvisol. Further, substantial amounts of available P and S were released from the residue-amended versus the control aggregates at day 126, with Vertisol releasing 2–3 times more available P than Luvisol. In conclusion, our findings showed the importance of returning crop residues to enhance nutrient availability from all aggregate-size classes in different soils and farming systems. In particular, the tillage (versus no-till) and canola (versus wheat) residue induced a greater release of nutrients, generally in the pattern of micro- ≥ macro- > mega-aggregates. Clearly, the input of crop residues enhanced the release of SOM-bound nutrients, possibly via positive priming, and may have mobilised mineral-bound nutrients, such as P and S in each aggregate-size class, with tillage intensity and soil type modulating these processes.

Conservation tillage and nutrient management effects on productivity and soil carbon sequestration under double cropping of rice in north eastern region of India

Abstract The rice (Oryza sativa)–rice system (RRS) is the most important agricultural production system, and it provides staple food, income, employment, and livelihoods to millions of farmers in the Indian sub- continent, especially in the eastern and north eastern region (NER) of India. However, soil degradation, due to loss of soil carbon (C) and nitrogen (N) pools, is declining the productivity of RRS and threatening the region’s food security. Intensive tillage along with improper residues and nutrient management practices are among the reasons of the loss of soil C and N pools and decline in rice productivity. Therefore, a 3-year (2013-15) field study was conducted to evaluate the effects of tillage, residues and nutrient management practices on productivity, soil C and N sequestration in RRS at the Indian Council of Agricultural Research (ICAR)-Research Complex for the North Eastern Hill (NEH) Region, Lembucherra (52 m, above sea level), Tripura, India. The experiment consisted of five combinations of tillage [conventional tillage (CT), reduced tillage (RT) and no-till (NT)], residue [30% rice residue incorporation (RI) and/or residue retention (RR)] and nutrient management practices [inorganic, organic (FYM-farmyard manure, GLM-green leaf manuring) and biofertilizers] in wet (WR) and dry season rice (DR). Results revealed that RT along with improved plant nutrient management (IPNM) comprising 25% N (20 kg N) through GLM + 60 kg N, 9 kg phosphorus (P), 17 kg potassium (K), 2 kg Boron (B) and 5 kg zinc (Zn) ha−1 through fertilizer + cellulose decomposition microorganism and RR in WR produced significantly higher grain yield (5.15 Mg ha−1) as compared to other treatments. However, the DR transplanted under CT + integrated nutrient management (INM) comprising 25% N through FYM and 75% N and remaining P and K (after deducting quantity supplied by FYM) through inorganic fertilizer + RI produced more grain (5.1–5.3 Mg ha−1), straw (7.0–7.2 Mg ha−1), root (1.3–1.4 Mg ha−1) and total biomass (13.4–13.9 Mg ha−1) yield than that of the farmers’ practice (FP) and other treatment combinations, across the years. The highest system productivity of RRS was recorded under T3 (RT + IPNM + RR in WR and CT + INM + RI in DR). Therefore, the highest biomass, C, and N were also recycled in the system through the same treatment combinations. Soil under T3 had a lower bulk density (ρb), the highest soil organic carbon (SOC)/N concentration, pool, accumulation, sequestration, C retention efficiency, soil microbial biomass C and dehydrogenase activities than other treatments. A total amount of 1.30 Mg C ha−1 was accumulated under soils of T3 with the rate of SOC sequestration of 427.9 kg ha−1 yr−1 under RRS. Thus, adopting RRS under RT/NT with INM/IPNM and effective residue recycling is recommended for enhancing the system productivity, C and N sequestration in paddy soils of the NER of India.

Impact of agricultural management practices on the nutrient supply potential of soil organic matter under long-term farming systems

Soil organic matter (SOM) has the potential to supply substantial quantities of nutrients [i.e nitrogen (N), phosphorus (P) and sulphur (S)] for plant uptake. Yet there is little understanding of the impact of management on the nutrient supply potential in soils (particularly, P and S). To quantify N, P and S availability from SOM, surface soils (0–10cm) were collected from 14 management practices across three long-term (16–46 years) experimental sites under semi-arid (Luvisol), Mediterranean (Luvisol) and sub-tropical (Vertisol) environments in Australia. The practices comprised conventional (CT) and reduced tillage (RT) with mixed farming, no-till with continuous cropping (NT), and perennial pasture (PP) in the semi-arid Luvisol, while in a Mediterranean direct-drilled continuous cropping system, stubble was either retained (SR) or burnt (SB). Practices on the Vertisol comprised a factorial combination of CT, NT, SR, SB with either 0 (0N) or 90kg urea-Nha−1 (90N) in a continuous cropping system. Soils were incubated under controlled soil moisture and temperature, and cumulative organic C mineralised (Cmin), and net available N, P and S were measured over 126days. In the semi-arid Luvisol, CT and/or RT showed significantly higher Cmin and net available N, P and S than NT and PP. In the Mediterranean Luvisol, Cmin and net available P were not influenced by stubble management. In the Vertisol, CT-SR (cf. CT-SB and NT-SR/SB) with or without N fertilisation significantly increased Cmin, and CT-SR and/or -SB with N fertilisation (cf. CT-SR/SB without N fertilisation and NT-SR and/or -SB with or without N fertilisation) significantly increased net available N and P. This study found a continuous release of net available N (11–49kgNha−1 over 126days) across all management practices, whereas, the release of available P and S was evident only during the first 30days (6–74kgPha−1, −4 to 22kgSha−1), after which microbial immobilisation or clay fixation of P and S predominated, particularly in the Vertisol. In conclusion, the results indicate that SOM is a ready source of plant available P and S (in addition to N), and tillage and stubble retention generally enhanced SOM mineralisation and nutrient release, which varied with soil type.

Changes in soil surface chemistry after fifty years of tillage and nitrogen fertilization

Knowledge gained on the long-term effects of crop management practices on soil fertility is critical in developing nutrient management strategies to optimize crop yields. This study examined the long-term effects of nitrogen (N) fertilizer application rates (0, 22, 45 and 67kgNha−1) and tillage intensity [conventional tillage (CT), reduced tillage (RT) and no-tillage (NT)] on soil phosphorus (P), micronutrients and soil acidity in a dryland winter wheat (Triticum aestivum L.) – sorghum (Sorghum bicolor L.) – fallow cropping system. Results showed soil organic matter (SOM), iron (Fe) and manganese (Mn) concentrations were greater under NT compared to CT or RT. Similarly, NT (32mgkg−1) increased P accumulation in the upper 7.5cm soil depth compared to CT (21mgkg−1) or RT (26mgkg−1). After 50-yr of tillage and N fertilizer application, pH at the soil surface (0 to 7.5cm) declined markedly with increasing N application, ranging from 6.4 with the unfertilized control to 5.7 when 67kgNha−1 was applied. Averaged across N rates, Δ pH in the soil surface over the 50-yr was greater with NT compared to CT or RT treatments. Iron and Mn concentrations increased with increasing N application rates, possibly due to the decrease in pH associated with N application. Based on our findings, growers adopting NT need to monitor changes in soil surface chemistry and take necessary corrective measures such as liming to maintain satisfactory pH and nutrients levels to optimize crop yields.

Management Systems Effect on Fertility Indicators of a Ferralsol with Vegetable Crops, as Determined by Different Statistical Tools

ABSTRACT The intensive nature of soil use in vegetable production areas has led to a marked decrease in soil quality. The objective of this study was to evaluate the effects of adoption of soil management systems on vegetable production with regards to the chemical properties of a Rhodic Ferralsol after five years and to evaluate the use of the Principal Component Analysis (PCA) statistical tool in discriminating the different treatments. The experiment was conducted under field conditions in central Brazil in a randomized block design with four replications and a 3 × 2 factorial arrangement (three soil management systems × two cover crops). The soil management systems used were NT (no-tillage), RT (reduced tillage), and CT (conventional tillage). The cover crops used were corn (Zea mays) alone and corn intercropped with the gray velvet bean (Stizolobium niveum). Reduced tillage showed the highest values of sum of bases, cation exchange capacity (T), and total organic carbon contents in the 0.00-0.05 m layer. In the same layer, RT and CT showed higher values of pH and K content. No-tillage and RT showed the highest P and Ca2+ contents and H+Al and T values. In the 0.05-0.10 m layer, RT had higher a pH value and Mg2+ contents. No-tillage and CT had higher potential acidity in this layer. The management systems (0.10-0.30 m) and the cover plants (all layers) had no effect on the properties analyzed. The use of PCA determined that the two principal components explained the following percentage of the data variance: 90.8 % (0.0-0.05 m), 79.8 % (0.05-0.10 m), and 83.1 % (0.10-0.30 m). Analysis of the eigenvectors and the grouping of treatments in PCA also showed that RT was most effective in improving soil fertility properties. Reduced tillage was most effective in increasing soil fertility after five years. The PCA is recommended as a useful tool and it allowed the identification of patterns not revealed by traditional tools.

Effect of different crop management practices on soil Collembola assemblages: A 4-year follow-up

Soil biota are a major component of agroecosystems, playing a decisive role in ecosystem services with synergistic effects on crop production. The conservation of their diversity has become a key component of a strategy towards agricultural sustainability. Over four years (2010–2014), under the “SOil Functional diversity as an Indicator of sustainable management of Agroecosystems” (SOFIA) project, we followed soil Collembola assemblages in response to the set-up of 5 cropping systems differing in crop rotations (annual or perennial), rate of N fertilization, and in tillage intensity (annual ploughing vs. shallow). Our results demonstrated that shifting from a conventional to conservation cropping system had a strong positive effect upon species richness and density of Collembola. Specifically, all treatments with a reduction in intensity of soil tillage fostered Collembola assemblages. At the end of our study, density and species richness were 3 to 4 times higher in reduced tillage (RT) than in conventional tillage (CT). Nevertheless, differentiation between the assemblages only occurred after 2 years but steadily increased until 4 years. At the last sampling date, all treatments contained significantly different Collembola assemblages (Anosim with Bray-Curtis distance). In parallel, we noticed shifts in the functional structure of the assemblages, even if globally, all life-forms were promoted under reduced tillage. However, contrary to our expectations, euedaphic Collembola were not promoted by restitution of crop residues. Our study over several years under field conditions showed that Collembola assemblages were more sensitive to tillage intensity than to either residue management or N fertilization. Clearly, conservation agriculture can foster one of the numerous services provided by the soil compartment, namely the soil biodiversity and therefore improve soil quality and health.

Determination of Soil Aggregate Porosity Using the Modified Water Saturation Method

The need to find a simple method for measuring soil aggregate porosity (φ) is justified by the growing interest of researchers in this important parameter of soil physical status. The aim of this study was to present a simple method (AM) for estimating the total 0 of a single soil aggregate. In this case, soil aggregate 0 was calculated as the quotient between the pore volume, estimated from the weight of the aggregate saturated with ethanol, and the total volume (VT) of aggregate, calculated from the particle density and dry aggregate weight. The VT estimated with AM was compared with the corresponding volume measured with the photogrammetry (PHM) technique using soil aggregates of 8–16 mm in diameter and collected from three different tillage systems: conventional tillage (CT), reduced tillage (RT), and no tillage (NT). Next, the AM was used to study the effects of the tillage system on soil aggregate φ. Although a strong relationship (R2 = 0.99, P < 0.000 1) between aggregate VT measured with PHM and that estimated with AM was obtained, AM tended to underestimate aggregate VT with an average deviation of 2.85%. This difference may be due to ethanol evaporation during the first 10 s before the ethanol-saturated aggregate was weighed. The use of AM to determine the effects of different tillage systems on aggregate φ showed that this method was sensitive to detect significant differences among the tillage treatments. The results showed that AM could be an accurate, simple, and inexpensive alternative to estimate φ of a single soil aggregate.

Long and short term changes in crop yield and soil properties induced by the reduction of soil tillage in a long term experiment in Switzerland

To address the influence of soil tillage reduction on crop yield and soil properties, an experiment was set up in 1969 in the western part of Switzerland. A conventional tillage treatment with plough was compared to a minimum tillage treatment and a deep non inversion tillage treatment, converted to no till in 2007. Evolution of crop yield through time was investigated, as well as the soil properties in 2013. Mean soil properties and their stratification with depth were assessed. The results showed that, after 44 years, globally, all tillage treatments allowed to maintain similar yields in the long term. However, during the same time, soil properties have changed deeply. Soil organic carbon has decreased compared to the initial situation, in all treatments except in the minimum tillage. This treatment also allowed to reach high clay to carbon ratio in the upper layer, suggesting good soil structural quality compared to the other treatments. In contrast, this did not result in significant differences in carbon stocks between tillage treatments, probably due to low carbon inputs in all treatments. In addition, a strong stratification pattern with depth was observed for most of the nutrients in the minimum tillage treatment, while the situation was more homogeneous in the plough treatment. The adoption of no till also modified soil properties and lead to clear stratification patterns after only six years. These results showed that crop yield could globally be maintained in reduced tillage systems, while insuring high soil fertility and structural quality. The important decrease in the number of tillage interventions and intensity of disturbance induced an improvement of soil properties. Reduced tillage practices could thus be advantageously adopted to insure crop production together with soil fertility improvement in rather short time period.

Organic farmer perceptions of reduced tillage: A Michigan farmer survey

AbstractA common critique of organic farming is that it is very tillage intensive, and therefore deleterious to soil quality. However, little information is available on the tillage practices currently employed by organic farmers, as well as organic farmers’ attitudes toward reduced tillage (RT). To address these knowledge gaps, a detailed written survey of Michigan organic field crop and vegetable farmers was conducted to investigate their current tillage practices, as well as their perceptions of the barriers and benefits to adoption of RT. Respondents reported a wide range in tillage frequency and intensity, both across and within production of specific crops, with operations split evenly between field preparation and cultivation. Compared with field crop growers, vegetable growers were generally smaller scale and relied more heavily on a limited set of tillage (e.g., rototiller) and cultivation tools. Interest in adoption of RT practices among respondents was low to moderate with median Likert scale ratings (0–7 scale with 0 representing no interest and 7 extreme interest) of 4 or less for all forms of RT. Vegetable growers were most interested in permanent beds, rotational tillage and strip tillage, whereas field crop growers were most interested in rotational tillage and strip tillage. The greatest perceived benefits to adoption of RT were improved soil quality and fuel savings. Both groups ranked weeds, impacts on yields, residue management and crop establishment as high barriers to RT adoption. Vegetable growers also cited lack of scale appropriate equipment as a major barrier. Survey results suggest that future research efforts should focus on overcoming key barriers to adoption, such as weed management and access to low-cost adaptable RT equipment rather than reiterating relatively well-known soil quality benefits. Our results also suggest that promotion of incremental reductions in the frequency and intensity of tillage operations on organic farms may be more realistic and equally valuable compared with promotion of more extreme forms of RT such as no-till.

Effect of tillage systems on weed infestation of durum wheat

Weed infestation of durum wheat was determined in the systems of conventional tillage(CT), reduced tillage (RT) and herbicide tillage (HT). Cultivations measures performed after theharvest of the previous crop included shallow ploughing (at a depth of 10-12 cm) and pre-winterploughing (25-30 cm) in the CT system; only field cultivation (10-15 cm) in the RT system; andspraying with glyphosate (Roundup 360 SL) in the HT system. In the springtime, a tillage setconsisting of a cultivator, a string roller and a harrow (10-12 cm) was applied on all plots. It wasdemonstrated that wheat cultivation in the RT and HT systems was increasing the number andweight of weeds, compared to the CT system. The highest number of weeds occurred at themiddle level of wheat crop, whereas the highest air-dry weight was produced by the weeds atthe upper and middle crop levels. In the HT system, weed community was constitutedexclusively by short-term species, whereas in CT and RT systems – by short-term and perennialspecies.

Conventional tillage decreases the abundance and biomass of earthworms and alters their community structure in a global meta-analysis.

The adoption of less intensive soil cultivation practices is expected to increase earthworm populations and their contributions to ecosystem functioning. However, conflicting results have been reported on the effects of tillage intensity on earthworm populations, attributed in narrative reviews to site-dependent differences in soil properties, climatic conditions and agronomic operations (e.g. fertilization, residue management and chemical crop protection). We present a quantitative review based on a global meta-analysis, using paired observations from 165 publications performed over 65years (1950-2016) across 40 countries on five continents, to elucidate this long-standing unresolved issue. Results showed that disturbing the soil less (e.g. no-tillage and conservation agriculture [CA]) significantly increased earthworm abundance (mean increase of 137% and 127%, respectively) and biomass (196% and 101%, respectively) compared to when the soil is inverted by conventional ploughing. Earthworm population responses were more pronounced when the soil had been under reduced tillage (RT) for a long time (>10years), in warm temperate zones with fine-textured soils, and in soils with higher clay contents (>35%) and low pH (<5.5). Furthermore, retaining organic harvest residues amplified this positive response to RT, whereas the use of the herbicide glyphosate did not significantly affect earthworm population responses to RT. Additional meta-analyses confirmed that epigeic and, more importantly, the bigger-sized anecic earthworms were the most sensitive ecological groups to conventional tillage. In particular, the deep burrower Lumbricus terrestris exhibited the strongest positive response to RT, increasing in abundance by 124% more than the overall mean of all 13 species analysed individually. The restoration of these two important ecological groups of earthworms and their burrowing, feeding and casting activities under various forms of RT will ensure the provision of ecosystem functions such as soil structure maintenance and nutrient cycling by "nature's plough."

Carbon and nitrogen mineralization kinetics as affected by tillage systems in a calcareous loam soil

Tillage systems may affect soil carbon (C) and nitrogen (N) kinetics. However, the effects of tillage on C and N kinetics have not yet been studied for the major calcareous soils (Calcixerepts) from Iran. The aim of this study was to assess the effect of four tillage systems on soil C and N mineralization kinetics in a semi-arid loam soil after six years of two conventional tillage (CT) systems (moldboard plow, MP and disk plow, DP) and two reduced tillage (RT) systems (chisel plow, CP and rotary plow, RP) under similar plant residue inputs and cover crops in Shahrekord, Central Iran. We tested the hypothesis that soil C and N mineralization kinetic parameters are higher in RT than CT systems because of differential soil disturbance and mixing. Tillage systems were established in 2005 and, an experiment was arranged in a randomized complete block design with each tillage system replicated three times and sampled over three years (2008, 2009 and 2011). Soil samples (0–20cm) were incubated (at 25°C for 11 weeks) to measure the cumulative C and N mineralization throughout the incubation and to estimate the potentially mineralizable C (Co) and N (No), and the rate constants for labile C (kC) and N (kN) using the first-order kinetic single model. Soil C, N and particulate organic matter (POM) remained unaffected by tillage systems and thus these properties are not a sensitive indicator of changes in soil C and N contents. The cumulative C and N mineralization; and Co indicated the effect of tillage systems over the period of study. RT systems had lower soil cumulative C mineralization (20%), Co (17%) and kC (10%) than CT systems. The cumulative N mineralization was also lower (23%) in RT (20.7-34.3mgkg−1) than CT (28.1-42.2mgkg−1), while No tended to increase only in RP (231mgkg−1) when compared with other tillage systems (151–177mgkg−1). The kN was generally lower (33%) in RT (0.017 week−1) than CT (0.024 week−1). The initial potential rates of C (Co×kC) or N (No×kN) mineralization tended to be lower in RT and were found to be more suitable indicators to differentiate tillage effects. Differences in C and N mineralization among tillage systems were much larger in 2011 than 2008. The data rejected our hypothesis with regard to higher C and N mineralization kinetic parameters in RT systems with less soil disturbance. In conclusion, when crop residue is maintained, RT systems can protect the labile C pools and decrease the incorporation of crop residues into the soil matrix with a lower supply of mineralizable organic C and N for microbes under the studied environmental settings. Our findings indicate that soil C and N kinetic parameters might be a more sensitive indicator of tillage effects on C and N turnover than the whole soil organic matter (SOM) and POM fraction, with a potential consequence for the soil CO2 emissions and N transformation rates.

Energy conservation and greenhouse gas mitigation under different production systems in rice cultivation

Identification of a suitable cultivation method with low energy use, GWP and high productivity is the need of the hour. A 16-year old field study in the Indo-Gangetic Plains (IGP) with different methods of rice cultivation viz., zero tillage (ZT), happy turbo seeder (HTS), bed planting (BP), reduced tillage (RT), conventional sowing (CS), direct sowing (DS), broadcast method of sowing (BS), manual transplanting (HT) and selected transplanting methods like, manual transplanter (MT) and mechanical transplanter (MaT) was used to evaluate the energy input and GWP. HT method of rice cultivation recorded higher energy use than ZT, HTS, BP, RT, CS, DS and BS methods, respectively. Whereas HTS method recorded highest net grain energy (NEg) and this was followed by ZT and MaT, The PTR method recorded 61–66% higher GWP compared with direct sown unpuddled method of rice cultivation. Among direct sown unpuddled methods of rice cultivation, HTS, BP, RT and ZT had lower GWP than farmers' practice. MaT recorded higher carbon output than ZT, HTS, BP, RT, CS, DS and BS methods. The study indicated that direct seeded method of rice cultivation is energy efficient with lower GWP and thus may be recommended.

Reduced Tillage and No-Till in Organic Farming Systems, Germany—Status Quo, Potentials and Challenges

Only 34% of all German farms apply reduced tillage (RT), while approximately 1% of the arable land is under no-tillage (NT). Statistics for organic farming are not available, but the percentages are probably even lower. The development of German organic RT and NT has been strongly driven by pioneer farmers for 40 years, and supported by field trials since the 1990s. The main motive for conversion to RT is increased soil quality, followed by reduced labor costs. NT combined with high-residue cover crops plays only a very small role. Rather, German organic farmers resort to shallow ploughing, a reduced number of ploughing operations in the rotation and/or substitution of the ploughing with non-inversion tillage. In field trials, winter wheat (Triticum aestivum L.) yields were reduced up to 67% by using RT methods compared to inversion tillage treatments due to reduced mineralization and increased weed pressure, both of which are major obstacles that impede the wider adoption of RT and NT by German organic farmers. Improvement of NT and RT (rotations, implements, timing) in organic farming is a task of both agricultural practice and science. A number of conventional farmers who have recently converted to organic farming are already familiar with RT. These farmers will act as a thriving factor to implement their experience after conversion and contribute to further innovations of RT in organic farming.

Least limiting water range for different soil management practices in dryland farming in Iran

ABSTRACTIntegrated evaluation of soil physical properties using the least limiting water range (LLWR) approach may allow a better knowledge of soil water availability. We determined the LLWR for four tillage practices consisted of conventional tillage (CT), reduced tillage (RT), no-tillage (NT) and fallow no-tillage (NTf). In addition, LLWR was determined for abandoned soils (i.e. control), compacted soils, ploughed compacted soils and abandoned soils with super absorbent polymers (SAPs) application. Soil water retention, penetration resistance (PR), air-filled porosity and bulk density were determined for the 0–5 and 0–25-cm depths. Mean LLWR (0.07–0.08 cm3 cm−3) was lower in compacted soils than the soils under CT, NT, NTf, RT, tilled, abandoned and SAP practices but it was not different among tillage practices. The values of LLWR were 0.12 cm3 cm−3 for NT and CT. LLWR for tilled plots (0.12 cm3 cm−3) became greater than compacted soils by 1.3 times. Analysis of the lower and upper limits of the LLWR further indicated that PR was the only limiting factor for soil water content, but aeration was not a limiting factor. The LLWR was more dependent on soil water content at permanent wilting point and at PR.

Application of DSSAT Model to Simulate Corn Yield under Long-Term Tillage and Residue Practices

Long-term (1991-2013) field experiments were conducted to study the effects of different tillage and residue management practices on grain corn production in eastern Canada. Three different tillage practices, namely conventional tillage (CT), reduced tillage (RT), and no tillage (NT), along with two residue management practices, namely with residue (R) and without residue (NR), were considered. Field measurements of grain yield, biomass, soil organic carbon (SOC), soil moisture, and mineral nitrogen were used to evaluate the performance of the DSSAT model and to understand the impacts of long-term tillage and residue management practices. The observed corn yield, biomass, LAI, and nitrate-nitrogen (NO3-N) were not found to be significantly different under the various tillage and residue practices. The observed soil moisture showed a significant difference in the upper 10 cm soil layer. The SOC pool at 0-20 cm depth was reduced by 9.5% for CT and increased by 17.3% and 7.6% for RT and NT treatments, respectively. The DSSAT model was able to simulate corn and biomass yield, LAI, soil moisture, and SOC with RMSE ranging from 2% to 31%, indicating reasonable model performance. The model did not provide accurate results for NO3-N and soil moisture simulations, with RMSE ranging from 34% to 78%. Further improvements in the model are needed to better simulate soil moisture and N dynamics under different tillage and residue practices.

Impact of reduced tillage on greenhouse gas emissions and soil carbon stocks in an organic grass-clover ley - winter wheat cropping sequence

Organic reduced tillage aims to combine the environmental benefits of organic farming and conservation tillage to increase sustainability and soil quality. In temperate climates, there is currently no knowledge about its impact on greenhouse gas emissions and only little information about soil organic carbon (SOC) stocks in these management systems. We therefore monitored nitrous oxide (N2O) and methane (CH4) fluxes besides SOC stocks for two years in a grass-clover ley – winter wheat – cover crop sequence. The monitoring was undertaken in an organically managed long-term tillage trial on a clay rich soil in Switzerland. Reduced tillage (RT) was compared with ploughing (conventional tillage, CT) in interaction with two fertilisation systems, cattle slurry alone (SL) versus cattle manure compost and slurry (MC). Median N2O and CH4 flux rates were 13μg N2O-Nm−2h−1 and −2μg CH4Cm−2h−1, respectively, with no treatment effects. N2O fluxes correlated positively with nitrate contents, soil temperature, water filled pore space and dissolved organic carbon and negatively with ammonium contents in soil. Pulse emissions after tillage operations and slurry application dominated cumulative gas emissions. N2O emissions after tillage operations correlated with SOC contents and collinearly to microbial biomass. There was no tillage system impact on cumulative N2O emissions in the grass-clover (0.8–0.9kgN2O-Nha−1, 369days) and winter wheat (2.1–3.0kg N2O-Nha−1, 296days) cropping seasons, with a tendency towards higher emissions in MC than SL in winter wheat. Including a tillage induced peak after wheat harvest, a full two year data set showed increased cumulative N2O emissions in RT than CT and in MC than SL. There was no clear treatment influence on cumulative CH4 uptake. Topsoil SOC accumulation (0–0.1m) was still ongoing. SOC stocks were more stratified in RT than CT and in MC than SL. Total SOC stocks (0–0.5m) were higher in RT than CT in SL and similar in MC. Maximum relative SOC stock difference accounted for +8.1MgCha−1 in RT-MC compared to CT-SL after 13 years which dominated over the relative increase in greenhouse gas emissions. Under these site conditions, organic reduced tillage and manure compost application seems to be a viable greenhouse gas mitigation strategy as long as SOC is sequestered.

Environmental impacts of energy use in wheat tillage systems: A comparative life cycle assessment (LCA) study in Iran

The agricultural sector is facing increasing societal expectations to contribute to the global reduction of impacts on the environment. This study aims to evaluate energy use and environmental impacts of different winter wheat tillage systems in the central Fars province, Southwest Iran. To meet the objectives, different energy indices and environmental impact categories were assessed for five wheat tillage systems; two conventional tillage systems: CT1 and CT2, and three conservation tillage systems: CMT (moldboard plough and combined seeder), RDT (reduced tillage) and NT (no-tillage). Total average energy consumption was estimated at 30,000 MJ/ha caused mainly by fertilizers, diesel fuel, water and seed inputs. The highest output-input energy ratio and energy productivity were observed in the conservation tillage systems RDT followed by NT and CMT. The LCA analysis confirmed that system RDT is the wheat tillage system in the region with the lowest impacts on the environment, the lowest energy input and the highest benefit to cost ratio compared to all other considered systems.

Long-term impact of reduced tillage on water and pesticide flow in a drained context

Influence of more than 20years (1988-2010) of reduced tillage (RT) practices on water and pesticide balances and dynamics is analyzed and compared to results from a conventional tillage plot (CT). The field study soils are described as silty clay stagnic luvisol, developed on a low permeable schist layer. A drainage network was set up according to French criteria (0.9m deep, 10m space) to avoid soil winter waterlogging. Climate is temperate oceanic and drainage generally occurs from November to March. Data were analyzed at yearly, weekly (pesticides) and hourly (water) time steps. Over the long term, cumulated drainage decreases significantly on RT (3999mm) compared to CT (5100mm). This differentiation becomes significant from 1999, 10years after plowing was stopped. Strikingly, hourly drainage peak flows are higher under RT, especially during the second period (2000-2010), associated with low or no base flow. These results suggest a strong influence of the macropore network under RT practice. In particular, drainage peaks are higher at the beginning of the drainage season (mid-October to December). Consistently, pesticides applied in late autumn, which are the most quantified on this site, are often significantly more exported under RT. For atrazine, applied in spring, fluxes are linked to cumulative flow and are de facto higher under CT. For others pesticides, losses appear to be heterogeneous, with generally low or null export rates for spring application. Generally speaking, higher concentrations are measured on RT plot and explain observed exportation rate differences. Finally, there is no clear evidence of correlation between pesticide losses and long-term impacts of RT on hydrodynamics, pointing the importance of studying the short-term effect of tillage on water and especially solute flow.