Adoption Of Conservation Tillage Systems Research Articles

The Remarkable Journey of a Weed: Biology and Management of Annual Ryegrass (Lolium rigidum) in Conservation Cropping Systems of Australia.

Annual ryegrass (Lolium rigidum Gaud.), traditionally utilised as a pasture species, has become the most problematic and difficult-to-control weed across grain production regions in Australia. Annual ryegrass has been favoured by the adoption of conservation tillage systems due to its genetic diversity, prolific seed production, widespread dispersal, flexible germination requirements and competitive growth habit. The widespread evolution of herbicide resistance in annual ryegrass has made its management within these systems extremely difficult. The negative impacts of this weed on grain production systems result in annual revenue losses exceeding $93 million (AUD) for Australian grain growers. No single method of management provides effective and enduring control hence the need of integrated weed management programs is widely accepted and practiced in Australian cropping. Although annual ryegrass is an extensively researched weed, a comprehensive review of the biology and management of this weed in conservation cropping systems has not been conducted. This review presents an up-to-date account of knowledge on the biology, ecology and management of annual ryegrass in an Australian context. This comprehensive account provides pragmatic information for further research and suitable management of annual ryegrass.

Soil physical properties and soil organic carbon content in northeast Brazil: long-term tillage systems effects

ABSTRACT Concerns about the negative effects of agriculture on soil physical quality and soil organic carbon (SOC) pools have spurred on the adoption of conservation tillage systems in tropical regions. This study aimed to evaluate the long-term impacts (16th year) of conventional (CT), minimum (MT) and no-tillage (NT) practices and different cover crops (sunn hemp and a bean/millet sequence) on soil physical properties and SOC content of a corn cultivated Ultisol in the northeast of Brazil. Soil bulk density (Bd), soil penetration resistance (SPR), soil aggregation, and total aggregate-associated carbon (C) (4-2 mm) were evaluated. Tillage practices exerted strong control on soil physical properties and total aggregate-C content but were influenced by cover crop species. Minimum tillage presented the lowest Bd, irrespective of cover crop, while NT with bean/millet sequence resulted in the lowest SPR. However, as regards soil aggregation and total aggregate-C, the results indicated that there were no differences between MT and NT, with both systems presenting greater mean weight diameter (MWD) and total aggregate-C content than CT. Total aggregate-C content in the 0.00-0.05 m soil layer in conservation tillage was increased by the adoption of a bean/millet sequence. Increased mechanical disturbance through CT practices was harmful to Bd, soil aggregation and SOC accrual. Overall, more conservative tillage practices and the proper choice of cover crops might yield greater soil quality. Low intensity of soil disturbances due to the adoption of MT favors soil aggregation and the accrual of SOC in weakly structured soils through increases in contact between organic and mineral particles while not causing significant destruction of soil aggregates.

Performance of Flooded Rice Grown in Succession to Winter Cover Crops

ABSTRACT: Mean grain yield of flooded rice in southern Brazil has increased in recent years due to the use of high-yield cultivars and improvement of crop management practices. Nevertheless, stagnation in grain yields has been observed in some rice-producing regions. Adoption of conservation tillage systems based on cover crops may be a strategy to increase rice grain yield potential. The objective of the present study was to evaluate the effect of winter cover crops on initial establishment, development, and grain [...]

Conservation tillage and weed management in smallholder agriculture: Issues and opportunities

Constraint to effective weed management is one of the major reasons for limited adoption of conservation tillage systems in smallholder farming in India. Conservation tillage (CT) has variable effects on soil weed seed bank dynamics, seed germination and seedling emergence, and efficacy of weed control measures. In CT system, a large portion of the weed seeds accumulates in the upper soil layer in contrast to conventional tillage, where large proportion of seeds are buried and maintained in deeper soil layers. In general, CT system increases populations of perennial and summer annual grass where as densities of large seeded dicot species and winter annuals decreases. Due to restricted tillage options, weed control in CA system is largely depends on use of herbicides which often fail to provide adequate weed control in presence of crop residues on soil surface. The present paper highlights the weed management issues and opportunities in CT systems.

Impact of atrazine prohibition on the sustainability of weed management in Wisconsin maize production.

Controversy has surrounded atrazine owing to its susceptibility to leaching and run-off, with regular calls for a ban or restrictions on its use. In the context of a decreasing trend in the percentage of US maize using no-till since 2008, coinciding with the trend of glyphosate-resistant weeds becoming problematic in the Midwestern United States, we empirically examine how atrazine use restrictions have impacted the diversity of weed management practices used by Wisconsin maize farmers. Using survey data from farms inside and outside atrazine prohibition areas, we found that prohibiting atrazine did not directly impact tillage practices, but rather it increased the adoption of herbicide-resistant seed, which then increased adoption of conservation tillage systems. We also found that prohibiting atrazine and using herbicide-resistant seed reduced the number of herbicide sites of action used. The results indicate that prohibiting atrazine reduced the diversity of weed management practices, which increased the risk of herbicide resistance. Our concern is that a regulatory policy to address one issue (atrazine in groundwater) has induced farmer responses that increase problems with another issue (herbicide-resistant weeds) that longer term will contribute to water quality problems from increased soil erosion and offset the initial benefits. © 2016 Society of Chemical Industry.

The development and adoption of conservation tillage systems on the Canadian Prairies

One of the major agricultural innovations on the Canadian Prairies over the last 40 years has been the introduction of conservation tillage (CT). Conservation tillage-a system that includes minimum and zero tillage (ZT) -was introduced as an alternative to traditional (conventional) tillage (TT) to control soil degradation and to promote agricultural sustainability. The development and adoption of CT systems involved pioneer farmers, engineers, scientists, and farmer associations. By the end of the 1970s, CT started to take shape on the Prairies, but for a number of economic, technical, political and social reasons, the adoption of CT did not occur on any major scale before the 1990s. Today, more than 75% of the Prairie's cropland is under some form of CT with more than 50% under ZT. In this paper, the factors behind the development and adoption of conservation tillage technology on the Prairies in the period between 1930 and 2011 are reviewed. Then, some of the benefits of the adoption of CT on the Prairies are highlighted. The data show that CT and ZT became profitable for the majority of farmers during and after the 1990s, and that the increased use of CT contributed to the dramatic decrease in the area under summerfallow and to the increase in the area sown to canola and pulse crops. These changes contributed to the reduction of all forms of land degradation and to decreases in agricultural greenhouse gas (GHG) emissions.

Dynamics of aggregate destabilization by water in soils under long-term conservation tillage in semiarid Spain

Abstract Due to particular soil and climate conditions and inappropriate agricultural practices, Aragon (NE Spain) is a region prone to land degradation by water erosion. For this reason, the adoption of conservation tillage systems has been encouraged as an alternative to preserve soil and water in this region. However, little information concerning soils on which these techniques are applied is available. The main objectives of this study were to assess the effect of long-term no tillage (NT) on water aggregate stability in five different cereal production areas of Aragon and identify the main mechanisms involved on aggregate breakdown. The study was conducted under on-farm conditions where pairs of adjacent fields under NT and conventional tillage (CT) were compared. In all cases, a nearby undisturbed soil under native vegetation was included. Soils were slightly to highly calcareous with medium textures ranging from sandy loam to silty clay loam. Results indicate that NT increased surface aggregate stability with respect to CT systems through lower soil disturbance and higher organic carbon (OC) content at the soil surface (0–5 cm depth). Slaking was the dominant disaggregation process of the cultivated soils, representing 40–80% of total soil disruption, and was strongly and negatively affected by aggregate-associated OC. This soil property together with the silt content (weak and positive effect) explained more than 80% of the slaking variation. Swelling and clay dispersion were less frequent processes and their occurrence seemed to be associated with high silt and CaCO 3 contents. This study shows that, under the rainfed conditions of semiarid Aragon, NT reduces the susceptibility of soil surface to crusting and water erosion as compared to CT systems.

Cotton Production as Affected by Irrigation Level and Transitioning Tillage Systems

Identifying management practices that conserve and protect water resources are very important to a wide variety of stakeholders within semiarid environments. The objective of this study was to develop water management strategies for transitioning tillage systems in cotton (Gossypium hirsutum L.) production within the Texas Rolling Plains when in a subsurface drip irrigation (SDI) system. Five irrigation regimes (0, 33, 66, 100, and 133% evapotranspiration [ET] replacement) and four tillage systems (conventional till, reduced till, no‐till, and no‐till with a terminated cover crop) were evaluated. The study was conducted for 3 yr and treatments were replicated three times in a randomized complete block design. Lint yields were not affected by the main effects of tillage or the interaction of tillage and ET replacement. In contrast ET replacement was a significant factor for lint yields, irrigation water use efficiency, and net returns. Greatest lint yields and net returns were achieved at 100% ET replacement. Fitted models indicated that optimum lint yields and net returns were achieved at 104.5% ET and 102% ET, respectively. Irrigation at 83% ET was within the 95% confidence interval for lint yield. Net returns were significantly higher for no‐till systems compared with conventional till. Thus, adoption of conservation tillage systems should not negatively affect lint yield or net returns in deficit irrigated SDI cotton systems within the Texas Rolling Plains, particularly during the transition from intensively tilled systems to conservation tilled systems.

Yield and water use efficiency of barley in a semiarid Mediterranean agroecosystem: Long-term effects of tillage and N fertilization

Conservation tillage systems (no-tillage, NT; and minimum tillage, MT) are being adopted in rainfed agroecosystems of the Mediterranean basin where water availability is the main limiting factor for crop productivity. We hypothesized that long-term adoption of conservation tillage systems would increase water use efficiency (WUE) and its response to N fertilizer additions due to improved soil water content. A field experiment was established in 1996 on a loamy Xerofluvent Typic in the Ebro river valley (NE Spain). The experiment compared three nitrogen (N) fertilization levels (zero, 0 kg N ha −1, medium, 60 kg N ha −1, and high, 120 kg N ha −1), under three tillage systems (CT, conventional tillage; MT and NT), annually cropped to barley ( Hordeum vulgare, L.) as is usual in the region. Ten years after the experiment establishment, during four consecutive growing seasons, 2005–2006 to 2008–2009, we evaluated the response of soil water content, soil nitrate, above-ground dry matter, grain yield and yield components to long-term (>10 years) tillage and N fertilization treatments. The long-term sustainability of NT and MT was confirmed. Mean yield and WUE under long-term conservation tillage systems were 66% and 57% higher than under CT, respectively. This improvement was mainly attributed to improved soil water usage under conservation tillage, mainly due to reduced water use during the pre-anthesis period. However, in a wet year yield did not significantly differ among tillage systems. The improvement of WUE with N fertilization was confirmed under NT, which medium and high N fertilizer level increased 98% mean grain yield and 77% mean WUE compared to CT. The increased response of crop and yield to N fertilization under NT was due to improved soil water content. Soil N accumulation together with the lower water accumulation explained the lack of response to N fertilization under CT, even on a wet growing season (i.e., 2008–2009). Long-term NT adoption was a sustainable practice for barley monoculture in the region, allowing for reduced costs and yield increase with N fertilizer additions. N fertilizer rates on rainfed Mediterranean croplands should be adjusted depending on the reduction of tillage intensity and rainfall of the year. In our system and as an example for this agroecosystems, N fertilizer rates should be kept at or below 60 kg N ha −1, and should be further reduced on intensively cultivated soils.

Tillage system effects on weed ecology, herbicide activity and persistence: a review

In the past few years, there has been a growing trend towards reducing tillage in cropping systems to allow stubble retention, earlier planting and improved soil structure. However, the adoption of conservation tillage systems will change weed control practices. Different tillage systems interact with the micro-environment of weed seeds and can influence the pattern of recruitment from the weed seed bank. Here, we present a review of the effect of different tillage systems on weed ecology, herbicide activity and herbicide persistence. Tillage systems can have a major influence on the vertical distribution of weed seeds in the soil seed bank. However, the impact of the changes in the vertical seed distribution on weed seedling recruitment is not well understood. Usually weed seedling recruitment increases if tillage equipment brings buried seed to, or close to, the soil surface, and seedling recruitment decreases if surface seed is buried deeper in the soil. However, tillage responses have a tendency to be species specific and can also be influenced by the intensity of tillage. Any weed species in which germination is stimulated by exposure to light is likely to become more prevalent under reduced tillage systems. Similarly, species that require burial for germination may become less prevalent. Crop residue present on the soil surface can also influence weed seedling recruitment by modifying the physical environment (mainly temperature) of weed seeds. Weed responses to plant residue could also be influenced by the allelopathic activity of the residue and the sensitivity of the weed species present. Few studies have investigated the fate of weed seeds that fail to germinate under any tillage system. Further research is needed to determine whether the weed seeds that fail to germinate decay before the start of the next growing season or become part of a persistent seed bank. Crop residues present on the soil surface can intercept a considerable amount of the applied herbicide and, depending on the herbicide, this intercepted component is susceptible to losses. Therefore, conservation tillage systems are expected to have lower efficacy of soil active herbicides. However, there has been little investigation of rate of loss of soil active herbicides under reduced tillage systems and the results reported have been inconsistent. Much of the research on these effects is from overseas and may not be true in Australian conditions. Therefore, further work is needed to clearly understand the impact of changing tillage systems on weed ecology, herbicide performance and persistence.

Finger millet ( Eleucine corocana L. Gaertn.) as a cover crop on weed control, growth and yield of soybean under different tillage systems

Adoption of conservation tillage systems has become more popular in recent years due to erosion control and economics. Weed control is often identified as the limiting factor in the adoption of such systems. Although herbicides are efficient and convenient, the need to reduce herbicide use has been emphasized. Cover crops have become a viable option in this context, but the contribution of cover crops to weed control has not been clearly defined. A 2-year field experiment compared minimum tillage (MT), no-tillage (NT) and conventional tillage (CT) for soybean [ Glycine max (L.) Merr.] following paddy rice ( Oryza sativa L.) with finger millet ( Eleucine corocana L. Gaertn.) as a cover crop. Weed emergence, cover crop biomass, main crop growth and yield were observed. Finger millet effectively controlled weeds but total weed biomass was greater with NT than other tillage methods and seeding method had no effect at early stage of growth. Neither crop growth nor leaf chlorophyll content was affected by finger millet under given tillage treatments. Weed biomass was almost half under MT than NT. Finger millet was able to effectively manage weed biomass under MT to a level achieved under CT without a cover crop at the early stage of growth. Number of seeds per pod and 100 seed weight were not affected by tillage treatments but number of pods per square meter was significantly higher with row seeding than broadcast seeding of finger millet cover crop in 2002. The absence of finger millet under MT in 2003, significantly reduced soybean grain yield. Finger millet can be managed with a single mechanical suppression as a cover crop under MT with no yield reduction.

Denitrification and nitrous oxide to nitrous oxide plus dinitrogen ratios in the soil profile under three tillage systems

There is a growing interest in the adoption of conservation tillage systems [no-till (NT) and reduced tillage (RT)] as alternatives to conventional tillage (CT) systems. A 2-year study was conducted to investigate possible environmental consequences of three tillage systems on a 2.4-ha field located at Macdonald Research Farm, McGill University, Montreal. The soil was a sandy loam (0.5 m depth) underlain by a clay layer. Treatments consisted of a factorial combination of CT, RT, and NT with the presence or absence of crop residue. Soil NO3 --N concentrations tended to be lower in RT than NT and CT tillage treatments. Denitrification and N2O emissions were similar among tillage systems. Contrary to the popular assumption that denitrification is limited to the uppermost soil layer (0–0.15 m), large rates of N2O production were measured in the subsurface (0.15–0.45 m) soil, suggesting that a significant portion of produced N2O may be missed if only soil surface gas flux measurements are made. The N2O mole fraction (N2O:N2O+N2) was higher in the drier season of 1999 under CT than in 2000, with the ratio occasionally exceeding 1.0 in some soil layers. Dissolved organic C concentrations remained high in all soil depths sampled, but were not affected by tillage system.

Tillage system effects on weed communities in a 4-year crop rotation under Mediterranean dryland conditions

Effective weed management has been identified as a limiting factor in the adoption of conservation tillage systems. In view of this fact, weed communities were characterized in order to evaluate similarities and differences under three tillage systems: chisel (minimum tillage), moldboard plow (conventional tillage), and no-tillage. The study was carried out near Barcelona throughout a 4-year (1997–1998 to 2000–2001) rotation of winter crops (pea: Pisum sativum L., wheat: Triticum aestivum L., wheat–barley: Hordeum vulgare L.) on a deep silt loam Calcixerollic Xerochrept soil. Analyses of variance based on a randomized complete block design were performed on total aboveground weed biomass (g m −2), monocotyledon and dicotyledon biomass, and the biomass of each species. Three main effects were considered: tillage, block and year (crop). Data were combined in order to compute one Shannon–Wiener diversity index for each year and tillage system. The year (crop) effect was the most important factor, followed by the year (crop)×tillage interaction; winter pea had the lowest weed biomass. Tillage system had no effect on total weed biomass. The mean biomass of Avena sterilis L. was greatest under minimum tillage, while those of Diplotaxis erucoides (L.) DC and Sonchus tenerrimus L. were greatest under no-tillage. The highest Shannon–Wiener diversity index was obtained for the no-tilled weed community, and was related to the highest richness and highest evenness. As tillage system had no effect on weed biomass and although the no-tillage system had the richest and most diverse weed community, the weed flora would not constitute an obstacle to an increasing use of no-tillage system for cereal production in the study area.

Tillage effects on barley residue cover during fallow in semiarid Aragon

Maintenance of crop residues on the soil surface is considered the most effective method to control wind erosion. In semiarid Aragon (NE Spain), where the risk of wind erosion can be high, the adoption of conservation tillage systems has been encouraged as a fallow management alternative. However, little information concerning the dynamics of residue cover during fallow is available for this area. We report here results on the evolution of barley residues during two fallow periods under conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). The three tillage treatments were compared under both continuous cropping (CC) and cereal–fallow (CF) rotation. The CC system involves a summer fallow period of 5–6 months and the CF rotation a long-fallow of 17–18 months. Effects of specific tillage operations on soil cover are also presented and discussed in relation to wind erosion control during the long-fallow period. Average dry mass of barley residues at harvest was 1395 and 729 kg ha −1 in the first and second year of the study, respectively. In general, crop residues at harvest were not significantly affected by tillage or cropping system. Primary tillage operations had the major influence on residue incorporation with reduction percentages of residue cover of 90–100% in CT (mouldboard ploughing) and 50–70% in RT (chiselling). During the two long-fallow periods, large clods (4–10 cm diameter) produced by mouldboard ploughing did not fully compensate for the complete burial of residues and the soil surface was insufficiently protected against wind erosion (soil covers <3% and random roughness ≈4%). The most critical period corresponded to that elapsed between primary and secondary tillage operations. The lack of residue-disturbing operations in NT makes this practice the best strategy for fallow management. After 17–18 months of fallow, the NT plots still conserved a surface residue cover of 10–15%. Similarly, standing residues, representing between 20 and 50% of the total residue mass, were also present on the no-tilled surface during the first 11–12 months of fallow. In general, RT plots maintained a soil erodibility condition similar to that of NT due to the combined effect of soil cover by clods and residues retained after tillage (5–15%) and the roughness created by clods (6–13%).

Effect of tillage systems, N, and cover crop on the composition of weed flora

The adoption of conservation tillage systems has been challenged by concerns potential weed species shifts. A 9-yr study from 1988 to 1996 was conducted Delhi, Ontario, on a loamy sand soil to evaluate the effect of tillage systems (conventional [CT] and no-till [NT]), cover cropSecale cereale, and nitrogen (N) rate (0, 50, 100, 125, 150, and 200 kg N ha−1) on monocropZea maysL. (corn) yield and changes in the composition of the weed flora. CT consisted of spring moldboard plowing followed by cultivation with a tooth cultivator. Weed counts were taken in the last 3 yr of the study (1994, 1995, and 1996) prior to postemergence herbicide application and then again 2 to 3 wk after herbicide treatment. Composition or the weed flora was analyzed by canonical discriminant analysis (CDA). The relationship between weed density and tillage system was not consistent. Weed species composition differed between CT and NT systems.Chenopodium albumandAmaranthus retroflexuswere associated with CT andDigitaria sanguinaliswith NT. N rate and cover crop did not affect weed density or species composition. Proper management of weeds with herbicides appeared to minimize any long-term effect on the weed flora resulting from varying N rates.Zea maysyields did not differ between CT and NT systems but were greater in both systems with a cover crop at the higher N rates. Disturbance caused by tillage was more important than N rate and cover crop as a mechanism influencing composition of the weed flora.

Distribution of phosphorus fractions in a Brazilian Oxisol under different tillage systems

Changes in residue management resulting from adoption of conservation tillage systems have the potential to alter the concentration and distribution of phosphorus (P) in the soil surface. The objective of this study was to determine the effect of methods of tillage management on the distribution and concentration of organic and inorganic forms of soil P near the soil surface (0–10 cm depth) for an Oxisol in southern Brazil. The tillage systems included zero tillage (ZT) (seeding directly onto the standing stubble of the previous crop), minimum tillage (MT) (seeding the crop after chisel plowing to 15-cm depth and disk harrowing to 7.5 cm), or conventional tillage (CT) (seeding after disk plowing to 20-cm depth with nearly total soil inversion plus two disk harrowings to 10-cm depth). After a period of five years, reducing tillage through adoption of MT or ZT practices increased total P in the surface 10 cm by 15% when compared to CT. Although there were no differences in amounts of total P between MT and ZT systems, under ZT management larger amounts of labile organic and inorganic forms of P accumulated close to the soil surface, followed by a reduction below the 6-cm depth. Under MT, the labile organic and inorganic forms of P were uniformly distributed within the surface 10 cm of soil. The accumulation of high levels of labile P near the soil surface under ZT followed a distribution pattern similar to the accumulation of organic residues in the soil. This would help explain why other workers have found increased P uptake by crops grown under ZT, and why more available P can be extracted by common soil testing methods from the surface 7 to 10 cm of soils under ZT than under CT management.

Palmer Amaranth (Amaranthus palmeri) Control in a Conservation Tillage System for Cotton (Gossypium hirsutum)

Weed control is a limiting factor for adoption of conservation tillage systems on the Texas Southern High Plains. A field study was established to evaluate Palmer amaranth control with strip-tillage dinitroaniline herbicide incorporation in wheat residue. Preemergence herbicides were applied alone and in combination with strip-tilled incorporated herbicides. Significant cotton injury or stand reductions were not observed with any treatment. Effective (&gt;80%) early season Palmer amaranth control was achieved with trifluralin or pendimethalin in conjunction with preemergence herbicides. Preemergence herbicides alone did not provide adequate control.