No-till Wheat Research Articles

Combining Site-Specific Nutrient Allocation Tools Can Decrease Input Demands in No-Till Wheat Farming

ABSTRACT Wheat cultivated under conservation agriculture faces challenges in nutrient management due to altered soil dynamics and heavy residue loads. This often necessitates excessive nutrient applications to address the nutritional demands of the crop. Conducted at the Norman E. Borlaug Crop Research Centre during the winter seasons of 2020–21 and 2021–22, this study explored the effects of different nitrogen (N) application strategies on the ‘HD 2967’ wheat cultivar planted amidst rice residues using a super-seeder. The Nutrient Expert® (NE) combined with LCC-based N top dressing (NE+LCC) demonstrated the most optimal nutrient balance, leading to a 5.9% increase in grain yield and a 42.8% increase in dry matter accumulation compared to traditional methods. The composite SSNM treatments like NE+SPAD and NE+LCC recorded 48.9% and 41.9% higher SPAD values, respectively, as compared to RDF. The NE treatments resulted in significant savings, with a reduction of 60% in phosphorus usage and 5% in potassium. Economically, the NE treatment proved superior, showcasing a 12.7% higher net return compared to the RDF approach. The study concludes that site-specific nutrient management, facilitated by advanced tools like LCC and SPAD, when integrated with software-driven strategies, boosts wheat yield and fosters sustainable farming practices. This approach minimizes environmental impacts by optimizing nutrient applications and aligns with the sustainability development goal of responsible consumption and production.

Prospects and Issues in the Adoption of Conservation Agriculture in India

Conservation agriculture involves practices such as crop rotations, minimal soil disturbance, and maintaining permanent soil cover through crop residues or cover crops. Despite various challenges to its widespread adoption, India has made significant progress over the past two decades in developing, refining, and promoting conservation-based agricultural technologies. Notable advancements have been made in the Indo-Gangetic plains, especially in the adoption of no-till wheat within the rice-wheat cropping system. Advocates of conservation agriculture understand the trade-offs but recognize that the benefits outweigh the drawbacks. These methods offer potential advantages including reduced production costs, improved water and nutrient conservation, increased crop diversity and yields, and more efficient resource utilization.

Continuous no‐tillage winter wheat response to nitrogen fertilizer by yield environment

AbstractMaintaining crop residue through no‐tillage (NT) has allowed increased water storage and continuous cropping in dryland wheat (Triticum aestivum L.)‐based systems. However, there is little information regarding nitrogen (N) fertilizer rates for a continuous NT wheat cropping system across various yield environments. The main objective of this study was to determine agronomic optimum N rates for a continuous NT wheat in different yield environments. The study was conducted from 1981 through 2003 at the Kansas State University Agricultural Research Center near Hays, with six N fertilizer rate treatments (0, 22, 45, 67, 90, and 112 kg N ha−1). Experimental years were divided into four yield environments: very low yielding (VLY), low yielding (LY), high yielding (HY), and very high yielding (VHY). Results showed that LY environments required a relatively greater N amount (79–98 kg N ha−1) than HY to VHY environments (72–73 kg N ha−1) to attain optimal yields. The optimal yields at low‐yield environments were smaller (1184–1654 kg ha−1) than in high‐yield environments (2181–2733 kg ha−1). Protein yield increased by 120 g for 1 kg increase in grain yield. We concluded that the optimum N fertilizer rates for continuous NT wheat ranged from 70 to 100 kg N ha−1, but these rates should be adjusted based on yield environments.

No-till annual wheat increases plant productivity, soil microbial biomass, and soil carbon stabilization relative to intermediate wheatgrass in a Mediterranean climate

As interest in the production of perennial grain crops increases, it is critical to quantify differences in above ground biomass (AGB) productivity and soil carbon stabilization potential between annual and perennial grain crops, and to understand the factors determining these relationships. This study measured the effects of crop type and nitrogen (N) fertilization on AGB, soil microbial biomass, and soil carbon while controlling for the effect of tillage in rainfed annual and perennial grain crops in a Mediterranean climate. AGB and associated soil samples from tilled annual wheat (Triticum aestivum), no-till annual wheat, and intermediate wheatgrass [Kernza ® (Thinopyrum intermedium)] (IWG) were collected annually across three years under various N fertilization rates. We quantified AGB yields, soil microbial biomass (via phospholipid fatty acid analysis), permanganate oxidizable carbon (POXC) and mineralizable soil carbon (MinC). Across N rates and years, IWG yielded approximately 25% less AGB than tilled and no-till annual wheat (p ≤ 0.001). The lack of soil disturbance in no-till wheat and IWG contributed foremost to greater soil microbial biomass in the topsoil by year three of the experiment (p < 0.1). Crop type and the associated AGB productivity had the greatest influence on whether microbial communities trended toward stabilizing versus mineralizing soil carbon. More specifically, higher soil carbon stabilization processes were primarily driven by the increased plant productivity of tilled and no-till annual wheat compared to IWG. Within the annual wheat systems, lack of tillage also contributed to soil carbon stabilization, but primarily in the top 30 cm of soil. Compared to the other treatments, no-till annual wheat resulted in 25% (IWG) and 36% (tilled annual wheat) greater soil microbial biomass in the top 30 cm by the final year of the experiment and had higher soil carbon stabilization potential than IWG at 0–15 and 15–30 cm and tilled annual wheat at 0–15 cm across time (p ≤ 0.01). This was achieved by matching tilled annual wheat in aboveground biomass productivity and IWG in lack of soil disturbance. Results from this study suggest that no-till annual wheat is better suited than tilled annual wheat or IWG to increase soil microbial biomass and soil carbon stabilization in shallow soil, while maintaining stable aboveground biomass yields over time in a Mediterranean climate.

Effects of different land use patterns on soil properties and N2O emissions on a semi-arid Loess Plateau of Central Gansu

Nitrous oxide (N2O) is one of the significant greenhouse gases in the atmosphere. Different land use patterns are the sink or source of N2O, which plays a vigorous role in controlling N2O emissions. Yet, how different land use patterns affect soil N2O emissions in the Loess Plateau of Central Gansu is still not clear. Therefore; in order to fill this gap, six different land use patterns, including Picea asperata (PA), Hippophae rhamnoides (HR), Medicago sativa (MS), No-tillage wheat field (NT) and Conventional tillage wheat field (T) were studied. The objective of this study was to examine the impact of different land use patterns on soil properties and N2O emission flux. Our results showed that compared with other treatments, Picea asperata woodland increased the soil bulk density, organic matter and soil water content, total nitrogen accumulation and microbial biomass nitrogen whilst reduced the soil pH. The wheat field is more favorable to accumulating soil nitrate nitrogen and ammonium nitrogen. Moreover, soil N2O emission rates followed the trend of T&amp;gt;NT&amp;gt;HR&amp;gt;GL&amp;gt;MS&amp;gt;PA. In addition, soil physicochemical properties were closely related to N2O emission flux and soil temperature was the most significant factor affecting N2O emission. General, Picea asperata woodland could significantly increased soil nutrient and reduce N2O emissions. We suggest that more forest land should be selected as the optimal site for nitrogen fixation and emission reduction for sustainable development of the terrestrial ecosystem on the Loess Plateau in Central Gansu.

Nitrogen fertilizer and tillage intensity affected winter wheat macronutrient uptake and utilization efficiencies

AbstractApplication of N fertilizer and no‐tillage (NT) can increase winter wheat (Triticum aestivum L) production through improvements in plant available soil water and nutrient availability. However, long‐term tillage and N management interaction effects on winter wheat nutrient uptake are not well known. The objective of this study was to quantify winter wheat grain yield, macronutrient removal, and utilization responses to N fertilizer application and tillage intensity. The study was conducted in 2019 and 2020 at Hays, Kansas after 45 years of tillage and N fertility experiment. Treatments were a combination of two tillage practices (CT, conventional tillage; NT) and four rates of N (0, 45, 90, and 134 kg ha−1). Results showed a significant tillage and N fertilizer interaction effect on wheat grain yield, nutrient removal (NR) (grain‐N, ‐P, ‐K, ‐Mg; stover‐K, and total P), and nutrient concentration (stover‐K and ‐S). Two different quadratic models fit the N rate‐to‐yield relation for CT and NT with yields of 4.3 and 5.2 Mg ha−1 at agronomic optimal N rates of 119 and 199 kg N ha−1, respectively. This suggests that the N rates were not high enough to predict optimum N rate for NT in this environment. With an average yield of 3.30 Mg ha−1, wheat removed about 113 kg N ha−1, 17 kg P ha−1, 56 kg K ha−1, 7 kg Ca ha−1, 8 kg Mg ha−1, and 8 kg S ha−1, irrespective of tillage practice. Grain yields and NR were greater for CT at smaller N rates (&lt;90 kg N ha−1) and for NT at greater N rates (&gt;90 kg ha−1). Findings of the study suggest that adequate N fertility (&gt;90 kg ha−1) should be maintained to improve grain yield, nutrient uptake, and utilization efficiency in dryland NT wheat production systems.

Design and Experiment of Side-Shift Stubble Avoidance System for No-Till Wheat Seeder Based on Deviation-Perception Fusion Technology

To improve the stubble avoidance rate of no-till wheat seeders under the environment of corn stubble, the side-shift stubble avoidance system was developed in the present study based on deviation-perception fusion technology. Firstly, the amount of implement deviation compensation was accurately obtained by the information sensing system. Then, a fuzzy PID algorithm was proposed to optimize the performance of the control system. Finally, the simulation model of the control system was developed by Matlab/Simulink. The simulation results showed that the regulation time required for the system response curve to reach the steady state was 1.0 s, and the maximum overshoot was 8.2%. To verify the performance of the side-shift stubble avoidance system, an orthogonal test was conducted. The optimal combination of parameters was obtained, including the operation speed of 1.3 m/s, the hydraulic cylinder speed of 25 mm/s, and the straw mulch amount of 1.2 kg/m2. The field verification test was performed under the optimal parameters, showing the stubble avoidance rate was 90.6%, and the mean value of the sowing variation coefficient was 27.12%, which fully satisfied the requirements of stubble avoidance and sowing operation.

Diverse systems and strategies to cost-effectively manage herbicide-resistant annual ryegrass (Lolium rigidum) in no-till wheat (Triticum aestivum)-based cropping sequences in south-eastern Australia

Context Herbicide-resistant annual ryegrass (Lolium rigidum; ARG) is a major weed of commercial significance globally, including no-till wheat-based production systems in south-eastern Australia. Aims To compare the cost-effectiveness of different crop sequences and intensities of weed management to control ARG in rainfed grain production. Methods Two on-farm studies in southern New South Wales, Australia, compared the effect of combinations of 3-year crop-sequence options (continuous wheat, 1- or 2-years of break crops), conservative or aggressive weed-control measures, hay cuts, legume brown manure (BM), and/or weed-free winter fallow on in-crop ARG infestations and soil seedbanks. Gross margins were calculated for each combination of treatments to compare system economic performance. Key results Double-breaks consisting of two consecutive broadleaf crops, or canola–cereal hay, were frequently the most profitable and effective ARG control strategies. Single canola or lupin crops, BM, cereal hay, and fallow all significantly reduced subsequent in-crop ARG and seedbank numbers compared with continuous wheat. Aggressive in-crop control measures in wheat were more expensive than those applied to break crops. Gains in ARG control could be lost by a single year of poor weed control. Conclusions High levels of control (&gt;95%) over three consecutive seasons are required to reduce ARG seedbanks, and this is most cost-effectively achieved with diverse crop sequences. Implications Farmers with high populations of ARG can reduce seedbanks by growing three crops sequentially that achieve complete weed seed control. This must be followed with ongoing high levels of control in subsequent years to keep ARG seedbanks low.

Water quality effects of cover crop, grazing and tillage implementation in a long-term no-till wheat system

Agricultural anthropogenic nitrogen (N) and phosphorus (P) continue to be major surface and subsurface water pollutants in developed countries. Integrated crop-livestock systems in the semi-arid Texas Rolling Plains are characterized by continuously cultivated monoculture combined with grazing. Improperly managed grazing can increase soil compaction, and subsequently, decrease infiltration, which leaves the soil exposed to erosion. Grazing is therefore of paramount importance to water quality. Cover crop (CC) use improves soil ecosystem services and functions. The objective of the current study was to characterize soil water quality following CC under continuous wheat (Triticum aestivum), grazing, tillage, and no-till practices under a typic Haplustepts, Rotan clay loam soil type. Treatments evaluated include 1) conventional tillage without a CC (CT); 2) no-till without a CC (NT); 3) no-till with a CC (NTC); and 4) no-till with a grazed CC (NTCG). Portable rainfall simulators were used to assess surface runoff water quantity and quality after CC implementation in a long-term no-till continuous wheat system. Cover crop treatments, both grazed and un-grazed, reduced the amount of runoff by 4–6 times compared to no CC treatments (NT and CT). Converting 12-year-old NT to CT reduced infiltration by at least 43 % and increased runoff by 58 % compared to long-term NT. Consequently, total solids load and concentration for CT were 4–14 times greater than all NT treatments (NT, NTC, NTCG). Conventional tillage (CT) also increased total P loads and concentrations by 2–11-fold compared to all NT treatments (p < 0.05). Rainfall events occurring within three weeks after CC termination resulted in about 6 times greater soluble reactive P (SRP) (except NTCG) and about 2–3 times greater dissolved organic C (DOC) concentrations from CC treatments than non-CC treatments, although this was not observed for subsequent runoff events. Tilling the soil had more deleterious effects compared to flash grazing CC. Adopting NT, either alone, or long-term in combination with CC (either flash grazed or un-grazed) are potentially sustainable viable practices in semiarid regions that can reduce environmental contamination.

Spring‐planted cover crop effects on weed suppression, crop yield, and net returns in no‐tillage dryland crop production

AbstractIntegrating cover crops (CCs) into dryland crop rotations could provide options for herbicide‐resistant (HR) weed control in no‐tillage (NT) systems. Field experiments investigated weed suppression potential of spring‐planted CCs and their effects on plant available water, crop yields, and net returns. The CC treatments were implemented during the fallow phase of NT wheat (Triticum aestivum L)–sorghum (Sorghum bicolor Moench)–fallow rotation at two locations: Brownell and Colby, over 3 yr in western Kansas. Treatments were oat–triticale (OT), oat–triticale–pea (Pisum sativum; OTP), spring pea, and fallow. Spring pea aboveground biomass was 3,290 kg ha−1, whereas OT produced 5,640 kg ha−1 and OTP produced 5,260 kg ha−1. Regardless of location, weed biomass was reduced between 86 and 99% with CCs relative to weedy fallow. Cover crops reduced plant available water at winter wheat planting in three out of the six site‐years. Averaged across years, CCs reduced winter wheat yields by 18% compared with fallow at Brownell but not at Colby. Replacing fallow with spring pea increased gross revenue but generated negative net returns because of high cost of herbicide and pea seed. Net return with OT or OTP CCs were negative in four out of six site‐years when used strictly for weed suppression. However, net returns were mostly positive when OT ($110–876) or OTP (−$110–832) CCs were used as forage. Our results showed replacing fallow with spring‐planted CCs for weed suppression in dryland cropping system is profitable only when the CCs are used for forage.

Enhancing long-term no-till wheat systems with cover crops and flash grazing

Monoculture practices under conventional tillage (CT) are detrimental to sustainable soil ecosystem functions and services under intensive agriculture practices, ultimately diminishing net benefits. Conservation practices, such as no-till (NT) and cover crops (CC) can nurture sustainable soil ecosystem functions and services. The impact of introducing CC, grazing, intercropping, and reverting to tillage in a long-term NT continuous wheat system on soil properties was evaluated in three years of implementation. Treatments were CT and combinations of NT, CC, grazing, and intercropping wheat with radishes and turnips. Tillage significantly decreased large macroaggregates (33–39%), mean weight diameter (21–26%), and POX-C (21–29%) within large macroaggregates and increased small macroaggregates (40–65%) compared to all CC treatments (including grazed and intercropped) within a 3-year period. Reverting to tillage after 12 years of NT significantly increased bulk density by 19%, reduced total porosity by 21% and soil water content by 28% compared to all CC treatments. In addition, Cover crops (including grazed and intercropped) enhanced NT as evident in significant improvements in POX-C (19–32%), large macroaggregates (37–51%), mean weight diameter (22–31%), bulk density (8–13%), total porosity (10–18%), and measured soil water content (11–14%). Flash grazing CC did not result in any adverse effects compared to all other treatments for measured parameters. Ultimately, reverting to tillage in a long-term NT system significantly degraded soil physicochemical properties. In contrast, implementing CC to long-term continuous wheat systems resulted in rapid soil improvements within the 3-year study period which were reflected in enhanced stored soil moisture storage of up to 39% higher under CC compared to CT. Flash grazing CC can be successfully implemented in NT systems without adversely affecting soil physicochemical properties. Intercrops did not show pronounced effects possibly due to winterkill.

Early sowing can boost grain production by reducing weed infestation in organic no-till wheat.

Conservative tillage techniques have several agro-ecological benefits for organic farming. The application of these techniques, however, can create quite a few challenges due to the increased weed competition. Here, we report the results of an organic field experiment in which the responses of wheat and weeds to no tillage (NT) were evaluated compared with conventional tillage (CT). We also tested the hypothesis that, under NT, moving up the sowing date, compared with using the ordinary sowing date for the study area, can result in increased competitiveness of the crop against weeds. Two wheat genotypes, a modern variety and an ancient landrace, were tested. Substantial reductions in grain yield and protein content were observed in wheat under NT than under CT when the ordinary sowing date was used. This was mainly due to the considerable increase in weed biomass under NT. The tillage system also altered the composition of weed flora, with some species favored under NT and others under CT. In general, early sowing mitigated the detrimental effect of NT on yield. The two genotypes responded differently to the treatments. The early sowing in the modern variety reduced but did not eliminate the advantages of CT over NT, whereas no appreciable differences in grain yield were observed between CT and NT in the landrace. Our results show clearly that, under organic management, using NT alone as a substitute for CT is not agronomically feasible. Moving up the sowing date and using a competitive genotype can help mitigate the negative effects of NT, but surely a more effective application of NT could be achieved by acting simultaneously on other factors of the cropping management system (e.g. crop rotation, fertilization strategy, type of seeder). © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Development of Sustainable Production of Rainfed Winter Wheat with No-Till Technologies in Southern Kazakhstan

The production of rainfed crops in arid regions is an extremely difficult task, especially without tillage. In southern Kazakhstan, in 2020–2021, the approbation of various nutrition regimes for winter wheat grown in conditions of no-tillage rainfed lands has been studied. The effect of different doses and terms of application of growth stimulators, micronutrients, bio-fertilizers and mineral fertilizers, as well as their economic efficiency, was studied in ten variables. The use of a combination of growth stimulators and microfertilizers produced the highest grain yield and was the most cost-effective. The greatest value of the nominal net profit of 223.25 euro and 244.10 euro from one hectare was provided and calculated with the recommended target grain yield of 2.0 t/ha dose of mineral fertilizers, respectively; however, the production cost of one ton of grain in these treatments was also highest. Further research is continuing with a wider range and combination of amendments and various crops in a rainfed no-till winter wheat farm in southern Kazakhstan.

Diverse Systems and Strategies to Manage Herbicide-Resistant Annual Ryegrass (Lolium Rigidum) in No-Till Wheat (Triticum Aestivum)-Based Cropping Sequences in South-Eastern Australia

Diverse Systems and Strategies to Manage Herbicide-Resistant Annual Ryegrass (Lolium Rigidum) in No-Till Wheat (Triticum Aestivum)-Based Cropping Sequences in South-Eastern Australia

Enhancing Long-Term No-Till Wheat Systems with Cover Crops and Flash Grazing

Enhancing Long-Term No-Till Wheat Systems with Cover Crops and Flash Grazing

Long-term tillage effect on with-in season variations in soil conditions and respiration from dryland winter wheat and soybean cropping systems

Soil respiration from agricultural soils is a major anthropogenic source of CO2 to the atmosphere. With-in season emission of soil CO2 from croplands are affected by changes in weather, tillage, plant row spacing, and plant growth stage. Tillage involves physical turning of soils which accelerate residue decomposition and CO2 emission. No-tillage lacks soil disturbance and residues undergo slower decomposition at the surface. In this study, we compared with-in season soil conditions (temperature and moisture) and soil respiration from two major crops (soybean and winter wheat) by making high temporal frequency measurements using automated chambers at half-hourly intervals. The experiment lasted for 179 days. Total number of measurements made from conventional and no-tillage soybean and winter wheat plots were 6480 and 4456, respectively. Average flux after the winter-dormancy period of wheat was 37% higher in tilled soil compared to no-till soil. However, average flux during the soybean growing season was 8% lower in conventional till compared to no-till soil. This differential response of soil respiration in wheat and soybean was primarily due to tillage-induced changes in surface characteristics (residue cover) and soil environmental conditions (soil temperature and soil moisture). Results from this study can help elucidate relationships for modeling and assessment of field-scale soil CO2 emissions from dryland wheat and soybean crops grown in sub-tropics.

Minimum tillage and no-tillage winter wheat–summer fallow for low precipitation regions

Dryland wheat (Triticum aestivum L.) is the principal crop grown on 3.35 million ha (8.28 million ac) of the semiarid Inland Pacific Northwest of the United States. In areas with less than 300 mm (12 in) of annual precipitation, challenges for wheat production are similar to those found in the Mediterranean region and Australia. Successful crop production depends on adequate precipitation capture and storage and weed control, which prove problematic under no-tillage (NT), the most effective soil conservation practice. Sweep-tillage (ST) is proposed as an equally effective conservation system, with local conventional wisdom saying that it produces higher yields than NT systems. A study established in 2006 and concluded in 2018 evaluated the performance of NT and ST winter wheat–summer fallow production systems. The null hypothesis for this research assumed no statistically significant differences in any of the soil and plant characteristics measured between NT and ST treatments. Sixteen 0.04 ha (0.10 ac) plots were established in a randomized complete block design, with two rotation entry points for a total of four treatment plots per year replicated in four blocks. Data were analyzed using a generalized linear mixed model. The NT system produced significantly higher crop yields and higher precipitation use efficiencies than the ST system (NT 3.38 ± 0.33, ST 2.66 ± 0.27 Mg ha–1 [NT 50 ± 5, ST 40 ± 4 bu ac–1]). Infiltration rates were higher and soil temperatures were lower in the NT system. The higher yields and lower soil temperatures in the NT system were unexpected and contrary to previous research conducted in this region.

Soil acidification modifies soil depth-microbiome relationships in a no-till wheat cropping system

Soil pH is among the most important drivers of soil bacterial community composition and diversity. However, most studies exploring the spatial distribution of soil bacterial communities have focused on the top 10–20 cm of soil, leaving our knowledge of the composition, diversity, and forces structuring subsoil communities relatively unexplored. Moreover, in agricultural soil managed without tillage (no-till), fertilizers often generate an acidified soil layer in the seed zone, rendering no-till soils a unique system in which to study the relative impacts of pH and soil depth on microbial communities. We characterize the composition and diversity of bacterial communities in a no-till wheat-based cropping system from eastern Washington, across soil depths (0 cm, 10 cm, 25 cm, 50 cm, 75 cm, and 100 cm). Soil depth was a strong driver of bacterial community composition and diversity. Proteobacteria and Actinobacteria dominated the soil surface, Acidobacteria peaked in relative abundance at 10 cm, and Actinobacteria and unidentified taxa were greatest in relative abundance below 25 cm. However, acidified soil disrupted relationships between soil depth and bacterial communities, resulting in a low diversity and distinct composition of bacterial communities at the 10 cm depth. Co-occurrence networks of bacterial taxa revealed groups of co-occurring taxa that responded primarily to soil pH or depth. This work provides an insight on the distribution and drivers of bacterial communities in deep soil profiles in dryland wheat-based cropping systems.

Nitrogen Rate Increase Not Required for No-Till Wheat in Cool and Humid Conditions

An increased nitrogen (N) supply was proposed to avoid grain yield (GY) reductions and successfully implement conservation agriculture (CA). We investigated interactions effects of tillage system and N supply on winter wheat (Triticum aestivum L.) at two sites in the Swiss midlands with no (0 kg N ha−1) and high (150–160 kg N ha−1) N supply using 15N-labelled ammonium nitrate in selected treatments. Wheat’s GY, yield components, N related traits and soil mineral N content (Nmin) under conventional tillage (CT), minimum tillage (MT), and no-tillage (NT) were studied following two preceding crops: oilseed rape (Brassica napus L.) and maize (Zea mays L.). Wheat after oilseed rape had significantly higher GY and biomass than after maize while a yield decrease under NT compared with CT and MT was observed regardless of N supply level. Differences in soil Nmin among tillage systems were seldom found and were inconsistent. No differences in 15N fertilizer recovery were found between NT and CT while residual Nmin after harvest was lower under NT than CT or MT. In conclusion, we did not found consistent reductions in soil N availability and N uptake under NT that would justify an increased N supply for wheat under CA.

Nitrogen levels and rotation with cover crops in wheat under no-tillage

The spread of the conservationist agriculture system involving green fertilization, crop rotation, and no-tillage has altered the dynamics of production, which can benefit the development and productivity of the successor crop, as well as the N fertilizer economy. In this context, the objective of this experiment was to study the effect of single maize cropping and maize intercropping with four cover crops in conjunction with the application of N doses under cover on wheat. The experiment was carried out in 2015 and 2017, in an experimental area using a 5 × 4 factorial randomized block experimental design with four replicates. Treatments consisted of the combination of five cover crops (maize, maize + Crotalaria spectabilis, maize + Cajanus cajan, maize + Canavalia ensiformis, and maize + Urochloa ruziziensis) with four N doses (0, 40, 80, and 120 kg ha-1) in no-tillage wheat production. The main production components and yield of wheat were evaluated. It was concluded that the plant residues of maize + Canavalia ensiformis and maize + Urochloa ruziziensis enhanced the yield of wheat cultivated in the winter of 2015 and 2017, when compared with the other treatments. The effect of N doses on wheat grain yield was positive (with significant increase in grain yield) and the maximum average was obtained with the application of 74 and 86 kg ha-1 of N in 2015 and 2017, respectively.