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Interest in intercropping semi-leafless field peas (Pisum sativum L.) is increasing as a means of weed control in organic production. We evaluated field pea (cv. CDC Amarillo) grown alone or intercropped with three seeding rates of either barley (Hordeum vulgare L.), mustard (Brassica juncea L.), or oat (Avena sativa L.). A full seeding rate of field pea was used in each instance, resulting in an additive intercropping design. Each crop combination was conducted in a separate experiment, three times over two years (2019 and 2020) in Carman, MB. Measurements included crop and weed biomass production, grain yield and quality, and net return. Intercrops reduced weed biomass at maturity from 17% to 44% with barley and oat being more suppressive than mustard. Intercrops also reduced field pea yield from 6% to 26%, but increased field pea seed mass. Barley at the high seeding rate provided the most weed suppression per unit of field pea yield loss (2.62 kg of weed suppression per kg of field pea yield loss) compared with oat (1.29) and mustard (0.87). Barley and mustard intercrops decreased net return compared with monoculture field pea. Under low weed pressure (1150 kg·ha−1 weed biomass at maturity) and earlier seeding, oat intercrops reduced net return. However, under weedy conditions (2649 kg·ha−1) and later seeding, field pea-oat intercrops significantly increased net return. In conclusion, while all three intercrop mixtures reduced weed biomass, reductions in field pea yields were observed, and net return benefits were observed only in certain circumstances.

Aggregate stability (AS) was measured in the 25th year of a long-term organic — conventional comparison field study. Located in southern Manitoba, the study includes two, four-year crop rotations under conventional and organic management, plus a grassland. The forage-grain rotation includes alfalfa (Medicago sativa)–alfalfa–wheat (Triticum aestivum)–flax (Linum usitatissimum). The grain only rotation includes wheat–flax–oat (Avena sativa)–soybean (Glycine max); hairy vetch (Vicia villosa) is substituted for soybean in the organic system. Composted manure was added every 4 yr to half of the organic forage-grain rotation to correct a phosphorus deficiency. The wheat and flax phases were sampled at depths (0–10 cm; 10–20 cm) in spring 2017, and wet aggregate stability was measured using the Yoder method with stacked sieves. Mean weight diameter (MWD) was calculated. AS in the organic systems was never lower than that of comparable conventional systems, but had more large aggregates in only a few cases. Our hypothesis that including alfalfa would increase AS was supported in only a few instances. The largest aggregates (1–2 mm and 2–6.3 mm) and the fewest smallest aggregates (0.25–0.5 mm) were observed in the grassland. For the intermediate aggregate size class (0.5–1 mm), the organic forage-grain systems had levels similar (P > 0.05) to the grassland. While adding manure increased plant growth by about 40% in the organic forage-grain rotation, no AS differences were observed. Limited AS response in the arable systems may be due to suboptimal soil C contents; only the grassland had a C content above the minimum 35 g·kg−1 postulated for Vertisols.

Grass-fed ruminant production does not have the convenience of feeding easily-storable grains during periods of low forage availability. This study examined the forage yield, quality, and utilization of warm- and cool-season annual forages grown under organic management during the mid-summer “feed gap” period. Annual ryegrass (Lolium multiflorum Lam. cv. Tetra Brand), winter triticale (× Triticosecale Wittmack cv. common), oat (Avena sativa L. cv. Souris), millet (Panicum miliaceum L. cv. Crown Proso), corn (Zea mays L. cv. BMR84 and CM440 Canamaize), and sorghum-sudangrass (Sorghum bicolor [L.] Moench × Sorghum sudanense [Piper] Stapf cv. common) were grown in Carman, Manitoba, over 3 site-years in 2018 and 2019. Combined forage and weed dry matter (DM) yield was 7159 kg·ha−1 for sorghum-sudangrass (29% weeds), 5506 kg·ha−1 for corn (36% weeds), 4687 kg·ha−1 for oat (45% weeds), 4617 kg·ha−1 for annual ryegrass (95% weeds), 4542 kg·ha−1 for millet (28% weeds), and 2945 kg·ha−1 for winter triticale (51% weeds); significant differences in crop and weed biomass were observed. All forage systems were palatable to sheep with utilization rates from 47% to 65%. When all quality parameters were considered, corn, winter triticale, millet, and oat displayed adequate quality for mid-summer grazing, while sorghum-sudangrass had suboptimal crude protein concentrations. Direct measurements of forage quality on weeds showed that weeds did not compromise forage quality. This Canadian first study demonstrated the potential of forage production for mid-summer grazing in an organic, grass-fed regime with oat, millet, and corn resulting in the best combination of yield and quality.

AAC Oravena is a white-hulled spring oat (Avena sativa L.) cultivar selected and developed under organic management. AAC Oravena yields well under organic and conventional production systems, compared with check cultivars. AAC Oravena has good milling quality. AAC Oravena was registered (Reg. No. 7561) by the Variety Registration Office, Canada Food Inspection Agency, on 3 July 2014.

The challenges associated with the global phosphorus (P) cycle are complex and multifaceted, from geological resource limitation, to P deficiency on arable farmland, to environmental contamination via excess P fertilization. Although no single solution can address all of the challenges associated with the P cycle, the principle of circularity provides a framework toward a more sustainable and food-secure P system. Phosphorus deficiency on farmland is widespread, particularly on organically managed farms due to negative P balances in low-input cropping systems. Recycled nutrient sources divert food and human wastes back onto farmland; they have the potential to ameliorate both the global-scale issues of phosphate rock depletion and environmental contamination and the farm-scale issue of P deficiency, particularly for organic farms. For recycled nutrients to act as viable alternatives to conventional nutrient sources, their ability to supply P and improve yields must be demonstrated. This paper provides an introduction to the importance of recycled fertilizer sources in the global P cycle, and the key role they can play on organic farmland in Canada.

The challenges of soil degradation and low crop yield are being addressed in East Africa using a number of soil health-promoting farming systems including Conservation Agriculture (CA). CA is based on principles of minimal soil disturbance, continuous soil cover, and crop diversity, though implementation on farms may vary due to local circumstances. This study evaluated the effect of CA, as practiced by farmers, and compared farmer descriptions of soil health with scientific measures. CA and non-CA fields were compared in regions of Ethiopia (23 farms), Kenya (23 farms), and Tanzania (13 farms) with most fields repeatedly sampled for 2 to 3 years. CA and non-CA fields were located within meters, on soils with the same texture, growing similar crops. CA systems used precision planting, mostly with basins. Soil parameters were assessed using a participatory approach where farmers and field technicians collected data. CA practices improved qualitative soil characteristics as sensed by farmers (e.g., hoe-ability, crusting, smell, water infiltration), and this positive response was consistent across most fields. For qualitative data, the logarithm of the odds ratio estimates method was used to test the probability that CA would provide soil improvement. Fields under the CA treatment had a higher probability of rating better than non-CA fields. Quantitative measurements of pH and microbial respiration validated farmer assessments. CA-managed soils were weakly associated with darker colour, indicating higher soil organic matter. Sandy soils did not appear to improve with CA as dramatically as clay and loam soils, suggesting different CA strategies may be required. We discuss both benefits and drawbacks of this type of participatory, on-farm research. We conclude that farmer participation as citizen scientists will advance soil restoration in East Africa and increase the potential for farmer-to-farmer knowledge exchange of soil-improving practices.

Soil phosphorus (P) availability may be impacted by management practices, thereby affecting plant P uptake and plant response to P amendments. The aim of this study was to determine the effects of long-term management on soil P pools and to assess the response of P bioavailability, plant growth, and P uptake to mineral versus manure P treatments. Soils were collected from plots under organic (ORG), organic with composted manure (ORG + M), conventional (CONV), and restored prairie (PRA) management. Italian ryegrass (Lolium multiflorum L.) seedlings were grown in the greenhouse for 106 d in soils amended with various rates of manure or mineral P. The ORG soil had lower concentrations of labile P (resin-P and NaHCO3-P) compared with the CONV and PRA soils, as determined by sequential P fractionation prior to planting. Ryegrass biomass (root + shoot) and shoot P uptake from soils receiving no P were significantly lower for the ORG than all other management systems. Although apparent P use efficiency of the whole plant was increased by low P rate in the ORG management system, the source of applied P, manure > mineral, only influenced Olsen test P.

Fall-seeded rye (Secale cereale) is known to suppress weeds through physical and allelopathic properties. This study examined the effects of fall rye cover crops on weed and dry bean (Phaseolus vulgaris) productivity over four site–years in Manitoba. In addition to rye, we tested early versus late spring rye termination times as well as herbicide use in a factorial experiment with four replicates. In the absence of herbicides, rye reduced early-season broadleaf and grassy weed plant populations by 44%–72% and 43%–88%, respectively. Terminating rye at the four-leaf stage (∼1100 kg dry matter ha−1) provided the same level of weed suppression as termination at booting (∼3100 kg dry matter ha−1). Early rye termination increased bean plant populations (significant at three out of four sites), bean development (four out of four sites), bean biomass (two out of four sites), and bean yield (three out of four sites) compared with later termination. Lower bean yield with rye at one site–year was attributed to dry early season conditions, where rye reduced soil water content. While the rye cover crop provided multiple benefits to bean production, early termination resulted in the best agronomic outcome. Rye was beneficial to weed control even when herbicides were used.

How to engage farmers that have limited formal education is at the foundation of environmentally-sound and equitable agricultural development. Yet there are few examples of curricula that support the co-development of knowledge with farmers. While transdisciplinary and participatory techniques are considered key components of agroecology, how to do so is rarely specified and few materials are available, especially those relevant to smallholder farmers with limited formal education in Sub-Saharan Africa. The few training materials that exist provide appropriate methods, such as compost making, but do not explain relationships and synergies between nutrition, social inequalities, climate change and agroecology. Some food sovereignty and agroecology courses aim at popular political education for those with more formal education. Here we describe the process of development of an innovative curriculum, which integrates agroecology, nutrition, climate change, gender and other dimensions of social equity across 2 weeks of training explicitly for smallholders in southern Africa with limited formal education. The curriculum is highly participatory; we use concepts in popular education, transformative and experiential-based learning, and theatre. It is also integrative; we link agroecology with climate change, human and soil nutrition, gender, and related components of social equity. Developed in partnership with Malawian farmers, community development experts and academics from five countries, the curriculum was piloted with 520 smallholder farming households in Malawi and Tanzania, and evaluated using qualitative techniques. Clashes of language, cultural norms, and terminology were as great of a challenge as agreeing on and conveying technical information, to weave into a coherent whole. However, farmers who participated in the curriculum training demonstrated high interest, comprehension of material and interest in immediate application to their lives.

Greater seeding depths are often used in organic production to compensate for drier soil conditions caused by pre-seeding tillage. We hypothesized that reduced crop performance from deeper seeding could be compensated through larger seed. Field experiments were conducted in Carman, Manitoba, Canada, in 2015 and 2016. Barley (Hordeum vulgare) and oat (Avena sativa) seed lots were sieved using standard industry sieves (from 0.08 cm to > 0.32 cm × 1.91 cm in barley seed lots and from 0.08 cm to > 0.28 cm × 1.91 cm for the seed lots of oats) and classified into small, medium, and large seed sizes for each seed lot. The proportion of small, medium, and large seeds varied depending on farmer seed lot. Seed lots were sown at shallow (2.5 cm) and deep (6.4 cm) depths in organic fields. Deeper seeding and use of small seed size resulted in decreased grain yield and increased weed biomass. This trend occurred in both years but was only significant in 2015. No seed size by seeding depth interactions were observed for crop emergence, weed biomass, grain yield, or dockage for oat or barley over the 2-year study. In two instances, crop biomass was greater with larger compared with smaller seed at shallow seeding depths. This research indicated that large seed did not compensate for lower crop productivity and higher weed biomass owing to deep seeding, but that large seed and shallow seeding independently led to more positive outcomes for organic barley and oat production.

Intermediate wheatgrass yielded 519 and 446 kg seed ha−1in years one and two after establishment. Autumn grazing increased seed yield compared with post-harvest residue removal or chopping. Inter-seeding legumes (alfalfa (Medicago sativa), sweet clover (Melilotus officinalis), and white clover (Trifolium repens) did not affect intermediate wheatgrass seed production.

Soil phosphorus (P) deficiency is common in organic cropping systems in which access to manure or other suitable P sources is limited. Insufficient P supply may be particularly detrimental to crop yields in systems relying on biological nitrogen fixation by legumes. High-purity struvite (magnesium ammonium phosphate hexahydrate) recovered from wastewater is gaining attention as a potential P source for organic crops, but little is known about the soil-crop dynamics associated with struvite application to legumes in organic cropping systems. Our objective was to assess the effect of struvite application on alfalfa productivity, P uptake, and apparent fertilizer recovery efficiency in soils with low soil test P (STP) under both field and controlled conditions. A field experiment was conducted in Manitoba, Canada (clay soil, pH 8, Olsen-P 2-3 mg kg-1), in which an existing alfalfa-grass forage stand was amended with differential rates of granular struvite and monitored over three growing seasons. A complementary pot experiment compared alfalfa response to differing rates of struvite application, relative to a soluble P fertilizer (monoammonium phosphate, MAP), in two low-STP but otherwise contrasting soils (clay texture, pH 8.0, organic matter 5.6%, Olsen-P 6 mg kg-1; sandy loam texture, pH 7.1, organic matter 3.2%, Olsen-P 10 mg kg-1). Struvite application increased forage shoot biomass yield and P concentration in the field experiment, with larger yield gains relative to the control in the second and third growing seasons. Apparent fertilizer P recovery was 26-27% over three growing seasons, regardless of struvite application rate. In the pot experiment, alfalfa yield was similar for plants fertilized with struvite or MAP but differed with soil type. Overall, our results indicate that struvite is an effective P source for organically grown alfalfa and can help to alleviate P deficiency in organic cropping systems.

Long-term agricultural studies contribute to knowledge in ways that short-term projects simply cannot. In this chapter, we highlight some observations from the Glenlea long-term crop rotation study, Canada's oldest organic field crops experiment initiated in 1992. We then discuss how this knowledge has been used to build capacity in organic crops and soils research, student training, and education of farmers and advisors. The main nutrient management challenges discovered at Glenlea regarded phosphorous (P) depletion in the organic hay export system and lack of nitrogen (N) in the organic grain-only system. Capacity development to address these challenges included intensive research on new innovations in legume-based green manure systems, development of a tool for assessing P sufficiency in organic systems, and development of a second tool for budgeting nutrients in whole rotations. We have taught the lessons from Glenlea to approximately 300 students and have embarked on “Organic Agronomist Training,” where over 160 advisors and farmers are given information and trained using our tools. The Glenlea long-term rotation continues to be critical to develop capacity in the organic grain and forage sector in Canada.

Smallholder farmers in sub-Saharan Africa (SSA) are under increasing pressure due in part to climate change and soil degradation, with many farming households unable to achieve even basic food self-sufficiency. Conservation Agriculture (CA) is a possible solution to these challenges, but the lack of sufficient biomass for mulch has limited wide-scale adoption, and many farmers who practice CA resort to adding supplemental mulch to their CA plots. Legume intercropping would not only provide biological and nutritional diversity, it may also provide an in situ cover, thereby reducing the amount of mulch required for soil and water conservation. Farmer managed research experiments were used in two semi-arid areas of Zimbabwe to test whether intercropping a cereal crop [maize (Zea mays)] with a legume [cowpeas (Vigna unguiculata), lablab (Lablab purpureus) or pigeon pea (Cajanus cajan)] could increase the total amount of biomass produced. The experimental design included two replicates with legume species and presence or absence of mulch cover as factors in the design. Maize yields were increased more by adding mulch than by legume intercrops in the absence of mulch. Therefore, intercrops were not a substitute for mulch. However, adding intercrops did significantly increase the amount of total biomass (maize and intercrop dry matter) produced at the sites and therefore, in addition to contributing protein rich grains, intercrops may reduce the amount of mulch required for soil and water conservation in CA systems. Farmer participation allowed the research to be conducted in the context of small-holder CA. Key words: Intercropping, cowpea, lablab, pigeon pea, soil conservation, farmer-based research.

Agriculture is the major anthropogenic contributor to global nitrous oxide (N2O) emissions. Many studies have examined soil N2O emissions from synthetic nitrogen (N) fertilizer additions, however, in organic production where plough-down of forage legumes are often used as a nitrogen source, emissions are as not well understood. In the current study, the Glenlea Long-Term Organic Crop Rotation Study near Winnipeg, Manitoba, was used to compare N2O emissions of a conventional annual grain and an organic mixed forage-grain system. Static-vented chambers were used to determine N2O emissions for the 2014 and 2015 crop years; from spring planting to freeze-up and again during thaw following spring. plots monitored were spring wheat and two-cut harvest with late-summer or early-fall plough-down alfalfa for the organic system, and spring wheat and soybean for the conventional system were monitored in each study year. The organically produced alfalfa received composted dairy manure in 2014 and only conventional wheat crops received fertilizer N as urea. Cumulative emissions (g N2O-N ha−1) with organic wheat were half that of conventional management. Cumulative emissions for the legume crops in the 2014 crop year were very low (

Most non-genetically modified (GM) soybean ( Glycine max Merr.) cultivars are bred and performance-tested under conventional conditions and have rarely been tested in organic production. Twelve non-GM soybean cultivars were evaluated in weed-free and weedy conditions on 5 organic farms and 1 transitional farm in southern Manitoba in 2014 and 2015. The mean cultivar yield ranged from 1384 to 1807 kg ha −1 . Weed biomass at soybean maturity ranged from 1289 to 2553 kg ha −1 and was significantly affected by cultivar. Significant site–cultivar interactions were observed for soybean biomass, height, and yield. Site accounted for 72.4% of yield variability; cultivar accounted for only 1%. Our hypothesis that cultivars with greater early season height are more competitive with weeds was not supported. Yield loss due to weeds ranged between 20 and 44%; lower yield loss was associated with timely weed management. Partial least squares regression was used to assess the main factors controlling grain yield. Higher soil nitrate (N) status negatively impacted final grain yield in this study, suggesting that soil nutrient status impacted the soybean cultivars’ competitive ability against weeds. Results suggest that weed management and soil N status are of equal importance to cultivar choice for successful organic soybean production in Manitoba.

TheGlenlea long-term study in Manitoba, Canada compares annual grain and forage-grain rotations under organic and conventional management. Organic systems are split into compost manure amended and no compost treatments. The objective of this study was to evaluate selected soil biological parameters over one entire growing season (2011). Microbial biomass carbon (MBC), microbial metabolic quotient (qCO 2 ), and microbial biomass phosphorus (MBP) were measured five times in spring wheat ( Triticum aestivum L.) and compared with a restored prairie grassland system. Significant interactions between management system and sample occasion were attributed to stronger recovery for MBC and MBP after soil rewetting in the organic vs the conventional system. The qCO 2 was lowest (0.37 mg C g MBC h −1 ) under dry mid-summer conditions and highest in late spring and after soil rewetting in fall (1.19 mg C g MBC h −1 ). When qCO 2 levels increased, the increase was greater in the forage-grain than the annual grain rotation. Organic management increased MBC compared with conventional management in the forage-grain rotation (1718 vs 1476 μg g −1 ) but decreased MBC in the annual grain rotation (1080 vs 1115 μg g −1 ). Among the six arable treatments, only the organic treatments in the forage-grain rotation behaved similarly (P > 0.05) to the grassland in terms of MBC, soil respiration and qCO 2 . N 2 O emissions per unit of MBC were 60–80% lower in organic compared with conventional systems. In conclusion, seasonal changes in soil biological C and P parameters were observed. Under conditions conducive to increased soil biological activity, organic systems outperformed conventional systems, especially in the forage-based rotation.

Low-tillage systems are needed to improve soil conservation in organic farming. This study evaluated three no-till/low-till cover crop termination strategies on the basis of weeds, N dynamics and growth and yield of a wheat (Triticum aestivum L.) test crop. Field experiments were conducted in two different Canadian provinces. The blade roller, flail mower, and undercutter cultivator were comparable with standard tillage for controlling a full-season barley (Hordeum vulgare L.)–pea (Pisum sativum L.) cover crop. Reduced tillage implements resulted in some depression of soil temperature the following spring and some delay in spring wheat development. Yield differences between treatments were related to weed and N consequences not seedbed quality or wheat development. Undercutting sometimes resulted in better perennial weed control than blade rolling. Blade roll plus late-season tillage treatment improved perennial weed control but provides less residue for soil protection. Flail mowing resulted in more rapid cover crop biomass mulch decomposition, allowing weeds to establish. Reducing tillage reduced N availability to the following wheat crop relative to tillage, and reduced N leaching. Poor weed suppression in low-till treatments meant that a higher proportion of available N was sometimes captured by weeds compared with the wheat crop. Future studies should test combinations of alternative tillage and crop termination approaches aimed at specific weed and nutrient challenges.

Reducing tillage in organic bean ( Phaseolus vulgaris ) production may be facilitated by strategic use of fall-seeded cover crops. This study characterized the effects of fall rye ( Secale cereal L.), barley ( Hordeum vulgare L.) and oat ( Avena sativa L.) cover crops on soil environment, weeds, and bean growth and development. It was repeated twice in Manitoba, Canada with cover crop type and tillage treatments in a factorial experiment. Cover crops were seeded in fall each year (2010 and 2011). Greater cover crop biomass and lower available soil N at bean planting for rye was attributed to rye spring growth. In the till managed treatment, cover crops were tilled immediately before bean planting. Cover crop management in the no-till treatment involved flail mowing (18 days after bean planting in 2011 and 11 days after bean planting in 2012) in the fall rye treatment and flaming immediately after bean planting in the frost-killed barley, oat and control treatments. Rye reduced soil temperature and early season bean development. Bean population density was unaffected by tillage or cover management despite 5604 kg ha −1 of rye biomass at planting. Green foxtail ( Setaria viridis ) populations were decreased with rye only in no-till plots. Dandelion ( Taraxacum officinale ) was unaffected by treatments, while redroot pigweed ( Amaranthus retroflexus ) and barnyard grass ( Echinochloa crus-galli ) populations were lower in no-till plots. Rye reduced weed biomass but not bean biomass at harvest; however, bean yield was lower with rye compared with other cover crops in both years. It was concluded while frost-killed cover crops did not provide sufficient weed suppression, fall rye provided too much competition against the bean crop. No-till management did not improve rye’s overall effectiveness.

Decomposition of cover crop mulches has received little attention in the scientific literature, particularly in the context of the organic rotational no-till systems adapted for the climatic conditions of the northern Great Plains of Canada. The objective of the study was to determine the effect of plant species and mulch application rate on cover crop decomposition and mulch quality parameters over time. Using the litter bag technique, six plant species and two mulch application rates were tested twice in field studies at Carman, Manitoba, Canada. Among the plant species tested, decomposition was the fastest with oilseed radish (Raphanus sativus L.) and the slowest with barley (Hordeum vulgare L.). The effect of application rate on mulch biomass was not consistent between experiments. Mulches released a large amount (46.4%) of their initial N content after only 30 days of field placement, for all levels of plant species and mulch application rates combined. Forty-four percent of initial N content still remained in the mulches by early May (Day 250), and may be available for the subsequent crops seeded in the spring or later in the crop rotation. This research provides us with valuable information on nutrient release, soil cover, and potential weed control from mulches.

Reducing tillage in herbicide-free cropping systems is a challenge for farmers and few studies have attempted to identify the limitations of organic no-till systems over a period of time greater than two years. The objective of the study was to determine the effect of tillage [no-till (NT) and conservation tillage (CT)] and management [organic (ORG) and conventional (CONV)] systems on mulch biomass, weeds, and crop productivity, over time. A six-year field study was conducted in Carman, MB, Canada, between 2008 and 2012. The crop rotation was barley (Hordeum vulgare L.)/hairy vetch (Vicia villosa Roth) cover crop in 2008, flax (Linum usitatissimum L.) in 2009, oats (Avena sativa L.) followed by a 4-species fall-seeded cover crop mixture in 2010, barley/hairy vetch cover crop in 2011, and spring wheat (Triticum aestivum L.) followed by fall-seeded cereal rye (Secale cereale L.) in 2012. From 2008 until mid-2010, the experiment design consisted of two tillage systems (NT and CT), both under ORG management. In mid-2010, the experiment was modified into a split-plot design to allow for the comparison between the ORG and CONV management systems, within each tillage system. In ORG NT, cash crops of flax and spring wheat were seeded into 4.5 and 4.7 Mg ha−1 of rolled cover crop mulch in 2009 and 2012, respectively. Differences in weed communities between treatments were statistically noticeable in the fifth year of the study only (2012), with higher weed biomass and weed species richness in the ORG management system. Crop yields were reduced in ORG NT in 2009 (flax) and 2012 (spring wheat). Little difference in weed and crop responses between ORG and CONV tilled systems were identified. Results suggest that additional innovative soil and weed management practices are needed to make organic continuous no-till cropping system productive for a period longer than six years, in a cool subhumid continental climate.

Changes in land management practices may have significant implications for soil microbial communities important in organic P turnover. Soil bacteria can increase plant P availability by excreting phosphatase enzymes which catalyze the hydrolysis of ester-phosphate bonds. Examining the diversity and abundance of alkaline phosphatase gene harboring bacteria may provide valuable insight into alkaline phosphatase production in soils. This study examined the effect of 20 years of no input organic (ORG), organic with composted manure (ORG + M), conventional (CONV) and restored prairie (PRA) management on soil P bioavailability, alkaline phosphatase activity (ALP), and abundance and diversity of ALP gene (phoD) harboring bacteria in soils from the northern Great Plains of Canada. Management system influenced bioavailable P (P < 0.001), but not total P, with the lowest concentrations in the ORG systems and the highest in PRA. Higher rates of ALP were observed in the ORG and ORG + M treatments with a significant negative correlation between bioavailable P and ALP in 2011 (r2 = 0.71; P = 0.03) and 2012 (r2 = 0.51; P = 0.02), suggesting that ALP activity increased under P limiting conditions. The phoD gene abundance was also highest in ORG and ORG + M resulting in a significant positive relationship between bacterial phoD abundance and ALP activity (r2 = 0.71; P = 0.009). Analysis of phoD bacterial community fingerprints showed a higher number of species in CONV compared to ORG and ORG + M, contrary to what was expected considering greater ALP activity under ORG management. In 2012, banding profiles of ORG + M showed fewer phoD bacterial species following the second manure application, although ALP activity is higher than in 2011. This indicates that a few species may be producing more ALP and that quantitative gene analysis was a better indicator of activity than the number of species present.

Bacterial transformation of phosphorus (P) compounds in soil is largely dependent on soil microbial community function, and is therefore sensitive to anthropogenic disturbances such as fertilization or cropping systems. However, the effect of soil management on the transcription of bacterial genes that encode phosphatases, such as phoD, is largely unknown. This greenhouse study examined the effect of long-term management and P amendment on potential alkaline phosphatase (ALP) activity and phoD gene (DNA) and transcript (RNA) abundance. Soil samples (0–15 cm) were collected from the Glenlea Long-term Rotation near Winnipeg, Manitoba, to compare organic, conventional and prairie management systems. In the greenhouse, pots of soil from each management system were amended with P as either soluble mineral fertilizer or cattle manure and then planted with Italian ryegrass (Lolium multiforum). Soils from each pot were sampled for analysis immediately and after 30 and 106 days. Significant differences among the soil/P treatments were detected for inorganic P, but not the organic P in NaHCO3-extracts. At day 0, ALP activity was similar among the soil/P treatments, but was higher after 30 days for all P amendments in soil from organically managed plots. In contrast, ALP activity in soils under conventional and prairie management responded to increasing rates of manure only, with significant effects from medium and high manure application rates at 30 and 106 days. Differences in ALP activity at 30 days corresponded to the abundance of bacterial phoD genes, which were also significantly higher in soils under organic management. However, this correlation was not significant for transcript abundance. Next-generation sequencing allowed the identification of 199 unique phoD operational taxonomic units (OTUs) from the metagenome (soil DNA) and 35 unique OTUs from the metatranscriptome (soil RNA), indicating that a subset of phoD genes was being transcribed in all soils.

Late season catch crops could be an effective tool to conserve highly available N after grazing of green manures. An experiment was established to investigate the productivity and N capturing abilities of barley (Hordeum vulgare cv. Cowboy) and oilseed radish (Raphanus sativus L.) crops seeded after a grazed green manure. Green manure was a mix of forage pea (Pisum sativum cv. 40–10), soybean (Gylcine max cv. Prudence) and oat (Avena sativa cv. Legget). The experiment was repeated twice in Carman, Manitoba in 2010 and 2011. Catch crops were seeded in late summer either no-till or after soil cultivation of the grazed plots. Wheat (Triticum aestivum cv. Waskada) was seeded in the second year as a test crop for both experiments. Catch crop productivity and N uptake was influenced by season (greater in the wetter year) and catch crop type (barley and radish produced 1990 and 1490 kg ha−1, respectively) but not tillage system. The catch crops had their greatest overall effect on soil NO3-N content in 2010 under conditions of high autumn precipitation when N leaching was more severe. Here, the catch crops significantly reduced NO3-N at all depths. Under drier conditions in 2011, catch crops only reduced NO3-N in the top 30 cm. There was average 57 and 12 kg ha−1 more soil NO3-N in plots with no catch crops than plots where catch crops were grown in 2010 and 2011, respectively. Wheat N uptake at maturity was reduced around 25% when grown after catch crops. Similarly, wheat grain yield was 12–31% less after catch crops than no catch crops. This study showed that catch crops can be used to capture excess nutrients after grazing, but N release from the selected catch crops in the following year was not in synchrony with the wheat N demand.

Studies comparing crop agronomic response in organic production systems under contrasting tillage practices are lacking. The objective of the study was to compare the effect of organic rotational no-till and two organic tilled systems on the basis of mulch biomass, soil chemical properties, weed control, and subsequent crop productivity. A field study consisting of two-year sequences was conducted three times at three close sites in Carman, Manitoba, Canada (2009–2010 at site A, 2010–2011 at site B, and 2011–2012 at site C), on Chernozem soils. Three management systems of cover crops were tested, in a randomized complete block design. A barley ( Hordeum vulgare L.)/hairy vetch ( Vicia villosa Roth) cover crop was grown in the first year of the study and terminated by rolling (no-till), rolling and tillage (Roll + Till), or haying and tillage (Hay + Till). Flax ( Linum usitatissimum L.) was seeded the following year. Our first hypothesis that a full-year growth of barley/hairy vetch cover crop allows the production of between 6 and 8 Mg ha −1 of mulch biomass for the subsequent crop was confirmed in two of three years. Flax was no-till seeded into 6.7, 7.7, and 4.2 Mg ha −1 of mulch at sites A, B, and C, respectively. At two of three sites, flax seed yields were significantly higher in no-till than in the two tillage treatments. There was no penalty on flax seed yield for haying the cover crop in mid-summer instead of incorporating it into the soil by tillage, across all three sites. There was an overall trend towards lower contents of soil nitrate-N in no-till, although it did not greatly influence total plant nitrogen uptake at two of three sites. This corroborates our second hypothesis that while flax N uptake would be reduced by the reduced soil N status in no-till, there will be sufficient N for optimum flax yield. The third hypothesis that barley/hairy vetch cover crop mulches have the ability to provide adequate weed control was generally supported, though there were important exceptions when insufficient mulch biomass was produced. Success of flax crop grown in an organic rotational no-till system in southern Manitoba depended on weather, mulch biomass production (>6.7 Mg ha −1 ), and weed species present. The fourth hypothesis that there is no yield penalty for eliminating tillage for 1.5 years in an organic flax crop in southern Manitoba held true only if that minimum mulch biomass benchmark of 6.7 Mg ha −1 was reached.

There is a need to design intensive cropping systems that can reap multiple benefits from annual forages including animal feed, soil fertility and weed control. Considering pea/oat (Pisum sativumcv. 40–10/Avena sativacv. Legget) as a standard green manure, this study investigated the productivity, weed competitiveness, utilization and nitrogen (N) benefit from grazed and ungrazed green manures to spring wheat (Triticum aestivumcv. Waskada) and fall rye (Secale cerealecv. Hazlet). A set of 3-year experiments was carried out in Carman, Manitoba, Canada in 2009, and was repeated in 2010 and 2011. Green manures were grazed by 2–3 ewes and 2–5 lambs for 24 h (1111–1667 sheep days per ha). Averaged over experiments pea/oat mix, hairy vetch (Vicia villosaL.) and sweetclover (Melilotus officinaliscv. Norgold) above-ground dry matter (DM) production were 5036, 5032 and 4064 kg ha−1, respectively. Lentil (Lens culinariscv. Indianhead), a mixture of seven species and soybean (Glycine maxcv. Prudence) produced the least amount of DM over 3 years; 3589, 3551, 3174 kg ha−1, respectively. Pea/oat and hairy vetch were the most weed-competitive species and, averaged over 3 years, contained less than 15% weed DM. Utilization of green manures by grazing animals varied little among species across years and ranged from 28 to 86% for individual species and years. When combined across experiments grazing increased N availability to the wheat crop. The grazing effect was significant for wheat DM production, N uptake and grain N, but not significant for yield across experiments. Averaged over 3 years, wheat took up 107 kg N ha−1from grazed plots versus 98 kg N ha−1from ungrazed plots. A significant species×management interaction for total (wheat+fall rye) N uptake in 2009 indicated that increasing the proportion of legumes in the green manure increased N benefit from grazing. Fall rye productivity was not affected by grazing. We recommend pea/oat and hairy vetch as two green manure species to enhance the overall system performance to achieve high level of DM production, good weed competition, utilization by sheep and provision of N benefit to the following wheat and fall rye crops.

Grazing green manures may improve N availability and productivity in integrated crop–livestock systems. We hypothesized that grazing green manures, compared with standard soil incorporation with tillage, would increase autumn soil profile NO3–N concentrations and grain yields in subsequent years. Three multiyear experiments were carried out for three years between 2009 and 2011 in Manitoba, Canada. For all three experiments, spring-seeded oat (Avena sativa cv. Leggett) and pea/oat (A. sativa/Pisum sativum cv. 40-10) green manure crops were grazed with sheep or left ungrazed in year one. Both treatments were soil incorporated with a tandem disk after grazing. Spring wheat (Triticum aestivum cv. Waskada) and fall rye (Secale cereale cv. Hazlet) test crops were grown in the second and third years, respectively. Biomass production was greater for pea/oat than oat in experiment 1; in experiment 2 pea/oat = oat; and in experiment 3 pea/oat

Water-extractable organic matter (WEOM) in soil affects contaminant mobility and toxicity, heterotrophic production, and nutrient cycling in terrestrial and aquatic ecosystems. This study focuses on the influences of land use history and agricultural management practices on the water extractability of organic matter and nutrients from soils. Water-extractable organic matter was extracted from soils under different crop rotations (an annual rotation of wheat-pea/bean-wheat-flax or a perennial-based rotation of wheat-alfalfa-alfalfa-flax) and management systems (organic or conventional) and examined for its concentration, composition, and biodegradability. The results show that crop rotations including perennial legumes increased the concentration of water-extractable organic carbon (WEOC) and water-extractable organic nitrogen (WEON) and the biodegradability of WEOC in soil but depleted the quantity of water-extractable organic phosphorus (WEOP) and water-extractable reactive phosphorus. The 30-d incubation experiments showed that bioavailable WEOC varied from 12.5% in annual systems to 22% for perennial systems. The value of bioavailable WEOC was found to positively correlate with WEON concentrations and to negatively correlate with C:N ratio and the specific ultraviolet absorbance of WEOM. No significant treatment effect was present with the conventional and organic management practices, which suggested that WEOM, as the relatively labile pool in soil organic matter, is more responsive to the change in crop rotation than to mineral fertilizer application. Our results indicated that agricultural landscapes with contrasting crop rotations are likely to differentially affect rates of microbial cycling of organic matter leached to soil waters.

Organic spring wheat (Triticum aestivum L.) breeding programs have been initiated, yet yield efficiency and N economy research is limited. We evaluated the performance of advanced lines selected from an organic breeding program initiated in 2003. Fourteen F8 and F9 lines in 2009 and 11 lines in 2010 were compared with commercial (check) cultivars. Field experiments were conducted under organic management at four site–years in Manitoba and Saskatchewan. Combined analysis showed no difference in biomass accumulation between organic lines and check cultivars; however, harvest index and grain yield were greater in organic lines compared with the checks. Organic lines were shorter than check cultivars, but yield efficiency, defined as kernel number per unit of crop biomass at anthesis, was higher (P

Field studies showed that hairy vetch (Vicia villosa) of “northern origin” produced more biomass than cultivars developed in milder climates. Hairy vetch biomass was greatest and weed biomass was l...

International audience; AbstractReduced tillage is increasingly promoted to improve sustainability and productivity of agricultural systems. Nonetheless, adoption of reduced tillage by organic farmers has been slow due to concerns about nutrient supply, soil structure, and weeds that may limit yields. Here, we compiled the results from both published and unpublished research comparing deep or shallow inversion tillage, with various categories of reduced tillage under organic management. Shallow refers to less than 25 cm. We found that (1) division of reduced tillage practices into different classes with varying degrees of intensity allowed us to assess the trade-offs between reductions in tillage intensity, crop yields, weed incidence, and soil C stocks. (2) Reducing tillage intensity in organic systems reduced crop yields by an average of 7.6 % relative to deep inversion tillage with no significant reduction in yield relative to shallow inversion tillage. (3) Among the different classes of reduced tillage practice, shallow non-inversion tillage resulted in non-significant reductions in yield relative to deep inversion; whereas deep non-inversion tillage resulted in the largest yield reduction, of 11.6 %. (4) Using inversion tillage to only a shallow depth resulted in minimal reductions in yield, of 5.5 %, but significantly higher soil C stocks and better weed control. This finding suggests that this is a good option for organic farmers wanting to improve soil quality while minimizing impacts on yields. (5) Weeds were consistently higher, by about 50 %, when tillage intensity was reduced, although this did not always result in reduced yields.

With 1 figure and 8 tables Abstract An important research question is whether wheat cultivars for organic production should be selected under organic field conditions. Yield, protein content and kernel weight (KWT) of seven populations of wheat (Triticum aestivum L.) selected in both organic and conventional growing conditions (termed selection environments) were compared at four organically and four conventionally managed sites (termed management environments). Selection environment was found to affect yield, protein and KWT in both management environments. At most sites, populations selected in organic environments had higher yields at organically managed sites relative to conventionally selected populations. When organically managed site-years were combined, the yields of organically selected populations were significantly higher than those of conventionally selected populations. Populations selected under organic management had higher protein content and KWT under both management environments. Direct selection in organically managed field conditions for genotypes targeted to organic agriculture offers advantages over indirect selection in conventionally managed field conditions.

Soil carbon stocks are useful indicators of both C sequestration capacity and sustainability of agricultural systems. Yet, most investigations have only studied the effects of agricultural management on soil carbon in surface layers (

Agricultural production systems that reduce the use of in-crop herbicides could greatly reduce risks of environmental damage and the development of herbicide-resistant weeds. Few studies have investigated the long-term effects of in-crop herbicide omissions on weed seedbank community size and structure. A crop-rotation study was sampled 10 yr after a strictly annual rotation and an annual/perennial rotation were exposed to different in-crop herbicide omission treatments. In-crop herbicides were applied either in all annual crops (control), omitted from oats only, or omitted from both flax and oats. Seedbank densities were greatest when in-crop herbicides were omitted from flax and oats, and this treatment also reduced crop yield. Shannon-Wiener diversity differed among crops in the annual crop rotation and among herbicide omission treatments in the perennial rotation. Herbicide omissions changed the weed-community structure in flax and in wheat and canola crops in the annual rotation enough to warrant alternate control methods in some treatments. The magnitude of the effects on the seedbank parameters depended largely on the competitive ability of the crop in which herbicides were omitted. No yield response to omitting herbicides in oats indicated that standard weed management practices have reduced weed populations below yield-loss thresholds.

Kirk, A. P., Entz, M. H., Fox, S. L. and Tenuta, M. 2011. Mycorrhizal colonization, P uptake and yield of older and modern wheats under organic management. Can. J. Plant Sci. 91: 663–667. Arbuscular mycorrhizal fungi (AMF) are important for plant nutrient uptake, and mycorrhizal dependence varies between wheat genotypes. Cultivar selection under fertilized conditions may have reduced mycorrhizal associations in modern cultivars. This study investigated AMF colonization, tissue P and grain yield of five modern (post 1990) and five older (pre 1970) spring wheat cultivars over 4 site-years in Manitoba. Older cultivars actually had significantly lower AMF colonization and grain yield than modern cultivars, but no tissue P concentration differences were observed. The two highest yielding lines were released after 2004, and one of these (FBC Dylan) was selected for suitability in organic farming systems.

Expansion of dry bean (Phaseolus vulgaris L.) production into saline soil areas of Manitoba has led to increased concern regarding its yield and quality response to soil salinity. The objective of this study was to evaluate the impact of salinity on dry bean productivity in southern Manitoba, including the application of a salt tolerance model for dry bean crops. Using a coulter-based sensor (Veris 3100, Veris Technologies, Salina, KS) to measure apparent soil electrical conductivity (EC a ), surveys of dry bean fields with five levels of soil salinity conditions (very low to very high salinity zones) were created for four sites over 2 yr. High values of EC a were associated with high values of soil saturation extract electrical conductivity (EC e ). Across all site years, average root-zone salinity (EC e ) values ranged from 0.77 to 11.16 dS m -1 . The lowest salinity zones resulted in greater crop biomass, grain yield, harvested seed weight, and grain number, and tended to have greater plant stand densities and grain protein content than the highest salinity zones. A 50% decrease in relative crop yield was caused by EC e values between 4.88 and 8.35 dS m -1 . EC a surveys were found to be an excellent tool for assessing the relative soil salinity status of study fields.

Organic farming systems often involve livestock and/or forages. However, managing soil nitrogen (N) availability by adjusting soil amendment rates and forage duration in crop rotations is a challenge. A 4-year experiment was conducted to evaluate N availability in the fourth year of organic potato systems with contrasting livestock and forage components. The experiment included three forage levels (0, 1, or 2 years of forage) through 4-year rotations starting with wheat (Triticum aestivum L.) and ending in potato (Solanum tuberosum L.). Within each forage level, three soil amendments (alfalfa meal, composted beef manure, and composted poultry manure) represented nutrient sources from stockless, ruminant, and monogastric systems, respectively. As farmers do, we modified the amendment application rate and timing by taking a system approach to reflect crop rotations. Nitrogen availability was higher in alfalfa meal compared with the composts varied with feedstocks. Nitrogen supply from soil amendments differ...

Land management practices affecting soil erosion risk on organic and conventional farms were described using a mail-out survey. Organic farmers had more forages and green manures in rotation than conventional farmers (66 vs. 46% and 84 vs. 6%, respectively). Organic farmers used more tilled summerfallow (52%) than conventional farmers (6%). Tilled summerfallow represents a risk to soil sustainability on organic farms; however, the net effect of common organic management practices (e.g., green manuring, composting and tillage) on soil erodibility is not known. Determing the combined effect of management practices as well as finding alternatives to tilled summerfallow should be research priorities.Key words: Soil erosion risk, tillage, crop rotation, summerfallow

Phosphorus is a nonrenewable resource, raising concerns that agricultural practices may deplete reserves. Organic farming with low P inputs can result in deficient levels of plant-available phosphorus (available-P). The purpose of this study was to determine if common organically managed rotations are depleting P reserves or iflarge reserves still exist in unavailable forms. The research was performed in the 13th year of the Glenlea Long-term Crop Rotation and Management study in southern Manitoba. The site has three 4-yr rotations under Organic and Conventional management: spring wheat (Triticum aestivum L.)-alfalfa (Medicago sativa L.)-alfalfa-flax (Linum usitatissimum L.) (forage grain) with and without manure compost, and spring wheat-field pea (Pisum sativum L.)-spring wheat-flax (grain only), as well as a restored prairie grass planting (Prairie). Conventional treatments received synthetic fertilizers and herbicides whereas the Organic received no inputs other than a one-time application of manure compost. The modified Hedley sequential P extraction procedure revealed organic management to have lower concentrations of readily available P than conventional but recalcitrant forms were similar between systems. The Prairie had P concentrations similar to conventional in all forms. Estimated cumulative P balance indicated that organic grain-only rotations compared to conventional had low P removal resulting in slightly lower concentration of available-P forms. The high yielding and P removal rotation of forage-grain decreased available-P forms to below an agronomic response threshold. Only high yielding, high P export organic rotations are a concern for developing P deficiency depending on initial reserves and the length of time without additional inputs.