Semiarid Canadian Prairies Research Articles

Comparing rooting characteristics and soil water withdrawal patterns of wheat with alternative oilseed and pulse crops grown in the semiarid Canadian prairie

Cutforth, H. W., Angadi, S. V., McConkey, B. G., Miller, P. R., Ulrich, D., Gulden, R., Volkmar, K. M., Entz, M. H. and Brandt, S. A. 2013. Comparing rooting characteristics and soil water withdrawal patterns of wheat with alternative oilseed and pulse crops grown in the semiarid Canadian prairie. Can. J. Soil Sci. 93: 147–160. To improve sustainability and increase economic returns, producers in the semiarid Canadian prairie are diversifying their cropping systems to include alternative crops such as pulses and oilseeds in rotation with wheat. Producers must adopt crops and cropping systems that use water most efficiently. We compared the root systems and water withdrawal patterns for three pulse crops (leguminous grain crops) [chickpea (Cicer arietinum L.), pea (Pisum sativum L.) and lentil (Lens culinaris Medik. L.)] and three oilseed crops [canola (Brassica napus L. and Brassica rapa L.) and mustard (Brassica juncea L.)] with one cereal crop [wheat (Triticum aestivum L.)] under well-watered, rain-fed, imposed drought water regimes during 1996–1998. Wheat withdrew the most water, whereas pulses withdrew the least amount of water from the soil profile. Pulses withdrew substantially less water than oilseeds and wheat below about the 80-cm depth, whereas oilseeds withdrew less water than wheat from the upper regions of the soil profile, thus increasing soil water available to the following crops. Therefore, producers can increase the overall efficiency of a crop rotation by growing deeper rooting crops, such as wheat and canola, following pulses, and by growing crops, such as wheat, that will use the increased soil water reserves following canola.

Yield of spring wheat and field pea seeded into standing and cultivated canola stubble on the semiarid Canadian prairie

Cutforth, H. 2013. Yield of spring wheat and field pea seeded into standing and cultivated canola stubble on the semiarid Canadian prairie. Can. J. Plant Sci. 93: 287–289. Previous research in the semiarid prairie showed that crop yields increased as the height of standing cereal stubble increased to ≥45 cm. A 3-yr (2008–2010) study was conducted at Swift Current, SK, to determine how seeding field pea and spring wheat into cultivated and tall (≥45 cm high) canola stubble affected crop yield. Similar to cereal stubble, crop yield and water use efficiency were significantly greater for crops grown in the tall standing canola stubble compared to the cultivated stubble. Water use by each crop was independent of stubble management.

Temperature trends in the semiarid prairie of southwestern Saskatchewan revisited

Cutforth, H. and Judiesch, D. 2012. Temperature trends in the semiarid prairie of southwestern Saskatchewan revisited. Can. J. Soil Sci. 92: 803–806. Average annual and seasonal temperatures for 1950–2007 were compared with 1950–1997 for warming trends in the semiarid Canadian prairie south of Swift Current, SK. The additional 10 yr did not alter the direction or magnitude of the warming trends. Briefly, late winter–early spring (January through April) continued to experience the largest warming trend, whereas there continued to be no warming trend for the fall–early winter (September through December) period.

Temperature trends in the semiarid prairie of southwestern Saskatchewan revisited

Cutforth, H. and Judiesch, D. 2012. Temperature trends in the semiarid prairie of southwestern Saskatchewan revisited. Can. J. Soil Sci. 92: 803-806. Average annual and seasonal temperatures for 1950-2007 were compared with 1950-1997 for warming trends in the semiarid Canadian prairie south of Swift Current, SK. The additional 10 yr did not alter the direction or magnitude of the warming trends. Briefly, late winter-early spring (January through April) continued to experience the largest warming trend, whereas there continued to be no warming trend for the fall-early winter (September through December) period.

Carbon footprint of spring wheat in response to fallow frequency and soil carbon changes over 25 years on the semiarid Canadian prairie

Growing interest in environmental quality has provided a strong incentive to examine how farming practices affect agricultural products’ carbon footprints (CF), an environmental quality indicator. This study determined (i) the CF of spring wheat (Triticum aestivum L.) grown in different cropping systems over 25 years, and (ii) the effect of soil organic carbon (SOC) changes over years on wheat CF. Wheat was grown in four cropping systems: (a) fallow-wheat (FW), (b) fallow-wheat-wheat (FWW), (c) fallow-wheat-wheat-wheat-wheat-wheat (FWWWWW), and (d) continuous wheat (ContW), in replicated field plots in Saskatchewan, Canada. Wheat CF was calculated at a system level with measured variables coupled with modeling approaches. Over the 25-year period, the soil under the ContW system gained organic C of 1340kgCO2eqha−1 annually, or 38%, 55%, and 127% more than those gained in the FWWWWW, FWW, and FW systems, respectively. The SOC gain more than offset the greenhouse gas (GHG) emissions occurred during wheat production, leading to negative emission values at −742kgCO2eqha−1 annually for ContW, and −459, −404, and −191kgCO2eqha−1 for FWWWWW, FWW, and FW systems, respectively. Wheat in the ContW system produced the highest grain yield and gained highest SOC over the years, leading to the smallest (more negative) CF value at −0.441kgCO2eqkg−1 of grain, significantly lower than the CF values from the three other systems (−0.102 to −0.116kgCO2eqkg−1 of grain). Without considering the SOC gain in the calculation, wheat CF averaged 0.343kgCO2eqkg−1 of grain and which did not differ among cropping systems. Wheat is the largest agricultural commodity in Saskatchewan, and the way the crop is produced has significant impacts on environmental quality, reflected by its carbon footprint. Cropping systems with decreased fallow frequency was shown to significantly enhance soil carbon gains over the years, increase annualized crop yields, and effectively lower the carbon footprint of this important commodity.

Extra-tall stubble can increase crop yield in the semiarid Canadian prairie

Cutforth, H., McConkey, B., Angadi, S. and Judiesch, D. 2011. Extra-tall stubble can increase crop yield in the semiarid Canadian prairie. Can. J. Plant Sci. 91: 783–785. Previous research in the semiarid prairie showed that crop yields increased as the height of standing stubble increased to 30 cm. Recent technology permits seeding into higher standing stubble. A 3-yr (2001–2003) study was conducted at Swift Current, SK, to determine how seeding canola, pulse, and wheat into cultivated, short (about 15 cm high), tall (about 30 cm high), and extra-tall (about 45 cm high) standing stubble affected crop yield. Crop yield and the overall average water use efficiency increased linearly as stubble height increased to 45 cm. Water use was independent of stubble height.

Effects of input management and crop diversity on economic returns and riskiness of cropping systems in the semi-arid Canadian Prairie

AbstractProducers in the semi-arid Dark Brown Chernozemic (Typic Boroll) soil zone of the Canadian Prairie are contemplating changes to land-use practices, moving away from conventional high-input production systems that specialize in one or two annual grain crops to more diversified and extended cropping systems that use reduced-input and organic management practices. This study examined the economic merits of nine cropping systems, consisting of a factorial combination of three input management methods and three levels of cropping diversity. It was conducted over the 1996–2007 period on a loam soil at Scott, Saskatchewan. The input treatments were: (1) high input (HIGH), which used conventional tillage and full recommended rates of fertilizers and pesticides ‘as required’; (2) reduced input (RED), which used conservation tillage and integrated weed and nutrient management practices in an effort to lower requirements for fuel, fertilizers and pesticides; and (3) organic input (ORG), which used tillage, non-chemical pest control, higher seeding rates, delayed seeding and legume crops to replenish soil nutrients. The crop diversity treatments included: (1) a fallow-based rotation with low crop diversity (LOW); (2) a diversified annual rotation of cereal, oilseed and pulse grains (DAG); and (3) a diversified rotation using annual grains and perennial forages (DAP). All crop rotations were 6 years in length. At the 2007 input costs and prices, average net returns and 12-year net present values were higher for organic than for non-organic treatments, with the ORG input/LOW crop diversity system being the most profitable (net returns=$234 ha−1yr−1and net present value=$1953 ha−1). Net returns averaged about 10% less for ORG/DAG compared to the most profitable system, and about 22% less for HIGH/DAG and RED/DAG (the best non-organic systems). The DAP treatments that included forage were not economically competitive with the other treatments, often producing economic losses. The relative profitability of the organic treatments was highly dependent on the existence of organic price premiums. When price premiums for organic crops were reduced to less than 70% of the 2007 levels, the organic treatments were less profitable than the comparable non-organic treatments. The organic treatments also experienced significantly lower (and often negative) net returns compared to the non-organic treatments during completion of the 3-year organic certification period. We estimated that it required 5–7 years after completion of certification for the organic treatments to break even with the comparable non-organic treatments. Thereafter the organic treatments produced consistently higher net earnings. Production costs averaged 16% lower with ORG management compared to the HIGH-input treatments, but we found little difference in total costs between the respective HIGH- and RED-input treatments. The organic treatments also displayed lower income variability than the non-organic treatments, with the ORG/LOW system being preferred by risk-averse producers, who do not subscribe to all-risk crop insurance, and with the ORG/LOW and ORG/DAG systems preferred by low and medium risk-averse producers when having the added financial protection from the Canada/Saskatchewan all-risk crop insurance program.

Cropping frequency and N fertilizer effects on soil water distribution from spring to fall in the semiarid Canadian prairies

In the semiarid Canadian prairies, water is the most limiting and nitrogen (N) the second most limiting factor influencing spring wheat (Triticum aestivum L.) production. The efficiency of water- and nitrogen use needs to be assessed in order to maintain this production system. The effects of cropping frequency and N fertilization on trends in soil water distribution and water use were quantified for an 18-yr (1967-1984) field experiment conducted on a medium textured Orthic Brown Chernozem (Aridic Haploboroll) in southwestern Saskatchewan, Canada. Soil water contents were measured eight times each year and plant samples were taken at five phenological growth stages. The treatments studied were continuous wheat (Cont W), summer fallow - wheat, F-(W) and summer fallow - wheat - wheat, F-W-(W) each receiving recommended rates of N and phosphorus (P) fertilizer, and (F)-W-W and (Cont W) each receiving only P fertilizer, with the examined rotation phase shown in parentheses. Soil water conserved under fallow during the summer months averaged 25 mm in the root zone, and was related to the initial water content of the soil, the amount of precipitation received, its distribution over time, and potential evapotranspiration. Under a wheat crop grown on fallow, soil water contents between spring and the five-leaf stage remained relatively constant at about 250 mm, but those under a stubble crop, with 40 mm lower spring soil water reserves, increased slightly until about the three-leaf stage. During the period of expansive crop growth (from the five-leaf to the soft dough stage) soil water was rapidly lost from all cropped phases at rates of 1.87 mm·day –1 for F-(W) (N+P), 1.23 mm·day –1 for Cont W (N+P) and 1.17 mm·day –1 for Cont W (+P). The initial loss was from the 0 - 0.3 m depth, but during the latter half of the growing season from deeper depths, although rarely from the 0.9 - 1.2 m depth. In very dry years (e.g., 1973, with 87 mm precipitation between spring and fall) summer fallow treatments lost water. In wet years with poor precipitation distribution (e.g., 1970, with 287 mm precipitation between spring and fall but 142 mm of this in one week between the three- and five-leaf stages) even cropped treatments showed evidence of leaching. The above-ground biomass water use efficiency for Cont W was 19.2 and 16.7 kg·ha –1 ·mm –1 , respec

Canola Response to ESN and Urea in a Four‐Year No‐Till Cropping System

Nitrogen fertilizer is a major input cost in canola (Brassica napus L.) production and farmers are interested in improving N use efficiencies. A multi‐site study in western Canada was conducted to determine the merits of polymer‐coated urea (Environmentally Smart Nitrogen, ESN) compared with urea on weed management and yield of hybrid and open‐pollinated (OP) canola. Treatments included a hybrid and OP canola cultivar, ESN and urea, 100 and 150% of soil test N fertilizer rates, and 50 and 100% of registered in‐crop herbicide rates. Canola was grown in rotation with barley (Hordeum vulgare L.) in a no‐till system and both crops of the rotation were present each year. Fertilizer and herbicide rate treatments were applied to the same plots in four consecutive years to determine annual and cumulative effects. Hybrid compared with OP canola reduced weed tissue N concentration in 40% of the cases and reduced weed biomass in 80% of the cases. Additionally, weed tissue N concentration was lower with ESN than with urea in 70% of the cases, indicating that crop–weed competition for soil N might be reduced if ESN were used. Canola yield was greater for the hybrid cultivar in 15 of 20 site‐years. Both cultivars expressed a positive yield response to the 150% N fertilizer rate in 10 of 20 site‐years. This yield response occurred in three additional site‐years with hybrid canola, indicating that hybrid cultivars have a higher N demand under favorable growing conditions. Canola yield was similar with ESN and urea in 14 of 20 site‐years. The ESN compared with urea increased canola yield in 4 site‐years and in one additional site‐year for hybrid canola, indicating that ESN may be advantageous in some situations. Canola seed oil concentration was similar with ESN and urea in 19 of 20 site‐years. Information gained in this study will be used to develop improved fertilization strategies for canola production on the semiarid Canadian prairies.

Suitability of legume cover crop-winter wheat intercrops on the semi-arid Canadian Prairies

Farmers on the Canadian prairies are interested in including legume cover crops in their cropping systems to reduce fertilizer inputs and improve farm sustainability. A field study was conducted to determine the merits of establishing alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.) or Austrian winter pea (Pisum sativum L.) cover crops in fall or in spring with winter wheat (Triticum aestivum L.). Spring-planted legumes emerged well within the winter wheat crop, but their growth was limited under these semi-arid conditions. Fall-planted red clover had low plant densities following winter in two of three experiments and fall-planted winter pea reduced winter wheat yield by 23 to 37% compared with the no cover crop control. In contrast, fall-planted alfalfa exhibited good winterhardiness, provided some weed suppression without reducing winter wheat yield, caused only a slight reduction in soil water content, and contributed an extra 18 to 20 kg ha-1 of available soil N at the time of seeding the following spring crop. Additionally, fall-planted alfalfa increased the yield of succeeding canola (Brassica napus L.) in unfertilized plots in two of three experiments. Further research is warranted to better understand the agronomic and economic benefits of alfalfa-winter wheat intercrops under a wider range of environmental conditions.Key words: Cover crops, intercropping, relay crops, soil nitrogen, soil conservation

Comparing plant water relations for wheat with alternative pulse and oilseed crops grown in the semiarid Canadian prairie

Understanding the drought physiology of alternate crops is essential to assess the production risks of new cropping systems. We compared the water relations of dry (field) pea (Pisum sativum L.), chickpea (Cicer arietinum L.), canola (Brassica napus L.) and mustard (Brassica juncea L.) with spring wheat (Triticum aestivum L.) under different moisture availabilities in field trials conducted in 1997 and 1998 at Swift Current, SK. Stress experience and stress responses varied with crop type. In general, there were similarities in drought physiology between the two pulse crops and between the two oilseed crops. The mean predawn leaf water potential of pea was frequently lowest, while the mean midday leaf water potential of wheat was at least -0.40 MPa lower than for any other crop. The crops exhibited different strategies to overcome water stress. Wheat had the lowest osmotic potential at full turgor, except under drought when turgor was lowest for chickpea and wheat; the highest values were observed in Brassica spp. Mean midday pressure potentials were lowest in wheat (and mostly negative, indicating loss of turgor) and highest for the pulse crops. Mean midday pressure potential for canola was positive when well-watered, otherwise it was near 0. Despite lowering osmotic potential, wheat could not maintain positive turgor much of the time at midday. Pulse crops, with the contributions from both osmotic adjustment and cell elasticity, maintained positive turgor over a wider range of water potentials compared with the other crops. With regard to both osmotic adjustment and tissue elasticity, we ranked the crops from high to low ability to adjust to moderate to severe water stress as pulses > wheat > Brassica oilseeds. Key words: Leaf water, osmotic, turgor potentials, wheat, pulse, canola, semiarid prairie

Fertilizer N response and canola yield in the semiarid Canadian prairies

Canola is a viable crop when grown under fallow in the semiarid prairie, but is also grown in longer rotations, most often no-till seeded into standing stubble. Selecting the proper N fertilizer rate is a very challenging production decision, but most of the available nitrogen response for canola has been derived for the more subhumid parts of the Canadian prairies. We developed simple quadratic equations to describe the yield relationship for stubble-seeded open-pollinated and hybrid canola in the semiarid Canadian prairie. These relationships indicate that hybrid canola produced higher grain yields at all fertilizer rates and had optimum N fertilizer rates about 50% higher than those for open-pollinated canola. Key words: Canola, fertilizer N, grain yield, water use, semiarid prairie

Nitrogen mineralization under summer fallow and continuous wheat in the semiarid Canadian prairie

The ability of soils to provide a portion of the N required by crops via N mineralization of organic matter is of economic and environmental importance. Over a 40-yr period (1967–2006), soil NO3-N and plant-N measurements were made under summer fallow and in systems cropped to spring wheat (Triticum aestivum L.), on a medium-textured Orthic Brown Chernozem (Aridic Haploboroll), at Swift Current, Saskatchewan. These values were used to estimate net N mineralization (Nmin). Each year, above-ground plant N was measured at harvest and soil NO3-N was measured before seeding, soon after harvest, and just prior to freeze-up in October. Also, in the first 18 yr of this study NO3-N and above-ground plant N were measured eight times between spring and fall in selected treatments; these data were used to make a more detailed estimate of Nmin. In a third experiment, conducted on the same soil at a nearby site in 1975, many small lysimeters were sampled six times between spring and harvest of spring wheat. We used this lysimeter study to assess the effect of N fertilizer rate and soilwater on net Nmin. Results from the more frequent sampling were more plausible than those from sampling at three different times per year. On average, net Nmin in the 20-mo summer fallow period was about 118 kg ha-1 (15 kg ha-1 between harvest and the first spring, 93 kg ha-1 between the first spring and second fall, and 10 kg ha-1 between the second fall and seeding). The average net Nmin under a wheat crop between spring and fall was between 53 and 63kg ha-1. Net Nmin increased with water, but excessive water appeared to reduce apparent net Nmin, probably due to leaching and denitrification losses of N, which were not assessed in our estimation of Nmin. Regression analysis was used to show a positive association between net Nmin and precipitation, between spring and fall, for most of the systems examined. There was evidence that tillage promotes N mineralization. At normal rates of N fertilizer (i.e., < 100 kg ha-1), fertilizer had no effect on Nmin. Net Nmin was directly proportional to fallow frequency, averaging 68, 83, and 90 kg ha-1 yr-1 for continuous wheat, fallow-wheat-wheat, and fallow-wheat rotations, respectively. Although our results may only be applicable to medium-textured soils of similar organic matter content in the Brown and Dark Brown Chernozemic soil zone, they provide data and information against which process-based models can be tested. They also provide useful first approximations of Nmin measured under field conditions where few long-term data currently exist. Key words: N mineralization, plant-N, fertilizer-N, crop rotation, irrigation, tillage

Adaptation of alternative pulse and oilseed crops to the semiarid Canadian Prairie: Seed yield and water use efficiency

Diversification and intensification of the cropping systems in the traditional wheat-fallow area of the semiarid Canadian prairie is necessary to improve sustainability. Selection of alternate crops to include in cropping systems requires information on production risks with different climate regimes. To understand water use/yield relationships of alternate crops, three pulse crops (leguminous grain crops) [chickpea (Cicer arietinum L.), pea (Pisum sativum L.) and lentil (Lens culinaris Medik.)], three oilseed crops [canola (Brassica napus L. and B. rapa L.) and mustard (B. juncea L.)], and one cereal crop [wheat (Triticum aestivum L.)] were studied under varying water regimes: during 1996–1998 under well-watered, rainfed, imposed drought conditions, and in 2001 under rainfed conditions. Generally, the relative ranking between crops for water use was maintained across water regimes, such that the crops separated into three general groups of water users (high: wheat, B. napus, mustard; medium: chickpea, B. rapa, lentil; low: pea) with pea using an average of 34 mm and 13 mm less water than high- and medium-water-using crop groups, respectively. The exceptions included desi chickpea, which tended to use less water and B. rapa, which tended to use more water relative to the other crops as water use decreased. Generally, pea and wheat produced the most grain and biomass, had the highest water use efficiency, and had moderately high to high harvest indices. Wheat and pea are well adapted to variable rainfall amounts inherent in semiarid climates. Desi chickpea and lentil produce good grain yields under dry conditions, and grain yields relative to those of other crops can be increased by some drought stress, especially mid- to late-season stress. Therefore, because of their relatively good performance under water-stressed conditions, they are also well adapted to semiarid climates. Conversely, the Brassica oilseeds yielded relatively poorly compared with wheat and pulse crops under severe water-stressed conditions, so they are not as well adapted to the semiarid climate. In 2001, grain yield of wheat and pulses seeded on stubble was ≥30% of the yield on fallow, whereas stubble-seeded Brassica oilseeds yielded only about 10% of that on fallow. Compared with stubble seeding, production of Brassica oilseeds on fallow will decrease the risk of very low yields under drought. We found little indication that mustard was more drought tolerant than B. napus. Key words: Yield, water use efficiency, oilseeds, pulse, semiarid prairie

Meeting water requirements of cattle on the Canadian prairies

This paper examines some of the issues producers have in meeting the drinking water requirements of livestock on the Canadian prairies where they are dependent on varied ground and surface water sources. In supplying water for their cattle, producers often have problems that can affect their present and future operations. Water quality is one such problem as it can affect both the health and performance of livestock. The impact of the water quality in earthen reservoirs, the presence of sulphates in both surface and ground water, and toxins from cyanobacteria all have the potential to reduce herd productivity in the Canadian prairies. Another concern is the impact that grazing cattle can have on riparian vegetation, stream morphology, fish habitat and pollution of waterways. Damage is often caused by uncontrolled and season long grazing of cattle along water courses; options for controlling the damage are discussed. Finally, competition for a diminishing supply of water in the semi-arid Canadian prairies will become a major problem in the future. To remain viable and competitive, the livestock industry will have to develop and adopt strategies to address these issues.

Effect of dew temperature, post-inoculation condition, and pathogen dose on suppression of scentless chamomile by Colletotrichum truncatum1

Scentless chamomile, a noxious weed in western Canada, has a high natural tolerance to many herbicides. Colletotrichum truncatum, a host specific fungal pathogen, is suppressive to scentless chamomile when applied inundatively. A broadcast application was used at 200 L ha−1 to evaluate biocontrol potential of this pathogen under a range of dew temperatures (DT), post-inoculation conditions (PIC), and pathogen doses (PD). A DT between 20 and 25°C was more conducive to infection, resulting in higher levels of disease and weed suppression as compared to 15 and 30°C. Under similar post-inoculation temperature regimes, disease was only slightly more severe in growth chambers than in the greenhouse. There was a positive linear relationship between the PD and weed suppression. An inoculum concentration >1×108 spores mL−1 reduced plant fresh weight by approximately 50% when compared to untreated controls. These results indicate that biocontrol of scentless chamomile using C. truncatum in the semi-arid Canadian prairies will likely encounter frequent non-favourable field conditions.

Stubble management and microclimate, yield and water use efficiency of canola grown in the semiarid Canadian prairie

Standing stubble traps snow and creates a favorable microclimate, which increases yields in wheat (Triticum aestivum L.) and pulses [chickpea (Cicer arietinum L.), field pea (Pisum sativum L.) and lentil (Lens culinaris L.)]. Generally, the taller the stubble the greater is the effect on microclimate and yield. A field study using farm-scale seeding and harvesting equipment was conducted over four seasons (1999 to 2002) to assess the effect of stubble management on the microclimate, water use and seed yield of argentine canola (Brassica napus L. ‘Arrow’) in the semiarid prairie surrounding Swift Current. Tall (30 cm), short (15 cm) and cultivated stubble treatments were deployed in fall and in spring. An additional tall stubble treatment with extra fertilizer N (application rate recommended for the Black soil zone in the subhumid prairie) was included to assess the role of fertilizer in canola response to stubble management practices. The differences in wind velocity, soil temperature and solar radiation reaching the soil surface indicated significant modification of the microclimate by tall compared with cultivated stubble. Yields were highest from the tall stubble receiving extra fertilizer. Further research is needed to determine optimum fertilizer rates to maximize canola yields in the semiarid prairie. For treatments receiving equivalent rates of fertilizer, tall stubble increased seed yield of canola by about 24% and water use efficiency (WUE) by about 19% compared with stubble cultivated in the fall. Comparing between stubble treatments deployed on fields that overwintered as tall stubble and which received equivalent rates of fertilizer, tall stubble increased canola yield by about 16% and WUE by about 11% compared with cultivated stubble. Crop water use was not affected by stubble management so the increased grain production was due to increased WUE. Key words: Stubble height, microclimate, canola, yield, water use efficiency

Response of lentil to microbial inoculation and low rates of fertilization in the semiarid Canadian prairies

The use of microbial inoculation may increase nodulation and seed yield of annual legumes. A study was conducted to determine the effect of formulations (seedapplied powder vs. soil-applied granular inoculants), placement of granular inoculants in soils (applied in the seed-row vs. sidebanded), and low rates of fertilizers in comparison to P-solubilizing microbes Penicillium bilaii on plant establishment, maturity, and seed yield of lentil (Lens culinaris Medik.) in the semiarid Canadian prairies. Green lentil was grown on a silt loam and a heavy clay soil in southwestern Saskatchewan from 1999 to 2002. Inoculated lentil with Rhizobium increased seed yield by 45% averaged across all 6 site-years. Granular soil inoculants increased lentil seed yield by 19% over seed-applied inoculants. Placement of soil inoculants in the seed row or side-bands produced similar results. On the silt loam soil, the use of rhizobial inoculants increased lentil seed yield by 15%, while the yield increase was 70% on the heavy clay. Starter N applied at a rate of 15 kg ha-1 increased seed yield by 13% for lentil grown on the heavy clay, but there was no effect on the silt loam. Phosphorus fertilizer applied at a rate 15 kg P ha-1 did not influence lentil establishment, growth or seed yield. Similarly, the P-solubilizing microbes P. bilaii did not influence plant growth or development, nor did it affect the seed yield of lentil. Soil granular rhizobial inoculants are preferred over seed-applied inoculants, fertilizers, or P-solubilizing microbes in lentil because of their strong and consistently positive impact on plant growth and seed yield in the semiarid Canadian prairies. Key words: Lens culinaris, nodulation, seed yield, Penicillium bilaii, P-solubilizing microbes

Effect of formulation and placement of Mesorhizobium inoculants for chickpea in the semiarid Canadian prairies

The use of bacterial inoculants can increase root nodulation and the seed yield of annual legumes. A six site-year study was conducted to determine the effect of formulations (peat-based powder vs. granules) and placement in the soil (seed-row vs. side-band) of Mesorhizobium inoculants on plant establishment and seed yield of chickpea (Cicer arietinum L.) in the semiarid Canadian prairies. Two market classes of chickpea, namely desi and kabuli, were grown on silt loam and heavy clay soils in southwestern Saskatchewan from 1999 to 2002. Inoculation reduced plant population by 10% for desi chickpea, but had no effect on kabuli chickpea. However, the use of inoculant increased seed yield by an average of 35% for desi chickpea and 7% for kabuli chickpea. On the heavy clay, soil inoculation increased seed yield by 16% for desi and 9% for kabuli compared with seed inoculation, whereas the yield increase due to soil inoculation, over seed inoculation, was 3% when the crops were grown on the silt loam. Granular inoculant applied in the seed row produced similar seed yields to side-banded inoculant. Inoculation delivery systems had a marginal impact on plant height, with no effect on the lowest pod height from the soil surface or days to maturity. Regardless of placement, soil inoculation with a granular form of Mesorhizobium was preferred over seed inoculation because of its greater positive impacts on plant establishment and seed yield for both desi and kabuli chickpea in this semiarid region. Key words: Cicer arietinum, seed weight, heavy clay, silt loam, harvestability

Soil microbial populations and activities as influenced by legume green fallow in a semiarid climate

Tilled fallow–wheat ( Triticum aestivum L.) (F–W) is the most commonly used cropping system in the semiarid Canadian prairie. However, because frequent fallowing degrades soil, a partial fallow with annual legumes as green manure [i.e. ‘green fallow’ (GF)] has been proposed as a soil conserving and more bio-resource efficient alternative to bare fallow. We conducted a 6-year study to compare the influence of four GF–W, a F–W and a continuous W (Cont. W) system, on soil microbial communities, microbial biomass (MB) and activities in an Orthic Brown Chernozem, silt loam (Aridic Haploboroll) at Swift Current, Sask., Canada. The four GF legumes used were black lentil ( Lens culinaris Medikus), Tangier flatpea ( Lathyrus tingitanus L.), chickling vetch ( Lathyrus sativus L.) and feedpea ( Pisum sativum L.). They were grown to full bloom and then incorporated with a tandem disk. Analysis of soil taken from 0 to 10 cm depth after growing wheat in the sixth year of the experiment (i.e. 15 months after the most recent legume GF had been turned under) showed that most of the soil biochemical and microbiological attributes assessed were significantly improved (compared to F–W) by increasing cropping intensity (Cont. W), and even more by using the GF systems. The average improvement gained from the four GF legumes relative to F–W, was 385% for number of bacteria, 210% for filamentous fungi, 170% for MB-C, 191% for MB-N, 205% for cumulative C mineralization in 30 days at 21 °C, 202% for dehydrogenase, 171% for phosphatase, and 287% for arylsulfatase activity. The biologically active C and N, when expressed as ratios of MB-C or MB-N to total soil C or N, increased from 1.6 and 2.0% in F–W to 1.9 and 2.6% in Cont. W and to an average of 2.4 and 3.5% in GF–W. A sensitivity analysis (ratio of other treatment values to value for F–W) showed that Cont. W, and the GF–W systems even more, increased all major soil biological attributes tested. Among the GF systems, lentil-W consistently increased sensitivity the most, while Tangier flatpea-W usually increased it the least. The dynamic direct and indirect microbiological attributes were more sensitive indicators of changes in soil productivity than total organic C or N. The sensitivity of the attributes decreased in the sequence: Bacteria>Arylsulfatase>Filamentous fungi≈Cumulative C mineralization≈Dehydrogenase>MB-N>Phosphatase≈MB-C. Compared to the earlier published sensitivities of select physical and chemical attributes of soil quality to these same agronomic treatments, the microbiological attributes proved to be far more sensitive and more responsive to the beneficial influence of legume green fallowing in this semiarid loam.