Toby Entz

Differential response of weed species to added nitrogen

Abstract Information on responses of weeds to various soil fertility levels is required to develop fertilizer management strategies as components of integrated weed management programs. A controlled environment study was conducted to determine shoot and root growth response of 23 agricultural weeds to N fertilizer applied at 0, 40, 80, 120, 180, or 240 mg kg−1 soil. Wheat and canola were included as control species. Shoot and root growth of all weeds increased with added N, but the magnitude of the response varied greatly among weed species. Many weeds exhibited similar or greater responses in shoot and root biomass to increasing amounts of soil N, compared with wheat or canola. With increasing amounts of N, 15 weed species showed a greater increase in shoot biomass, and 8 species showed a greater increase in root biomass, compared with wheat. Ten weed species exhibited increases in shoot biomass similar to that exhibited by canola, and five weed species showed greater increases in root biomass than did canola, as N dose was increased. All crop and weed species extracted > 80% of available N at low soil N levels. At the highest N dose, 17 of 23 weed species took up similar or greater amounts of soil N than did wheat, and 6 weed species took up N in amounts similar to that taken up by canola. These findings have significant implications as to how soil fertility affects crop–weed competition. The high responsiveness of many weed species to N may be a weakness to be exploited through development of fertilizer management methods that enhance crop competitiveness with weeds. Nomenclature: Canola, Brassica napus L. ‘Excel’; spring wheat, Triticum aestivum L. ‘Katepwa’.

Weed species response to phosphorus fertilization

Abstract Information on weed responses to soil fertility levels is needed to aid development of fertilizer management strategies as components of integrated weed management programs. A controlled environment study was conducted to determine shoot and root growth response of 22 agricultural weeds to fertilizer phosphorus (P) applied at 5, 10, 20, 40, or 60 mg kg−1 soil. An unfertilized control was included. Wheat and canola were included as control species. Shoot and root growth of all weeds increased with added P, but the magnitude of the response varied greatly among species. Many weeds exhibited similar or greater responses in shoot and root biomass to increasing amounts of soil P compared with wheat or canola. With increasing amounts of P, 17 weed species increased shoot biomass more than wheat, and 19 weed species increased shoot biomass more than canola. However, only 10 weed species exhibited greater increases in root biomass than canola, and no weed species increased root biomass more than wheat with added P. Canola was among species taking up the greatest percentage of available P at all P doses. However, percentage P uptake by wheat relative to other species varied with P dose. Only four weed species extracted more P than wheat at low P levels, but 17 weed species extracted more P at high soil P levels. These findings have significant implications as to how soil fertility may influence crop–weed competition. Nomenclature: Canola, Brassica napus L. ‘Excel’; spring wheat, Triticum aestivum L. ‘Katepwa’.

EFFECTS OF DIETARY SUNFLOWER SEEDS ON RUMEN PROTOZOA AND GROWTH OF LAMBS

Linoleic acid-rich sunflower-seed supplements (SSS) were used in two experiments (experiment 1, high-concentrate diets; experiment 2, high-forage diets) to study effects on rumen protozoa and the growth of lambs. Both experiments consisted of four treatments, two with a low-protein diet (120 g/kg) and two with a high-protein diet (160 g/kg). For both diets, one treatment was without (control) and one with the SSS (140 g/kg dietary DM). The lambs were fed ad libitum for 70 and 140 d in experiments 1 and 2, respectively. Thereafter, the digestibility of organic matter (OM), acid-detergent fibre and neutral-detergent fibre were determined for each diet with four lambs, and then all lambs were slaughtered and rumen fluid samples were collected and analysed. The results showed substantial decreases (P < 0.001) or total elimination of protozoa in the rumen fluid of the SSS-receiving lambs. In the first experiment the SSS also decreased (P < 0.05) feed intake, but an increase in average daily gain (P < 0.06) resulted in an improved (P < 0.05) feed:gain ratio. Also, the SSS increased (P < 0.05) the digestibility of fibre. In the second experiment the SSS decreased (P < 0.05) the OM digestibility, feed intake and growth of lambs. It was concluded that the use of sunflower-seed supplementation in high-concentrate diets of ruminants reduces rumen fauna, resulting in savings on dietary protein supplements and an increased digestion of feed.

Combining agronomic practices and herbicides improves weed management in wheat–canola rotations within zero-tillage production systems

Abstract Development of more comprehensive and cost-effective integrated weed management systems is required to facilitate greater integrated weed management adoption by farmers. A field experiment was conducted at two locations to determine the combined effects of seed date (April or May), seed rate (recommended or 150% of recommended), fertilizer timing (applied in fall or spring), and in-crop herbicide dose (50% or 100% of recommended) on weed growth and crop yield. This factorial set of treatments was applied in four consecutive years within a spring wheat–spring canola–spring wheat–spring canola rotation in a zero-till production system. Both wheat and canola phases of the rotation were grown each year. Weed biomass was often lower with May than with April seeding because more weeds were controlled with preplant glyphosate. However, despite fewer weeds being present with May seeding, wheat yield was only greater in 1 of 7 site-years, and canola yield was never greater with May compared with April seeding. Higher crop seed rates had a consistently positive effect on reducing weed growth and the weed seedbank. Crop yield was sometimes greater, and never lower, with higher seed rates. Fertilizer timing did not have a large effect on crop yield, but applying N in the spring compared with fall was less favorable for weeds as indicated by lower weed biomass and a 20% decrease in the weed seedbank. In-crop herbicides applied at 50% compared with 100% doses often resulted in similar weed biomass and crop yield, especially when higher crop seed rates were used. Indeed, the weed seedbank at the conclusion of the 4-yr experiment was not greater with the 50% compared with 100% herbicide dose at one of two locations. This study demonstrates the combined merits of early seeding (April), higher crop seed rates, and spring-applied fertilizer in conjunction with timely but limited herbicide use to manage weeds and maintain high crop yields in rotations containing wheat and canola. Nomenclature: Glyphosate; canola, Brassica napus L.; wheat, Triticum aestivum L.

Soil temperature and soil water effects on henbit emergence

Abstract Henbit is increasing in abundance in western Canada, and control recommendations are largely limited to herbicides. Increased knowledge of henbit biology may allow the development of more integrated control programs. A controlled environment study was conducted to determine the combined effect of various soil temperature and soil water levels on the emergence of henbit. Henbit emerged at soil temperatures ranging from 5 to 25 C, but the highest emergence of 81 to 83% occurred at 15 to 20 C. Henbit emergence declined as soil water content decreased. The interaction of cool and dry soils caused the greatest inhibition of henbit emergence. At progressively lower soil water levels of −0.03, −0.28, −0.53, −0.78, −1.03, and −1.53 MPa, henbit emergence was 78, 61, 64, 40, 38, and 11% at 10 C, respectively. Rate of henbit emergence was affected less by soil water than by soil temperature. A decrease in soil water content from −0.03 to −1.53 MPa increased the time to reach 50% emergence (ET50) by 1 to 5 d, whereas a decrease in temperature from 25 to 5 C increased the time to reach ET50 by 13 to 16 d. The implications of these results in terms of improved management of henbit are discussed. Nomenclature: Henbit, Lamium amplexicaule L. LAMAM.

Differential response of weed and crop species to potassium and sulphur fertilizers

Fertilization may affect the relative competitive ability of weeds and crops if the growth response to fertilizer differs among species. Greenhouse studies were conducted to evaluate the relative biomass yield response of 19 weed species and the crops canola (Brassica napus L.) and spring wheat (Triticum aestivum L.) to potassium (K) and sulphur (S) fertilization. Seven weed species showed a significant increase in biomass production at 6 wk with K fertilization, but biomass production of canola and wheat did not increase with K addition. Sulphur fertilizer increased the biomass production of canola, flixweed (Descurainia sophia L.) and wild mustard (Sinapis arvensis L.), three of the four Cruciferae species evaluated, as well as that of hairy nightshade (Solanum sarrachoides Sendtner), round-leaved mallow (Malva pusilla Sm.) and stork’s-bill [Erodium cirutarium (L.) L’Her. Ex. Ait.]. Sulphur fertilizer did not increase the biomass production of spring wheat or of any grass weed species. The data from the...

Net irrigation water requirements for major irrigated crops with variation in evaporative demand and precipitation in southern Alberta

Weather variability has a profound influence on crop and irrigation water requirements. Estimates of crop evapotranspiration (ETc) and net irrigation water requirements are needed for water allocation, risk management and irrigation system planning. Seasonal ETc and net irrigation water requirement estimates based on the standardized Penman-Monteith method were examined through frequency analysis of historical weather data. Seasonal ETc calculated using the Penman-Monteith equation is based on daily solar radiation, air temperature, relative humidity, and wind speed. Historical weather data from 1983 to 2012 at Lethbridge and Vauxhall were used to determine seasonal ETc, seasonal precipitation and net irrigation water requirements for 11 major (most prevalent) irrigated crops in southern Alberta. Seasonal ETc was consistently greater at Lethbridge than Vauxhall, whereas seasonal precipitation was generally less at Vauxhall than Lethbridge for all major crops. Mean seasonal ETc ranged from 355 mm for barley silage at Vauxhall to 728 mm for alfalfa hay at Lethbridge at a 10% chance of exceedance. Mean net irrigation water requirements ranged from 273 mm for barley silage at Vauxhall to 526 mm for alfalfa hay at Lethbridge at a 10% chance of exceedance. Area-weighted seasonal ETc demand within the irrigation districts is currently about 500 mm (2.8 billion m3) and the net irrigation water requirement within the irrigation districts is at least 380 mm (2.1 billion m3) at a 10% chance of exceedance. Annual gross diversion requirements for the irrigation districts could approach the licensed water allocation limit of 3.45 billion m3 at a 10% chance of exceedance when conveyance losses, irrigation system application efficiencies, and current irrigation management practices are considered. The frequency with which annual gross irrigation water requirements approach or exceed this licensed water allocation limit may increase in the future with climate change in southern Alberta. La variabilité des conditions météorologiques influence grandement les besoins en eau des cultures et pour l’irrigation. Les estimations d’évapotranspiration des cultures et les besoins net en eau d’irrigation sont nécessaires pour l’attribution de l’eau, gestion des risques et la planification stratégique de développement de l’irrigation. Les estimations d’évapotranspiration saisonnière et les besoins net en eau d’irrigation basés sur la méthode normalisée de Penman-Monteith ont été comparés aux données météorologiques historiques. Les estimations d’évapotranspiration saisonnière calculées à l’aide de l’équation de Penman-Monteith reposent sur le rayonnement solaire, la température de l’air, l’humidité relative et la vitesse du vent. Les données météorologiques historiques de 1983 à 2012 pour Lethbridge et Vauxhall ont servi à déterminer l’évapotranspiration saisonnière, les précipitations saisonnières et les besoins net en eau d’irrigation pour les 11 cultures irriguées les plus répandues dans le sud de l’Alberta. L’évapotranspiration saisonnière moyenne était constamment supérieure à Lethbridge comparativement à Vauxhall, tandis que les précipitations saisonnières étaient généralement inférieures à Vauxhall qu’à Lethbridge pour les principales cultures. L’évapotranspiration saisonnière moyenne variait de 355 mm pour l’orge fourragé à Vauxhall à 728 mm pour la luzerne fourragère à Lethbridge pour une chance de dépassement de 10%. Les besoins net en eau d’irrigation variaient de 273 mm pour l’orge fourragé à Vauxhall à 526 mm pour la luzerne fourragère à Lethbridge pour une chance de dépassement de 10%. L’évapotranspiration saisonnière dans les districts d’irrigation correspond actuellement à environ 500 mm (2,8 milliards de m3) d’eau et le besoin net en eau d’irrigation dans les districts d’irrigation est d’au moins 380 mm (2,1 milliards de m3) pour une chance de dépassement de 10%. Le volume de diversion brute annuelle nécessaire pour combler les besoins des districts d’irrigation pourrait s’approcher de la limite de la licence d’allocation en eau de 3,54 milliards de m3 pour une chance de dépassement de 10% lorsque les pertes lors de l’adduction, l’efficacité des systèmes d’irrigation et les pratiques actuelles de gestion de l’irrigation sont considérées. La fréquence à laquelle les besoins annuels bruts en eau d’irrigation atteignent ou dépassent la limite d’allocation en eau sous licence peut augmenter dans l’avenir en considérant les changements climatiques potentiels pour le sud d’Alberta.

Do Introduced Grasses Improve Forage Production on the Northern Mixed Prairie

Abstract Relative benefit of introducing forage species to the Northern Great Plains have been examined with contradictory conclusions. In most cases, studies were either confounded by time of establishment or treatments were not randomized and lacked independence. We examined aboveground net primary production (ANPP) in northern mixed prairie using a randomized complete block design with four treatments: crested wheatgrass (Agropyron cristatum [L.] Gaertn.), Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski), a native control that was not harvested, and a harvested native. The experiment was conducted in a Stipa–Agropyron–Bouteloua site and a Stipa–Bouteloua site over 13 yr and 12 yr, respectively. The data were analyzed by sampling period (Stipa–Agropyron–Bouteloua: 1, 1994 to 1997; 2, 1998 to 2001; 3, 2002 to 2006; and Stipa–Bouteloua: 1, 1995 to 1998; 2, 1999 to 2002; 3, 2003 to 2006). ANPP among treatments was influenced (P < 0.05) by site and its interaction with treatment and sampling period (1 to 3). ANPP from the native-control, harvested-native, crested wheatgrass, and Russian wildrye treatments was 220.9, 183.9, 300.8, and 189.6 g · m–2 (SEM  =  11.2), respectively, in the Stipa–Agropyron–Bouteloua site and 122.9, 98.2, 216.3, and 115.9 g · m–2 (SEM  =  12.0), respectively, in the Stipa–Bouteloua site. Mean ANPP (SEM) within each sampling period (1 to 3) was 186.4 (9.1), 135.4 (5.8), and 263.9 (8.8) g · m–2 in the Stipa–Agropyron–Bouteloua site, respectively, and 124.5 (6.4), 138.6 (6.1), and 151.3 (10.5) g · m–2 in the Stipa–Bouteloua site, respectively. Russian wildrye in the Stipa–Bouteloua site and crested wheatgrass in both sites was relatively more productive in the first period after establishment than in subsequent years. The study confirms the relative ANPP advantage of crested wheatgrass over native on the Stipa–Bouteloua site but not on the Stipa–Agropyron–Bouteloua site, whereas Russian wildrye exhibited no ANPP advantage over the native on either site.

Duodenal flow and digestibility in fauna-free sheep and in sheep monofaunated with Entodinium caudatum or Polyplastron multivesiculatum

Three groups of five rumen and duodenum cannulated fauna-free sheep were used in a 28 d experiment. One group remained fauna-free, whereas the second (EN) and third (PP) groups, respectively, were inoculated intraruminally with the protozoan species Entodinium caudatum and Polyplastron multivesiculatum. Rumen fluid, duodenal digesta and faecal samples were collected during the last 12 d. The flow of digesta to the duodenum was determined using Yb and Co as dual-phase markers. (15)Nitrogen and phosphatidylcholine were used as markers to calculate the duodenal flow of bacterial and protozoal N, respectively. Results showed an increase (P < 0.1) in the rumen concentration of NH3-N and total volatile fatty acids, and a decrease (P < 0.05) in the duodenal flow of non-NH3-N and bacterial N in sheep with EN and PP monofaunas, compared with fauna-free sheep. There were no differences (P > 0.05) in these variables between the two monofauna groups. Protozoal N accounted for 8 % of the duodenal non-NH3-N flow in the EN-monofaunated sheep, whereas no such flow was detected in the PP-monofaunated sheep. Apparent rumen digestibility of organic matter, neutral detergent fibre and acid detergent fibre were similar (P > 0.05) in the monofaunated groups of sheep, but rumen acid detergent fibre digestibility was higher (P < 0.05) in the monofaunated than in the fauna-free groups. Experimental results suggested that, unlike EN, the PP monofauna might not contribute to the duodenal flow of microbial protein, whereas both monofaunas showed a virtually equal degree of predation on rumen bacteria.

Productivity and profitability of straw-tillage and nitrogen treatments on irrigation in southern Alberta

Straw-tillage treatment and N fertilizer rate were assessed for their impact on plant growth, N uptake, and profitability of irrigated cereals and oilseeds on a Dark Brown Chernozemic Lethbridge loam in southern Alberta. Straw was either retained or removed by baling. Tillage treatments were fall plowing, spring plowing, and direct seeding. Four N fertilizer rates (0, 50, 100, and 200 kg ha-1) were imposed on the straw-tillage treatments. The data were analyzed by crop using analysis of covariance with year and replication as random factors, straw-tillage treatment as a fixed effect, and fertilizer and fertilizer squared as covariates. Grain and straw yields were higher for fall plowing than for spring plowing or direct seeding at zero N rate, but were not different at the high N rate (200 kg ha-1). Grain and straw N concentrations were higher for fall plowing than spring plowing or direct seeding at the low N rate (50 kg ha-1), but similar at the high N rate. Total N uptake was higher for fall plowing or...