Tillage, nitrogen and crop residue effects on crop yield, nutrient uptake, soil quality, and greenhouse gas emissions

Management practices that simultaneously improve soil properties and yield are crucial to sustain high crop production and minimize detrimental impact on the environment. The objective of this study was to determine the influence of tillage and crop residue management on crop yield, N uptake and C removal in crop, soil organic C and N, inorganic N and aggregation, and nitrous oxide (N₂O) emissions on a Gray Luvisol (Boralf) soil near Star City, Saskatchewan, Canada. The 4-year (1998–2001) field experiment was conducted with two tillage systems: no tillage (NT), and conventional tillage (CT); two levels of straw: straw retained (S), and straw removed (NS); and four rates of fertilizer N: 0, 40, 80, and 120 kg N ha⁻¹, except no N to pea phase of the rotation. The plots were seeded to barley (Hordeum vulgare L.) in 1998, pea (Pisum sativum L.) in 1999, wheat (Triticum aestivum L.) in 2000 and canola (Brassica napus L.) in 2001. Tillage and straw treatments generally had no effect on crop yield during the first three years. But in 2001, NT produced 55, 32, and 20% greater canola seed, straw and chaff than CT, respectively, whereas straw retention increased seed and straw yield by 33 and 19% compared to straw removal. Seed, straw and chaff yield of canola increased with N rate up to 40 kg N ha⁻¹, and root mass (0–15 cm depth) with N rate to 80 kg N ha⁻¹. Amount of N uptake and C removed in wheat and canola generally increased with N rate, but tillage and straw management had no consistent effect. After four crop seasons, total organic C (TOC) and N (TN), light fraction organic matter (LFOM), C (LFC), and N (LFN) were generally greater with S than NS treatments. Tillage did not affect TOC and TN in soil, but LFOM, LFC, and LFN were greater or tended to be greater under NT than CT. There was no effect of tillage, straw and N fertilization on NH₄-N in soil, but CT and S tended to have higher NO₃-N concentration in 0–15 cm soil than NT and NS, respectively. Concentration of NO₃-N increased substantially with N rate ≥80 kg ha⁻¹. The NT + S treatment had the lowest proportion (34%) of wind-erodible (<0.83 mm diameter) aggregates and greatest proportion (37%) of larger (>12.7 mm) dry aggregates, compared to highest (50%) and lowest (18%) proportion of corresponding aggregates in CT + NS, indicating less potential for soil erosion when tillage was omitted and crop residues were retained. Amount of N lost as N₂O was higher from N-fertilized than from zero-N plots, and it was substantially higher from N-applied CT plots than from N-applied NT plots. Retaining crop residues along with no-tillage improved soil properties and may also be better for the environment.     

Contributions of visual cues to cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), resistance in novel host genotypes

Herbivorous insects can demonstrate great selectivity among visual cues. The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) (syn. Ceutorhynchus assimilis (Paykull)) is also influenced by visual cues. Here, we present results of a study examining the attractiveness of flowers and foliage of Sinapis alba (a suboptimal host for larval development), Brassica napus (an excellent host for larval development) and novel lines derived from S. alba x B. napus; several of these have been demonstrated to be resistant in field and laboratory tests. Attractiveness, reflectance properties and resistance demonstrated in field trials were related. Responses to host plants differed among plant genotypes and were related to the amounts of UV and yellow reflected from flowers. Moderate UV reflectance greatly increased the attractive effects of yellow. Fewer weevils responded to test plants with greater or lesser floral UV reflectance.     

Influence of subsurface drainage on the productivity of poorly drained paddy fields

Because of the relatively flat topography of Northern Iran consolidated paddy fields and inadequate natural drainage facilities, these lands are usually confronted with waterlogging due to periodic excess of water from rainfall during the wet months. The productivity of these areas could be greatly increased if their drainage problems were solved by subsurface drainage. Subsurface drainage may also facilitate the mid-season drainage (MSD), one of the water management methods during the rice growing season. A drainage pilot consisting of surface and subsurface drainage with different drain depths and spacings was designed at Sari Agricultural Sciences and Natural Resources University, Iran, to explore the effect of different drainage systems on the productivity of paddy fields. Rice cultivation was carried out during two cropping seasons, 2011 and 2012. In 2011, after rice harvest, canola seed was cultivated in the subsurface drained area. For MSD, the fields were drained 25 days after rice transplanting and remained drained for 7 days. Randomized complete block design was used to find the effect of drainage on crops. The implementation of MSD through subsurface drainage, significantly increased yield, yield components and growth parameters of rice. Rice yield of the subsurface drained area was approximately 1.22–1.66 and 1.32–1.7 times higher than that of the surface drained area in 2011 and 2012, respectively. Subsurface drainage provided better condition for canola cropping while, because of waterlogging, it was not possible under surface drainage. An economic analysis showed that the cost of installing subsurface drainage systems was readily justified by annual increased rice and canola yields. Based on the results, the introduction of the subsurface drainage resulted in an increase in both crop yield and cropping intensity in the study area.     

Effects of dietary canola oil level on growth performance, fatty acid composition and ionoregulatory development of spring chinook salmon parr, Oncorhynchus tshawytscha

This study assessed the potential of refined canola oil (CO) as a source of supplemental dietary lipid for pre-smolt spring chinook salmon (Oncorhynchus tshawytscha) over a period of 30 weeks. Triplicate groups of 320 fry (∼ 0.80 g), reared in flow-through well water (8-11.5 °C), were fed one of four steam-pelleted dry diets with equivalent gross energy (24.3 MJ/kg), protein (∼ 51.3%) and lipid (∼ 21.6%) content on a dry-weight basis. CO furnished either 0%, 33%, 67%, or 100% of the supplemental dietary lipid, with the remainder from a commercial blend of 1:1 anchovy oil and poultry fat (APF). Thus, CO comprised either 0% (dAPF), 25% (CO25), 49% (CO49), or 72% (CO72) of total dietary lipid content. Overall fish growth rate, feed intake, feed efficiency, protein utilization, percent survival, and terminal whole body proximate constituents were unaffected by diet treatment. Dietary lipid compositions reflected the ratios of CO and APF in the supplemental lipid and their respective fatty acid compositions. Whole body fatty acid compositions mirrored those of diet treatments. However, some essential fatty acids, namely, arachidonic acid (20:4n-6; AA), and docosahexaenoic acid (22:6n-3; DHA) were conserved in fish regardless of dietary CO level. Direct relationships were found between dietary and whole body concentrations of: 18:2n-6 (R² = 0.94; slope = 0.72), 18:3n-3 (R² = 0.99; slope = 0.58), 20:4n-6 (R² = 0.84; slope = 0.42), 20:5n-3 (R² = 0.99; slope = 0.43) and 22:6n-3 (R² = 0.82; slope = 1.25). High dietary levels of 18:3n-3, 18:2n-6, and 20:5n-3 may have been utilized for energy or converted to more unsaturated derivatives. Overall development of ionoregulatory ability, as assessed by 24-h seawater challenge tests, was unaffected by diet. However, whole body chloride content was generally inversely related to dietary CO level during early development. Our findings suggest that there is excellent potential for long-term replacement of fish oil with canola oil in the diet of pre-smolt spring chinook salmon, provided that some marine oil is present to ensure that the essential fatty acid needs of the fish are met.     

Effects of dietary canola oil level on growth, fatty acid composition and osmoregulatory ability of juvenile fall chinook salmon (Oncorhynchus tshawytscha)

This study assessed refined canola oil (CO) as a supplemental dietary lipid source for juvenile fall chinook salmon, Oncorhynchus tshawytscha, parr with respect to possible effects on their growth and osmoregulatory performance and body composition. Diets with equal protein ( 57%) and lipid ( 19%) content (dry weight basis) were supplemented with lipid from either anchovy oil (AO) or CO with AO so that CO comprised 0 (0CO), 11% (11CO), 22% (22CO), 33% (33CO), 43% (43CO) or 54% (54CO) of the dietary lipid content. Triplicate groups of juvenile chinook salmon were fed their prescribed diets for 104 days in freshwater (FW) and 31 days in seawater (SW) after a 4-day transition period. Dietary fatty acid compositions reflected the different proportions of AO and CO in the supplemental lipid. Diet treatment had no effect on fish growth, feed intake, feed efficiency, protein utilization, fish mortality or terminal whole body water and ash percentages. Whole body lipid percentages were higher in 11CO and 43CO fish than in 33CO fish and in 11CO fish versus 22CO fish. Whole body protein percentages were highest in 33CO, 43CO and 54CO fish and lowest in 0CO and 22CO fish. Terminal whole body fatty acid compositions were influenced strongly by the dietary fatty acid compositions. Haematocrit and muscle water percentages were not affected consistently and plasma Na⁺ and Cl⁻ concentrations were unaffected by diet treatment in FW or 24-h seawater challenges during FW residency. Also, diet treatment had no effect on the physiological parameters after SW residency. We conclude that dietary treatment had no effect on fish growth performance under our experimental conditions. Also, the dietary inclusion of CO neither facilitated nor impaired the transfer of chinook salmon parr to seawater. Thus, CO was found to be an excellent and cost-effective source of supplemental dietary lipid for culture of juvenile fall chinook salmon during freshwater residency.     

Canola oil as a kairomonal attractant of rangeland grasshoppers: An economical liquid bait for insecticide formulation

Laboratory experiments and field trials demonstrated that canola oil, which is rich in fatty acids that are kairomonal cues in cannibalism, is an effective attractant of rangeland grasshoppers and a suitable oil-based carrier for insecticides. Laboratory-based olfactory tests revealed a significant, positive chemotaxis of Melanoplus sanguinipes in response to canola oil and olive oil mixtures. Small-scale field tests made by airbrush applications of 5 ml of canola oil (equivalent to 500 l/ha) to centres of aluminium rings (0.1 m²     

Yield Attributes and Oil Safety in the Hyperaccumulator Canola Plant Grown in a Bioremediated Sewaged Soil

A field experiment was carried out at Abu-Rawash sewage farm to appraise the effect of certain novel remediative amendments on the quality of oil as well as the vegetative parameters and yield criteria of canola plant used as hyperaccumulator for the remediation of sewaged soils. The treatments included fallow soil （irrigated without growing canola）, soil cultivated with canola （Brassica napus L.） and inoculated with arbuscular mycorrhiza （AM）, soil inoculation with Thiobacillus sp. （a mixture of Thiobacillus ferrooxidans and Thiobacillus thiooxidant）, soil treated with a mixture of 250 mg bentonite plus 250 mg rock phosphate/kg soil and inoculated with phosphate dissolving bacteria （PDB）, and soil treated with all the aforementioned remediative amendments. Results indicated that the vegetative parameters and yield criteria of canola plant did not exhibit any serious adverse impact under all treatments applied. The concentrations of Zn and Cu in canola oil extracted from plants grown in soil inoculated with AM and/or Thiobacillus sp. far exceeded the safe permissible levels. On the other hand, the content of both PTEs in the oil extracted from canola plants grown in soil treated with either probentonite or with mixture of all remediative amendments followed the permissible safe levels.     

Effect of Organic Acids on Heavy-Metal Uptake and Growth of Canola Grown in Contaminated Soil

Heavy-metal pollution of soils causes many environmental, animal, and human health problems. Phytoextraction of heavy metals from contaminated soils is an effective and economic technique. Humic acids are naturally occurring phenol body polymerisates, which form chelate compounds with heavy metals. In the present study the influence of soil- applied humic, citric, and malic acids on the lead (Pb), cadmium (Cd), and chromium (Cr) uptake from a contaminated soil by canola plant was examined in a greenhouse experiment. The experiment was arranged in factorial design based on randomized complete blocks with three replications. The factors of experiment included three organic acids (humic, citric, and malic acid) as first factor and five concentrations [0, 0.001, 0.002, 0.003, and 0.004 (v/v)] as second factor. The results showed that increase in organic acid concentration significantly increased heavy-metal uptake by canola plant, which accumulated heavy metals in different parts of the plant. In addition, crop growth representing by plant height and plant dry weight as well as seed production significantly decreased. Based on these results, canola can be considered as effective crop for phytoextraction of heavy metals from contaminated soils.     

Responses of Canola Morphological and Agronomic Characteristics to Zeolite and Zinc Fertilization under Drought Stress

Research was performed during the 2010 and 2011 growing seasons to investigate the effect of zeolite and zinc (Zn) foliar application on the qualitative characteristics and oil yield of canola cultivars at different moisture regimes. A factorial split-plot experiment was performed on the basis of the randomized complete block design with three replications in the Seed and Plant Improvement Institute, Karaj, Iran. The treatments were as follows: (1) irrigation (I), complete (I₁), and restricted (I₂) at the pod formation stage, (2) zeolite (Z), 0 (Z₁), and 15 t ha^?1 (Z₂), and (3) Zn, zinc sulfate concentrations of 0%, 0.1%, and 0.2 % (Zn₁, Zn₂, and Zn₃) at the pod formation stage. These treatments were applied on Licord, RGS003, and Opera cultivars. The results show that the simple effect of treatments were statistically significant for all assessed traits at P < 0; as well as the interaction effects of Z and Zn (P < 0.01) and the interaction effects of I and cultivar (P < 0.01). The greatest rates of all studied traits were obtained by applying Z₂Zn₂ (15 ton ha^?1 zeolite and 0.1% Zn sulfate) in both irrigation regimes. The rates of grain yield, biological yield, and harvest index improved by 43.82%, 73.99%, and 30.04%, respectively, using a combined application of Z and Zn. Therefore, based on the low cost of natural Z and a low Zn intake, these treatments could be used to enhance the performance of canola, especially in regions that are exposed to water stress.     

Effects of Zeolite and Zinc on Quality of Canola (Brassica napus L.) Under Late Season Drought Stress

The research was performed to investigate the effect of zeolite and zinc on the qualitative characteristics of canola cultivars at different moisture regimes. Factorial split plot experiment was performed on the basis of the randomized complete blocks design with three replications in Karaj, Iran. The treatments were: 1) irrigation (I): complete (normal irrigation) (I₁), and restricted irrigation (I₂) applied at the pod formation stage, 2) zeolite (Z): 0 (Z₁), and 15 t ha^?1 (Z₂), and 3) Zn: zinc sulfate concentrations of 0%, 0.1%, and 0.2% (Zn_1, Zn_2, and Zn₃) on Opera, Licord, and RGS003 cultivars. The highest rate of all studied traits was obtained by applying Z₂Zn₂ (15 ton ha^?1 zeolite and 0.1% zinc sulfate) in both irrigation regimes. Opera cultivar in normal irrigation and RGS003 cultivar in stress conditions had the highest yield and yield components, oil yield, and oil content.