• Authors:
    • Blum, A.
  • Source: Australian Journal of Agricultural Research
  • Volume: 56
  • Issue: 11
  • Year: 2005
  • Authors:
    • Irvine, B.
    • Chen, Y.
    • Doan, V.
  • Source: Canadian Biosystems Engineering
  • Volume: 47
  • Year: 2005
  • Summary: A two-year field study was conducted to investigate the performance of seeding canola crop as influenced by types of residue (canola, wheat, and pea) and types of seed opener (disc and hoe). Seed placement (seeding depth and seed scattering index), speed of crop emergence, and plant populations were used to evaluate the seeding performance. Seeding placement as affected by field wheel tracks (inside and outside wheel tracks) was also examined. The results showed that the disc opener produced a greater seeding depth and faster emergence than the hoe opener. The two openers resulted in the same level of plant population. In the first year, plots with pea residue resulted in greater and more uniform seeding depth, faster emergence, and higher plant population than plots with wheat and canola residues. In the second year, a better uniformity of seeding depth was observed for pea residue than the other two types of residue, while there were no significant differences between residue types in the other measured variables due to the extremely dry soil condition in the spring of that year. Seeds were placed more uniformly outside the wheel track than inside the wheel track, while the mean seeding depths were similar inside and outside the wheel track.
  • Authors:
    • Sweeney, D.
    • Kelley, K.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 3
  • Year: 2005
  • Summary: In the eastern Great Plains, winter wheat ( Triticum aestivum L.) is often rotated with other crops to diversify cropping systems. In these multicropping systems, wheat typically is planted with conservation tillage methods, but previous crop residues influence fertilizer N management. This field study was conducted from 1992 through 2001 in southeastern Kansas on a Parsons silt loam soil (fine, mixed, thermic, Mollic Albaqualf). The objectives were to determine effects and interactions of previous crop {grain sorghum [ Sorghum bicolor (L.) Moench] and soybean [ Glycine max (L.) Merr.]}, tillage system [reduced tillage (RT) and no-tillage (NT)], N rate (67 and 134 kg ha -1), and preplant placement (surface-broadcast and subsurface-knife) of urea ammonium nitrate solution (UAN, 280 g kg -1) on wheat grain yield, yield components, and plant N uptake in a 2-yr cropping rotation. Wheat yields averaged 3.39 Mg ha -1 following soybean compared with 2.90 Mg ha -1 following grain sorghum. Tillage effects on grain yield were smaller than other treatment factors, averaging 3.23 Mg ha -1 for RT and 3.06 Mg ha -1 for NT. Grain yields were greatest in all cropping systems for the high-N-rate subsurface-knife treatment. Plant N uptake responses indicated that grain yield differences were primarily related to greater immobilization of both fertilizer and soil N following grain sorghum, compared with soybean, and to better utilization of subsurface-knifed N than surface-broadcast N. Results indicate that wheat yield potential is more strongly influenced by previous crop, fertilizer N rate, and N placement method than tillage system.
  • Authors:
    • Johnston, A.
    • Turkington, T.
    • Harker, K.
    • Clayton, G.
    • Lupwayi, N.
  • Source: Better Crops with Plant Food
  • Volume: 89
  • Issue: 3
  • Year: 2005
  • Summary: A field experiment was conducted at Fort Vermilion in northwestern Alberta, Canada, during 1998-99 and 1999-2000 to determine the amount of potassium (K) released from crop residues of four different crop rotations that included red clover [ Trifolium pratense] green manure, field pea, canola [rape] and spring wheat, under conventional and no-till seeding systems. Crops were grown on soils that had soil test levels of 150 ppm K (0.5M NaHCO 3-extractable), and no fertilizer K was added. Crop residues dry matter returned to the soil by the different crops were considerably higher in 1999-2000 relative to 1998-1999, reflecting the higher crop production during the 1999 growing season. Crop residue yield showed a large difference between the two study periods in the amount of total K being returned to the field. The results illustrate that all crop residues considered released more than 90% of their accumulated K in the 52-week period. The tillage system had no effect on the release of K from the crop residues.
  • Authors:
    • Reeves, D.
    • Torbert, H.
    • Rogers, H.
    • Runion, G.
    • Prior, S.
  • Source: Global Change Biology
  • Volume: 11
  • Issue: 4
  • Year: 2005
  • Summary: Increasing atmospheric CO 2 concentration has led to concerns about potential effects on production agriculture as well as agriculture's role in sequestering C. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional and conservation) to elevated CO 2. The study used a split-plot design replicated three times with two management systems as main plots and two CO 2 levels (ambient=375 L L -1 and elevated CO 2=683 L L -1) as split-plots using open-top chambers on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system was a grain sorghum ( Sorghum bicolor (L.) Moench.) and soybean ( Glycine max (L.) Merr.) rotation with winter fallow and spring tillage practices. In the conservation system, sorghum and soybean were rotated and three cover crops were used (crimson clover ( Trifolium incarnatum L.), sunn hemp ( Crotalaria juncea L.), and wheat ( Triticum aestivum L.)) under no-tillage practices. The effect of management on soil C and biomass responses over two cropping cycles (4 years) were evaluated. In the conservation system, cover crop residue (clover, sunn hemp, and wheat) was increased by elevated CO 2, but CO 2 effects on weed residue were variable in the conventional system. Elevated CO 2 had a greater effect on increasing soybean residue as compared with sorghum, and grain yield increases were greater for soybean followed by wheat and sorghum. Differences in sorghum and soybean residue production within the different management systems were small and variable. Cumulative residue inputs were increased by elevated CO 2 and conservation management. Greater inputs resulted in a substantial increase in soil C concentration at the 0-5 cm depth increment in the conservation system under CO 2-enriched conditions. Smaller shifts in soil C were noted at greater depths (5-10 and 15-30 cm) because of management or CO 2 level. Results suggest that with conservation management in an elevated CO 2 environment, greater residue amounts could increase soil C storage as well as increase ground cover.
  • Authors:
    • Klepker, D.
    • Yamada, M.
    • Hitsuda, K.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 1
  • Year: 2005
  • Summary: Sulfur deficiency symptoms are more often observed in crops at early stages of growth since S can be easily leached from the surface soil. The objectives of this study were to evaluate some of the popular rotation crops grown in Brazil for tolerance to low external S levels and to determine the critical tissue concentration for S deficiency during early stages of growth. Germinated seedlings of soybean [ Glycine max (L.) Merr.], rice ( Oryza sativa L.), maize ( Zea mays L.), field bean ( Phaseolus vulgaris L.), wheat ( Triticum aestivum L.), cotton ( Gossypium spp.), sorghum ( Sorghum bicolor L.), and sunflower ( Helianthus annuus L.) were transferred to water culture with 0.0 to 32.0 mg S L -1 and were grown for 29 d. The minimum S concentration required in nutrient solutions was 2.0 mg L -1 for sunflower; 1.0 mg L -1 for cotton, sorghum, wheat, and soybean; and 0.5 mg L -1 or less for field bean, rice, and maize. All crops achieved optimum growth at 2.0 mg S L -1. Critical shoot S concentration at early stages of growth was 0.8 g kg -1 in maize and soybean; 1.1 to 1.3 g kg -1 in cotton, sorghum, and rice; and 1.4 to 1.6 g kg -1 in wheat, sunflower, and field bean. Our results demonstrate that the tolerance to low external S (
  • Authors:
    • Jamiokowska, A.
  • Source: Ochrona Roślin
  • Volume: 50
  • Issue: 1
  • Year: 2005
  • Summary: The importance of cover crops for protection of soil from water and aerial erosion, as well as leaching of nutrients from soil is emphasized. Use of green manures as a mechanical barrier against weeds, and beneficial effects of exudates of green manures on control of weeds, pests and diseases of vegetables are discussed. Recommendations are included for autumn and spring sowing of cover crops (e.g. rye, wheat, oat, barley, sorghum, vetch, rape and mustard), which are cut or desiccated in the spring and are left in the field as mulch. Negative effects of mulching are considered, i.e. a decrease of soil temperature in the spring resulting in a slower growth rate and later ripening of tomato. It is also stated that yield of some vegetables, including tomato, can be lower in the no-tillage cultivation compared with traditional cultivation. However, the dry matter content is higher in tomato grown with no-tillage. Field trials were conducted in Lublin, Poland, to study the effect of cover crops, such as rye, white and red clover, and field pea on health of tomato. Data are tabulated on fungi isolated from soil under tomato grown with rye and field pea as mulch crops compared with the traditional cultivation system during 1998-2000. The results showed that use of cover crops resulted in a good control of plant pathogens, especially Fusarium oxysporum f.sp. lycopersici, and an increase in the number of antagonistic fungi, e.g. Trichoderma spp. It is concluded that use of cover crops allows decrease of the number of mechanical cultivations, as well as decrease of the use of fertilizers, fungicides, insecticides and herbicides.
  • Authors:
    • Shimi, P.
    • Kazemi, H.
  • Source: Iranian Journal of Weed Science
  • Volume: 1
  • Issue: 1
  • Year: 2005
  • Summary: An isolate of F. moniliforme [Gibberella moniliformis], a pathogen of winter wild oat (A. ludoviciana [A. sterilis var. ludoviciana]), was obtained from Tehran Province, Iran, in 1994. A host range test performed on wheat, barley, maize, rye, millet, crested wheatgrass, faba bean, red bean, green bean, sunflower, soyabean, oilseed rape, cotton, safflower, cucumber, water melon, berseem clover, and sainfoin, resulted in no symptom induction by the pathogen. However, winter wild oat, crested wheatgrass, johnsongrass and tomato showed susceptibility to the pathogen with 78, 24, 19 and 17% mortality, respectively. The results indicate that this pathogen could be considered as a potential biological agent for the control of winter wild oat.
  • Authors:
    • Negrila, E.
    • Negrila, M.
  • Source: Probleme de Agrofitotehnie Teoretica si Aplicata
  • Volume: 27
  • Issue: 2
  • Year: 2005
  • Summary: Mineral fertilizer application on crops is one of the reliable ways of increasing soil productivity, improving the yield, quality and soil fertility. The nitrogen and phosphorus long-term fertilizer application in the cambic chernozem, under non-irrigated condition at the A.R.D.S. Teleorman, Romania, caused plants and soil modifications. The annual nitrogen and phosphorus (NP) fertilizer application (in 28 years) with moderate amounts and balanced ratios resulted in a yield increase of 12-17 kg wheat/1 kg NP, 7-11 kg maize/1 kg NP, 4-6 kg sunflower/1 kg NP, the smallest increase was during the drought years. The use of coefficient depends on crop and climatic evolution. The best nitrogen and phosphorus use efficiency was with wheat, followed by maize and sunflower. During the drought years, both elements use was reduced to half. It also had a positive influence on the crude protein content (4.08% for winter wheat and 3.76% for maize), on the other quality indices: technological flour indices, macro- and microelements. The P:Zn ratio of 57-100 also indicated a good ratio between the two elements which does not lead to occurrence of Zn deficiency. The values of N:S indicated some disorders in sulfur metabolism which can generate sulfur deficiency, especially in maize. The long-term fertilizer application (1977-2000) determined the improvement in soil fertility: maintenance of the humus content, the improvement of the mobile phosphorus content, of the saturation degree in alkali up to 83% and the reaction up to 5.9 pH, without mobile aluminium and Mn coming out. The absence of nitrogen and phosphorus fertilizers during 24 years led to soil fertility, yield and yield quality reduction.
  • Authors:
    • Clayton, G. W.
    • Harker, K. N.
    • Blackshaw, R. E.
    • O'Donovan, J.
    • Maurice, D. C.
  • Source: Canadian Journal of Plant Science
  • Volume: 85
  • Issue: 4
  • Year: 2005
  • Summary: Various regression equations based on weed density alone, or relative time of weed and crop emergence or crop density in addition to weed density have been developed in western Canada to estimate the effects of wild oat (Avena fatua L.) and volunteer cereals on yield loss of field crops, and to advise farmers on the economics of weed control with herbicides. In 1997, 1998, and 1999, several of these equations were evaluated in 9 barley (Hordeum vulgare L.), 9 wheat (Triticum aestivum L.) and 11 canola (Brassica napus L.) fields in Alberta. Wild oat was the dominant weed in the barley and wheat fields, and wild oat or volunteer cereals in the canola fields. In barley and wheat, more complex equations based on both weed density and either crop density or relative time of weed and crop emergence were more reliable in estimating yield losses due to wild oat than those based on weed density alone. In canola, an equation based on volunteer barley and canola density provided the most reliable estimates. Under the assumed crop prices and herbicide costs, these equations also resulted in the best estimates of whether or not a herbicide application resulted in a net profit or loss. Herbicide application was rarely economical in barley, but usually economical in wheat and canola reflecting the different market value of the crops. The implementation of the weed economic threshold concept is likely to be more feasible in low-value crops such as feed barley than in higher-value crops such as canola.