• Authors:
    • Hansson, M.
    • Adler, A.
    • Bergkvist, G.
    • Weih, M.
  • Source: Weed Research
  • Volume: 50
  • Issue: 5
  • Year: 2010
  • Summary: P>Elytrigia repens (syn. Elymus repens) is a perennial grass weed that is controlled by herbicides or by tillage. Both methods are expensive and may have negative effects on the environment. Therefore, alternative methods of weed control, such as using competition from under-sown perennial forage crops, are of interest. Red fescue can be sown together with winter wheat as a non-flowering understorey crop that has its main growth during late summer and autumn. This study quantified the effect of red fescue and E. repens on wheat biomass and tested the hypothesis that under-sown red fescue reduces the amount of E. repens rhizomes and thus the need for herbicides or tillage. Two field experiments in which winter wheat, red fescue and E. repens were grown in all possible combinations were conducted between 2003 and 2005. Elytrigia repens reduced wheat biomass by 8%, while red fescue had no significant effect on wheat biomass. Red fescue reduced late autumn biomass of E. repens rhizomes by 40%. The results suggest that red fescue sown with winter wheat can reduce propagation of E. repens during summer and autumn, without a significant reduction in wheat biomass.
  • Authors:
    • Maghirang, R. G.
    • Casada, M. E.
    • Boac, J. M.
    • Harner, J. P.,III
  • Source: Transactions of the ASABE
  • Volume: 53
  • Issue: 4
  • Year: 2010
  • Summary: Experimental investigations of grain flow can be expensive and time consuming, but computer simulations can reduce the large effort required to evaluate the flow of grain in handling operations. Published data on material and interaction properties of selected grains and oilseeds relevant to discrete element method (DEM) modeling were reviewed. Material properties include grain kernel shape, size, and distribution; Poisson's ratio; shear modulus; and density. Interaction properties consist of coefficients of restitution, static friction, and rolling friction. Soybeans were selected as the test material for DEM simulations to validate the model fundamentals using material and interaction properties. Single- and multi-sphere soybean particle shapes, comprised of one to four overlapping spheres, were compared based on DEM simulations of bulk properties (bulk density and bulk angle of repose) and computation time. A single-sphere particle model best simulated soybean kernels in the bulk property tests. The best particle model had a particle coefficient of restitution of 0.6, particle coefficient of static friction of 0.45 for soybean-soybean contact (0.30 for soybean-steel interaction), particle coefficient of rolling friction of 0.05, normal particle size distribution with standard deviation factor of 0.4, and particle shear modulus of 1.04 MPa.
  • Authors:
    • Kaul, H. -P
    • Loiskandl, W.
    • Himmelbauer, M.
    • Bodner, G.
  • Source: Agronomy for Sustainable Development
  • Volume: 30
  • Issue: 2
  • Year: 2010
  • Summary: Cover crops are plants that are integrated in the crop rotation between two cash crops. The main objectives of cover cropping are organic matter input, mitigation of nitrate leaching and reduction of soil erosion. These benefits will only be achieved efficiently if the selected cover crop species are adapted to local environmental conditions and appropriate for the defined agro-ecological target. Therefore, a main limitation in cover cropping is the lack of a comprehensive species description. An improved cover crop characterization could be achieved with quantitative parameters derived from growth functions. Here, we show the use of this approach to assess plant traits relevant for erosion control by cover cropping. An experiment with four cover crop species (phacelia, vetch, rye and mustard) was performed over two years at a semi-arid site in Eastern Austria. Canopy cover was measured four times over the vegetation period. Root length density measurements were made to 40 cm soil depth before winter. Canopy dynamics were characterized by parameters from the asymptotic Gompertz function and from an extended logistic model that includes a parameter for decay after maximum coverage. Our results show that vetch had the lowest early vigor after dry conditions at sowing, with +45% longer time to attain maximum growth rate (parameter t(max)) than the other species. Drought during the later autumn growing period led to the highest reduction in maximum canopy cover (parameter y(max)) for phacelia (-41%). The rooting pattern was assessed by parameters from the exponential distribution function of Gerwitz and Page. The most intense rooting near the soil surface (parameter L(0)) was found for phacelia (9.7 cm cm(-3)). Vetch had the lowest L(0) (4.6 cm cm(-3)) but highest root allocation to deeper soil layers. Mustard combined high average values in y(max) (76%) and L(0) (6.3 cm cm(-3)) with a stable growth over both years. The potential strengths of phacelia and vetch were more dependent on the particular year. Rye showed a stably high L(0) (8.6 cm cm(-3)), but had only a low average value of y(max) (55.1%). The quantitative parameter sets we derived for plant traits required for erosion control improved cover crop comparison and analysis of their local adaptation. Based on this extended species description our approach allows a better evaluation of cover crops and can be used for the optimization of management and decision support.
  • Authors:
    • Domuta, C.
    • Sandor, M.
    • Bara, L.
    • Bara, C.
    • Bara, V.
    • Domuta, C.
    • Borza, I. M.
    • Brejea, R.
    • Vuscan, A.
  • Source: Analele Universităţii din Oradea, Fascicula: Protecţia Mediului
  • Volume: 15
  • Year: 2010
  • Summary: The paper based on the researche carried out in the Agricultural Research and Development Station Oradea in the long term trial placed in 1990 on a preluvosoil. Two factors were studied: crop rotation (maize-monocrop; maize-wheat; maize-soybean-wheat) and water regime (unirrigated and irrigated). In comparison with unirrigated and irrigated monocrop, in the maize-wheat crop and especially in the maize-soybean-wheat crop rotation very significant yield gains were obtained all the three years. The irrigation determined the yield gains very significant statistically every year and in every crop rotation. The smallest protein content and protein production were registered in the variant with maize monocrop and the biggest in the variant with wheat-maize-soybean crop. The irrigation determined the increase of the protein content.
  • Authors:
    • Kochsiek, A. E.
    • Knops, J. M. H.
    • Walters, D. T.
    • Arkebauer, T. J.
  • Source: Agricultural and Forest Meteorology
  • Volume: 149
  • Issue: 11
  • Year: 2009
  • Summary: The litter carbon (C) pool of a single litter cohort in an agroecosystem is the difference between net primary productivity and decomposition and comprises 11-13% of the total C pool (litter and soil 0-15 cm depth) post-harvest. This litter-C pool is highly dynamic and up to 50% can be decomposed in the first 12 months of decomposition. Thus, understanding litter-C dynamics is key in understanding monthly and annual total ecosystem carbon dynamics. While the effects of management practices such as irrigation and fertilization on productivity are well understood, the effects on decomposition are less studied. While irrigation and fertilization increase productivity, this will only lead to increased litter-C residence time and litter-C pool accretion if these techniques do not also result in equivalent or greater increases in decomposition. Management could potentially have impacts on litter-C accretion by increasing litter inputs, changing plant-C allocation, plant tissue quality, or decomposition rates. We examined carbon loss of one annual cohort of maize litter using in situ nylon litter bags for 3 years in three no-till fields with differing management regimes: irrigated continuous maize with a pre-planting fertilization application and two fertigation events, irrigated maize-soybean rotation with the same fertilization regime as the irrigated continuous maize management regime, and rainfed maize-soybean rotation with a single pre-planting fertilization event. We addressed the effects of these different management regimes on net primary productivity and litter inputs, litter nitrogen (N) concentrations and carbon quality measures, plant C allocation, decomposition rates and the potential changes in the overall litter-C balance. We found that irrigation/fertigation management increased litter inputs, led to changes in plant tissue quality, had no effect on carbon allocation, and increased decomposition rates. This balance of both greater litter inputs and outputs of C from the irrigated management regimes led to a similar litter-C balance for this litter cohort in the irrigated and rainfed management regimes after 3 years of decomposition. Our data clearly show that merely increasing litter-C inputs through irrigation/fertigation practices is not sufficient to increase litter-C residence time because decomposition rates also increase. Therefore, close monitoring of decomposition rates is essential for understanding litter-C pool dynamics.
  • Authors:
    • Paltridge, N.
    • Tao, J.
    • Unkovich, M.
    • Gason, A.
    • Grover, S.
    • Wilkins, J.
    • Coventry, D.
    • Tashi, N.
    • Bonamano, A.
  • Source: Crop & Pasture Science
  • Volume: 60
  • Issue: 7
  • Year: 2009
  • Summary: In the south of the Tibet Autonomous Region of China there is a network of valleys where intensive agriculture is practiced. Although considered highly productive by Tibetans, farm incomes in the region are low, leading to a range of government initiatives to boost grain and fodder production. However, there is limited information available on current farming practices, yields, and likely yield constraints. The present paper uses available data and farmer interviews to describe the agro-climate and current systems of crop and livestock production, and considers possible strategies to boost production. Although winters in Tibet are cold and dry, summer and autumn provide ideal conditions for crop growth. Cropping systems are characterised by heavy tillage, frequent irrigation, high seeding rates and fertiliser applications, some use of herbicides, and little stubble retention or mechanisation. Spring barley and winter wheat are the predominant crops, followed by rapeseed, winter barley, and minor fodder and vegetable crops. Average yields for the main grain crops are around 4.0 t/ha for spring barley and 4.5 t/ha for winter wheat, significantly lower than should be possible in the environment. Farmers typically keep five or six cattle tethered near the household. Cattle are fed diets based on crop residues but are generally malnourished and rarely produce beyond the needs of the family. It is suggested that research and extension in the areas of crop nutrition, weed control, irrigation, seeding technology, and crop varieties should enable significant increases in grain yield. Increases in cattle production will require increases in the supply of good quality fodder. Cereal/fodder intercrops or double crops sown using no-till seed drills might enable the production of useful amounts of fodder in many areas without jeopardising food grain supply, and allow more crop residues to be retained in fields for improved soil health.
  • Authors:
    • Basnyat, P.
    • Liu, P.
    • Lemke, R.
    • Janzen, H.
    • Campbell, A.
    • Gan, T.
    • McDonald, C. L.
  • Source: Canadian Journal of Plant Science
  • Volume: 89
  • Issue: 5
  • Year: 2009
  • Summary: Crop roots transport water and nutrients to the plants, produce nutrients when they decompose in soil, and provide organic C to facilitate the process of C sequestration in the soil. Many studies on these subjects have been published for cereal crops, but little is known for oilseed and pulse crops. This study was conducted at Swift Current, Saskatchewan, in 2006 and 2007 to characterize the root growth and distribution profile in soil for selected oilseed and pulse crops. Three oilseed [canola ( Brassica napus L.), mustard ( Brassica juncea L.), flax ( Linum usitatissimum L.)], three pulse crops [chickpea ( Cicer arietinum L), dry pea ( Pisum sativum L.) lentil ( Lens culinaris Medik.)], and spring wheat ( Triticum aestivum L.) were grown in 100 cm deep * 15 cm diameter lysimeters pushed into a silt loam soil. Crops were studied under rainfed and irrigated conditions. Lysimeters were removed from the field and sampled for above-ground (AG) and root mass at different depths at five growth stages. Root mass was highest for canola (1470 kg ha -1) and wheat (1311 kg ha -1), followed by mustard (893 kg ha -1) and chickpea (848 kg ha -1), and was lowest for dry pea (524 kg ha -1) and flax (440 kg ha -1). The root mass of oilseeds and pulses reached a maximum between late-flowering and late-pod stages and then decreased to maturity, while wheat root mass decreased to maturity after reaching a maximum at boot stage. On average, about 77 to 85% of the root mass was located in the 0-40 cm depth. Canola, mustard, and wheat rooted to 100 cm, while the pulses and flax had only 4 to 7% of the root mass beyond the 60 cm depth. Irrigation only increased root mass in the 0-20 cm depth. Roots developed more rapidly than AG biomass initially, but the ratio of root biomass to AG biomass decreased with plant maturity. At maturity, the ratio of root biomass to AG biomass was 0.11 for dry pea, and between 0.20 and 0.22 for the other crops tested. Our findings on rooting depths and root mass distribution in the soil profile should be useful for modelling water and nutrient uptake by crops, estimating C inputs into soil from roots, and developing diverse cropping systems with cereals, oilseeds and pulses for semiarid environments.
  • Authors:
    • Berzy, T.
    • Hegyi, Z.
  • Source: Cereal Research Communications
  • Volume: 37
  • Issue: Suppl. 1
  • Year: 2009
  • Summary: If maize production is to be successful it is essential to be clear about the intended end-use and the farm conditions in order to make a wise choice of variety and technology. Recommendations on the end-use of the varieties can only be made based on knowledge of both yield levels and chemical quality. A total of 96 hybrids from four FAO maturity groups were examined at four locations in 2008 in order to analyse their yield and quality and to determine the effect of ecological factors on a number of parameters. The highest yield averages were recorded for hybrids in the FAO 300 group (12.95 t ha -1) at locations with the highest rainfall (Debrecen). In Debrecen and Iregszemcse the plants were able to develop a second ear, thus increasing the yield average (12.31 t ha -1, 11.75 t ha -1). In Szarvas irrigation helped to achieve good yields and reduce drought damage (10.97 t ha -1), while in Martonvasar, although rainfall sums were adequate, the uneven distribution and atmospheric drought led to lower yields (9.65 t ha -1). In this experiment, early hybrids (FAO, 200, FAO 300) had the best yield stability. The starch content of the grain exhibited a close correlation with the yield average. The greatest starch incorporation was recorded for FAO 300 hybrids (72.86%). The expected negative correlation between starch content and protein/oil content was observed. The FAO 200 hybrids had the highest protein and oil contents (9.70 and 3.89%), which gradually declined at later maturity dates (FAO 500: 9.14 and 3.51%). The thousand-kernel mass and the length of the main ear were closely correlated with the maturity date, being lowest for the earliest hybrids (326.39 g, 18.91 cm) and highest in the latest group (346.91 g, 19.74 cm). For protein and oil content, genetic differences between the hybrids were greater (1.50, 1.00%) than between locations (0.97, 0.82%), while in the case of starch the latter caused greater differences (2.84, 4.06%).
  • Authors:
    • Wang, H.
    • Schoenau, J. J.
    • Brandt, S.
    • Lafond, G.
    • Malhi, S. S.
    • Mooleki, S. P.
    • Lemke, R. L.
    • Thavarajah, D.
    • Hultgreen, G.
    • May, W. E.
  • Source: Canadian Journal of Plant Science
  • Volume: 89
  • Issue: 1
  • Year: 2009
  • Summary: No-till (NT) requires all fertilizer nutrients to be applied during planting, but high rates of fertilizer nitrogen (N) in close proximity to the seed can negatively affect seedling development; therefore, different placement technologies have been developed to place seed and N in a single operation while maintaining an adequate separation between them. We conducted a 3-yr field study (2000 to 2002) at four sites in Saskatchewan. The objective was to determine the effects of N fertilizer form [urea (U) and anhydrous ammonia (AA)], placement [broadcast, side-band (SB) and mid-row band (MRB)], timing (fall vs. spring), rate (0 to 90 or 120 kg N ha -1), and P fertilizer placement on yield, seed protein content and N uptake in canola. The N fertilizer managements had no significant effect on crop emergence. Yield, seed protein concentration and N uptake increased with increasing N fertilizer rate. Seed protein was significantly higher on SB compared with MRB and on U compared with AA. Seed yield and seed and straw N uptake were higher when U was SB compared with broadcast. Plant density was higher when P was placed in SB rather than with the seed, but the reverse was true for seed yield and seed N uptake.
  • Authors:
    • He, J. -S.
    • Tan, K.
    • Rao, S.
    • Hu, H. F.
    • Ji, C. J.
    • Chen, A. P.
    • Tang, Y. H.
    • Smith, P.
    • Fang, J. Y.
    • Yang, Y. H.
  • Source: Global Change Biology
  • Volume: 15
  • Issue: 11
  • Year: 2009
  • Summary: Climate warming is likely inducing carbon loss from soils of northern ecosystems, but little evidence comes from large-scale observations. Here we used data from a repeated soil survey and remote sensing vegetation index to explore changes in soil organic carbon (SOC) stock on the Tibetan Plateau during the past two decades. Our results showed that SOC stock in the top 30 cm depth in alpine grasslands on the plateau amounted to 4.4 PgC (1 Pg = 10(15) g), with an overall average of 3.9 kg C m(-2). SOC changes during 1980s - 2004 were estimated at -0.6 g C m(-2) yr(-1), ranging from -36.5 to 35.8 g C m(-)2 yr(-1) at 95% confidence, indicating that SOC stock in the Tibetan alpine grasslands remained relatively stable over the sampling periods. Our findings are nonconsistent with previous reports of loss of soil C in grassland ecosystems due to the accelerated decomposition with warming. In the case of the alpine grasslands on the Tibetan Plateau studied here, we speculate that increased rates of decomposition as soils warmed during the last two decades may have been compensated by increased soil C inputs due to increased grass productivity. These results suggest that soil C stock in terrestrial ecosystems may respond differently to climate change depending on ecosystem type, regional climate pattern, and intensity of human disturbance.