• Authors:
    • Melander, B.
    • Munkholm, L. J.
    • Hansen, E. M.
    • Olesen, J. E.
  • Source: Soil & Tillage Research
  • Volume: 109
  • Issue: 1
  • Year: 2010
  • Summary: Finding ways of reducing nitrate leaching in Northern Europe has become an extremely important task, especially under the projected climate changes that are expected to exacerbate the problem. To this end, two field experiments were established under temperate coastal climate conditions to evaluate the effect of tillage, straw retainment and cropping sequences, including cover crops, on nitrate leaching. The experiments were established in autumn 2002 on a loamy sand with 92 g clay kg(-1) and a sandy loam with 147 g clay kg(-1). The tillage treatments were stubble cultivation to 8-10 cm or 3-4 cm, direct drilling, or ploughing to 20 cm. The hypothesis was that (i) decreasing soil tillage intensity would decrease leaching compared to ploughing, (ii) leaving straw in the field would decrease leaching compared to removing straw, and (iii) a spring/winter crop rotation with catch crops would be more efficient in reducing nitrate leaching than a winter crop rotation. Overall, we were not able to confirm the three hypotheses. The effect of soil tillage on leaching might be blurred because the studied crop rotations had a high proportion of winter crops and because catch crops were grown whenever the alternative would have been bare soil in autumn and winter. The spring/winter crop rotation with catch crops was not found to be more efficient in reducing nitrate leaching than the winter crop rotation. In contrast, in a single year the winter crop rotation showed significantly lower leaching than the spring/winter crop rotations, probably due to the spring/winter crop rotation including peas, which may be considered a high-risk crop. Our study highlights that management practices that improve biomass production throughout the year are crucial in order to tighten the nitrogen cycle and thereby reduce nitrate leaching. (C) 2010 Elsevier B.V. All rights reserved.
  • Authors:
    • Evans, K.
    • Deliopoulos, T.
    • Haydock, P. P. J.
    • Minnis, S. T.
  • Source: Crop Protection
  • Volume: 29
  • Issue: 10
  • Year: 2010
  • Summary: The soil fumigant 1,3-dichloropropene (1,3-D) has been used in the UK for the control of potato cyst nematodes (PCN), Globodera pallida (Stone) and Globodera rostochiensis (Wollenweber), but its potential herbicidal activity has not been extensively investigated in this country. Field and glasshouse studies were therefore conducted to evaluate the potential of 1,3-D for the control of weeds in potatoes, and observations were made on the severity of potato stem canker, caused by the fungus Rhizoctonia solani Kuhn [teleomorph: Thanatephorus cucumeris (Frank) Donk]. Autumn application of 1,3-D at 211.5 L active substance (as.) ha(-1) significantly suppressed the number of germinating weeds and the percentage of weed ground cover by 83% and 79%, respectively, relative to controls. There were also species-specific significant decreases (field pansy, Viola arvensis, in particular) in the number of weed seeds germinating in field soil in the glasshouse post-1,3-D treatment. The effect of 1,3-D declined in time and single (autumn or spring) or combined application produced a slight, but not significant, reduction in the number of weeds germinated on potato ridges relative to those recorded in untreated soil. The severity of stem canker on potato plants was not significantly reduced by 1,3-D but both mean number and weight of stems per plant were significantly increased compared with plants from untreated plots. These studies demonstrated that 1,3-D, in addition to giving PCN control, has efficacy against weeds; implications are the potential for reduced herbicide input in the crop rotation with accompanying economic and environmental benefits. (C) 2010 Elsevier Ltd. All rights reserved.
  • Authors:
    • Acko, D. K.
  • Source: Acta agriculturae Slovenica
  • Volume: 95
  • Issue: 1
  • Year: 2010
  • Summary: A number of factors influenced the increased number of crops on Slovenian farms legal limitation of maize production to two years on the same field, introduction of integrated crop production and certain measures of the Slovene Agri-Environmental Programme. Crop rotation on hop fields that has already been analyzed on 22 hop growing and livestock farms in Spodnja Savinjska dolina in 2008 show that the maize monoculture has been supplemented by some other crops like wheat, barley, lucerne, clover-grass mixtures and high beans; compared to the conventional production in the past, the crop rotation is now longer. Phytosanitary adequacy of two- and three-year rotation could be improved with supplementary crops, that is with fodder crucifers (fodder rapeseed and rape, forage kale), green manure (white mustard, oil radish), legume crops (soya, peas, vetch, field bean, white lupin, crimson clover, Persian clover, Egyptian clover) and compound fodders like Landsberger mixture and mixtures of vetch with oat or barley. Prohibition to sow broad-leafed plants in the quarantine rotation due to hop wilting limits the selection of crops to grasses (Italian rye-grass) and fodder grains (maize, barley), but the farmers could increase the selection of grains with oats, rye, triticale, mixture of wheat and rye, millet, sorghum and Sudan grass. With the use of recommended crop rotations in two-, three- and four-year rotation, we can expect the increased influence of crop rotation on improved health condition of the new hop plantations in the future with simultaneous reduction of the use of pesticides as well.
  • Authors:
    • Hoffmann, A. A.
    • Umina, P. A.
    • Weeks, A. R.
    • Arthur, A. L.
  • Source: Experimental and Applied Acarology
  • Volume: 52
  • Issue: 2
  • Year: 2010
  • Summary: Balaustium medicagoense and Bryobia spp. have recently been identified as emerging pests of winter crops and pastures in Australia. These mites have a high natural tolerance to currently registered pesticides, highlighting the need to develop alternative control strategies such as cultural controls which require an understanding of plant associations. In shade-house experiments, Bryobia spp. survived and reproduced successfully on pasture, lupins and oats, but progeny failed to reach the adult stage on canola and wheat. Balaustium medicagoense progeny failed to produce a generation on any crop but parental adults survived a few months on all crops, particularly wheat. Bryobia spp. damaged canola, pasture and lupins, but caused minimal damage to oats and wheat, whereas Ba. medicagoense caused considerable damage to wheat and lupins, but only moderate damage to canola, oats and pasture. Field survey data, taken from approximately 450 sites across southern Australia, combined with analysis of historical pest reports, suggest broadleaf crops such as canola, lucerne, lupins and weeds appear particularly susceptible to attack by Bryobia species. Balaustium medicagoense was more commonly found on cereals and grasses, although they also attacked broadleaf crops, particularly canola, lucerne and lupins. These findings show that the mites have the potential to be an important pest on several winter grain crops and pasture, but there are important differences that can assist in management strategies such as targeted crop rotations.
  • Authors:
    • Nel, A. A.
  • Source: South African Journal of Plant and Soil
  • Volume: 26
  • Issue: 3
  • Year: 2009
  • Summary: Crop rotation is known to enhance crop yields. It is therefore recommended, regardless of rainfall and soil type, as a counter measure for the risks associated with monoculture maize ( Zea mays). Experience in the western Highveld where rainfall is low and erratic, has shown that the yield of maize does not necessarily improve as expected when preceded by alternative crops, but in fact, is often reduced. The present study was initiated to determine the effect of crop rotation with cowpea, groundnut, soyabean, sunflower or fallow on the yield and rainfall use efficiency of maize under marginal conditions on the western Highveld. Dryland maize was grown in five crop rotation systems on Mutton type soils at the farms Holfontein (four years) and Noodshulp (five years), both situated close to Ottosdal (2649′S; 2600′E). The soil profiles had an effective depth of >1.5 m at Holfontein and 1.25 m at Noodshulp. Crop rotation systems consisted of two-year rotations of cowpea-, groundnut, soybean-, sunflower-, and fallow-maize; as well as groundnut-, soybean-, and sunflower-fallow. A continuous monoculture maize treatment was included to serve as control. At Noodshulp where the rainfall was more variable, crop rotation induced maize yield deviations from the monoculture control occurred more often than at Holfontein. Apart from yield neutral and positive effects, instances of a decline in maize yield in some years due to crop rotation with cowpea, groundnut and sunflower also occurred. Taking the long-term rotational effect and the possibility of a yield decline into account, fallowing and the rotational crops ranked from best to worse were groundnut, soyabean, fallowing, cowpea and sunflower. The long-term effect of cowpea on the yield of maize was neutral and that of sunflower negative. The mean rainfall use efficiency of monoculture maize was, with the exception of maize preceded by groundnut, similar to that of maize grown in rotation.
  • Authors:
    • Lawson, A. R.
    • Greenwood, K. L.
    • Kelly, K. B.
  • Source: Agricultural Water Management
  • Volume: 96
  • Issue: 5
  • Year: 2009
  • Summary: Knowledge of the components of the water balance - evaporation, transpiration and deep drainage - would be beneficial for targeting productivity improvements for irrigated forages in northern Victoria. We aimed to estimate these components using a simple water balance and the dual crop coefficients provided in FAO-56. Soil water deficits from a field experiment, comparing the water use of six border-check and one spray irrigated forage system, agreed well with the modelled values, except for alfalfa where irrigation intake was restricted. About 85% of the water applied to perennial forages (perennial ryegrass/white clover, tall fescue/white clover and alfalfa) was used for transpiration, 10% for evaporation and 5% was lost as drainage below the root zone. Evaporation was highest from the double-cropped (oats/millet) system (30%) and was 5-25% of the water used by winter-growing annual pastures (Persian clover/Italian ryegrass and both border-check and spray irrigated subterranean clover/Italian ryegrass). The high proportion of water used as transpiration by the perennial forages was due to their high ground cover maintained throughout the year. When compared over similar seasonal conditions, actively growing forages used similar amounts of water, indicating that any increases in water productivity will be mainly due to higher production and/or to matching the growing season of the forage to periods of lower potential evapotranspiration.
  • Authors:
    • Isk, D.
    • Ngouajio, M.
    • Mennan, H.
    • Kaya, E.
  • Source: PHYTOPARASITICA
  • Volume: 37
  • Issue: 4
  • Year: 2009
  • Summary: Weed control is a major concern for organic farmers around the world and non-chemical weed control methods are now the subject of many investigations. Field studies were conducted in tomato ( Solanum lycopersicum L.) from 2004 to 2006 at the Black Sea Agricultural Research Institute experiment field to determine the weed suppressive effects of winter cover crops. Treatments consisted of ryegrass ( Lolium multiflorum L.), oat ( Avena sativa L.), rye ( Secale cereale L.), wheat ( Triticum aestivum L.), gelemen clover ( Trifolium meneghinianum Clem.), Egyptian clover ( Trifolium alexandrinum L.), common vetch ( Vicia sativa L.), hairy vetch ( Vicia villosa Roth.) and a control with no cover crop. Treatments were arranged in a randomized complete block design with four replications. To determine the weed suppressive effects of the cover crops, weed density and total weed dry biomass were assessed at 14, 28, and 56 days after termination (DAT) of the cover crops from all plots using a 50*50 cm quadrat placed randomly in each plot. After cover crop kill and incorporation into soil, tomato seedlings variety 'H2274' were transplanted. Broadleaved weed species were the most prominent species in both years. Total weed biomass measured just prior to cover crop incorporation into the soil was significantly lower in S. cereale plots than in the others. The number of weed species was lowest at 14 DAT and later increased at 28 and 56 DAT, and subsequently remained constant during harvest. This research indicates that cover crops such as L. multiflorum, S. cereale, V. sativa and V. villosa could be used in integrated weed management programs to manage some weeds in the early growth stages of organic tomato.
  • Authors:
    • Kindred, D. R.
    • Wiltshire, J. J. J.
    • Sylvester-Bradley, R.
    • Hatley, D. L. J.
    • Clarke, S.
  • Source: HGCA Project Report
  • Volume: i + 47 pp.
  • Issue: 460
  • Year: 2009
  • Summary: This report describes a second year of research that tested whether soil nitrogen supplies to cereal crops can be detected using canopy sensors; the first season was reported in HGCA Project Report No. 427. Nitrogen fertiliser experiments on cereals were established at four sites in 2006-7. In the following year, commercial cereal crops (wheat, oats or barley) were grown and, at each site, plot positions as used in the previous year were marked out for testing with a reflectance sensor. Reflectance was measured four times during tillering, between December and May (dependant on site), using a Crop Circle instrument (provided by Soilessentials Ltd) which measured reflectance at 880 nm (near-infrared, NIR) and 590 nm (orange). A Normalised Difference Vegetation Index (NDVI) was calculated to give a measure of vegetation cover. Soil mineral N (SMN) data were obtained for the sites. No fertiliser N was applied in 2008 and total N uptake at harvest was taken to represent the 'soil N supply' (SNS). Data were interpreted for relationships between canopy reflectance and soil N. The best level of tillering and ground cover was achieved at High Mowthorpe, which was sown early. Boxworth and Terrington crops were smaller, and the crop at Rosemaund was very small. High levels of N applied in 2007 had large effects on SMN at Boxworth and Terrington, but maximum amounts were smaller at High Mowthorpe or Rosemaund and maximum SMN and SNS levels were small. Use of the sensor successfully detected the differences in SMN residues at Boxworth and Terrington, especially below 120-140 kg/ha, as was found in the previous year's experiments. The relationships improved with later assessment of NDVI. Change in NDVI between assessment dates showed that canopies always grew during the 2007/08 winter but change in NDVI was less useful for predicting SNS than absolute values of NDVI. Merged data from both seasons of the study showed that NDVI signals overwinter could be interpreted according to their differences from the theoretical NDVI of an unlimited crop. It was concluded that young canopies can signal soil N status where SMN is less than 120-140 kg/ha. Effects were more certain as crops grew, so canopy sensing for soil N supplies should prove more useful as the season progresses.
  • Authors:
    • Cameron, C.
    • Kearney, G.
    • Dowling, P.
    • Quigley, P.
    • Cousens, R.
    • Chapman, D.
    • Tozer, K.
  • Source: Crop & Pasture Science
  • Volume: 60
  • Issue: 11
  • Year: 2009
  • Summary: A field experiment was established in a southern Australian temperate pasture to investigate the effects of identity and proximity of perennial grasses on the demography of the annual grasses Vulpia spp. ( V. myuros, V. bromoides) and Hordeum leporinum (barley grass). Annual grasses were grown either alone or in mixtures, at different distances from rows of Dactylis glomerata (cocksfoot) and Phalaris aquatica (phalaris). Dactylis had a greater suppressive effect than Phalaris on Vulpia and Hordeum. Biomass, tiller production, and panicle production of annual grasses increased linearly with increasing distance from the perennial row. Tiller and panicle production were greater for Vulpia than Hordeum. The estimated rate of population growth (lambda) for annual grasses was greater in Phalaris than in Dactylis and in Vulpia than in Hordeum, and increased with sowing distance from perennial grass rows. It was estimated that lambda, when seeds were sown directly adjacent to a row of perennial grasses, was 1 and 0.4 for Vulpia and Hordeum, respectively, within Dactylis stands, and 7 and 3, respectively, within Phalaris stands. However, 15cm from the row, lambda reached 50 and 39 for Vulpia and Hordeum, respectively, within Phalaris stands, and 39 and 16, respectively, within Dactylis stands. In grazed, dryland pastures, perennial competition alone is therefore unlikely to prevent population growth of annual grasses, especially in systems heavily disturbed by grazing or drought. However, Dactylis showed more promise than Phalaris in limiting the abundance of these weeds.
  • Authors:
    • Smith, M.
    • Barnard, A.
  • Source: Field Crops Research
  • Volume: 112
  • Issue: 2/3
  • Year: 2009
  • Summary: Preharvest sprouting (PHS) is a risk factor in winter cereal farming in certain environments as even mild sprouting affects the suitability of wheat for end-use products. This is because even mild sprouting affects the suitability of wheat for end-use products. The extent of PHS is hard to predict. To establish a quantitative relationship between PHS and different climatic characteristics, eighteen winter wheat cultivars were planted in three regions representative of the wheat growing conditions of the Free State Province of South Africa over four years. Climatic characteristics during six environmental periods were investigated, namely planting to harvest (PH), anthesis to harvest (AH), grain filling (GF), 14 days prior to physiological maturity (14M) and 10 and 20 days prior to harvest (10H and 20H) respectively. These data sets were correlated with PHS resistance determined in a rain simulator to determine if climate during various stages of grain development had an effect on the expression of dormancy and subsequent PHS. Principal component analysis (PCA) on mean PHS values identified three distinct groupings of cultivars, ranging from PHS susceptible to PHS resistant. A fairly strong positive correlation ( r=0.715, P=0.008) was found between PHS and minimum temperature during grain filling. Large variations in PHS values were also observed between the various cultivars, indicating that certain cultivars, such as Caledon, Gariep, Limpopo, Matlabas, PAN 3118, PAN 3120, PAN 3377 and SST 334, are more sensitive to environmental effects than others and that the variation in cultivar PHS is not consistent across sites and years.