• Authors:
    • Souza, R. A.
    • Crispino, C. C.
    • Franchini, J. C.
    • Torres, E.
    • Hungria, M.
  • Source: Soil & Tillage Research
  • Volume: 92
  • Issue: 1/2
  • Year: 2007
  • Summary: The objective of this work was to identify soil parameters potentially useful to monitor soil quality under different soil management and crop rotation systems. Microbiological and chemical parameters were evaluated in a field experiment in the State of Parana, southern Brazil, in response to soil management [no-tillage (NT) and conventional tillage (CT)] and crop rotation [including grain (soybean, S; maize, M; wheat, W) and legume (lupin, L.) and non-legume (oat, O) covers] systems. Three crop rotation systems were evaluated: (1) (O/M/O/S/W/S/L/M/O/S), (2) (O/S/L/M/O/S/W/S/L/M), and (3) (O/S/W/S/L/M/O/M/W/M), and soil parameters were monitored after the fifth year. Before ploughing, CO 2-emission rates were similar in NT and CT soils, but plough increased it by an average of 57%. Carbon dioxide emission was 13% higher with lupin residues than with wheat straw; decomposition rates were rapid with both soil management systems. Amounts of microbial biomass carbon and nitrogen (MB-C and MB-N, respectively) were 80 and 104% higher in NT than in CT, respectively; however, in general these parameters were not affected by crop rotation. Efficiency of the microbial community was significantly higher in NT: metabolic quotient ( qCO 2) was 55% lower than in CT. Soluble C and N levels were 37 and 24% greater in NT than in CT, respectively, with no effects of crop rotation. Furthermore, ratios of soluble C and N contents to MB-C and MB-N were consistently lower in NT, indicating higher immobilization of C and N per unit of MB. The decrease in qCO 2 and the increase in MB-C under NT allowed enhancements in soil C stocks, such that in the 0-40 cm profile, a gain of 2500 kg of C ha -1 was observed in relation to CT. Carbon stocks also varied with crop rotation, with net changes at 0-40 cm of 726, 1167 and -394 kg C ha -1 year, in rotations 1, 2 and 3, respectively. Similar results were obtained for the N stocks, with 410 kg N ha -1 gained in NT, while crop rotations 1, 2 and 3 accumulated 71, 137 and 37 kg of N ha -1 year -1, respectively. On average, microbial biomass corresponded to 2.4 and 1.7% of the total soil C, and 5.2 and 3.2% of the N in NT and CT systems, respectively. Soil management was the main factor affecting soil C and N levels, but enhancement also resulted from the ratios of legumes and non-legumes in the rotations. The results emphasize the importance of microorganisms as reservoirs of C and N in tropical soils. Furthermore, the parameters associated with microbiological activity were more responsive to soil management and crop rotation effects than were total stocks of C and N, demonstrating their usefulness as indicators of soil quality in the tropics.
  • Authors:
    • Bateman, G.
    • Jenkyn, J.
    • Gutteridge, R.
  • Source: Annals of Applied Biology
  • Volume: 150
  • Issue: 1
  • Year: 2007
  • Summary: Take-all disease ( Gaeumannomyces graminis var. tritici) in wheat crops is known to be suppressed by naturally occurring antagonistic fungi, closely related to the pathogen, that infect grasses and cereals. This form of suppression was re-investigated because of the changing importance and role of grass weeds and grass covers in arable farming. Natural populations of the competitive fungus Gaeumannomyces cylindrosporus, allowed to develop under rye-grass, were more effective than artificially introduced populations in suppressing the development of take-all in following wheat crops. To be effective, the antagonist needs to be present before the start of wheat cropping. Introducing G. cylindrosporus, but not G. graminis var. graminis (a potential antagonist that is faster growing), into a previous crop, or just after the previous crop, sometimes suppressed take-all, but the effect was small. It is concluded that, for any future attempts at biocontrol by these fungi, they should be introduced into a preceding crop not susceptible to take-all. Take-all inoculum in the soil should be at a minimum and effective hosts of the take-all pathogen must not be present as weeds or volunteers.
  • Authors:
    • Moravcikova, P.
    • Kuniak, L.
    • Hozova, B.
    • Gajdosova, A.
  • Source: Czech Journal of Food Sciences
  • Volume: 25
  • Issue: 6
  • Year: 2007
  • Summary: Water-insoluble beta-(1,3)-D-glucan (lichenan) was determined in 43 samples of various cereal (i.e., oats, barley, wheat, millet) and pseudocereal (i.e., buckwheat, amaranth) cultivars using a modified procedure with fungal alpha-amylase (Fermizyme P 300). The content of water-insoluble beta-glucan varied with dependence on the cereal species and cultivars. The highest content was observed in covered oat cultivars (Cyril and the new breeding cultivar PS-100), ranging from 26.7 to 28.2 g/100 g dry matter (d.m.), followed by less traditional cereals such as millet ( Panicum miliaceum), amaranth ( Amaranthus sp.), and buckwheat ( Fagopyrum) - more than 20 g/100 g d. m. A somewhat lower average content of water-insoluble beta-glucan was found in wheat - 12.7-16.2 g/100 g d. m., in spelt wheat - 8.5 g/100 g d. m., and in oats - varying between 15.3 and 18.7 g/100 g d. m.
  • Authors:
    • Rodrigues, E.
    • Marchetti, M.
    • Goncalves, M.
    • Souza, L.
    • Ontocelli, R.
    • Lourente, E.
  • Source: Acta Scientiarum Agronomy
  • Volume: 29
  • Issue: 1
  • Year: 2007
  • Summary: Some plants for mulching have the capacity to increase the availability of nutrients in the soil - nitrogen in particular - for crop succession, thus producing positive effects on the interaction between mineral fertilizer and green manure. As a result, there is a greater possibility to obtain higher incomes than by using each one separately. The objective of this study was to evaluate the effect of antecedent crops, levels and sources of nitrogen on yield compounds and foliar nitrogen content of maize by means of no-tillage system. These were constituted by crops preceding maize, i.e., black oat, wheat, pasture turnip, hairy vetch and one fallow treatment during winter. Subplots were established by four levels of nitrogen (0; 50; 100 and 200 kg ha -1 of N), which were applied as cover. Sub-subplots were represented by two sources of nitrogen (ammonium sulfate and urea). Results showed that antecedent crops had some influence upon yield, mass of 1000 grains and foliar nitrogen content of maize. The highest yield of maize was obtained after the winter rest, the pasture turnip and also in the absence of nitrogen fertilizer application as cover. Maximum yield of maize was also obtained when sowing was done after wheat and black oat, in nitrogen levels of 140 and 137 kg ha -1, respectively. The nitrogen sources utilized had some influence only upon the index of harvest, the number of grains per ear and the foliar nitrogen content.
  • Authors:
    • Pedersen, J. B.
  • Source: Oversigt over Landsfors<o>gene 2007. Fors<o>g og unders<o>gelser i de land<o>konomiske foreninger
  • Year: 2007
  • Summary: Work conducted by Landsforsgene, a collaborative body that undertakes field trials and experiments on crop plants in Denmark, is reported. A general introduction gives details of conditions in the 2007 growing season (warmer in spring and wetter than usual in summer), and their effects on factors such as the efficacy of fertilizer application and the harvest. The aim is to give growers a basis for future planning, taking account of environmental conditions and profitable plant production. Most of the report is devoted to separate sections covering individual crops: winter barley, winter rye, triticale, winter wheat, spring barley, oats, spring wheat, field peas, grass seeds, rape, hemp, spinach, strawberries, potatoes, sugar beet, pasture plants (grasses and clovers), and maize. Within these sections details of varieties, fertilizers, weeds, and diseases are provided in the text and in numerous tables and photographs. Other small sections deal with topics including organic production, fertilizers, plant breeding, statistical methods, policies, and names and addresses of suppliers. The report concludes with a list of the 23 authors of sections, and a comprehensive index.
  • Authors:
    • Marais, G. F.
    • Pakendorf, K. W.
    • Pretorius, Z. A.
    • Prins, R.
    • Komen, J. S.
  • Source: Australian Journal of Agricultural Research
  • Volume: 58
  • Issue: 6
  • Year: 2007
  • Summary: The cultivation of small grain cereals was introduced to South Africa by Dutch settlers in the 17th Century. According to historical records the first documented epidemic of wheat stem rust occurred in the south-western parts of the current Western Cape in 1726. Recurring stem and leaf rust epidemics were associated with expanding wheat production and became particularly severe in the winter-rainfall regions of the Western and Eastern Cape, as well as in the summer-rainfall regions of the Free State. The wheat stripe rust pathogen was first detected in South Africa in 1996. Due to susceptibility of cultivars at the time of this exotic introduction, stripe rust has caused significant losses in commercial wheat production over the past 10 years. Pathotype surveys of Puccinia graminis and P. triticina were initiated in the 1920s, but were discontinued until research on wheat stem rust was resumed in the 1960s. Recent evidence has shown that P. graminis f. sp. tritici continues to evolve. In addition, the annual number of wheat stem rust collections is increasing, emphasising the sustained threat of this damaging pathogen. A stem rust pathotype first detected in 2000, with newly acquired virulence for Sr8b and Sr38, currently constitutes more than 80% of all collections. Leaf and stem rust diseases also occur on barley, oat, triticale, and rye and are important production constraints in several regions. Some studies have described variability in these pathogens but long-term records of pathogenicity changes in barley and oat rust are not available. Cereal rust diseases have clearly played an important role in South African agriculture and many production regions remain favourable for rust development. Current expertise in cereal rusts covers most technologies necessary to study the respective host-pathogen systems. However, a general lack of capacity and fragmentation of research groups prevent a unified approach and remain a challenge for sustainable cereal rust control in South Africa. A national strategy for cereal rust control, with particular emphasis on pathogen and host resources, and breeding for resistance, is urgently needed.
  • Authors:
    • Balkcom, K. S.
    • Gamble, B. E.
    • Patterson, M. G.
    • Reeves, D. W.
    • Price, A. J.
    • Arriaga, F. J.
    • Monks, C. D.
  • Source: Peanut Science
  • Volume: 34
  • Issue: 1
  • Year: 2007
  • Summary: Information is needed on the role of cover crops as a weed control alternative due to the increase in adoption of conservation-tillage in peanut production. Field experiments were conducted from autumn 1994 through autumn 1997 in Alabama to evaluate three winter cereal cover crops in a high-residue conservation-tillage peanut production system. Black oat ( Avena strigosa Schreb.), rye ( Secale cereale L.), and wheat ( Triticum aestivum L.) were evaluated for their weed-suppressive characteristics compared to a winter fallow system. Three herbicide systems were utilized: no herbicide, preemergence (PRE) herbicides followed by (fb) postemergence (POST) herbicides, and PRE fb sequential POST herbicides. The PRE fb POST herbicide input system consisted of pendimethalin at 1.12 kg ai/ha fb an additional early POST application of paraquat at 0.14 kg ai/ha plus bentazon at 0.56 kg ai/ha. The PRE fb sequential POST herbicide input system contained the aforementioned herbicides fb 2,4-DB at 0.22 kg ai/ha plus chlorimuron at 0.14 kg ai/ha applied late POST. No cover crop was effective in controlling weeds without a herbicide program. However, when black oat or rye was utilized with PRE fb POST herbicides, weed control was similar to the high input system in two out of three years. Yield increased in 14 of 27 comparisons following conservation-tilled peanut using the Brazilian cover crop management system, compared to a winter fallow system. Yields never decreased following a winter cover crop compared to winter fallow. The winter fallow, high herbicide input system yielded between 7 and 26% less peanut compared to the highest yielding system that included a winter cover crop. The Brazilian system using black oat or rye cover crop has potential to increase peanut productivity and reduce herbicide inputs for peanuts grown in the Southeast.
  • Authors:
    • Chauhan, S. K.
    • Baljit, S.
    • Saralch, H. S.
  • Source: Agroforestry: systems and practices
  • Year: 2007
  • Summary: Punjab is the richest state in the country in term of per capita income and has earned the name as food bowl of the country by putting 84-85 per cent of its geographical area under highly intensive, technical and mechanical agriculture with cropping intensity as high as 185 per cent and contributing more than one third of rice and half of its wheat production to the central pool of food reserve. The food grain production in the state has increased approximately twelve times in a span of about 50 years after independence from 20 lac tones in 1950-51 to 234.89 lakh tonnes in 2002-2003. Achieving this high productivity without caring for natural resources has resulted in a considerable loss in the inherent production potential and deterioration of soil health. As a result, man is getting serious warning signals in the form of lowering of water table, drought, high rate of environmental pollution, extremes of climatic parameters, etc. Agriculture in the state has become too intensive, wasteful and reckless and the radical changes are required to maintain the balance. Therefore, there is a strong thinking to diversify farming in the state to maintain the sustainability of the whole system. The state government is stressing hard to save the natural resources through the diversification in traditional crop rotation and adopt resource-conserving measures. With the introduction of fast growing multipurpose tree species in Punjab during sixties, agroforestry has been recognized as a sustainable system of high potential to boost the state's meager forest resources and to check the further degradation of natural resources. Highly productive block planting of poplar intercropped with wheat, sugarcane, turmeric, oats, berseem, mustard, medicinal plants, seasonal flowers, vegetables, etc. has become popular in irrigated tracts of the state. Boundary planting of eucalypts in the wheat- paddy cropping system and scattered trees of kikar, khair, shisham, dek, etc. on cultivated lands under rainfed conditions, especially in the sub-montane foot hill zone, play an important role in soil conservation and boosting the socio-economic status of the farmers. These tree species have inherent potential of increasing the productivity of problematic lands of the state. Therefore, the diversion of farmlands towards agroforestry will not only increase tree cover but also achieve the desired objective of National Forest Policy-1988 and conserve the precious natural resources like ground water, soil, biodiversity, etc. and prove to be a viable alternative sustainable land use system, which is renewable and eco-friendly as compared to sole agricultural crops in the years to come. The profitability of tree plantations on farmers' fields will further improve with the implementation of trading of carbon credits under Kyoto Protocol.
  • Authors:
    • Valverde, B.
  • Source: Weed Technology
  • Volume: 21
  • Issue: 2
  • Year: 2007
  • Summary: Twenty-one grass weeds have evolved resistance to herbicides in Latin America, particularly in rice, soyabean, wheat, and orchards. Junglerice, the most widespread and economically important rice weed, evolved resistance to propanil, acetyl-coenzyme A carboxylase (ACCase)-inhibitor herbicides, quinclorac, and imazapyr in Central America, Colombia, and Venezuela. Some junglerice populations are resistant to at least three herbicide modes of action. Other herbicide-resistant (HR) rice weeds are barnyardgrass and gulf cockspur to quinclorac in Brazil, and saramollagrass to ACCase-inhibitor herbicides in Colombia and bispyribac in Venezuela. Populations of weedy rice resistant to imidazolinones are now emerging, most likely originated from gene flow from imidazolinone-resistant rice. Saramollagrass also became resistant to nicosulfuron in corn in Venezuela. Eight species associated with soyabean are resistant to ACCase-inhibitor herbicides in Brazil (alexandergrass, goosegrass, and southern crabgrass) and Bolivia (Louisiana cupgrass, itchgrass, sudangrass, and two common wild sorghum species). Four more ACCase-inhibitor-resistant species (hedgehog dogtailgrass, wild oat, rigid ryegrass, and Italian ryegrass) are found in Chile infesting canola and wheat. ACCase-inhibitor-resistant hood canarygrass, littleseed canarygrass, and wild oat are important in wheat in Mexico. Resistance to acetolactate synthase (ALS)-inhibitor herbicides has been reported in itchgrass, goosegrass, and Mexican grass. Italian ryegrass populations resistant to glyphosate have been found in Chile and Brazil. Glyphosate resistance has also evolved in goosegrass in Bolivia and johnsongrass in Argentina. In general, little is done to prevent resistance evolution. An exception is the stewardship programs aiming to prevent gene flow from imidazolinone-resistant rice to weedy rice. Once resistance evolves, HR populations are mostly managed by shifting to herbicides with different modes of action and, in some cases, by slightly modifying agronomic practices. Propanil formulations containing a synergist are used to manage propanil-resistant junglerice. Increased no-till agriculture and planting of glyphosate-resistant crops are likely to select more glyphosate-resistant weeds.
  • Authors:
    • Hons, F.
    • Dou, F.
    • Wright, A.
  • Source: Soil Science
  • Volume: 172
  • Issue: 2
  • Year: 2007
  • Summary: Crop species and conservation tillage may enhance carbon (C) and nitrogen (N) sequestration potential in subsurface soils. The objectives of this study were to determine the effects of crop species and tillage on soil organic C (SOC) and total N distribution in six soil depth intervals from 0 to 105 cm after 20 years of treatment imposition. Tillage had the most influence on soil C and N at 0 to 5 cm, and impacts extended to the 15- to 30-cm depth for wheat and sorghum. Overall, SOC and total N for wheat were 18 and 15% higher than sorghum and soybean. Dissolved organic C (DOC) depth distribution was similar to SOC and total N. The proportion of SOC as DOC ranged from 1.3 to 3.3% and increased with soil depth. The highest soil C and N levels occurred for wheat under no tillage. The depth of soil impacted by crop species was shallower for conventional tillage than no tillage, and the depth distribution exhibited a logarithmic pattern. Soil organic C, total N, and DOC decreased 404, 507, and 205%, respectively from 0-5 to 80-105 cm. The maximum depth interval below which no further decreases in SOC and total N occurred was 30 to 55 cm for soybean, 55 to 80 cm for wheat, and 80 to 105 cm for sorghum, demonstrating the importance of subsurface soils for C sequestration. Crop management impacts below the depth of tillage demonstrate the importance of crop rooting and belowground biomass, or translocation of dissolved organic matter, to subsoil C sequestration.