• Authors:
    • Egli, D. B.
  • Source: Field Crops Research
  • Volume: 106
  • Issue: 1
  • Year: 2008
  • Summary: The increases in crop yield that played an important role in maintaining adequate food supplies in the past may not continue in the future. Soybean ( Glycine max L. Merrill) county yield trends (1972-2003) were examined for evidence of plateaus using data (National Agricultural Statistics Service) for 162 counties (215 data sets) in six production systems [Iowa, Nebraska (irrigated and non-irrigated), Kentucky and Arkansas (irrigated and non-irrigated)] representing a range in yield potential. Average yield (1999-2003) was highest in irrigated production in Nebraska (3403 kg ha -1) and lowest in non-irrigated areas in Arkansas (1482 kg ha -1). Average yield in the highest yielding county in each system was 31-88% higher than the lowest. Linear regression of yield versus time was significant ( P=0.05) in 169 data sets and a linear-plateau model reached convergence (with the intersection point in the mid-1990s) in 35 of these data sets, but it was significantly ( P=0.10) better in only three data sets (
  • Authors:
    • Blackshaw, R. E.
    • Johnson, E. N.
    • Beckie, H. J.
    • Gan, Y.
  • Source: Canadian Journal of Plant Science
  • Volume: 88
  • Issue: 2
  • Year: 2008
  • Summary: Competitive crops or cultivars can be an important component of integrated weed management systems. A study was conducted from 2003 to 2006 at four sites across semiarid prairie ecoregions in Saskatchewan and Alberta to investigate the productivity and quality of canola (Brassica napus L.) and mustard cultivars under weed competition. Four open-pollinated canola cultivars, four hybrid canola cultivars, two canola-quality mustard and two oriental mustard cultivars [Brassica juncea (L.) Czern. & Coss.], and two yellow mustard (Sinapis alba L.) cultivars were grown under weedy and weed-free conditions. When combined across site-years, crop aboveground biomass at maturity and seed yield were reduced by weed interference, except for yellow and oriental mustard. However, seed oil and protein content of cultivars were not affected by weed competition. Among crop types, yellow and oriental mustard were best able to maintain biomass and seed yield under weed interference, followed in decreasing order of competitiveness by hybrid and open-pollinated canola, then canola-quality mustard.
  • Authors:
    • Jia, H.
    • Ma, C.
    • Yang, Q.
    • Liu, Z.
    • Li, G.
    • Liu, H.
  • Source: Nongye Jixie Xuebao = Transactions of the Chinese Society for Agricultural Machinery
  • Volume: 38
  • Issue: 12
  • Year: 2007
  • Summary: The present status of dry farming in northern China was analyzed and a three-year rotation tillage method suitable for the ridged cultivation region of northeastern China and the techniques for efficient utilization of natural rainfall in the Loess Plateau region of northwestern China was put forward. The tests conducted in the northeast showed that stalk mulching increased the percentage of soil moisture content by 10% and the content of soil organic matter by 0.06 percentage point after three years, decreased the volume density of soil by 0.09 g/cm 3, chiseling increased the percentage of soil moisture content by 26.2%, and less tillage increased the percentage of soil moisture content by 3 percentage point. The tests conducted in the northwest showed that for winter wheat, the percentage of water storage increased by 18-5%; for spring corn, the percentage of soil moisture content increased by 30%. The stalk mulching tests for two years showed that the content of soil organic matter increased by 0.05%-0.1% and the content of total nitrogen increased by about 0.1 g/kg.
  • Authors:
    • Payero, J. O.
    • Schneekloth, J. P.
    • Klocke, N. L.
  • Source: Transactions of the ASABE
  • Volume: 50
  • Issue: 6
  • Year: 2007
  • Summary: Dwindling water supplies for irrigation are prompting alternative management choices by irrigators. Limited irrigation, where less water is applied than full crop demand, may be a viable approach. Application of limited irrigation to maize ( Zea mays) was examined in a study conducted at the West Central Research and Extension Centre of the University of Nebraska-Lincoln at North Platte, Nebraska, USA. Maize was grown in crop rotations with dryland, limited irrigation, or full irrigation management from 1985 to 1999. Crop rotations included maize following maize (continuous maize), maize following wheat ( Triticum aestivum), followed by soyabean ( Glycine max) (wheat-maize-soyabean), and maize following soyabean (maize-soyabean). Full irrigation was managed to meet crop evapotranspiration requirements (ETc). Limited irrigation was managed with a seasonal target of no more than 150 mm applied. Precipitation patterns influenced the outcomes of measured parameters. Dryland yields had the most variation, while fully irrigated yields varied the least. Limited irrigation yields were 80 to 90% of fully irrigated yields, but the limited irrigation plots received about half the applied water. Grain yields were significantly different among irrigation treatments. Yields were not significantly different among rotation treatments for all years and water treatments. For soil water parameters, more statistical differences were detected among the water management treatments than among the crop rotation treatments. Economic projections of these management practices showed that full irrigation produced the most income if water was available. Limited irrigation increased income significantly from dryland management.
  • Authors:
    • Carbonell, R.
    • Perea, F.
    • González, P.
    • Rodríguez-Lizana, A.
    • Ordóñez-Fernández, R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 79
  • Issue: 3
  • Year: 2007
  • Summary: With the aim of assessing the benefits of crop remains left on the soil surface, a study was carried out on the decomposition and characteristics of residue deposited on a clay soil in southern Spain during the agricultural seasons of 2001/02, 2002/03 and 2003/04, in which a legume-cereal-sunflower rotation was followed. Each of the residues studied possessed a characteristic justifying its inclusion in the rotation. The legume residue (Pisum sativum L. cv. Ideal) supplied the highest amount of nitrogen to the soil since, throughout its decomposition cycle, it lost 76.6% of its initial content in nitrogen, compared to the 48 and 56% of N released by wheat residues (Triticum durum L. cv. Amilcar) and sunflower (Helianthus annus L. cv. Sanbro), respectively. At the beginning of its decomposition cycle, the wheat residue had the lowest mass, and gave the most cover, with values of 65%, which was 8.6 and 20.2% more than the cover estimated for the pea and sunflower residues, respectively. The sunflower residue lasted longest, only losing 18% of its initial cover over 109 days of decomposition, compared to 47% for wheat and 53% for pea. The amount of carbon released was similar for the three residues and was around 500 kg ha(-1). The straw decomposition rates under our conditions indicate that the residue of the most common crops in the area under dry farming makes protection possible during the intercrop period.
  • Authors:
    • Radford, B. J.
    • Yule, D. F.
    • McGarry, D.
    • Playford, C.
  • Source: Soil & Tillage Research
  • Volume: 97
  • Issue: 2
  • Year: 2007
  • Summary: Heavy wheel traffic causes soil compaction, which adversely affects crop production and may persist for several years. We applied known compaction forces to entire plots annually for 5 years, and then determined the duration of the adverse effects on the properties of a Vertisol and the performance of maize and sorghum crops under no-till dryland cropping with residue retention. For up to 5 years after a final treatment with a 10 Mg axle load on wet soil, soil shear strength at 70-100 mm and cone index at 180-360 mm were significantly ( P<0.05) higher than in a control treatment, and soil water storage and grain yield were lower. We conclude that compaction effects persisted because (1) there were insufficient wet-dry cycles to swell and shrink the entire compacted layer, (2) soil loosening by tillage was absent and (3) there were fewer earthworms in the compacted soil. Compaction of dry soil with 6 Mg had little effect at any time, indicating that by using wheel traffic only when the soil is dry, problems can be avoided. Unfortunately such a restriction is not always possible because sowing, tillage and harvest operations often need to be done when the soil is wet. A more generally applicable solution, which also ensures timely operations, is the permanent separation of wheel zones and crop zones in the field-the practice known as controlled traffic farming. Where a compacted layer already exists, even on a clay soil, management options to hasten repair should be considered, e.g. tillage, deep ripping, sowing a ley pasture or sowing crop species more effective at repairing compacted soil.
  • Authors:
    • Sainju, U. M.
    • Caesar-TonThat, T.
    • Lenssen, A. W.
    • Evans, R. G.
    • Kolberg, R.
  • Source: Soil Science Society of America Journal
  • Volume: 71
  • Issue: 6
  • Year: 2007
  • Summary: Long-term management practices are needed to increase dryland C storage and improve soil quality. We evaluated the 21-yr effects of combinations of tillage and cropping sequences on dryland crop biomass (stems + leaves) returned to the soil, residue C, and soil C fractions at the 0- to 20-cm depth in a Dooley sandy loam (fine-loamy, mixed, frigid, Typic Argiborolls) in eastern Montana. Treatments were no-till continuous spring wheat (Triticum aestivum L.) (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat-barley (Hordeum vulgare L.) (1984-1999) followed by spring wheat-pea (Pisum sativum L.) (2000-2004) (FSTW-B/P), and spring-tilled spring wheat-fallow (STW-F). Carbon fractions were soil organic C (SOC), soil inorganic C (SIC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Mean crop biomass was 53 to 66% greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue amount and C content in 2004 were 46 to 60% greater in NTCW and FSTCW than in STW-F As a result, soil C fractions at 0 to 20 cm were 23 to 141 % greater in all other treatments than in STW-F due to increased C input. At 0 to 5 cm, SOC, SIC, POC, and PCM were greater in NTCW than in FSTW-B/P. At 5 to 20 cm, POC was greater in NTCW than in FSTW-B/P and PCM was greater in STCW than in FSTCW. Long-term reduced tillage with continuous nonlegume cropping increased dryland crop biomass, residue and soil C storage, and soil quality by increasing microbial biomass and activities compared with a conventional system such as STW-F.
  • Authors:
    • Sau, F.
    • Pineiro, J.
  • Source: Fourrages
  • Issue: 190
  • Year: 2007
  • Summary: The natural conditions in Galice and northern Spain are favourable for the production of forage, compared to the rest of the country. Agriculture in the country has undergone deep restructurations for the last 50 years, especially on the dairy farms. From 1960s onwards, the acreages of grass-clover leys and of forage maize have been constantly increasing, in parallel with an increasing milk production. The proportion of milk produced from forage crops have remained at 20 to 25%, and a particular effort should be made to reach the goal of 40%. In order to overcome water shortage during summer, the farmers make silage with their spring cuts, use lucerne and purchased feeds, and irrigate at a small scale. The few trials made show that irrigated pastures can increase the average yearly production by 40-45%. Since the water resources are scarce, and must be distributed with other economic activities, there should be no large development of irrigation. To overcome the water shortage during summer, it would seem more realistic to have recourse to more intensive rotations (2 crops per year), in which a crop better adapted to high temperatures and to dry spells would take over the leys. This intensified dry-land system would increase the yearly production by from 50 to 82%.
  • Authors:
    • Young, D. L.
    • Schillinger, W. F.
    • Kennedy, A. C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 120
  • Issue: 2-4
  • Year: 2007
  • Summary: The tillage-based winter wheat (Triticum aestivum L.)-summer fallow (WW-SF) cropping system has dominated dryland farming in the Pacific Northwest USA for 125 years. We conducted a large-scale multidisciplinary 8-year study of annual (i.e., no summer fallow) no-till cropping systems as an alternative to WW-SF. Soft white and hard white classes of winter and spring wheat, spring barley (Hordeum vulgare L.), yellow mustard (Brassica hirta Moench), and safflower (Carthamus tinctorius L.) were grown in various rotation combinations. Annual precipitation was less than the long-term average of 301 mm in 7 out of 8 years. Rhizoctonia bare patch disease caused by the fungus Rhizoctonia solani AG-8 appeared in year 3 and continued through year 8 in all no-till plots. All crops were susceptible to rhizoctonia, but bare patch area in wheat was reduced, and grain yield increased, when wheat was grown in rotation with barley every other year. Remnant downy brome (Bromus tectorum L.) weed seeds remained dormant for 6 years and longer to heavily infest recrop winter wheat. There were few quantifiable changes in soil quality due to crop rotation, but soil organic carbon (SOC) increased in the surface 0-5 cm depth with no-till during the 8 years to approach that found in undisturbed native soil. Annual no-till crop rotations experienced lower average profitability and greater income variability compared to WW-SF. Yellow mustard and safflower were not economically viable. Continuous annual cropping using no-till provides excellent protection against wind erosion and shows potential to increase soil quality, but the practice involves high economic risk compared to WW-SF. This paper provides the first comprehensive multidisciplinary report of long-term alternative annual no-till cropping systems research in the low-precipitation region of the Pacific Northwest.
  • Authors:
    • Schmidt, C. J. J.
    • Adriaanse, F. G.
    • Preez, C. C. du
  • Source: South African Journal of Plant and Soil
  • Volume: 24
  • Issue: 1
  • Year: 2007
  • Summary: The principle objective of this study was to establish P fertilizer guidelines for dryland maize on the South African Highveld according to the sufficiency concept of soil extractable P. Data sets from nine different P fertilizer trials at various localities in the Free State, Gauteng, Mpumalanga and North West provinces were used. Different P treatments were applied for all trials in order to establish differences in extractable soil P levels, which were expected to have corresponding effects on maize yield. Long-term rainfall varied from 765 mm per annum for the Dirkiesdorp trial in the east to 494 mm per annum for the Wolmaransstad trial in the west. The duration of trials varied between one and nine seasons. The clay content of the top 150 mm soil at these localities ranged between 8.4 and 47%. Extractable P threshold values with varying R 2 values were derived for all localities. These values were related to soil properties and it was shown that the degree of leaching and silt-plus-clay content were the parameters that explained most of the variation. However, it was decided only to explore relationships between threshold P values and silt-plus-clay contents in more detail. By excluding data from two localities of which the topsoil contained free lime, the R 2 values of the mentioned relationships improved substantially so that P threshold values could be derived from the silt-plus-clay content range of the other seven localities. The extractable soil P threshold concentrations based on Bray 1 for the top 150 mm soil layer, to obtain 90% relative yield varied from 33.5 mg kg -1 at 13% silt-plus-clay to 14.6 mg kg -1 at 60% silt-plus-clay. These P thresholds were much higher on the sandy soils than the value of 19 mg P kg -1 (Bray 1) for 95% relative yield according to the ARC-Grain Crops Institute (1994) guidelines over all soils. This may not necessarily imply that overall more P fertilizers should be applied, since the corresponding soil sampling procedure also measures residual P from enriched zones over rows where P fertilizer was band-placed. Research results used to establish the ARC-Grain Crops Institute (1994) guidelines excluded sampling from enriched zones over rows.