• Authors:
    • Wilhelm, W. W.
    • Varvel, G. E.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 4
  • Year: 2008
  • Summary: Proposals promoting the use of massive amounts of crop residues and other lignocellulosic biomass for biofuel production have increased the need for evaluation of the sustainability of cropping practices and their effect on environment quality. Our objective was to evaluate the effects of crop rotation and N fertilizer management and their stover production characteristics on soil organic carbon (SOC) levels in a long-term high-yielding irrigated study in the western Corn Belt. An irrigated monoculture corn ( Zea mays L.), monoculture soybean [ Glycine max (L.) Merr.], and soybean-corn cropping systems study was initiated in 1991 on a uniform site in the Platte Valley near Shelton, NE. Soil samples were collected in 1991 before initiation of the study and in the spring of 2005 and analyzed for SOC. Significant differences in total SOC values were obtained between rotations and N rates at the 0- to 7.5- and 0- to 15-cm depths in 2005 and all total SOC values were equal to or greater than SOC values obtained in 1991. Residue production was greater than 6 Mg ha -1, a level that appears to be sufficient to maintain SOC levels, in all systems. Can residue amounts above this level be harvested sustainably for biofuel production in cropping systems similar to these? Though these results suggest that a portion of corn stover could be harvested without reducing SOC under the conditions of this investigation, the direct impact of stover removal remains to be evaluated.
  • Authors:
    • Zhu, D. W.
    • Jin, Z. Q.
  • Source: Acta Agronomica Sinica
  • Volume: 34
  • Issue: 9
  • Year: 2008
  • Summary: Nine scenarios of climatic change and climatic variability were generated in 19 sites in 3 agroecological zones in northeast China using the WGEN as a tool and based on the output of three general circulation models (GISS, GFDL, and UKMO GCMs), the local current daily weather data from 1961 to 2000 at each site, as well as on the three hypotheses on the increase in climatic variability in future. Four crop models (SOYGRO, CERES-Maize, CERES-Wheat, and CERES-Rice) were selected as the effect models and their parameter modification, validation and sensitivity analyses were carried out using the baseline weather, statistical yield data of the 4 crops and the local typical soil data. Finally, the potential impacts of changes in both climate and its variability on the food production in this regions with a doubling of CO 2 concentration doubled were assessed by running the effect models under both baseline and various (climatic change+climatic change variability) scenarios, and by comparing the outputs simulated. The results showed that the four effect models were available in the studied regions and can be used as a tool in climate impact study. Climate change would be favorable for soyabean and rice production in the region, especially in the northern cold zone and eastern wet zone, but unfavorable for both maize and spring wheat, where the simulated yields particularly maize yield, were significantly reduced under all the scenarios. With increasing of climatic variability, not only the yields were reduced compared with the control, but also the yield stabilities also decreased for the rainfed crops, such as soyabean, maize and spring wheat. However, there was no influence for the irrigated rice.
  • Authors:
    • Santini, J. B.
    • Vyn, T. J.
    • Faghihi, J.
    • Ferris, V. R.
    • Westphal, A.
    • Creech, J. E.
    • Johnson, W. G.
  • Source: Weed Science
  • Volume: 56
  • Issue: 1
  • Year: 2008
  • Summary: Certain winter annual weeds have been documented as alternative hosts to soybean cyst nematode (SCN), and infestations of such species have become common in no-till production fields in the Midwest. This research was conducted to determine the influence of herbicide- and cover-crop-based winter annual weed management systems and crop rotation on winter annual weed growth and seed production, SCN population density, and crop yield. Two crop rotations (continuous soyabean and soyabean-maize) and six winter annual weed management systems (a nontreated control, autumn and spring herbicide applications, spring-applied herbicide, autumn-applied herbicide, autumn-sown annual ryegrass, and autumn-sown winter wheat) were evaluated in no-tillage systems from autumn 2003 to 2006 at West Lafayette and Vincennes, Indiana. Autumn or spring herbicide treatments generally resulted in lower winter annual weed densities than cover crops. Densities of henbit and purple deadnettle increased over years in the cover crop systems but remained constant in the herbicide systems. Averaged over sites and years, winter annual weed densities were nearly 45% lower in the spring than the autumn due to winter mortality. Maize yield was reduced by the cover crops at West Lafayette but not Vincennes. Winter annual weed management system had no influence on soyabean yield. SCN population density was reduced by including maize in the crop sequence but was not influenced by winter annual weed management. The density of weedy host species of SCN in the experimental area was relatively low (less than 75 plants m -2) compared to densities that can be observed in production fields. The results suggest that inclusion of maize into a cropping sequence is a much more valuable SCN management tool than winter annual weed management. In addition, control of winter annual weeds, specifically for SCN management, may not be warranted in fields with low weed density.
  • 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:
    • Graef, G. L.
    • Elmore, R. W.
    • Cassman, K. G.
    • Dobermann, A.
    • Setiyono, T. D.
    • Bastidas, A. M.
    • Specht, J . E.
  • Source: Crop Science
  • Volume: 48
  • Issue: 2
  • Year: 2008
  • Summary: The sensitivity of soybean [ Glycine max (L.) Merr.] main stem node accrual to ambient temperature has been documented in greenhouse-grown plants but not with field-grown plants in the north-central United States. Biweekly V-node and R-stage, stem node number, internode length, and other traits were quantified in an irrigated split-plot, four-replicate, randomized complete block experiment conducted in Lincoln, NE, in 2003-2004. Main plots were early-, mid-, late-May, and mid-June sowing dates. Subplots were 14 cultivars of maturity groups 3.0 to 3.9. Node appearance was surprisingly linear from V1 to R5, despite the large increase in daily temperature from early May (10-15degreesC) to July (20-25degreesC). The 2003 and 2004 May planting date regressions exhibited near-identical slopes of 0.27 node d -1 (i.e., one node every 3.7 d). Cold-induced delays in germination and emergence did delay the V1 date (relative to planting date), so the primary effect of temperature was the V1 start date of linearity in node appearance. With one exception, earlier sowings led to more nodes (earlier V1 start dates) but also resulted in shorter internodes at nodes 3 to 9 (cooler coincident temperatures), thereby generating a curved response of plant height to delayed plantings. Delaying planting after 1 May led to significant linear seed yield declines of 17 kg ha -1 d -1 in 2003 and 43 kg ha -1 d -1 in 2004, denoting the importance of early planting for capturing the yield potential available in soybean production, when moisture supply is not limiting.
  • Authors:
    • Heitman, J. L.
    • Gaur, A.
    • Horton, R.
    • Jaynes, D. B.
    • Kaspar, T. C.
  • Source: Soil Science Society of America Journal
  • Volume: 71
  • Issue: 2
  • Year: 2007
  • Summary: Management of chemicals in soil is important, yet the complexity of field soils limits prediction of management effects on transport. To date, few methods have been available for field measurement of chemical transport properties, but a recently developed dripper-time domain reflectometry technique allows rapid collection of data for determining these properties. The objective of this work was to apply this technique for comparison of chemical transport properties for different soil management zones. Experiments were conducted in Iowa, USA, comparing four interrow management zones: no-till non-trafficked, no-till trafficked, chisel plough non-trafficked, and chisel plough trafficked. Drip emitters were positioned at 12 locations in each zone and used to apply water followed by a step input of CaCl 2 tracer solution. Breakthrough curves were measured via electrical conductivity with time domain reflectometry probes. The mobile-immobile model was fit to the breakthrough curves to determine chemical transport properties. Mean chemical transport properties were 0.34, 0.11 h -1, 10 cm h -1, 164 cm 2 h -1, and 5 cm, for the immobile water fraction, mass exchange coefficient, average pore-water velocity, mobile dispersion coefficient, and dispersivity, respectively. All five properties showed significant differences between management zones. Differences in mass exchange and mobile dispersion coefficients coincided with differences in tillage, while differences in mean pore water velocities coincided with differences in traffic. The immobile water fraction was largest for the no-till non-trafficked zone. These results represent one of very few reports for field measurement of chemical transport properties and the first application of this approach for comparison of chemical transport properties across management zones.
  • 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:
    • Deng, L.
    • Ren, C. Z.
    • Ma, B. L.
    • Burrows, V.
    • Zhou, J.
    • Hu, Y. G.
    • Guo, L.
    • Wei ,L.
    • Sha, L.
  • Source: Field Crops Research
  • Volume: 103
  • Issue: 3
  • Year: 2007
  • Summary: Increased land degradation and shortage of forage resources for animal production over-winter have accentuated the need for alternative cropping systems in northeast China. While short frost-free period and cool temperatures are major limitations to cereal grain production in the northern regions of China (45degreesN, 122degreesE), crop varieties that are able to produce food and feed in short growing season and tolerant to low temperature may extend the total cropping period. Three hulless oat ( Avena sativa L.) lines, Baiyan 9015, Baiyan 9017 and Baiyan 9044, were bred and tested for 3 years (2004-2006) to determine their suitability for summer seeding in a double cropping system. The new lines were sown both in the spring and summer to provide growers with opportunities to harvest two grain-crops in a year. Averaged across 3 years, Baiyan 9044 produced 2.5 and 1.6 Mg ha -1 yr -1 grain yield when sown in spring and summer, respectively. The new lines seeded in 20th or 21st July and harvested in early October allowed utilization of an average of over 1500 growing degree days (GDDs). For grain yield alone, the net income for two oat crops a year was up to 1390 Chinese yuan (RMB) ha -1, more than that of growing a single oat crop in 3 years, or in most cases, equivalent to monocultured corn ( Zea mays L.) production, the dominant crop in the region. In addition, an average of 5 Mg ha -1 of oat straw was produced as valuable forage fodder for the livestock industry, which was in great demand for over-wintering animals. Furthermore, in the traditional single small grain cereal cropping system, bare ground after harvest leads to severe water and wind erosions. Our results indicate that the new oat lines could be a potential crop for summer seeding, particularly when spring-seeded crops fail due to abiotic (hail, drought, etc.) or biotic (e.g. insects) stresses. The double cropping system provides growers with a potential opportunity to facilitate the farming strategy of food, cash crops and control soil erosion in the region.
  • Authors:
    • Dimitrova, T.
  • Source: Herbologia
  • Volume: 8
  • Issue: 1
  • Year: 2007
  • Summary: Field experiments were conducted in Pleven, Bulgaria, from 2003 to 2005, on slightly leached chernozem and a natural background of weed infestation, to determine the effect of weeds and their control by using the herbicide imazamox alone or combined with an adjuvant (Desh) and with oat as a cover crop, on the grain productivity of spring forage pea. It was found that at a high weed infestation degree and under the conditions of the study, the reduction of spring forage pea yield reached approximately 33%, imazamox 40 a.i./litre at 24 ml a.i./ha + 500 ml Desh/ha could be applied to spring forage pea at the 3-5 leaf stage to control the annual mono- and dicotyledonous weeds. The treatment with the herbicide at the mentioned rate resulted in a decrease of weed infestation degree by 96% and an increase of grain yield by 43% (on average for a 3-year period). Oat, sown as a cover crop for pea, decreased the weed infestation degree by 55% and the grain yield was 17% higher than that from the pure untreated stand.
  • Authors:
    • Gomezdelcampo, E.
    • Murphy, R. P.
    • Evans, J. E.
  • Source: JOURNAL OF GREAT LAKES RESEARCH
  • Volume: 33
  • Issue: SI2
  • Year: 2007
  • Summary: The Sandusky River basin, located in northwest Ohio, has been influenced by agriculture since the late-1800s. In 2003, the Ohio Environmental Protection Agency identified various tributaries of the Sandusky River as failing to meet biological water quality standards mainly due to siltation. To assess the effectiveness of best management practices (BMPs), a cutoff channel of the Sandusky River in Crawford County, Ohio was used as a unique archive of channel bed material that existed in the previous channel. Historical aerial photographs and USGS peak discharge data suggest the channel was likely abandoned between 1957 and 1964. Twelve sediment cores between 2 and 3 meters in depth were collected with a vibracore, and grain-size analyses of the cutoff channel substrate were compared to similar data collected from the modern channel. Results showed an historical fining-upward trend in the mean grain size of the coarse fraction, from gravel in the cutoff channel to sand in the modern channel, but no change in the mean grain size of the fine fraction. A series of alternative explanations were examined to elucidate this fining, including sediment storage, trends in population and crop cultivation, existence of BMPs, and sediment transport during floods. Evidence from this study strongly suggests that a shift from the cultivation of low-cover crops (hay and oats) to high-cover crops (corn and soybeans) has changed the proportion of coarse-grained to fine-grained sediment loading in this section of the Sandusky River. The results have implications both for the effectiveness of BMPs in Crawford County and possibly for Lake Erie sediment budgets.