• Authors:
    • Van Remortel, R.
    • Smith, E.
    • Mehaffey, M.
  • Source: Ecological Applications
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: Meeting future biofuel targets set by the 2007 Energy Independence and Security Act (EISA) will require a substantial increase in production of corn. The Midwest, which has the highest overall crop production capacity, is likely to bear the brunt of the biofuel-driven changes. In this paper, we set forth a method for developing a possible future landscape and evaluate changes in practices and production between base year (BY) 2001 and biofuel target (BT) 2020. In our BT 2020 Midwest landscape, a total of 25 million acres (1 acre = 0.40 ha) of farmland was converted from rotational cropping to continuous corn. Several states across the Midwest had watersheds where continuous corn planting increased by more than 50%. The output from the Center for Agriculture and Rural Development (CARD) econometric model predicted that corn grain production would double. In our study we were able to get within 2% of this expected corn production. The greatest increases in corn production were in the Corn Belt as a result of conversion to continuous corn planting. In addition to changes to cropping practices as a result of biofuel initiatives we also found that urban growth would result in a loss of over 7 million acres of productive farmland by 2020. We demonstrate a method which successfully combines economic model output with gridded land cover data to create a spatially explicit detailed classification of the landscape across the Midwest. Understanding where changes are likely to take place on the landscape will enable the evaluation of trade-offs between economic benefits and ecosystem services allowing proactive conservation and sustainable production for human well-being into the future.
  • Authors:
    • Twomlow, S.
    • Mupangwa, W.
    • Walker, S.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Proponents of conservation agriculture (CA) argue that the CA approach offers the greatest opportunity to increase the productivity in smallholder agro-ecosystems. This study was designed to assess (1) first year maize, cowpea and sorghum yield responses to a combination of reduced tillage and mulching and (2) maize yield responses to rotation with cowpea and sorghum in reduced tillage systems. Two conservation tillage methods (ripping and planting basins) combined factorially with seven mulch levels (0, 0.5, 1, 2, 4, 8 and 10 t ha -1) were compared with conventional mouldboard ploughing. The experiment was run for four consecutive growing seasons allowing for a rotation of maize, cowpea, sorghum and maize in some fields used in the study. Crop yields were determined across all tillage and mulch combinations in each year. Tillage system had no significant effect on maize yield while maize grain yield increased with increase in mulch cover in seasons that had below average rainfall. Mulching at 2-4 t ha -1 gave optimum yields in seasons with below average rainfall. Tillage system and mulching had no significant effect on cowpea yield when soil moisture was not limiting. However, the ripper and basin systems had 142 and 102% more cowpea grain than the conventional system in 2006/2007 because of differences in planting dates used in three systems and poor rainfall distribution. The conventional and ripper systems gave 26 and 38% more sorghum grain than the basin system. Rotating maize with cowpea and sorghum resulted in 114, 123 and 9% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize in the conventional system. In the ripper system, maize-cowpea-sorghum-maize rotation gave 98, 153 and 39% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize rotation. In the basin system, maize-cowpea-sorghum-maize rotation gave 274, 240 and 43% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize rotation. However, long term studies under different soil, climatic and socio-economic conditions still need to be conducted to substantiate the observations made in the reported study.
  • Authors:
    • Zhang, J.
    • Li, B.
    • Xie, G.-L.
    • Cui, Z.-Q.
    • Ojaghian, M. R.
  • Source: Australasian Plant Pathology
  • Volume: 41
  • Issue: 4
  • Year: 2012
  • Summary: This study was conducted to evaluate the potential of biofumigation in three Brassica crops including Brassica napus, Brassica juncea and Brassica campestris against potato stem rot caused by Sclerotinia sclerotiorum in field tests. Results from field trials carried out in three naturally infected potato fields during three cropping seasons of 2008-2010 showed that the Brassica crops used as green manure cover crops were able to significantly reduce disease incidence and mean percentage of dead plants (as a proportion of infected plants). Although results varied somewhat by field site and year, B. juncea generally provided the highest level of control, averaging greater than 55.6 % reduction in disease incidence over all fields and years, compared to average disease reductions of 31.6 and 45.8 % for the B. napus and B. campestris crop treatments, respectively. Furthermore reduction of dead plants averaged 61.6, 39.2 and 32.1 % for B. juncea, B. napus, and B. campestris, respectively. In this study, Brassica crops showed various significant inhibitory effects in different fields and years indicating that disease development is affected by other factors including environmental conditions.
  • Authors:
    • Evett, S. R.
    • O'Shaughnessy, S. A.
    • Colaizzi, P. D.
    • Howell, T. A.
  • Source: Transactions of the American Society of Agricultural and Biological Engineers
  • Volume: 55
  • Issue: 2
  • Year: 2012
  • Summary: Studies using the time-temperature threshold (TTT) method for irrigation scheduling have been documented for cotton, corn, and soybean. However, there are limited studies of irrigation management of grain sorghum ( Sorghum bicolor, L.) with this plant-feedback system. In this two-year study, the TTT method was investigated as an automatic irrigation control algorithm for a late-maturing grain sorghum hybrid (Pioneer 84G62) grown in 2009 and an early maturing hybrid (Moench, NC+ 5C35) grown in 2010. The method was evaluated by comparing grain sorghum responses of biomass and dry grain yields, crop evapotranspiration (ET c), water use efficiency (WUE), and irrigation water use efficiency (IWUE) between automatic and manual control methods of irrigation scheduling at different deficit irrigation treatments (i.e., 80%, 55%, 30%, and 0% of full replenishment of soil water depletion to 1.5 m depth). Irrigation scheduling using the TTT method produced mean response variables of yield (biomass and grain), WUE, and IWUE that were similar or better than those from the manually scheduled method in both years. Water use efficiency was highest at the 80% and 55% levels in 2009 and 2010, respectively. Average IWUE was highest at the 55% level in 2009 and at the 30% level in 2010. For both of these responses, differences among irrigation treatment levels were not always significant. Crop production functions were curvilinear in both years as dry grain yields began to plateau between water application amounts delivered from irrigation treatments at the 55% and 80% levels. Results from this study indicate that both late and early maturing hybrids of grain sorghum are responsive to the TTT method of irrigation scheduling. Irrigation management with this algorithm can produce biomass and dry grain yields, ET c, WUE, and IWUE levels that are similar to those achieved with an accurate irrigation scheduling method based on direct soil water measurement.
  • Authors:
    • Monk, Wendy A.
    • Baird, Donald J.
    • Peters, Daniel L.
    • Armanini, David G.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 1
  • Year: 2012
  • Summary: Agricultural land use can place heavy demands on regional water resources, strongly influencing the quantity and timing of water flows needed to sustain natural ecosystems. The effects of agricultural practices on streamflow conditions are multifaceted, as they also contribute to the severity of impacts arising from other stressors within the river ecosystem. Thus, river scientists need to determine the quantity of water required to sustain important aquatic ecosystem components and ecological services, to support wise apportionment of water for agricultural use. It is now apparent that arbitrarily defined minimum flows are inadequate for this task because the complex habitat requirements of the biota, which underpin the structure and function of a river ecosystem, are strongly influenced by predictable temporal variations in flow. We present an alternative framework for establishing a first-level, regional ecological instream flow needs standard based on adoption of the Indicators of Hydrologic Alteration/Range of Variability Approach as a broadly applicable hydrological assessment tool, coupling this to the Canadian Ecological Flow Index which assesses ecological responses to hydrological alteration. By explicitly incorporating a new field-based ecological assessment tool for small agricultural streams, we provide a necessary verification of altered hydrology that is broadly applicable within Canada and essential to ensure the continuous feedback between the application of flow management criteria and ecological condition.
  • Authors:
    • Zhang, Y. M.
    • Li, X. X.
    • Oenema, O.
    • Hu, C. S.
    • Wang, Y. Y.
    • Qin, S. P.
    • Dong, W. X.
  • Source: Atmospheric Environment
  • Volume: 55
  • Year: 2012
  • Summary: Emissions of nitrous oxide (N 2O) from agricultural soils contribute to global warming and stratospheric ozone depletion. Applications of fertilizer nitrogen (N) increase N 2O emission, but also increase agricultural production. Here, we report on the responses of crop yield, N 2O emission and yield-scaled N 2O emission (N 2O emission per unit N uptake by grain and aboveground biomass) to different N fertilizer rates in a winter wheat-summer corn double-cropping system in the North China Plain. Soil N 2O emission measurements were carried out for two years in a long-term field experiment, under semi-arid conditions with four flood irrigations events per year. Our results indicated that N 2O emissions were linear functions and yield-scaled N 2O emissions were cubic functions of N fertilizer application rate. Yield-scaled N 2O emissions were lowest at application rates of 136 kg N ha -1 yr -1. Using a quadratic-plateau model, it was found that maximal crop yields were achieved at an application rate of 317 kg N ha -1 yr -1, which is 20% less than current practice. This level is suggested to be a compromise between achieving food security and mitigation N 2O emissions.
  • Authors:
    • Saoub, H. M.
    • Akash, M. W.
    • Ayad, J. Y.
  • Source: Research on Crops
  • Volume: 13
  • Issue: 1
  • Year: 2012
  • Summary: In Jordan, the improvement of vetch production is becoming one of the main objectives as its growing areas are decreasing either because of environmental or cropping system changes. However, there is no literature concerning the assessment of genetic diversity of vetches landraces that harbour important genes for the development of new adapted varieties. The present study aimed at collecting, evaluating and characterizing vetch landraces covering different parts of Jordan. Twenty-six vetch landraces were collected from different parts of Jordan during a period extended from April to May in 2006-07 growing season and assessed in the field during 2008-09 growing season. The experiment was conducted at three stations (Ghwier Agricultural Research Station, Rabba Agricultural Research Station and Jubeiha Agricultural Research Station, The University of Jordan). Results indicated that grain yield of Vicia erivillia landraces was higher than grain yield of Vicia sativa landraces, regardless of the growing location. However, biological yield obtained from V. sativa entries [671 kg/ha (entry no. 6) upto 2514 kg/ha (entry no. 1)] was higher than that obtained from V. erivillia entries [536 kg/ha (entry no. 10) upto 2125 kg/ha (entry no. 23)]. Similar trend was shown for straw yield where V. sativa entries had more vegetative growth compared to V. erivillia entries. These differences attributed to the dissimilarity in genetic make-up of the two species. For example, some researchers mention that V. erivillia produces more grain yield due to its ability to tolerate drought when compared to V. sativa. The identification of these superior adapted local landraces is the first step in fulfilling the objective of the national vetch breeding programme.
  • Authors:
    • Feng, G.
    • Wendling, L.
    • Sharratt, B.
  • Source: Aeolian Research
  • Volume: 5
  • Year: 2012
  • Summary: Winter wheat - summer fallow is the crop rotation used on more than 1.5 million ha in the Pacific Northwest United States. Land maintained using conventional summer fallow is susceptible to wind erosion because multiple tillage operations during the fallow period expose the soil to high winds. Alternative management strategies are needed that protect the soil surface from erosion during summer fallow. Surface characteristics were examined after subjecting the loessial soil to seven (conventional), five (reduced), three (minimum), and zero (no) tillage operations during the fallow period. Surface residue biomass and roughness and soil crust, aggregation, strength, and water content were measured after tillage and sowing operations. No tillage resulted in a more persistent and thicker soil crust and greater residue cover, silhouette area index (SAI), and penetration resistance than conventional and reduced tillage. For those treatments subject to tillage, minimum tillage resulted in a thicker soil crust and greater residue cover, SAI, ridge roughness, mean aggregate diameter, and penetration resistance as compared to conventional or reduced tillage after primary tillage. Near the end of the fallow period, minimum tillage resulted in 15% greater residue cover than conventional tillage. Soil loss from minimum tillage is expected to be 50% of conventional tillage based upon these differences in residue cover. This study suggests that minimum tillage is an alternative strategy to conventional tillage for reducing wind erosion in the wheat-fallow region of the Pacific Northwest. Published by Elsevier B.V.
  • Authors:
    • Pruessner, E. G.
    • Stewart, C. E.
    • Follett, R. F.
    • Kimble, J. M.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Summary: Soils of the US Great Plains contain enormous stocks of soil organic carbon (SOC) and soil organic nitrogen (SON) that are vulnerable to predicted climate and land use change. Climate change scenarios predict a 2.2 degrees C to 3.6 degrees C (4 degrees F to 6.5 degrees F) increase and more variability in precipitation across most of the United States. This study quantifies management effects (native grassland, Conservation Reserve Program [CRP], and cropped) on SOC and SON stocks across the region and assessed soil variables (soil texture, cation exchange capacity and others) and climatic drivers (precipitation and temperature) to predict future changes in carbon (C) and nitrogen (N) stocks. Across all sites, cropped land had significantly lower C and N stocks in the 0 to 5 cm (0 to 2 in) and 0 to 10 cm (0 to 3.9 in) depths than native sites, while CRP sites were intermediate. Mean annual temperature (MAT), the ratio of mean annual precipitation to potential evapotranspiration (MAP:PET), soil bulk density (BD), and clay content were important covariates for SOC and SON stocks within land use. Soil C and N stocks under all three land uses were strongly negatively related to MAT and positively related to MAP:PET, suggesting that they are equally vulnerable to increased temperature and decreasing water availability Based on these empirical relationships, a 1 degrees C (1.8 degrees F) increase in MAT could cause a loss of 486 Tg SOC (536 million tn) and a loss of 180 kg SON ha(-1) (160 lb SON ac(-1)) from the top 10 cm (3.9 in) of soil over 30 years, but the decrease will be mediated by water availability (MAP:PET). Combined, increased temperature and conversion from CRP to cropland could decrease the existing SOC sink, but improved soil management and increased water availability may help offset these losses in the US Great Plains.
  • Authors:
    • Eigenberg, R. A.
    • Hubbard, R. K.
    • Powell, J. M.
    • Torbert, H. A.
    • Woodbury, B. L.
    • Albrecht, S. L.
    • Sistani, K. R.
    • Wienhold, B. J.
    • He, Z. Q.
    • Larkin, R. P.
    • Griffin, T. S.
    • Vandemark, G.
    • Honeycutt, C. W.
    • Fortuna, A. M.
    • Wright, R. J.
    • Alldredge, J. R.
    • Harsh, J. B.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 1
  • Year: 2012
  • Summary: Soil biotic and abiotic factors strongly influence nitrogen (N) availability and increases in nitrification rates associated with the application of manure. In this study, we examine the effects of edaphic properties and a dairy ( Bos taurus) slurry amendment on N availability, nitrification rates and nitrifier communities. Soils of variable texture and clay mineralogy were collected from six USDA-ARS research sites and incubated for 28 d with and without dairy slurry applied at a rate of ~300 kg N ha -1. Periodically, subsamples were removed for analyses of 2 M KCl extractable N and nitrification potential, as well as gene copy numbers of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Spearman coefficients for nitrification potentials and AOB copy number were positively correlated with total soil C, total soil N, cation exchange capacity, and clay mineralogy in treatments with and without slurry application. Our data show that the quantity and type of clay minerals present in a soil affect nitrifier populations, nitrification rates, and the release of inorganic N. Nitrogen mineralization, nitrification potentials, and edaphic properties were positively correlated with AOB gene copy numbers. On average, AOA gene copy numbers were an order of magnitude lower than those of AOB across the six soils and did not increase with slurry application. Our research suggests that the two nitrifier communities overlap but have different optimum environmental conditions for growth and activity that are partly determined by the interaction of manure-derived ammonium with soil properties.