• Authors:
    • Ozores-Hampton, M.
    • Fraisse, C. W.
    • Jones, C. D.
  • Source: Agricultural Systems
  • Volume: 113
  • Year: 2012
  • Summary: Agriculture is a significant contributor to rising atmospheric greenhouse gas (GHG) levels, which is expected to result in sea level rise and increased frequency of extreme weather events and is of increasing global concern. Tomatoes are an important agricultural commodity in Florida, accounting for 40% of the fresh market production in the United States. Quantification of GHG emissions from typical tomato production in Florida could improve understanding of the impact of different GHG emissions sources and identification of areas for potential GHG emissions reductions. A practical methodology was implemented to calculate a representative GHG emissions estimate using production inputs and practices used by the Florida tomato industry. Experts and grower surveys were used to characterize typical Florida tomato production practices. Existing methodologies were used to convert material use and farm operations into GHG emissions estimates. Results indicated that, depending on irrigation system type and water source, the overall average estimates of GHG emissions associated with a growing season ranged from 16,183 kg CO2-eq ha(-1) (0.19 kg CO2-eq kg fruit(-1)) to 22,426 kg CO2-eq ha(-1) (0.27 kg CO2-eq kg fruit(-1)). Irrigation and nitrogen (N) fertilizer accounted for the most emissions, with irrigation accounting for between 2.8% and 26.6% of average GHG emissions and N fertilizer accounting for between 17.7% and 22.8%. It was concluded that increased efficiency in irrigation and N use, and improved methods for polyethylene mulch use and disposal, were the best areas for GHG emissions reductions.
  • Authors:
    • Liska, A. J.
    • Archer, D.
    • Karlen, D. L.
    • Meyer, S.
  • Source: Council for Agricultural Science and Technology
  • Issue: 48
  • Year: 2012
  • Summary: Quantifying energy issues associated with agricultural systems, even for a two-crop corn ( Zea mays L.) and soybean ( Glycine max [L.] Merr.) rotation, is not a simple task. It becomes even more complicated if the goal is to include all aspects of sustainability (i.e., economic, environmental, and social). This Issue Paper examines energy issues associated with and affecting corn/soybean rotations by first defining the size of the system from both a U.S. and global perspective and then establishing boundaries based on the Farm Bill definition of sustainability. This structured approach is essential to help quantify energy issues within corn/soybean systems that are themselves best described as "systems of systems" or even "systems within ecosystems" because of their complex linkages to global food, feed, and fuel production. Two key economic challenges at the field and farm scale for decreasing energy use are (1) overcoming adoption barriers that currently limit implementation of energy-conserving production practices and (2) demonstrating the viability of sustainable bioenergy feedstock, production as part of a landscape management plan focused not only on corn/soybean production but on all aspects of soil, water, and air resource management. It is also important to look beyond direct energy consumption to address the complex economics affecting energy issues associated with corn/soybean systems. To help address the complex energy issue, life cycle assessment is used as a tool to evaluate the impact of what many characterize as a simple production system. This approach demonstrates the importance of having accurate greenhouse gas and soil organic carbon information for these analyses to be meaningful. Traditional and emerging market and policy forces affecting energy issues within corn/soybean systems are examined to project the effects of increasing bioenergy demand associated with the Energy Independence and Security Act of 2007. Uncertainty with regard to biofuel policy is a major factor affecting energy issues in all aspects of agriculture. This uncertainty affects investments in biofuel production and energy demand, which together influence commodity prices, price volatility for food and feed, and agricultural energy decisions. The authors conclude by offering an approach, including decreased or more efficient energy use, that can enhance all aspects of sustainability. Their strategy, defined as a "landscape vision," is suggested as an agricultural system approach that could meet increasing global demand for food, feed, fiber, and fuel in a truly sustainable manner.
  • Authors:
    • Williams, S.
    • Easter, M.
    • Paustian, K.
    • Lokupitiya, E.
    • Andren, O.
    • Katterer, T.
  • Source: Biogeochemistry
  • Volume: 107
  • Issue: 1-3
  • Year: 2012
  • Summary: Carbon (C) added to soil as organic matter in crop residues and carbon emitted to the atmosphere as CO(2) in soil respiration are key determinants of the C balance in cropland ecosystems. We used complete and comprehensive county-level yields and area data to estimate and analyze the spatial and temporal variability of regional and national scale residue C inputs, net primary productivity (NPP), and C stocks in US croplands from 1982 to 1997. Annual residue C inputs were highest in the North Central and Central and Northern Plains regions that comprise similar to 70% of US cropland. Average residue C inputs ranged from 1.8 (Delta States) to 3.0 (North Central region) Mg C ha(-1) year(-1), and average NPP ranged from 3.1 (Delta States) to 5.4 (Far West region) Mg C ha(-1) year(-1). Residue C inputs tended to be inversely proportional to the mean growing season temperature. A quadratic relationship incorporating the growing season mean temperature and total precipitation closely predicted the variation in residue C inputs in the North Central region and Central and Northern Plains. We analyzed the soil C balance using the crop residue database and the Introductory Carbon Balance regional Model (ICBMr). Soil C stocks (0-20 cm) on permanent cropland ranged between 3.07 and 3.1 Pg during the study period, with an average increase of similar to 4 Tg C year(-1), during the 1990s. Interannual variability in soil C stocks ranged from 0 to 20 Tg C (across a mean C stock of 3.08 +/- A 0.01 Pg) during the study period; interannual variability in residue C inputs varied between 1 and 43 Tg C (across a mean input of 220 +/- A 19 Tg). Such interannual variation has implications for national estimates of CO(2) emissions from cropland soils needed for implementation of greenhouse gas (GHG) mitigation strategies involving agriculture.
  • Authors:
    • Boyd, N. S.
    • Brennan, E. B.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: Long-term research on cover crops (CC) is needed to design optimal rotations. Winter CC shoot dry matter (DM) of rye (Secale cereale L.), legume-rye, and mustard was determined in December to February or March during the first 8 yr of the Salinas Organic Cropping Systems trial focused on high-value crops in Salinas, CA. By seed weight, legume-rye included 10% rye, 35% faba (Vicia faba L.), 25% pea (Pisum sativum L.), and 15% each of common vetch (V sativa L.) and purple vetch (V. henghalensis L.); mustard included 61% Sinapis alba L. and 39% Brassica juncea Czern. Cover crops were fall-planted at 1x and 3x seeding rates (SR); 1x SR were 90 (rye), 11 (mustard), and 140 (legume-rye) kg ha(-1). Vegetables followed CC annually. Cover crop densities ranged from 131 to 854 plants m(-2) and varied by CC, SR, and year. Year, CC, and SR affected DM production, however, the effects varied across the season and interactions occurred. Averaged across years, final DM was greater in rye and legume-rye (7 Mg ha(-1)) than mustard (5.6 Mg ha(-1)), and increased with SR through January. Dry matter production through the season was correlated significantly with growing degree days (GDD). Legumes contributed 27% of final legume-rye DM. Season-end legume DM was negatively correlated with GDD at 30 d, and legume DM in the 3x SR increased during years with frequent late-season rainfall. Seed costs per Mg of final CC DM at 1x SR were approximately three times higher for legume-rye than rye and mustard.
  • Authors:
    • Graham, J. H.
    • Wu, T.
    • Chellemi, D. O.
    • Church, G.
  • Source: Phytopathology
  • Volume: 102
  • Issue: 6
  • Year: 2012
  • Summary: Development of sustainable food systems is contingent upon the adoption of land management practices that can mitigate damage from soilborne pests. Five diverse land management practices were studied for their impacts on Fusarium wilt (Fusarium oxysporum f. sp. lycopersici), galling of roots by Meloidogyne spp. and marketable yield of tomato (Solanum lycopersicum) and to identify associations between the severity of pest damage and the corresponding soil microbial community structure. The incidence of Fusarium wilt was >14% when tomato was cultivated following 3 to 4 years of an undisturbed weed fallow or continuous tillage disk fallow rotation and was >4% after 3 to 4 years of bahiagrass (Paspalum notation) rotation or organic production practices that included soil amendments and cover crops. The incidence of Fusarium wilt under conventional tomato production with soil fumigation varied from 2% in 2003 to 15% in 2004. Repeated tomato cultivation increased Fusarium wilt by 20% or more except when tomato was grown using organic practices, where disease remained less than 3%. The percent of tomato roots with galls from Meloidogyne spp. ranged from 18 to 82% in soil previously subjected to a weed fallow rotation and 7 to 15% in soil managed previously as a bahiagrass pasture. Repeated tomato cultivation increased the severity of root galling in plots previously subjected to a conventional or disk fallow rotation but not in plots managed using organic practices, where the percentage of tomato roots with galls remained below 1%. Marketable yield of tomato exceeded 35 Mg ha(-1) following all land management strategies except the strip-tillage/bahiagrass program. Marketable yield declined by 11, 14, and 19% when tomato was grown in consecutive years following a bahiagrass, weed fallow, and disk rotation. The composition of fungal internal transcribed spacer 1 (ITS I) and bacterial 16S rDNA amplicons isolated from soil fungal and bacterial communities corresponded with observed differences in the incidence of Fusarium wilt and severity of root galling from Meloidogyne spp. and provided evidence of an association between the effect of land management practices on soil microbial community structure, severity of root galling from Meloidogyne spp., and the incidence of Fusarium wilt.
  • Authors:
    • Chase, C.
    • Cwach, D.
    • Delate, K.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 1
  • Year: 2012
  • Summary: Novel technologies to reduce tillage in organic systems include a no-tillage roller/crimper for terminating cover crops prior to commercial crop planting. The objective of this experiment was to compare: (1) weed management and yield effects of organic tilled and no-tillage systems for corn ( Zea mays L.), soybean [ Glycine max (L.) Merr.] and irrigated tomato ( Lycopersicon esculentum Mill.), using a roller/crimper and two cover crop combinations [hairy vetch/rye ( Vicia villosa Roth/ Secale cereale L.) and winter wheat/Austrian winter pea ( Triticum vulgare L./ Pisum sativum L. ssp. arvense (L.) Poir.)]; and (2) the economic performance of each system. Weed management ranged from fair to excellent in the organic no-tillage system for soybean and tomato crops, with the rye/hairy vetch mulch generally providing the most weed suppression. Corn suffered from low rainfall, competition from weeds and hairy vetch re-growth and, potentially, low soil nitrogen (N) from lack of supplemental fertilization and N immobilization during cover crop decomposition. No-tillage corn yields averaged 5618 and 634 kg ha -1 in 2006 and 2007, respectively, which was 42-92% lower than tilled corn. No-tillage soybeans in 2007 averaged 2793 kg ha -1 compared to 3170 kg ha -1 for tilled soybeans, although no-tillage yields were 48% of tilled yields in the dry year of 2006. Irrigated tomato yields averaged 40 t ha -1 in 2006 and 63 t ha -1 in 2007, with no statistical differences among tillage treatments. Economic analysis for the three crops revealed additional cover crop seed and management costs in the no-tillage system. Average organic corn returns to management were US$1028 and US$2466 ha -1 greater in the tilled system compared to the no-tillage system in 2006 and 2007, respectively, which resulted mainly from the dramatically lower no-tillage yields. No-tillage soybean returns to management were negative in 2006, averaging US$ -14 ha -1, compared to US$742 ha -1 for tilled soybeans. However, in 2007, no-tillage soybean returns averaged US$1096 ha -1. The 2007 no-tillage irrigated tomato returns to management averaged US$53,515 compared to US$55,515 in the tilled system. Overall, the organic no-tillage soybean and irrigated tomato system demonstrated some promise for reducing tillage in organic systems, but until economic benefits from soil carbon enhancement can be included for no-tillage systems, soil improvements probably cannot offset the economic losses in no-tillage systems. Irrigation could improve the performance of the no-tillage system in dry years, especially if grain crops are rotated with a high-value irrigated tomato crop.
  • Authors:
    • Davison, D. R.
    • Petersen, J. L.
    • Shaver, T. M.
    • Donk, S. J. van
  • Source: Transactions of the ASABE
  • Volume: 55
  • Issue: 1
  • Year: 2012
  • Summary: Reduced tillage, with more crop residue remaining on the soil surface, is believed to conserve water, especially in arid and semi-arid climates. However, the magnitude of water conservation is not clear. An experiment was conducted to study the effect of crop residue removal on soil water content, soil quality, and crop yield at North Platte, Nebraska. The same field plots were planted to soybean ( Glycine max) in 2009 and 2010. There were two treatments: residue-covered soil and bare soil. Residue (mostly corn residue in 2009 and mostly soybean residue in 2010) was removed every spring from the same plots using a flail chopper and subsequent hand-raking. The experiment consisted of eight, 12.2 m * 12.2 m, plots (two treatments with four replications each). Soybeans were sprinkler-irrigated, but purposely water-stressed, so that any water conservation in the residue-covered plots might translate into higher yields. After four years of residue removal, soil organic matter content and soil residual nitrate nitrogen were significantly smaller, and soil pH was significantly greater, in the bare-soil plots compared to the residue-covered plots. The residue-covered soil held approximately 90 mm more water in the top 1.83 m compared to the bare soil near the end of the 2009 growing season. In addition, mean soybean yield was 4.5 Mg ha -1 in the residue-covered plots, compared to 3.9 Mg ha -1 in the bare-soil plots. Using two crop production functions, it is estimated that between 74 and 91 mm of irrigation water would have been required to produce this extra 0.6 Mg ha -1. In 2010, mean soybean yield was 3.8 Mg ha -1 in the residue-covered plots, compared to 3.3 Mg ha -1 in the bare-soil plots. Between 64 and 79 mm of irrigation water would have been required to produce this extra 0.5 Mg ha -1. In both years, several processes may have contributed to the differences observed: (1) greater evaporation of water from the soil in the bare-soil treatment, and (2) greater transpiration by plants in the bare-soil treatment in the beginning of the growing season as a result of more vegetative growth due to higher soil temperatures in the bare-soil treatment.
  • Authors:
    • Sparks, R.
    • Dillon, M.
    • Delgado, J. A.
    • Essah, S. Y. C.
  • Source: HortTechnology
  • Volume: 22
  • Issue: 2
  • Year: 2012
  • Summary: There is the need to develop potato (Solanum tuberosum) cropping systems with higher yields and crop quality. Field studies were conducted with cover crops grown under limited irrigation (
  • Authors:
    • Wang, N. Y.
    • Mondal, S. N.
    • Sutton, B.
    • Jeyaprakash, A.
    • Palm, M. E.
    • Peres, N. A.
    • Dewdney, M. M.
    • Schubert, T. S.
    • Rascoe, J.
    • Picton, D. D.
  • Source: Plant Disease
  • Volume: 96
  • Issue: 8
  • Year: 2012
  • Summary: In March 2010, citrus black spot symptoms were observed on sweet orange trees in a grove near Immokalee, Florida, USA. Symptoms observed on fruit included hard spot, cracked spot and early virulent spot. Hard spot lesions were up to 5 mm, depressed with a chocolate margin and a necrotic, tan centre, often with black pycnidia (140-200 m) present. Cracked spot lesions were large (15 mm), dark brown, with diffuse margins and raised cracks. In some cases, hard spots formed in the centre of lesions. Early virulent spot lesions were small (up to 7 mm long), bright red, irregular, indented and often with many pycnidia. In addition, small (2-3 mm), elliptical, reddish brown leaf lesions with depressed tan centres were observed on some trees with symptomatic fruit. Chlorotic halos appeared as they aged. Most leaves had single lesions, occasionally up to 4 per leaf. The causal organism was identified as Guignardia citricarpa based on cultural, morphological and genetic (ITS) analyses. This is thought to be the first report of black spot in North America.
  • Authors:
    • Mexal, J. G.
    • Steiner, R. L.
    • Sammis, T. W.
    • Shukla, M. K.
    • Sharma, P.
  • Source: Agricultural Water Management
  • Volume: 109
  • Year: 2012
  • Summary: Nitrate leaching is a common problem in frequently fertilized agricultural crops in Southern New Mexico. The objectives of this study were to estimate the leaching depths, irrigation and plant uptake efficiencies for onion (Album cepa L), chile (Capsicum annuum), and cotton (Gossypium spp.) crops. The study aims to determine how existing best management practices for these three specialty crops could be improved. Soil samples collected monthly for two growing seasons starting April 2007 to June 2010 were analyzed for NO3-N and chloride concentrations. The NO3-N loadings below the rooting zone varied from 22 to 92 kg ha(-1) during growing season 1 and 18-90 kg ha(-1) during growing season 2 in all the three experimental fields. The leaching fractions (LFs) varied from 0.09 to 0.21 during growing season 1 and 0.08-0.22 during growing season 2 in the experimental fields. The irrigation efficiencies (1E = 1 - LF) ranged from 79 to 91% during growing season 1 and from 78 to 92% during growing season 2 in all the three fields. Nitrogen application efficiencies (NAEs) varied from 39 to 75% during growing season 1 and 40-76% during growing season 2 in all the experimental fields. Under the prevalent management conditions, cotton field showed higher irrigation efficiency as well as the NAE as compared to onion and chile fields. Based on the soil N content at the end of growing seasons, the results indicate that reducing fertilizer applications until bulb formation in onions and flower initiation in chile can decrease the amount of fertilizer applications to as much as half, thus can help in reducing the NO3-N leaching and improving nitrogen and water efficiencies. (C) 2012 Elsevier B.V. All rights reserved.