• Authors:
    • Li, Y. Q.
    • Liu, H. B.
    • Li, M. F.
    • Fan, L.
    • Wu, W.
  • Source: Transactions of the Chinese Society of Agricultural Engineering
  • Volume: 28
  • Issue: 3
  • Year: 2012
  • Summary: The records of daily solar radiation (Rs, MJ.m -2.d -1) are the important inputs for crop simulation models. However, for some model users, Rs at longer temporal intervals are more available than that at daily scale. The objective of this study was to analyze the sensitivity of simulated crop growth and production using CERES-Maize and GROPGRO-Soybean, two widely used crop growth models, to uncertainty in Rs at different time scales (5-day, 10-day, and monthly). Daily radiation data (1961-1990) from Vegetation/Ecosystem Modeling and Analysis Project (VEMAP) for the state of Georgia, USA were used to create 5-day, 10-day, and monthly mean daily Rs data sets. Datasets related to daily Rs were used as background baselines. The overall performance of the models was not significantly affected by Rs under the studied time scales. Within locations, the simulated days to anthesis and grain yields from 5-day, 10-day, and monthly Rs were close to that from daily Rs for maize and soybean under rainfed and irrigated conditions, respectively. Mean values of relative mean bias error (RMBE), mean bias error (MBE) and root mean square error (RMSE) of the simulated days to anthesis were 0, 0 and 3.5 d for the two crops under the studied scenarios, respectively. The simulated yields were underestimated for maize and overestimated for soybean using 5-day, 10-day, and monthly Rs for both rainfed and irrigated conditions, respectively. Under rainfed and irrigated conditions, the average RMBE and RMSE were -0.59%, 120 kg/hm 2 and -0.52%, 129 kg/hm 2 for maize yield, and 5%, 152 kg/hm 2 and 4.7%, 165 kg/hm 2 for soybean, respectively. Short-term bias in the difference between evaluated time scales and daily scale could affect the outputs of the crop models. Under the scenarios evaluated, CGOPGRO-Soybean model showed higher sensitivity to changes in multi-temporal Rs and water regimes than CERES-Maize model. Based on the results of this study, it can be concluded that 5-day, 10-day, and monthly mean daily Rs could be used as an input for crop growth simulation models when daily Rs are not available.
  • Authors:
    • Hayes, R. M.
    • McClure, M. A.
    • Yin, X. H.
  • Source: Agricultural Sciences
  • Volume: 3
  • Issue: 2
  • Year: 2012
  • Summary: Nitrogen concentration in the ear leaf is a good indicator of corn (Zea mays L.) N nutrition status during late growing season. This study was done to examine the relationship of late-season ear leaf N concentration with early- to mid-season plant height of corn at Milan, TN from 2008 to 2010 using linear, quadratic, square root, logarithmic, and exponential models. Six N rate treatments (0, 62, 123, 185, 247, and 308 kg.N.ha -1) repeated four times were implemented each year in a randomized complete block design under four major cropping systems: corn after corn, corn after soybean [Glycine max (L.) Merr.], corn after cotton [Gossypium hirsutum (L.)], and irrigated corn after soybean. The relationship of ear leaf N concentration determined at the blister growth stage (R 2) with plant height measured at the 6-leaf (V6), 10-leaf (V10), and 12-leaf (V12) growth stages was statistically significant and positive in non-irrigated corn under normal weather conditions. However, the strength of this relationship was weak to moderate with the determination coefficient (R 2) values ranging from 0.21 to 0.51. This relationship was generally improved as the growing season progressed from V6 to V12. Irrigation and abnormal weather seemed to have adverse effects on this relationship. The five regression models performed similarly in the evaluation of this relationship regardless of growth stage, year, and cropping system. Our results suggest that unlike the relationship of corn yield at harvest with plant height measured during early- to mid-season or the relationship of leaf N concentration with plant height when both are measured simultaneously during early- to mid-season, the relationship of late-season ear leaf N concentration with early- to mid-season plant height may not be strong enough to be used to develop algorithms for variable-rate N applications on corn within a field no matter which regression model is used to describe this relationship.
  • Authors:
    • Munoz-Carpena, R.
    • Gabriel, J. L.
    • Quemada, M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 155
  • Year: 2012
  • Summary: Using cover crops (CC) in semiarid irrigated areas is often limited by low nutrient and water-use efficiency. This work was conducted over 3.5 years to determine the effect on NO 3- leaching, water balance and soil mineral N accumulation of replacing fallow with CC in irrigated systems. Treatments studied during the maize ( Zea mays L.) intercrop period were: barley ( Hordeum vulgare L.), vetch ( Vicia villosa L.) and fallow. Soil water content was monitored daily to a depth of 1.3 m and used with the numerical model WAVE to describe the water balance. Determination of crop canopy parameters was based on digital image analysis, and root depth in capacitance sensor readings. Nitrate leaching was calculated multiplying drainage by the soil solution nitrate concentration. Soil mineral N was determined before sowing CC and maize. Over the study, cumulative nitrate leaching in the fallow, vetch, and barley was 346, 245, and 129 kg N-NO 3- ha -1, respectively; occurring more than 77% during the intercrop period. In dry winters, NO 3- accumulated in the topsoil, and CC controlled the NO 3- leaching during the initial maize growth stages. Vetch was less efficient than barley at controlling leaching, but enhanced soil N retention. The CC controlled NO 3- leaching and recycled N inside the cropping system.
  • Authors:
    • Stockert, C. M.
    • Muhammad, S.
    • Alsina, M. M.
    • Schellenberg, D. L.
    • Wolff, M. W.
    • Sanden, B. L.
    • Brown, P. H.
    • Smart, D. R.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 155
  • Year: 2012
  • Summary: The optimum yield-scaled global warming potential (GWP) of perennial crops on arid land requires effective strategies for irrigation and fertilization. In 2009-2010, N 2O emissions and CH 4 oxidation were measured from an almond [ Prunus dulcis (Mill.) D.A. Webb] production system irrigated with nitrogen (N) fertilizers. Individual plots were selected within a randomized complete block design with fertilizer treatments of urea ammonium nitrate (UAN) and calcium ammonium nitrate (CAN). Event-related N 2O emissions from irrigation and fertilization were determined for seasonal periods of post-harvest, winter, spring and summer. Peak N 2O emissions in summer occurred within 24 h after fertilization, and were significantly greater from UAN compared to CAN ( p<0.001). Cumulative N 2O emissions from UAN were on average higher than CAN though not significantly different. Air temperature, water-filled pore space (WFPS), soil ammonium (NH 4+) and soil nitrate (NO 3-) showed significant positive correlation with N 2O emissions and significant negative correlation was found for the number of days after fertilization (DAF). The percentage of N 2O loss from N fertilizer inputs was 0.23% for CAN and 0.35% for UAN while CH 4 oxidation offset 6.0-9.3% of N 2O emissions. Total kernel yield was not significantly different between fertilizer treatments. Yield-scaled GWP for almond from CAN (60.9 kg CO 2eq Mg -1) and UAN (91.9 kg CO 2eq Mg -1) represent the first report of this metric for a perennial crop. These results outline effective irrigation and fertilization strategies to optimize yield-scaled GWP for almond on arid land.
  • Authors:
    • Cassman, K. G.
    • Grassini, P.
  • Source: Proceedings of the National Academy of Sciences of the United States of America
  • Volume: 109
  • Issue: 4
  • Year: 2012
  • Summary: Addressing concerns about future food supply and climate change requires management practices that maximize productivity per unit of arable land while reducing negative environmental impact. On-farm data were evaluated to assess energy balance and greenhouse gas (GHG) emissions of irrigated maize in Nebraska that received large nitrogen (N) fertilizer (183 kg of N.ha(-1)) and irrigation water inputs (272 mm or 2,720 m(3) ha(-1)). Although energy inputs (30 GJ.ha(-1)) were larger than those reported for US maize systems in previous studies, irrigated maize in central Nebraska achieved higher grain and net energy yields (13.2 Mg.ha(-1) and 159 GJ.ha(-1), respectively) and lower GHG-emission intensity (231 kg of CO(2)e center dot Mg-1 of grain). Greater input-use efficiencies, especially for N fertilizer, were responsible for better performance of these irrigated systems, compared with much lower-yielding, mostly rainfed maize systems in previous studies. Large variation in energy inputs and GHG emissions across irrigated fields in the present study resulted from differences in applied irrigation water amount and imbalances between applied N inputs and crop N demand, indicating potential to further improve environmental performance through better management of these inputs. Observed variation in N-use efficiency, at any level of applied N inputs, suggests that an N-balance approach may be more appropriate for estimating soil N2O emissions than the Intergovernmental Panel on Climate Change approach based on a fixed proportion of applied N. Negative correlation between GHG-emission intensity and net energy yield supports the proposition that achieving high yields, large positive energy balance, and low GHG emissions in intensive cropping systems are not conflicting goals.
  • 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:
    • Tian, C.
    • Chen, F.
    • Wang, X.
    • Zhang, R.
    • Li, Z.
  • Source: PLOS ONE
  • Volume: 7
  • Issue: 11
  • Year: 2012
  • Summary: There is much interest in the role that agricultural practices might play in sequestering carbon to help offset rising atmospheric CO2 concentrations. However, limited information exists regarding the potential for increased carbon sequestration of different management strategies. The objective of this study was to quantify and contrast carbon dioxide exchange in traditional non-mulching with flooding irrigation (TF) and plastic film mulching with drip irrigation (PM) cotton (Gossypium hirsutum L.) fields in northwest China. Net primary productivity (NPP), soil heterotrophic respiration (R-h) and net ecosystem productivity (NEP) were measured during the growing seasons in 2009 and 2010. As compared with TF, PM significantly increased the aboveground and belowground biomass and the NPP (340 g C m(-2) season(-1)) of cotton, and decreased the R-h (89 g C m(-2) season(-1)) (p < 0.05). In a growing season, PM had a higher carbon sequestration in terms of NEP of similar to 429 g C m(-2) season(-1) than the TF. These results demonstrate that conversion of this type of land use to mulching practices is an effective way to increase carbon sequestration in the short term in cotton systems of arid areas.
  • Authors:
    • Cockfield, G.
    • Maraseni, T. N.
  • Source: Agricultural Water Management
  • Volume: 103
  • Year: 2012
  • Summary: Irrigated cropping helps stabilise farm and regional income and contributes to productivity gains but the net benefits should include the full cost of water and greenhouse gas (GHG) emissions. This study examines the costs and returns of switching from a dryland rotation for four crops in the Darling Downs region of Australia, to a rotation of the same crops under irrigation, including greenhouse gas (GHG) values. The value chain, including all inputs was identified and emissions estimated using a range of studies and models. Over four year cropping cycle, the irrigated system would result in more than six times the emissions than from the dryland system. If GHG and water prices are not embedded in the production process, irrigation is more profitable per hectare. In this scenario, the landholder makes more than twice as much from the irrigated crops, with gross margins for the dryland and irrigated crop rotations of $1597 and $3490/ha, respectively. If the value of GHGs is included, the gap closes but irrigated crops are still more profitable. If however, a relatively high cost of the water, based on price ranges from the last decade, is included, then dryland crops are financially preferable. These results could be useful in designing national mitigation and water buy-back policies, both of which are being developed in Australia.
  • 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.