• Authors:
    • Griffis, T. J.
    • Baker, J. M.
  • Source: Agricultural and Forest Meteorology
  • Volume: 149
  • Issue: 12
  • Year: 2009
  • Summary: Climate change and economic concerns have motivated intense interest in the development of renewable energy sources, including fuels derived from plant biomass. However, the specter of massive biofuel production has raised other worries, specifically that by displacing food production it will lead to higher food prices, increased incidence of famine, and acceleration of undesirable land use change. One proposed solution is to increase the annual net primary productivity of the existing agricultural land base, so that it can sustainably produce both food and biofuel feedstocks. This might be possible in corn and soybean production regions through the use of winter cover crops, but the biophysical feasibility of this has not been systematically explored. We developed a model for this purpose that simulates the potential biomass production and water use of winter rye in continuous corn and corn-soybean rotations. The input data requirements represent an attempt to balance the demands of a physically and physiologically defensible simulation with the need for broad applicability in space and time. The necessary meteorological data are obtainable from standard agricultural weather stations, and the required management data are simply planting dates and harvest dates for corn and soybeans. Physiological parameters for rye were taken from the literature, supplemented by experimental data specifically collected for this project. The model was run for a number of growing seasons for 8 locations across the Midwestern USA. Results indicate potential rye biomass production of 1-8 Mg ha(-1), with the lowest yields at the more northern sites, where both PAR and degree-days are limited in the interval between fall corn harvest and spring corn or soybean planting. At all sites rye yields are substantially greater when the following crop is soybean rather than corn, since soybean is planted later. Not surprisingly, soil moisture depletion is most likely in years and sites where rye biomass production is greatest. Consistent production of both food and biomass from corn/winter rye/soybean systems will probably require irrigation in many areas and additional N fertilizer, creating possible environmental concerns. Rye growth limitations in the northern portion of the corn belt may be partially mitigated with aerial seeding of rye into standing corn. Published by Elsevier B.V.
  • Authors:
    • Bhattarai, S. P.
    • Midmore, D. J.
  • Source: Journal of Integrative Plant Biology
  • Volume: 51
  • Issue: 7
  • Year: 2009
  • Summary: Impacts of salinity become severe when the soil is deficient in oxygen. Oxygation (using aerated water for subsurface drip irrigation of crop) could minimize the impact of salinity on plants under oxygen-limiting soil environments. Pot experiments were conducted to evaluate the effects of oxygation (12% air volume/volume of water) on vegetable soybean (moderately salt tolerant) and cotton (salt tolerant) in a salinized vertisol at 2, 8, 14, 20 dS/m EC e. In vegetable soybean, oxygation increased above ground biomass yield and water use efficiency (WUE) by 13% and 22%, respectively, compared with the control. Higher yield with oxygation was accompanied by greater plant height and stem diameter and reduced specific leaf area and leaf Na + and Cl - concentrations. In cotton, oxygation increased lint yield and WUE by 18% and 16%, respectively, compared with the control, and was accompanied by greater canopy light interception, plant height and stem diameter. Oxygation also led to a greater rate of photosynthesis, higher relative water content in the leaf, reduced crop water stress index and lower leaf water potential. It did not, however, affect leaf Na + or Cl - concentration. Oxygation invariably increased, whereas salinity reduced the K +:Na + ratio in the leaves of both species. Oxygation improved yield and WUE performance of salt tolerant and moderately tolerant crops under saline soil environments, and this may have a significant impact for irrigated agriculture where saline soils pose constraints to crop production.
  • Authors:
    • Jabro, J. D.
    • Sainju, U.
    • Stevens, W. B.
    • Evans, R. G.
  • Source: Journal of Environmental Management
  • Volume: 88
  • Issue: 4
  • Year: 2008
  • Summary: Among greenhouse gases, carbon dioxide (CO 2) is one of the most significant contributors to regional and global warming as well as climatic change. A field study was conducted to (i) determine the effect of soil characteristics resulting from changes in soil management practices on CO 2 flux from the soil surface to the atmosphere in transitional land from perennial forages to annual crops, and (ii) develop empirical relationships that predict CO 2 flux from soil temperature and soil water content. The CO 2 flux, soil temperature ( Ts), volumetric soil water content (theta v) were measured every 1-2 weeks in no-till (NT) and conventional till (CT) malt barley and undisturbed soil grass-alfalfa (UGA) systems in a Lihen sandy loam soil (sandy, mixed, frigid Entic Haplustoll) under irrigated and non-irrigated conditions in western North Dakota. Soil air-filled porosity (epsilon) was calculated from total soil porosity and theta v measurements. Significant differences in CO 2 fluxes between land management practices (irrigation and tillage) were observed on some measurement dates. Higher CO 2 fluxes were detected in CT plots than in NT and UGA treatments immediately after rainfall or irrigation. Soil CO 2 fluxes increased with increasing soil moisture ( R2=0.15, P<0.01) while an exponential relationship was found between CO 2 emission and Ts ( R2=0.59). Using a stepwise regression analysis procedure, a significant multiple regression equation was developed between CO 2 flux and theta v, Ts (CO 2 flux=e -3.477+0.123T s+6.381theta v ; R2=0.68, P≤0.01). Not surprisingly, soil temperature was a driving factor in the equation, which accounted for approximately 59% in variation of CO 2 flux. It was concluded that less intensive tillage, such as no-till or strip tillage, along with careful irrigation management will reduce soil CO 2 evolution from land being converted from perennial forages to annual crops.
  • Authors:
    • Currie, R. S.
    • Klocke, N. L.
    • Stone, L. R.
  • Source: Proceedings of the World Environmental and Water Resources Congress 2008: Ahupua'A
  • Year: 2008
  • Summary: A field study was conducted near Garden City, Kansas to measure corn grain yield response to a range of rates from full to deficit irrigation. The contributions of antecedent stored soil water to crop water use were determined from soil water measurements near the beginning and the end of the growing season. Above average winter precipitation contributed to pre-plant soil water accumulations and deficit irrigation caused more growing season stored soil water use. Field results were compared with the Crop Water Yield (CWY) predictions of field results. Correlation of relative yields from field results and the CWY simulation were good, showing that the CWY has potential to be used as a management tool to screen potential irrigation scheduling scenarios for deficit irrigation.
  • Authors:
    • Pringle, H.
    • Ebelhar, M.
    • Martin, S.
  • Source: Journal of Cotton Science
  • Volume: 12
  • Issue: 4
  • Year: 2008
  • Summary: Increasing available soil water for a crop can be accomplished with both deep tillage and irrigation. Both have the potential to replace or complement the other due to their common function. The addition of a crop rotation may also enhance or diminish the response from irrigation and/or deep tillage. The major objective of this study was to determine long-term effects of different levels of furrow irrigation and in-row subsoil tillage on lint yield and economic returns for cotton grown on alluvial silty clay loam soils in a cotton/corn cropping sequence. A secondary objective was to determine the ability and efficiency of deep tillage and irrigation to replace and/or complement each other in the cropping system. Field experiments were conducted at Tribbett, MS on silty clay loam soils from 1999 through 2004. In-row subsoil tillage was performed with a low-till parabolic subsoiler. A roll-out pipe system was used to furrow water the irrigated plots. Production costs were calculated and include direct costs plus total specified costs excluding land rent, general farm overhead, and returns to management. Growing non-irrigated cotton without deep tillage in this cotton/corn sequence on these silty clay loam soils that were prone to backwater flooding gave the highest average net returns. It appears producers should neither subsoil, nor furrow irrigate and the two should never be combined, based on this study. These results emphasize the need for drainage and support the need for further research on these type soils in the absence of drainage problems.
  • Authors:
    • Rodriguez-del-Bosque, L.
    • Salinas-Garcia, J.
  • Source: Journal of Entomological Science
  • Volume: 43
  • Issue: 2
  • Year: 2008
  • Summary: The effects of tillage, irrigation (10 cm each at 10- to 14-leaf stage, and silking and milk stages, and no supplemental irrigation) and fertilizer (NPK at 0:0:0 or 140:40:0 kg/ha) treatments on the incidence of lepidopteran insects and fungi infesting maize (cv. Pioneer 3025W) were studied in Tamaulipas, Mexico, during 2005-07. The tillage treatments consisted of mouldboard ploughing (discing stalks after harvesting, followed by mouldboard ploughing, discing and row establishment), subsoil-bedding (shredding stalks after harvesting, followed by subsoiling on row centres and establishment of beds), shred-bedding (shredding stalks after harvesting, followed by bedding on old rows), and no-tillage (shredding stalks after harvesting, and spraying 0.6 kg glyphosate and 0.72 kg 2,4-D/ha twice for weed control). Mouldboard ploughing represented conventional tillage, whereas subsoil-bedding and shred-bedding were reduced tillage systems. The lepidopteran species recorded were Helicoverpa zea (86%) and Spodoptera frugiperda (14%). The incidence of these pests was highest in 2006 (91.5%) and lowest in 2007 (49.3%). The most common fungi were Fusarium spp., the highest incidence of which was registered in 2005 (24.4%). The incidence of Aspergillus flavus and Ustilago maydis [ U. zeae] was less than 4.0% regardless of the year. The incidence of lepidopterans significantly varied between the irrigation levels only (greater pest population under dryland farming). Fusarium spp. and A. flavus occurred more frequently under no-tillage compared with other tillage practices. The incidence of Fusarium spp. was higher in irrigated than in dryland maize.
  • Authors:
    • Ahuja, L. R.
    • Nielsen, D. C.
    • Trout, T. J.
    • Ma, L.
    • Saseendran,S. A.
  • Source: Water Resources Research
  • Volume: 44
  • Issue: 7
  • Year: 2008
  • Summary: Increasing competition for land and water resources due to increasing demands from rapid population growth calls for increasing water use efficiency of irrigated crops. It is important to develop location-specific agronomic practices to maximize water use efficiency (WUE). Adequately calibrated and validated agricultural systems models provide a systems approach and a fast alternative method for developing and evaluating agronomic practices that can utilize technological advances in limited irrigation agriculture. The objectives of this study were to (1) calibrate and validate the CERES-maize model under both dryland and irrigated corn ( Zea mays L.) production in northeastern Colorado and (2) use the model with a long-term weather record to determine (1) optimum allocation of limited irrigation between vegetative and reproductive growth stages and (2) optimum soil water depletion level for initiating limited irrigation. The soil series was a Rago silt loam, and the initial water content on 1 January of each year was equal to field capacity in the upper 300 mm and half of the field capacity below this depth. Optimum production and WUE with minimum nitrogen (N) losses were found when (1) a water allocation ratio of 40:60 or 50:50 (uniform) between vegetative and reproductive stages for irrigations up to 100 mm, and a ratio of 20:80 for irrigations above 100 mm was used; and (2) irrigation was initiated at 20% plant-available water (PAW) (80% depletion). When available water for irrigation is limited to 100 mm, irrigating 50% of the area with 200 mm of water at 20:80 split irrigations between the vegetative and reproductive stages produced greater yield than irrigating 100% of the area with 100 mm water. Concepts developed in the study can potentially be adapted to other locations, climates, and crops. However, precise site-specific recommendations need to be developed for each soil-climate zone using the validated system model.
  • Authors:
    • Suyker, A. E.
    • Verma, S. B.
  • Source: Agricultural and Forest Meteorology
  • Volume: 148
  • Issue: 3
  • Year: 2008
  • Summary: In this paper, we present results from 4 years (May 2001-May 2005) of water and energy flux measurements made in a no-till, irrigated maize-soybean rotation system in eastern Nebraska, USA. The peak green leaf area index (LAI) reached 6.0 and 5.5 in maize (2001 and 2003, respectively) and 5.7 and 4.4 in soybean (2002 and 2004, respectively). The dependence of evapotranspiration (ET) on leaf area was consistent with previous studies. There was a nearly linear relationship between the daily ET/ET o (where ET o is the reference evapotranspiration over a grass reference crop) and LAI until a threshold LAI (between 3 and 4). Above this threshold LAI, the ET/ET o was virtually independent of LAI. The cumulative growing season (planting to harvest) evapotranspiration was 544 and 578 mm for maize, and 474 and 430 mm for soybean. The interannual variability in the growing season ET totals correlated very well with the number of days when the LAI was greater than 3. The non-growing season period (harvest to subsequent planting) contributed between 20 and 25% of the annual ET totals for both crops. The maximum canopy surface conductance ( Gsmax) was 29 mm s -1 for maize in both years, 41 mm s -1 for soybean in 2002 (peak LAI=5.7) and 36 mm s -1 for soybean in 2004 (peak LAI=4.4). The variability in Gsmax was largely explained by the leaf nitrogen concentration, consistent with the literature.
  • Authors:
    • Li, S.
    • Zhao, M.
    • Zhen, X.
    • Zhou, J.
    • Wang, C.
  • Source: Journal of Northwest A & F University - Natural Science Edition
  • Volume: 36
  • Issue: 1
  • Year: 2008
  • Summary: An experiment was conducted to investigate the effects of cultivation methods and N rates on N accumulation, distribution and utilization efficiency of winter wheat on manual loessial soils under the winter wheat-summer maize cropping rotation system. The treatments comprised 4 different cultivation methods, i.e. control (C), supplementary irrigation (SI), straw mulching (SM) and furrow planting (FP), and 3 N rates, i.e. 0, 120 and 240 kg/hm 2. Compared with the other 3 cultivation methods, the N residue in leaf and stem of wheat after harvesting was lower in the SI cultivation method, so was the rate of N residue to total N accumulation in the crop. However, the rate of N residue in grain to the N accumulated in shoot was increased. As the application rates of N increased, the N accumulation in leaf, stem, glume and rachis, and grain of wheat was significantly increased. When the N application was increased from 120 to 240 kg/hm 2, the N accumulation in wheat leaf, stem, and glume and rachis was increased after harvesting. However, the N accumulation in grain did not increased significantly. The application of N did not show significant effect on the distribution of N in the different organs of wheat. As the application rates of N increased, the N recovery, agronomic efficiency and physiological efficiency decreased. Compared with the other cultivation methods, the N recovery, agronomic efficiency and physiological efficiency of the SI pattern were higher during the 2 continuous years; the changes in the N efficiency indices of the other 3 cultivation methods varied in different years.
  • Authors:
    • Xia, J.
    • Wu, D.
    • Yu, Q.
    • Wang, E.
  • Source: International Journal of Climatology
  • Volume: 28
  • Issue: 14
  • Year: 2008
  • Summary: The North China Plain (NCP) is the largest agricultural production area in China. The extensive use of groundwater for irrigation agriculture under variable climatic conditions has resulted in the rapid decline of the groundwater table especially in areas north of the Yellow River, leading to hydrological imbalance and unsustainable agricultural production. This article analyses the sustainable level of vegetation/crop water use under the NCP climate by mimicking the evapotranspiration of a natural forest ecosystem. Such a system would have a mean annual evapotranspiration ranging from 470 mm/year in the northern to 910 mm/year in the southern part of the plain, leading to a mean annual water excess (rainfall minus evapotranspiration) ranging from 21 to 124 mm/year. The natural forest ecosystem would use less water than the current wheat/maize double cropping system. To mimic the water use of the natural system, dryland farming has to be practiced, and wheat and maize crops would have a water deficit of 90-435 and 0-257 mm/year, respectively. Under average conditions, this would mean that all the areas north of the 36 degrees N line have to abandon winter wheat production. Stopping irrigation will lead to significantly lower wheat yields (average yield 0.8 t/ha in the north to 5.2 t/ha in the south) and increased variability in wheat and maize yield both interannually and spatially. Better management practices, such as opportunity cropping (what and when to crop depending on climate and soil conditions rather than a set annual cycle), better use of climate forecast information to direct decision making, are required in order to achieve maximum return in good years while minimizing cost in bad years. Analysis on rainfall and potential evapotranspiration (PET) from 1961 to 2000 shows that there has been an increasing trend in crop water deficit in the northern part, but a decreasing trend in the southern part of the plain. It remains to be further studied whether this reflects long-term climate change or only a part of the climate variability.